La Terre Vol. 10 (English Version) by laterremagazine

LA TERRE OUR WORLD, SEISMIC WORLD

2018

indonesian undergraduate geophysics competition

@odc7216r www.iugc.info @iugc_terra @iugc_terra

Editorial Staff Person in Charge Dr. rer. nat Rachmat Sule S.T., M.T.

Managing Director Silvia Ayu Agatha

Head of Translators Diya Tabina Joebhaar

Layouting Director Dimas M. Zulfikar

Editor in Chief

Yohanes Nuwara

Translators

Suci Farissa Mahendra Dwi S Azhar Harisandi Diya Tabina Joebhaar Tara Annisa Pangestu Soekarno

Layouting Team

Najla Insyirah Firadila Ainunnisa Giovanni Pierre Jefri Bambang

Writers

Yohanes Nuwara Rafif Abdus Salam Niken Dyah Arum Sari Fara Yuniar Latifah Adisa Putri Utami Dzaky Irfansyah Dinda Putri Pramestiningrum Azarine Nurfairuz Kalyana Defiska Andang Nugraha Laurent Juliani Monica Nabiel Husein Shihab Irfani Sakinah M. Hasyim T.

Photography and Videography Kevyn Augusta Giovanni Piere Dimas M. Zulfikar M. Ababil Akram M. Hafiyyan Fikri Muhammad Devandra Ridho Pratama Zoughira Nabiel Husein Shihab

Diya Tabina Joebhaar Karya S. Hendra Fatimah Az Zahra Arivia Dian Pertiwi Rizka Amalia Dimas Zulfikar Bagas Arya Regina Nathasa Jefri Bambang

Publication

Editor in

Chief

We are really glad to finish the 10th edition of our valuable one and only student magazine with contributions from fellow writers, layouters, and translators. In current edition we come up with a really friendly visualization of the seismic technology, covered up with the theme "Our World, Seismic World". You shall wonder what seismic is about and why seismic. Seismic is a very popular method known in geophysics which is going to be more popular!Well, how can this method help us? Seismic can help us exploring the wonder of our our earth to hunting for the "black diamond", or petroleum. Wonderful, isn't it. We couldn't be wrong that our seismic technology in Indonesia can be overlooked. Last month I visited an Elnusa company's seismic vessel named Elsa Regent at Tanjung Priok harbor. This seismic vessel is purely operated and managed by 100% Indonesian crew and geophysicists. I was stunned (I'm still until now) by sophisticated technology which we surely cannot disregard. Carreer in seismic is also gleaming. So, why are we so anxious about the future? We will provide number of articles just in seconds to fulfil your curiosity. Enjoy reading the articles, suit up, and be ready for the future! There are still more interesting things about seismic that we will cover all in this little magazine. We hope you enjoy reading the articles. Suit up and be ready for the future!

Yohanes Nuwara Editor-in-chief

CON TENTS MYSTERY BENEATH ANTARCTIC ICE

MISTAKES IN SEISMIC INTERPRETATION

PERMAFROST, PANDORA BOX IN NORTHERN HEMISPHERE

“HOW IS OIL INDUSTRY?” CONVERSATION WITH PROFESSOR JOHN KALDI

FRONT

PAGE IVAN KOULAKOV, ARTISTIC RUSSIAN TOBA RESEARCHER

INCREDIBLE SPIRIT AND HARDWORK ESCORTED PALGU TO FRANCE

ANISOTROPIC AND ISOTROPIC, UNIQUE THINGS IN SEISMIC WORLD

27 73 67 53 39

BRIGHT, FLAT, DIM SPOT TO FIND OIL

STRUCTURE THAT CAN WITHSTAND EARTHQUAKES TOP 5 SEISMIC TOPICS POISSONâ&#x20AC;&#x2122;S RATIO, THE MULTIFUNCTIONAL EQUATION

MYSTERY BENEATH ANTARCTIC ICE by Dzaky Irfansyah

Source: Sumber animalli.com : animalli.com

As far as we have seen in the media, whether from photographs or videos, Antarctica is merely a continent located at the southern end of the Earth with ice and snow covering the entire surface of the continent. The continent was never inhabited by previous human civilizations due to very unfriendly climatic conditions. Antarctica is still a white plain inhabited by a flock of cute penguins. In fact, there are still many people who think that the Atlantic is a vast land of ice that floats on the sea, not a continent covered with ice. And fewer people know that there is an active volcano on the Antarctic continent.

A lot of people still think that Antarctica is just a massive ice floating above the ocean. But the truth is, Antarctica is a vast territory covered in ice. Only a small number of people really know that Antarctica have a volcanic mountain beneath it.

For most ordinary people, maybe Antarctica is just an ice plane that never thought to be included in the list of dream destinations. But for a few people, especially scientists and adventurers, the Antarctic continent still has many unknown mysteries, especially under ice. No one has ever seen what the land looks like under Antarctic ice directly. So far, scientists have discovered a more detailed Antarctic look through ice cores and geophysical methods. Throughout the explorations and discoveries of the researchers, what appears on the surface of the ice has a sharp contrast to the land it covers. The continent under the Antarctic ice has diverse topographical expressions and is the key to why volcanoes form in Antarctica, as well as storing riddles on Antarctic ice that affect Earth's future.

It turns out that below the vast ice surface in Antarctica, this is what it really looks like.

Andrew Lloyd, a researcher from Washington University of St. Louis, who was in charge of investigating Antarctic subsurface, placed a seismometer along the West Antarctic System and the Marie Byrd Plain to record the movement of the plates in the area for 2 years. Plate motion recordings are used to map the seismic wave velocity along the fracture system. Plate motion velocity modeling results indicate the presence of a large area of hot rock as deep as 60 miles below Mount Sidley, one part of a range of mountains in the Marie Byrd Highlands. In addition, the hot rock area is also found beneath the Bentley Subglacial Trough, located in the Western Antarctic Fracture System. The presence of hot rocks below the surface shows that the fracture system has a fairly active tectonism. According to Doug Wiens, a professor of earth and planetary science, as well as co-author of related papers, the mountain ranks of Mainland Marie Byrd, indicate a mantle plume that has not been fully identified. Antarctic plate movements produce mountain ranges

generated from stationary hot spots under the plates. Although the direction of Antarctic plate motion is well known, the pattern of mountain ranges does not show a uniform orientation. This is known by the existence of two rows of mountains have a different orientation. So, researchers have not been able to deduce the number and form of hot spots under Antarctica. However, the researchers believe one thing: there is a high enough heat flow below the Antarctic ice sheet. The mountain ridges formed by the hot zone of the mantle are also known as The Trans-Antarctic Mountains. The Trans-Antarctic Mountains are adjacent to the Western Antarctic System, where the Antarctic continent experiences plate thinning due to a diverging motion from mantle convection. The extensional style of the Western Antarctic Foam forms a valley of fractures located at a depth of one Kilometre below. If the ice in the West Antarctic region melts, the continent will be rebound (change in position and altitude due to the removal of the ice load) so that most of the continents will be above sea level. However, deep depression

areas are estimated to remain at a depth of about one kilometer below sea level if all the polar ice melts. Due to being covered with ice, the Western Antarctic Fracture System is not known as a whole as other rifting zones such as the East African Fracture or Rio Grande Fracture in the United States. Researchers estimate that the tectonism in the Western Antarctic System is similar to the Rio Grande Fracture system. No seismic activity has The team is assembling seismic station in Thwaites glacier. Seismometer is located in an orange case beneath Photo by Mike Roberts

been detected in the Western Antarctic Fault System, indicated by the stopping of the fracture there, but the heat flow in the West Antarctic System has not cooled completely. Mantle convection flows forms the fractures on the West Antarctic valley at the end of the Cretaceous period, about 100 million years ago. The more intensive extensional styles subsequently occurred in the Neogenic era, forming deeper depressions such as the Bentley Subglacial Trough and the Terror Craft in the Ross Sea. According to Lloyd, if the heat flow rate under these depressions is still high, it ispossible that the heat flow rate is also high in

One of the teamâ&#x20AC;&#x2122;s member uses skidoo to pull Canestoga (shelter for the team) in front of Sidley Mountain, a volcanic mountain that errupted as big as Mount Helens.

other depressions within the Western Antarctic Fault System. With the discovery of mantle plume beneath the ice of Antarctica, the next question is whether the rate of heat flow down there affects the Antarctic ice melt? According to Lloyd, the heat flow rate in the West Antarctic zone of friction does not directly affect the

polar ice melt. It is based on the time scale difference between the rate of heat flow from the Earth's mantle and the rate of melting and the formation of ice on the surface of the Earth. However, an understanding of the mantle plume and the heat flow rate in the fracture zone is also required to model how ice melts or how the Antarctic continent rebounds. To create a model of ice flow

rate, according to Lloyd, hot and geological flow rate data from the Antarctic continent are required. However, those data from both factors are still not enough to try to form a model. About less than 12 hotspots, of approximately 34,000 identified hot spots, are located in Antarctica. However, a study in July 2015 showed that

the heat flow rate at one of the Antarctic hot spots was four times higher than the average. The researchers themselves estimate that the extravagant motion of the Bentley Subglacial Trough, which is part of the Western Antarctic System, is proof why the rate of heat flow is high enough.

PERMA PANDORA BOX IN NORTHERN HEMISPHERE

By: Fara Yuniar L. & Niken Dyah A.

What is Permafrost? For something that is dangerous, Permafrost is merely deep layers of soil that have remained frozen at or below 0Â°C for at a minimum, two consecutive years. It mainly consists of a mix of soil, sediment, and rocks. Meanwhile, its thickness may range from 1 meter to 1,000 meters. Now, the layer of Permafrost, a thousand years old ground ice,

covers nearly 22.8 million square kilometers of northern hemisphere. Above that lies an Active layer. Unlike the Permafrost, it depends on seasons. When the spring comes, it thaws. Otherwise, it freezes. What is Talik? Talik is a layer of unfrozen ground in the permafrost area. Its temperature may vary between 0oC (cryotic) to above 0oC (noncryotic). So basically, it relies on the occurrence of the ice inside the layer. In Russian, it is known as tabetisol.

FROST

Lately climate change has created a ticking time bomb, hidden underground. The bomb; permafrost. The scientists fears, as the planet warms, the ice on the Active layer will melt. The unfrozen water will then penetrate the permafrost layer. As a result, the microbes concealed from years of decomposition, and even more so, carbon dioxides and methane gases, are unleashed.

These gases contributes to increasing global warming. Now, researchers escalate the increasing temperature to 1.7 degree of Fahrenheit in decades. â&#x20AC;&#x153;How much carbon dioxide and methane gases unleashed from the melting of permafrost is needed to be able to substantially increase temperature?â&#x20AC;?, questions Vladimir E. Romanovsky, a permafrost expert at the University of Alaska, Fairbanks. According to the data collected, the average CO2

emission from decades ago is 1.5 billions ton per year. Shockingly, this is similar to the average annual CO2 emission from the fossil fuels in U.S. By that, in the north Alaska, the temperature from 65 ft. rises 3°C in 10 years. Even more, its temperature near the surface increases from -8°C to -3°C.

Permafrost Distribution Continuous

Discontinuous Sporadic Isolated

“Permafrost is a good microbial and virus preservation,” says Jean-Michel Claverie, an evolutionary biology expert at the University of Aix-Marseille in France, He continues by stating that “it barely has oxygen. It is dark and cold”. What an excellent Pandora’s box. Interestingly, it holds unexpected diseases”.

For instance, scientists found fragment of RNA from the Spanish Influenza of 1918 and the smallpox outbreaks in Siberia of 1890 contained in the Permafrost. And many more. Not only that, but the infrastructures built above the permafrost are also threatened. The fallout may not only affect the survival of living creatures but also the buildings and other crucial infrastructure built above the permafrost. These buildings increase the temperature that affect the active layer. As a result, the permafrost layer melts and creates sinkholes. Consequently, these sinkholes may cause the buildings, roads, railroads, oil pipelines to collapse. As we have seen, a melting permafrost does unthinkable damage to not only living creatures but also crucial infrastructure.

Igniting fire caused by methane inside a permafrost Source : VideoYoutube/Rune Pettersen

Using Seismic Refraction to Investigate the Thawing Permafrost “Permafrost is melting”, warns Kevin Schaefer, a researcher at the University of Colorado. And the after-effect may cause more trouble. For that, scientists are escalating the time of permafrost to thaw by observing its thickness. Although drilling and thermal modelling are used, the methods are costly and fruitless. Consequently, scientists move to the Seismic Refraction Tomography (SRT) method. Fortunately, the method has produced results. It utilizes the ment of expansion of ice pressure to increase the velocity of P-wave (Draebing and Kraublatter, 2012). This method has been proven to distinguish the different layers of Permafrost. However, it needs more extension such as Electrical Resistivity Tomography (ERT) in order to differentiate the layer in a talus cone and slope that is covered in ruins. In addition, a repeated seismic refraction is also used to observe the evolution of Permafrost. This method depends on the variation of P-wave velocity due to its sensitivity toward ice and water. At its core, the whole concept of seismic refraction is simply basic physics at work. It is when a propagated wave enters different mediums and creates a critical angle. This is called Snell’s Law. Likewise, the law is applied on the Permafrost visualization process.

The image below depicts three scenarios of the propagation of seismic wave through the Permafrost and soil; the shade of blue shown as (b) indicates the lower level of Permafrost. Meanwhile, (c) depicts the composition of gas and ice of the soil, which yields different result.

Svalbard Global Seed Vault got affected from permafrost melting. Photo by AFP/Getty Images

Hilbich, C. 2010. “Time-lapse refraction seismic tomography for the detection of ground ice degradation” dalam www.the-cryosphere.net

The shallow part of Permafrost (0-50 meters) is observed by using a seismic refraction tomography. In contrast, for a deeper part, a time-lapse refraction by Landrø et al. (2004) is applied. Any ice in the pore spaces of sediments may increase the seismic velocity (Timur, 1968). But since a rock is more rigid than an ice, its seismic velocity decreases as a function of the porosity (Zimmerman and King, 1986).

For the most part, inversing seismic tomography produces a time-lapse seismic data. Moreover, a refraction seismic tomography algorithm, known as SIRT algorithm, is able to reconstruct the subsurface into multi-dimensional velocity pattern, (software REFLEXW, Sandmeier, 2008). Not only does the algorithm reckon the travel time, but also calculates the ray path of the seismic P-waves.

The conclusion from the tomographic data indicates that Permafrost is indeed gradually shallowing.

Miami

Bermuda

Do You Know? The Bermuda Triangle, mysterious ocean between Bermuda, Puerto Rico, dan coast of Miami, has -allegedly- 'eaten' many airplanes and ships. There are many theory about it, but we will mention some scientific facts about Bermuda. Methane gas that floated to the surface makes the ocean has lower density. This caused ships to sink. Magnetic anomaly around the Bermuda Triangle caused compass to spin very fast. The magnetic anomaly is caused by magnetic storm around Bermuda Triangle

Puerto Rico

Do You Know? Sahara dust carry both good news and bad news. The bad news is, dust from Sahara desert in Africa - the total amount of dust there is a staggering two to nine trillion pounds worldwide - has been a biblical plague on Texas and much of the Southern United States in recent weeks. The good news is, the very same dust appears to be a severe storm killer.

Incredible Spirit and Hardwork Escorted Palgu to France. By: Silvia Ayu Agatha In the previous edition, La Terre Team had chance to know more about an outstanding geophysicist, both in the profession and organization. In this chance of episode, we also got another inspirational geophysicist, an Alumni of Geophysical Engineering ITB, he is Kadek Hendrawan Palgunadi, or we call him as Palgu.

Palgu is alumni of Geophysical Engineering ITB class of 2012. After he finished his undergraduate study in ITB, he moved to France with Consortium Program from Universite Paris Diderot, Ecole des Mines Paris and Intitute Physique de Globe de Paris to get his master degree of earth and planetary science. Now Palgu has been continuing his further study to get Doctoral degree in King Abdullah University of Science and Technology, Saudi Arabia. La Terre team started the conversation by asking the beginning journey of his study in ITB. Palguâ&#x20AC;&#x2122;s very first vision was to become a Faculty of Mechanical and Aerospace Engineering student (known as FTMD). He wanted to study Aeronautics, but then his vision just became an ash as his parents suggested to join Faculty of Mining and Petroleum Engineering (known as FTTM). After finishing his first year well, Palgu then chose Geophysical Engineering for its flexibility of knowledge area in geoscience, it was his best option, especially when he has passion and very interested to learn about natural disaster phenomena.

After that interesting beginning, Palgu shared his struggles in ITB. He said that he was once really sad after given a C by a lecturer in a subject. However, that made him wanted to show and prove his capabilities more. For proving his capability, he made a paper in that subject and eventually succeed after getting published in SEG with the help of another lecturer. Furthermore, in his final year of study, Palgu had chosen micro seismic as undergraduate thesis topic. Itâ&#x20AC;&#x2122;s a rare field with few Indonesian people interested in it, but it has been becoming a very big topic abroad. Palgu chose tomography anisotropy rather than tomography velocity because he thought that anisotropy is more challenging and exciting, as it is not only using software but skills and critical thinking are required for solving the topic. Kindly and gently, Palgu told us that he had chosen S2 because he liked to work int the geoscience topic. He has the passion for it. Not only that, he wants to become a researcher, which means he needs to get his Doctoral degree. Palgu is one of a kind who never

Arc de Triomphe

grow tired to get what he wanted to know and understand. This is his very special features we can learn from him. Actually, there are many more excellent attributes we can learn from Palgu, especially in his dedication for doing the things he loved. His warm and kindly way of communicating makes a comfortable situation to talk and be open with him. He also believed that GPA has nothing to do with the success itself, “It is important if you want to continue your study but it’s not really needed when you want to become entrepreneur”, he added. Furthermore, Palgu believed that if we study because of our curiosity and inquiry, good GPA would also follow. It’s worse if we learn because of examination or just because of good score, it would go pointless although we got the good GPA we wanted. After graduated with Bachelor of Engineering degree in 2016, Palgu continued his master study in France. Actually, he had some other choice, like Germany, Netherland, and of course France. However only France gave full scholarship until he finished his master thesis. There are still few Indonesian people who study in France because of its known difficulty especially in Geoscience, after all learning French is quite a difficult task already. However, the program he took in France is an International Class Program, so the lectures were given in English.

(Meaning : Arch of Triumph) is a very famous monument in Paris, located at the centre of the Place de l'Étoile and the western end of the Champs-Elysées.

Palgu has just finished and got his master degree in June 2018. In a year, he earned his degree with Magna Cum Laude, an honor given only to the best graduates. His research thesis was about the advance development of detection, selection, and real time locating for monitoring mining micro seismic with high sampling rate. One of the disadvantages of real time method in seismic monitoring is that method requires high computational cost. However, Palgu solved that problem by creating such formula and mechanism to determine hypocenter faster and more effective. Now the program he made has already been implemented in a Garpenberg mine monitoring system, Sweden. The last but not least, it’s quite a priceless opportunity for La-Terre Team Magazines to had a talk with such incredible person, Palgu. He got some good

messages for the readers. “Do what you love, work patiently without considering just the result. Don’t force yourself if you’re not really into geophysics. If you into it, travel the world, learn from the expert from abroad. However, don’t use Master Study as an escape reason, think of the time you’ll be wasting if you study S2. Know your purpose, your dreams. There will always be problems and difficulties, but if you are doing what you like, you’ll eventually be succeed. There will always be a way to solve and learn through it.” Said Palgu as we close the interview epic and nicely. There are a lot of things we all can learn from Palgu’s journey in achieving his dreams. So, do you have something you like to do now? Do you have real purpose and dreams already? Get it on as soon as possible, it’s never late to have purposes and dreams, just like what Palgu did.

So, what have you done for the things you like?

INTENSE WITH PROFESSOR JOHN KALDI:

HOW OIL AND GAS INDUSTRY LOOKS LIKE? By: YOHANES NUWARA & SILVIA AYU A

Professor John Kaldi, whom we call John, is a great and motivational professor. John Kaldi is a professor of Petroleum Geology and Engineering at the Australian School of Petroleum, e University of Adelaide. He is very renowned among petroleum geoscientist academia, both in the universities and organizations namely e American Association of Petroleum Geologists (AAPG). His main study is development geology, reservoir and seal evaluation, capillary pressure principles in oil and gas exploration, and Carbon Capture and Storage or CCS.

He worked in Indonesia for 8 years, he worked in ARCO for 7 years in Jakarta as a Geological Specialist then he worked in VICO for 1 year in East Kalimantan. He studied Talang Akar outcrops in Sumartra, in O shore North West Jakarta (ONWJ) and also in Sulawesi. Not only Indonesia, he had so many experiences in other country for exploration. Having been for AAPG president candidacy in 2017, he has authored and presented over 150 journal articles, technical paper conferences, and books.

Q Discussing about the oil and gas companies in Indo-

nesia, what is your opinion about the business environment?

A Oil and gas business is a very dynamic industry

indeed! The growing interests and investments of international oil and gas companies in Indonesia started during the Soeharto era. Originally a Hungton Company (Hu co) company based in the United States, VICO made a working contract with Indonesian government to manage the oil and gas production in East Kalimantan. Hence, the government granted the oil eld to VICO. VICO is international company, but VICO works in Indonesia and bring resources and sta s from around the world. The joint-venture and collaboration among oil business entities often happen in this industry. US company Union Texas and British company Lasmo joined with VICO, so I encountered geologists and experts from various companies. When I moved to VICO, BP company bought ARCO. So, donâ&#x20AC;&#x2122;t be surprised with this environment if you work in oil and gas industries.

Q Why do such companies join? A Normally, they always find new business opportuni-

ties and new resources that make the companies to modify the existing management. Old companies need to be renewed, many things happened, and business modernization takes place. Especially, you often meet with old seniors who have worked for so long in a company.

Old men in a company tends to follow the culture of the company and will continuously ask you to do exactly what they have done before, so not many changes happen. When changes occur, companies will have to re-organize themselves.

Q You made an interesting remark about

the old men in oil and gas companies. Do you think that young men can make changes in the companies?

A Absolutely! Look, hierarchial system is a common culture in most workspaces, including in Indonesia. There are always gaps between the old men and the young men. Do not think that oil and gas company has a 100% ideal working environment for the freshgraduates. Many of them think they donâ&#x20AC;&#x2122;t have enough opportunity to create something new because their seniors like continuously doing something they have done before. For example, when a company drill a potential oil well and encounter a dry well, the company just simply moves to another prospect rather than analyzing why they cannot find the oil that they expected before, what is wrong with the well, and evaluate the lack of success. It must be a learning experience that only small portions of the geologist, petroleum engineers, and other experts worldwide do. Donâ&#x20AC;&#x2122;t be scared of making mistakes when you try something new and try understanding whatâ&#x20AC;&#x2122;s wrong with your work, because I believe your work will improve the next process.

In the middle of our Summer School program, we decided to interview John and thankfully, we had the opportunity. In this interview, he is about to share his great experiences working in oil industry in Indonesia and give insights about how oil industy works and looks like.

You know that Indonesia has large oil and gas potential but somehow the production is not as big as the potential due to small recovery factor. In your opinion, what things should Indonesia need to do to maximize its production?

One wrong mindset encountered while managed to do exploitation in oil and gas fields is moving to another oil field while the production of older oil field has start to diminish. There are many old oil wells left barren and no one has come back to the oil field. In other words,

the companies do not make the brown field green again. Hence, making the brown field green again is a good strategy to maximize resources potential in a country. You should also utilize new technologies to optimize the production.

Q As students, what things should we prepare while starting to work with industries?

your studies and have capability to pick up knowledge that is extremely valuable. Third, you will deal with many old seniors in the industry who dominate most of the decisions made. Therefore, you should accept their views if you have different opinion, but always ask their opinions. Just donâ&#x20AC;&#x2122;t hesitate to make questions. It is not hard to have those kinds of mindset while you are still undergraduate students.

First, you should open yourselves to new things. Do not just accept they way they are. Second, you should have free and young minds. Read lots of literature about

Q In Indonesia, we sometimes come accross some projects dealing with energy sources such as oil and gas, or geothermal energy that declare soon to close and terminate because the public acceptance is negative. Related to your experiences, what do you think about public acceptance and how to deal with it? A The public acceptance would be always

nice if the company was able to maintain good manner and relations with the locals. When we were working for ARCO in Kangean Block in East Java, we should be nice to the local people first. As a company, we run on a moral responsibility on working together with the locals by supporting their major daily needs as they will also support us. ARCO funded the building of schools and mosques and provide the locals activities as well. More interestingly, ARCO also funded the jerseys soccer team

players in Kangean. Companies should not change the environment and make people lose their jobs.

Q What do you want to say to undergrad-

uate students for reaching their future?

A First, be different and be yourself. There are so many good and smart people, but only some of them are authentic. Do not just accept the things the way they are. Listen carefully and ask question. Knowing what you are doing and what you are going to do. Second, work hard and do something useful. for humanity useful, for planet useful, for the economic, do something useful. Do like that at work and volunteer. And the most important one, whatever you do, have fun. Because if you are not having fun, you are not gonna do anything well.

Be different. Do Something Useful. Have Fun.

Ivan Koulakov ARTISTIC TOBA RESEARCHER FROM RUSSIA By: Dwi Julianti

Toba caldera according to Ivan Koulakov

Who is he?

van Koukalov is not only a graduate with a Master Degree in Geophysics from Novosibirsk State University but a highly skilled artist as well. From a ripe young age, Ivan Koukalov have already taken an interest in art, mostly influenced by his father, Yury Koukalov, who is a Physics Professor in Novosibirsk State University and an avid connoisseur of art. With his degree, Ivan keeps working on his love of the arts. As stated in his blog, the art he creates contains a certain mystery that manifests from years of careful study and meditation. The uniqueness of his craft comes from the application of certain guidelines through the touch of the colors which forms a composition that contradicts the very essence of the art itself from the dynamics of the very thing being created. At the very least, Ivan has successfully done 75 researches in his lifetime and did you know than in July 19th 2016, Ivan Koukalov published a well-known article about the Toba Supervolcano in Indonesia? Ivan wrote the article along with numerous esteemed geophysicist such as Ekaterina Kasatkina, Nikolai M. Shapiro, Claude Jaupart, Alexander Vasilevsky, Sami El Khrepy, Nassir Al-Arifi dan Sergey Smirnov. The following is a review of his article entitled â&#x20AC;&#x153;The Toba Volcanic Supply System From the Plates to the Shallow Reservoir.â&#x20AC;?

The Toba Caldera is one of many Volcanic Complexes from the Sundanese Arc, wherein the Indo-Australian plates would undergo oblique subduction with a speed of 56 km/year. However you look at it, the intensity and repetition of the Toba eruption is unique. Results of extensive research shows that there is an abnormality in the production of magma underneath the Toba Caldera mainly caused by a disturbance on the plates associated with the fault subduction zone. In the tomography model of the

Then what is the reason that a lot of explosive eruption in the Toba Caldera occurs numerous times in almost the same spot?

area, we could identify the

The main cause of this event is associated with the Investigator Fracture Zone (IFZ) fault zone, wherein the IFZ undergo subduction directly underneath Toba. The fault in the IFZ causes the seawater to pass through the crust, which leads to the IFZ transporting numerous irregular materials and fluids from

underneath the Moho

magma and the volatile trail on the mantle as well as two large magma reservoir Interface and on the top part of the crust, which is the main component responsible for a super eruption.

the crust to the mantle. This is the reason why its properties are different compared to the events on most common plates which in turn, produces more volatile materials. Some volatile materials could expel out of the plates in the first phase at a relatively shallow depth. The fluids release prints from the plates could potentially be the reason as to why there are two negative anomalies in the picture above which is located at the plate at 80km of depth under the fore-arc. If the unordinary accumulation of this fluid keeps increasing on the mantle, the subduction of IFZ would push the tore towards the plates which will increase magma production. When the tore on the plates occur, the fluids will certainly be easier to enter in or out of the inner part of the plates. These hot fluids will speed up the heating of the plates which will be the main contributor to the start of the Toba Super volcanic activity. A torn plate? A hard thing to imagine, but interesting nonetheless.

Why this great eruption on the Toba Caldera does occurs alternately in long intervals of time and a relatively peaceful one at that? The local seismic tomography indicates a configuration of the multilevel magma flow system underneath Toba. The lithosphere that will cause IFZ to undergo subduction is thicker and contain more water compared to the lithosphere in common oceans. The lithosphere also receives heat from the torn part of the plates. These 2 factors usually shows why the release of volatile materials in 150km of depth is uncommon which can be seen on the seismicity of the higher plates. When the fluids flow up to the mantle, they will react with peridotite and produce phlogophyte or

â&#x20AC;&#x153;Geomotorâ&#x20AC;? Art by Ivan Through these paintings he tells us to collaborate with various people with different educational background to build this world we live in.

Seismic tomographic section of Toba caldera

amphibolite which temperature is lower. This process causes the rising of other hot volatile materials from the mantle melt underneath. At 30-50m in depth, the magma rising will form a massive reservoir! This reservoir can produce a large amount of heat so that it can transfer numerous volatile materials upstream. When they touch the middle and top part of the mantle, the follicles will melt the rocks so that it forms

Here is Ivan Koulakovâ&#x20AC;&#x2122; s painting that illustrates volcanic work, made with watercolor paint.

This painting was made when Ivan Koulakov studied Indonesian Toba supervolcano. The painting illustrates thet magma chamber beneath it.

The painting was made around 2005 to 2013 for the Scientific Institutions comic graphics.

a shallow silicic magma reservoir. When the number upper crust is melted to a certain degree, a landslide will occur. The materials will continue upstream and decompress to change the hot fluid to gas. The pressure will keep on increasing and accelerates the flow of fluids and magma. The landslide process will eventually cause a huge explosion causing a super eruption. The process of fluids going upstream from a depth of 150km will result in an explosion around the surface which will take hundreds to thousands of years. This is why the super eruption occurs alternately in long intervals of time. Then, will the Toba Super Eruption will occur in a later date? The answer is yes, there is a possibility that in the long run, a massive eruption will occur repeatedly until the IFZ, the main reason for super volcanism to occur, will undergo subduction underneath Toba. The time span from the present to the last super eruption is 74000 years and it is relatively small compared to the period of volcanic events in Toba, which means that the next super eruption will most likely occur a dozen hundreds or thousands of years from now.

It must be very complicated to make all these paintings, but that gives us a really unique impression of Ivan’s interest in Earth’s “motor”.

Wow! Ivan Koulakov sure do have a lot of achievements. His prowess on the field of academics, particularly in geophysics is certainly recognized. You too can become like Professor Ivan Koulakov. For those of you with a passion for art, leaving it for another field of study is certainly not an excuse. Art comes from emotion and is evoked through the pieces created from it. Art is about letting go of one’s tiredness and boredom as well as balancing both sides of your brain. So, don’t be afraid to pursue you hobby even if you are currently deep in studies or your career.

Do You Know? The age of grand canyon is still a mystery because the Colorado River had swept a lot of clues. At first, Geologist found a theory that the Colorado River created Grand Canyon about 5-6 million years ago with a lot of evidence. However, after a new approach of research, it indicated that there are 2 ancestral canyons, located on the east and west. The western canyon can be as old as 70 years old. Average riverâ&#x20AC;&#x2122;s Depth

Feet

the upstream o the river located in the Rocky Mountains, Colorado

length of Canyon

277

miles

Do You Know? The most recent studies performed by the scientist on the University of Bristol indicates that if we didn't reduce the carbon dioxide emission, western Europe, and New Zealand would go back to the tropical climate on the Paleosen age - 56-48 Million years ago

The normal carbon dioxide level is

260-280 PPMV

The estimated carbon dioxide level at the end of the century is

1,000 PPMV

POISSON’S RATIO

THE MULTIFUNCTIONAL EQUATION By: Mohammad Hasyim Taufik & Adisa Putri Utami

What is Poisson’s Ratio (PR)? Poissons’s ratio is a measure of the transverse strain or contraction to longitudinal strain or extension resulting from a change in normal stress under compression or dilatation, as shown in figure 1. Generally speaking, Poisson’s ratio or compressional wave velocity are good indicators of the depth of saturation in deposits.

Source: www.whatisgeotech.org Figure 1. Poisson’s ratio definitive illustration

Source: https://en.wikipedia.org

In civil engineering, Poisson ratio is taken into account in some very important structures. It is also used indirectly in structural designs.

Poisson’s Ratio Values

The value of Poissons’s ratio can vary in the medium, the variety of its value reflects the physical properties if the medium itself. It can range from negative values to positive values, the negative values are usually symptomatic with the occurance of anisotropy, the higher negative values, represent the higher degree of anisotropy. The value of Poissons’s ratio will equal to 0.5 in liquids. The value of Poissons’s ratio in consolidated materials will range between 1.5 and 2. It’s also worth mentioning that in every cases, the compressional wave velocity will give higher values compare to the shear wave velocity. Poissons’s ratio will definitely vary through different litologies, and it often shows anomalously lof value in tight gas litology. The value of Poissons’s ratio, will also vary through the saturation of the fluid in the medium, the value of Poissons’s ratio in saturated medium will give relatively higher compared to dry medium.

v = Poisson Ratio B/G = Ratio of bulk to shear moduli Figure 2.

Source: http://rsnr.royalsocietypublishing.org

General Purpose of Poisson’s ratio

The use of shear wave together with the compressional wave may be very useful for fluid identification. Because combining shear wave and compressional wave velocities will give new parameter Vp/Vs. This parameter is more sensitive to fluid nature than P-wave or S-wave alone. Generally, seismic velocity ratio (compressional and shear wave velocity ratio, Vp/Vs) and Poisson’s ratio were obtained from compressional and shear waves using the seismic refraction measurements for surface soils and shallow sediments.

PR for geotechnical purposes

The analysis of Poissons’s ratio will also give some beneficial impacts in terms of geotechnical problems. One of the most popular one is related to rehabilitation design of road strucures. Basicaly, the use of this method is based on the fundamental definition of Poissons’s ratio itself. Analysing the value of Poissons’s ratio will give some benefitial informations of strain and stress related to the roads. It’s shown that Young’s moduli under seismic impulse small-strain loading can theoretically be as much as 3.5 times higher than those done at slower speed (higher strain) conditions on the same material, depending on the assumed Poissons’s ratio.

PR for fluid analysis purpose

Over the last few years, pre-stack seismic inversion has been used to estimate P wave velocity (Vp), S wave velocity (Vs) or P impedance (Ip), S impedance (Is) and density (ρ). This seismic inversion yields Ip, Is, Poisson’s ratio via Vp/Vs ratio and density. Generally, the Poissons’s ratio is a great tool in seismic data analysis. It’s a good tool for indicating the type of fluid in the medium. This method uses crossplot of ∆Tp – ∆Ts rather than Vp – Vs. With the assumption of the medium has the same porosity and litology, its recommended to use this method as a tool in fluid identification as well as litology identification.

PR for gas identification purpose

Another purpose of the Poissons’s ratio is for gas identification in the medium. From the discussion above, the Poissons’s ratio is symptomatic with strain and stress related constants, by reviewing about this feature, we can also use the Poissons’s ratio for gas identificatoion. This method’s done by using crossplot VP/V ratio against P impedance, the zone of low values of each parameter should correspond to gas.

PR for fracture and geothermal depth analysis purpose Another useful features of Poisson’s ratio is that it can be used for fracture analysis. Fracture analysis is an important issue in terms of many explorations, ranging from geothermal explorations to geotechnical explorations.

Source: puntoenfoque.es

Vp/Vs variaton or Poisson ratio can be seen with tomography tehcnic, where high Vp/Vs is related to partial melting of rocks that contain gas.

In geothermal exploration, The higher Poisson’s ratio associated with shallow hypocenters indicated by the fractured rocks, and the lower Poisson’s ratio associated with deeper hypocenters and un-fractured rocks with silicified rocks, figure 3 above shows that the high Vp / Vs dominates at a depth of 20 km, and continued to decline up to a depth of 40 km. Lower Vp / Vs is increasing with the depth indicates oceanic plate cooler is cooler and entrance under the continental plate, because the high of Vp / Vs is associated with partial melting that has a high temperature.. This method is done by simple calculation of Wadati diagram. The Vp and Vs data is obtained from the micro-earth

quake data that is available for permeability analyisis purpose. This method can lead to investigation of depth in geothermal field. The value of Poisson’s ratio is relatively lower in the deeper zone and higher in the shallower zone. For example, below is the study of crustal Central Java as done by Ivan Koulakov in 2007 using local tomography method. Ivan Koulakov is an important researcher who has already produce lots of researches on Indonesia. Read also article about Ivan Koulakov in this magazine!

Poisson Impedance (PI)

Another purpose of the Poissons’s ratio that’s recently developed is the Poisson Impedance. Proposed by Quackenbush in 2006, he show that Poisson Impedance’s like a scaled version of the product of Poissons’s ratio and density. This technique will eventually give another view of play identifications. The Poisson impedance take a great role in favor of AVO (Amplitude Variations with Offset) methods, it can be seen as a part of acoustic and shear impedance method in AVO. The AVO itself is a method to analyze fracture and reservoir properties in seismic interpretation. To conclude, PI is very favorable attribute for sandstone reservoir characterization. Using TCCA method, we can derive two attributes of PI namely Lithology Impedance (LI) and Fluid Impedance (FI). The results on log data show that sandstone and shale can be well distinguished by LI. Also FI provides a potential fluid content identification. Integrating with geological, petrophysical, and well test data, the sandstone reservoir can be characterized properly and new prospect can be identified directly.

Three figures above are Poisson’ ratio distribution beneath Central Java in various depths by Ivan Koulakov. Picture on the next page is a geothermal site in Iceland. (Photo by pbkphotos)

MISTAKES IN SEISMIC INTERPRETATION one of the most challenging job By: Azarine

In the exploration of petroleum and natural gasses, the seismic method is often used as a way to find information regarding the presence of petroleum on “trap”. The term “trap” refers to a place where natural oil accumulates and in the petroleum exploration industry, it is often called a literal trap. One of the advantages of using this method is that it can reflect the geological structure underneath the surface. In reality, the results from the data of seismic acquisition could produce a different interpretation. When defining the interpretation of a particular trap turns out to be wrong, it

Interpretation in differentiating the data is unclear whether it is the result of the difference in speed structure or if it truly has a geological structure, in this case fault.

petroleum accumulated inside a fault could mean that during the primary drilling, no oil is found. For instance, the structure or a fault trap, however it is interpreted as an anticline trap. This would explain why in a certain area that shows potential it is likely that during the primary drilling no oil is found. According to Tucker & Yorston (1973), the error in interpretation is classified into two types based on its structure, which is speed structure and geological structure. There also a few ways an error in seismic interpretation could occur, which includes:

Interpretation in differentiating whether a data is acquired from the difference in the speed structure or as a consequence of erosional truncation. Truncation can be described as the breaking of sediment layer called a strata along the unconformity caused by erosion after the deposition or its structural effects.

Velocity deterioration, is a case of anomaly that occurs inside an oil trap in a reef carbonate

The presence of velocity sag, which is a velocity anomaly caused by the delay in travel time on the seismic cross section. This usually happens because of the trap inside the salt dome structure.

The presence of fault shadows, which is an anomaly in seismic speed, is a difference in velocity between two ends of a fault. This is a phenomena often occurring in a seismic cross section which often misleads interpreters whether a fault is present inside a cross section

Syncline, is a type of folding wherein rocks with a relatively younger age is located in the middle of the fold.

43 47

There is a velocity pull-up, which is a speed anomaly caused by materials in a shallow depth with a relatively high velocity.

One of the reasons why an error in interpretation might occur is because of the vague defining of traps, wherein a systematic error is often done by its interpreter because of mistakes done in interpreting data as to create a recurring error. In seismic interpretation, the results obtained are usually in the form of 3D pictures of a reservoir. In analogical terms, one could look at it as building a house. A house has its blueprints for guidance and so the construction of the house is organized, the 2D print is needed as a skeleton of the home itself, as shown in the image above. This also applies to interpreting reservoirs, wherein every reservoir has its own characteristics when it comes to its cross section even though its volumetric properties are the same. Similarly, the house on the left side of the image, both design for the houses has the same volume, however the best house is the house on the right. By that conclusion, the interpretation is called a non-unique solution wherein its interpretation could widely vary. To simplify, the picture below shows the interpretation process progressively (clockwise).

The lack of understanding of seismic cross section, an error in interpretation, and the tendency to do cellular classification during geological modelling, as well as the map making process are some of the reasons on how defining a trap is often mistaken. A particular set of skills are required to help the interpreter in interpreting seismic cross section. This process of interpretation begins with first making a sketch of faults based on the data acquired from the seismic cross section as well as connecting the faults. With the help of various software, an area of the fault is made from the sketch. Next, the area we acquired will be checked through a process known as Faults Quality Control. If the structure of the area is suitable, one would mark important parts (delineation) with a method known as iteration. Delineation is done repeatedly in order to get the appropriate results, which will be used to make a contour map from the iteration. The end result would be a 2D map of the geological structure which serves as a skeleton that would distinguish the reservoir cross section with the others. In this process, the error of interpretation will likely happen in the faulting process. This is because the interpreter depends on the software to determine the suitable geological software, wherein the software itself does not come equipped with geological principles. An interpreterâ&#x20AC;&#x2122;s knowledge of geological principles is very crucial in determining the location of the Lorem Lorem ipsum ipsum drilling site. From that, it is essential for the interpreter to understand every process in interpretation so that the results would be as expected. So, to be a seismic interpreter is no easy job. You need repeated training in order to be able to identify various tricky cases.

Do You Know? Lake Toba was formed when Toba super volcano erupted around 73000-75000 years ago. The explosion occurred a week long and created ashes that floated to 10,000 meters above sea level. Now Lake Toba is a tourist spot. Many tourists come from Netherland, Malaysia, Singapore, Germany, Japan, and Korea. Some even come from America.

instagram.com/dedy_alrasyid

SASAK HOUSE

In Lombok, there are six villages that are still maintain the tradition of Sasak, that is the Sasak House. Those six villages didnâ&#x20AC;&#x2122;t get damaged when earthquake struck Lombok for the past few days. One of the village is Sade, which is inherited from their ancestors, around 1038 M.

instagram.com/vickaindrias To build a house, Sasak tribes use simple things. Things that can be acquired in our everyday life. The house foundation and floor are made of clay mixed with buffaloâ&#x20AC;&#x2122;s feces. The walls and the roof are made of woven bamboo and reeds.

TOP 5 BOOMING TOPICS IN SEISMIC WORLD By: Yohanes Nuwara

Do you feel like you’re only learning just that about seismic? If you like to read papers that were published a few years back, you know that the seismic world grows so rapidly. Supported by system growth, computer architecture that are becoming more advanced, and scientific manipulation, it makes geophysicists keener on solving various challenges regarding explorations, disasters, etc. You will find a lot of new terminologies if you like to follow the updates on this growth. What are the most important advancement on seismic world in this 21st century? Here’s the top 5 current booming topics in the seismic world that I’m going to summarize.

Geophysical data processing and geological interpretation. Photo by DMT-Group

Full Waveform Inversion The basics were first developed by Albert Tarantola, a Barcelona-born researcher, in 1984. This FWI method itself had just gotten popular two decades later.

TOP 5 SEISMIC TOPICS

Seismoacustic wavefield Seismoacoustic Wavefield was introduced by Stephen Arrowsmith from Los Alamos National Laboratory, United States of America, with his team in 2010. The idea from this method is combining the seismic waves phenomenon that move on the surface of the Earth and infrasonic waves (soundwaves) that move on the air so that this method is commonly used for learning natural phenomenons that happen on the borderline of Earth’s surface and atmosphere. Looking from its name, these two waves are viewed as a singular wavefield called seismoacoustic wavefield. How does it work? When an earthquake occurred, two kinds of pulse, which is the ground surface seismic waves and the infrasonic waves in the air were produced. These two pulses interacted with each other creating a merged seismoacoustic pulse. One of the example of source that can generates seismoacoustic pulse is volcanic eruptions (monopole source). When an eruption happens, a high pressure will radiates to all of the directions. The equation is an acoustic power equation (the power that were produced from the acoustic waves because of volcanic blast inside its crater) equals the square of pressure p that were measured on a certain distance from the crater and radiation Ω that are both inversely proportional to the atmospheric impedance ρc. Research also shows that the characteristics of a seismoacoustic pulses is different from different types of eruption and volcanoes, so the seismoacoustic wavefield method can be applied to study the type of eruptions and can effectively used for monitoring the eruptions itselves. Lorem ipsum

Mount Turrialba Eruption, photy by NIKONANDY/GETTY

Other than that, this method can be applied to predict the climate that has been learnt separately in metereology and also monitoring nuclear activities. There are a lot of benefits from this method, right guys?

5 TOP 5 SEISMIC TOPICS

Seismic microscopy

Geologist Daniele Heon is looking rock through magnifier, photo by Liz Hargreaves

Can you imagine this particular branch of science? You surely had once tried using the microscope to take a look on interesting features in plants or tiny organismâ&#x20AC;&#x2122;s cells. In geology, polarization microscopes are used to study rocks.

With this microscope, you can observe the interesting features of minerals and because of its unique characteristics, the minerals emit various shapes and sizes. Just like a cell, minerals are microscopic (1/1000 from 1 milimeter). Then, what is

the correlation between minerals and seismic waves? Yes, the isotropic and anisotropic characteristic of a mineral determines how the seismic waves spread through the minerals. If a seismic waves were given to different rocks, such as granite and sandstone, the respons will also be different. Seismic microscopy studies the characteristics and the movement of a seismic wave on a microscopic scale, in this case minerals. Seismic microscopy were popularized by Yang Zhang for Massassuchets Institute of Technology in 2008. It was such a great achievement because now, seismic waves can be observed in microscopic scale. Mineral and energy exploration now, on the last decade, experiences a wide-scale transformation from conventional to non-conventional way. One of it being the exploration of chromites that later are going to be used for amalgamation basic ingredient for producing superalloy metals, nichromes, and corrosion-resistent stainless steels. A fraction of chromites occur in serpentinite rocks that are an ocean-floor bedrock. Serpentinites are green and contain antigorite minerals and olivines. The seal shaped carving (see picture) is an Inuit tribe carving in Alaska that has serpentinites as its basic

material. Because of the industrial need of chromites and the rather difficult challenge to pan chromites from the sea-floor bedrocks, the exploration surveys have to shift to the non-conventional way, one of them is seismic surveys. One of the challenge is antigorite minerals and olivines are both anisotropic so that they need a specific treatment to study how waves spread on the minerals. A team of researchers from Japan that consisted of Watanabe, Shirasugi, and Michibayasi successfully learned about this in 2012. They developed seismic microscopy to studied the seismic waves movement on milonite serpentinite rock sample that contains antigorite. What did the find? The picture above shows us the velocity distribution of the seismic waves to various olivine and antigorite minerals orientations. On rocks, these minerals have orientation axis in the direction of x and z. They found out that on these rocks, seismic waves move faster (colored green-blue) on the x plane and move slower (colored red) on z plane. Not only serpentinites, seismic microscopy can also be applied to other rocks, opening a new era in explorations and is being warmly discussed now.

Serpentine as olivine substitute, and its seismic implication By Francoise Boudier, Alan Baronnet, dan David Mainprice

ANISOTROPY AND ISOTROPY, UNIQUE PHENOMENONS IN SEISMIC WORLD By: Irfani S & Defsika

Optycal photo taken by gypsum plate and petrology microscope for seismic rock study. (Barruol et al., 1992)

Anisotropy? Isotropy? These terms are common when we discuss rock physics. And those who are in material science are also familiar with the terms. But this time, we will delve into the terms from geophysics perspective, also known as Seismic Anisotropy. A medium is called anisotropy. It is when the intrinsic elastic property, measured from the same location, is changing in direction. Conversely, for a medium with isotropy property, it is uniform and independent to the direction. In most seismic data analysis, the subsurface is assumed to be seismically isotropic, but not anymore. Geophysicists now put more interest on bringing anisotropy concept into

seismic data analysis. Hence, seismic anisotropy term is introduced. Interestingly, part of it that currently gains substantial attention among exploration seismology is the change of velocity along the direction. The prevalent definition of seismic anisotropy is varying seismic velocity, dependent on the elastic property of the medium, along with the change of direction where the measurement is done. There are two cases of seismic anisotropy, both are actually categorized in a special case of transverse isotropy. A medium is said to be transverse isotropy when its elastic property does not vary in a direction that is inversely proportional to the symmetrical axis. To simplify this, just imagine the earth model has horizontal layers, then depict transverse isotropy aligned with model.

If so, the transverse isotropy will be classified as follows: 1) vertical transverse isotropy (VTI) or transverse isotropy, means velocity varies along the vertical plane on a certain lateral direction; 2) horizontal transverse isotropy (HTI) or azimuthal anisotropy, where velocity varies in lateral direction Transverse isotropy is a result of the deposition process; where velocities between layers are different in case of bedding orientation, and perpendicular to the beds. For instance, a thin isotropic layer that undergoes deposition will form anisotropy. The symmetrical axis of anisotropy is perpendicular to the bedding. Meanwhile, azimuthal anisotropy appears from tectonic processes. Rock materials from the same bed can have different rigidity in different azimuthal directions. As an example to that, anisotropy is created from a secondary fracture rock with higher velocity along its fracture orientation instead of vertical direction. However, the symmetrical axis will be parallel to the bedding.

Illustration of earth interior model, from the surface, crust, mantle, and core. From BBC

What is the importance of the anisotropy-isotropy concept in geoscience?

Until 1960, scientists were furious by the lack of knowledge about Earthâ&#x20AC;&#x2122;s interior. So, they decided to design a drill. The goal was to pass the seafloor (continental crust is very thick) and reach Mohorovicic discontinuity, then take samples from earthâ&#x20AC;&#x2122;s mantle for a study. The project is called the Mohole project. And it ended in disaster. The project was executed with offshore drilling in Mexico region. The initial attempt was to drill 4000 meters depth inside the Pacific Ocean and 5000 meters depth to penetrate the thin crust. But the attempts met failure. Besides, the earth crust only represents 0.3% of total planet volume. So, it never reached the goal; knowing the earthâ&#x20AC;&#x2122;s interior. Moreover, the farthest penetration ever done was only 180 meters depth. In 1966, Congress started to

concern about the unsatisfactory result of the project and the expensive expense. For those reasons, the Mohole project was discontinued. The earth’s interior remained unknown. Directly visualized the earth’s interior was impossible, therefore, scientists tried to find a method. It had to cover, as much as possible, wave recordings across the earth. And seismic wave was chosen. Seismic and its elastic property are useful to get indirect information from several earth crust aspects, such as structure, composition, and temperature gradient. The velocity of a seismic wave is directly linked to elasticity and mineral density. Because of that, seismic wave is used as an indicator of mineral composition. Furthermore, the velocity of a seismic wave also depends on direction. This is where the anisotropy concept goes in. Understanding anisotropy phenomenon can give precious information about crust’s deformation.

tic vibration in thermal to measure the velocity of an elastic wave. This noncontact optic method is suitable to determine even the elasticity of the smallest crystal (diameter of 0.1 millimeters)

Seismic wave provides the most detail map of subduction zone under the Japanese archipelago. Deep down the archipelago, the earth’s mantle are moving and Four lithospheres are

Japanese crust and rupturing. gathered,

In the earth’s crust level, seismic wave is used to investigate its elasticity behavior. While in rocks and minerals level, two methods are often used, ultrasonic wave and Brillouin scattering. Ultrasonic wave measures the time traveled past the minerals or rocks. It results in a quantitative calculation on the ultrasonic velocity. On the other hand, Brillouin scattering utilizes the interaction of light-wave and acous-

including Eurasia Continent, Sea of Okhotsk, Pacific Ocean, and the Philippine Sea. Strong interaction coming from the plate boundary makes Japanâ&#x20AC;&#x2122;s subduction zone as a good place for volcanoes, tsunami, and earthquakes. A seismic event such as earthquake also releases energy in form of a wave. As wave propagates through different materials, seismic anisotropy is recorded. In addition, it determines whether the traveling

velocity depends on direction and wave propagation angle. If a vertical fracture occurs, which often happens in subduction zone due to stress between the crust and mantle, azimuthal anisotropy will be formed. This shows the horizontal direction of wave propagation has a greater impact toward the rate of velocity. Researchers use Kiban system in 1,852 seismic stations to record the seismic waves travel time from 2,528 earthquakes under and around the Japanese archipelago. This includes reports from 747 teleseismic events and earthquakes at distances greater than 3,000 kilometers from the measurement site. Subsequently, researchers can now reconstruct the waves propagation. The result is a three-dimensional map of azimuthal anisotropy with high resolution located in Japan Trench at 700 kilometers depth. A study shows seismic wave travels faster along a Trough throughout subducted Pacific plates and the Philippine Sea. This happens due to orientation of some minerals or fault on the seafloor. However, researchers revealed an astonishing discovery inside earthâ&#x20AC;&#x2122;s mantle. Plate subduction and dehydration that gather with convective circulation appear to cause the energy to flow inversely proportional to the Trough. Interestingly, the flow goes on toroidal pattern around a hole inside the plate of the Philippine Sea.

Earthquake with magnitude of 6.1 struck Japan on September 19th, 2017. The epicenter is located about 175 miles east of Kamaishi. (from fortune)

A STRUCTURE THAT IS BUILT AGAINST EARTHQUAKES, COOL ISN’T IT? By: Dinda Putri P.

o you know that Indonesia is known across the globe as a country with a vast amount of natural resources? More specifically are the resources which fall under the oil and gas category. LNG or Liquefied Natural Gas is one of them. In Indonesia, LNG sectors can be found in various areas, such as: Arun Field (Aceh), Badak Field (Kalimantan), Donggi Senoro Field (Sulawesi), and the recently developed Tangguh LNG Field in Papua. Tangguh LNG Field which is located in Bintuni Bay, West Papua is considered to be one of the biggest LNG infrastructures in Indonesia currently. One thing that we have to be aware of is that in an LNG infrastructure, the liquefied natural gas has to be transported to several gas-generated power plants and then distributed to petrochemical industries using LNG Vessels. However, we know that LNG is potentially dangerous and there are significant environmental risks behind the process of acquiring the LNG itself. This raises a problem since we already know that Indonesia is quite famous for its active tectonic activity, especially in Papua, where the Tangguh LNG is located at. Therefore, we need

Tangguh LNG is located in Bintuni Bay, West Papua.

infrastructures—in this case jetties—which can withstand the impact of earthquakes. How can we achieve this? Before we delve into the nuts and bolts of what makes a structure to be earthquake-resistant, we have to first understand what happens to a structure during the event of an earthquake. Starting from the basics, we already know that when an earthquake strikes seismic waves

will be formed due to the displacement of earthâ&#x20AC;&#x2122;s particle. The motion will then be represented as wavelets by the seismograph. The acceleration of the particle motion along the wavelet is represented as the acceleration of earthquake with the unit m/s2. During the first occuring of an earthquake at hypocenter, the seismic wave propagates to all directions, including station where earthquake is recorded, and structure. The ground motion is recorded by the seismograph at station. The seismogram brings information about the seismic wave which is import2 ant as an input to delineate the motion of the structure due to earthquake. The PGA (Peak Ground Acceleration) would correlate with the response of the structure. A proper calculation is required for a structure to be able to withstand the damage caused by earthquake. In order to show the response of a structure to ground motion, we need an earthquake acceleration spectrum, which contains the information of how much energy (in amplitude) each frequency of the earthquake wavelet has. Using this spectrum, we can easily know the acceleration of the earthquake at any given frequency.

Motion of structure during earthquake

Stress Analysis and Peak Ground Analysis (PGA) It is known that during an earthquake, the accumulation of strain in the subsurface of Earth creates a deformation on rock parts. During this process, the stress will continue to accumulate and the stress will be released in the form of earthquake. Imagine you break a ruler, the thundering sound and blast will result on your hand like shaking.The stress released can be calculated to determine the magnitude of the earthquake. Then, PGA is counted. But what is PGA actually? PGA or Peak Ground Analysis is the value of how much the ground shakes during earthquake. So, the larger PGA is, the more hazardous it will be for houses or buildings.

To do this, they use information of three earthquakes in Bintuni happened in the last three decades (1992, 2002, and the latest 2016), all with large magnitude. And then, the PGA is counted. The result they found was pretty shocking. The area has pretty large PGA around 0.25 and 0.3. So, whatâ&#x20AC;&#x2122;s next? Designing the LNG Jetty

LGN Harbor from above

We are already aware that the Jetty structure is crucial for the process of transporting important LNG resources. Therefore, we have to make the structure to be earthquake-resistant in order to create a safe and sustainable LNG infrastructure. Here is a common design. The model that is deemed as ideal in this case is the dolphin model. Why? Because the dolphin model is more efficient to build and it needs less piles thus making it more suitable for LNG terminalsâ&#x20AC;&#x201D;which do not require a vast space for vehicles on its loading platform. In order to design an ideal jetty model, the first thing that is should be done is to calculate the mass of the loading platform with the dimension of 20x15x0.55 m. To support the side design, 4 piles are used meanwhile for the front design 5 piles are used for support. Next, they shall calculate the stiffness of the piles, both from the side and front design. They also calculate the thickness of the loading platform. Lastly, they have to determine the natural frequency on both sides. Since we want an earthquake-resistant structure, the structure has to be damped using damping system to prevent it from shaking too much during earthquake. Up to this point, geophysicists provide as much information as it be for the next analysis. The task of an ocean engineer next is making calculation of how much the structure can resist the earthquake.

The side of LGN Harbor

The Front of LGN Harbor

The Result? The plot below is made by an ocean engineer to find at which value of parameter can make the structure of LNG jetty safe during earthquake. These parameter determine how the structure must be made. According to the results, they find that their design suits the most for condition at which an LNG jetty structure could adapt with the vibration made by an earthquake. Although the force that results during earthquake is very large, the structure can still compensate the motion.

Earthquake damping curve for easting component

Earthquake damping curve for northing component

Whatâ&#x20AC;&#x2122;s next? This design can be surely applicable for all structures including LNG jetties in other places like Arun and Donggi-Senoro. LNG is one of new innovation in energy development in Indonesia, whereas earthquakes always threaten the people at any time. Without any proper preparation in the design of structures, the infrastructure would be really prone to collapsing. Geophysics and ocean engineering is somewhat an interesting collaboration on this field. What does geophysicists do? Geophysicists provide information about earthquake analysis based on seismogram recorded at a place, geological overview, and peak ground acceleration. How about ocean engineers? They make further calculations about ground response and structural dynamics. Notwithstandingly, these two engineering perspectives is not different, but completing each other. We could, too.

A research by Yohanes Nuwara from Geophysical Engineering ITB 2015 in collaboration with Attar Mahdi from Ocean Engineering ITB 2015

MIN RONG TANKER

Min Rong tanker from China is loading Liquified Natural Gas (LNG)

Bright, Flat, dan Dim Spot to Look for Oil By: Rafif Abdus & Dimas Zulfikar

Mankind needs on crude oil keep on rising every year, in 2018 Organization of the Petroleum Exporting Countries (OPEC) projected that there will be an increase in global crude oil demand in this year of 2018. Global oil consumption is predicted to reach the point of 98.85 MMbpd (million barrels of oil per day), 1.6 MMbbl (million barrels) higher than 2017. (CNBC International, 2018) Geophysicist plays a crucial role in oil industry, especially in the petroleum exploration stage. In determining the drilling point, geophysicist have to do analysis about the field subsurface condition. Geophysicists acts just like a doctor in petroleum exploration, they have to do some â&#x20AC;&#x153;x-rayâ&#x20AC;? pre-analysis before diagnosing one patient, in oil and gas industry, geophysicist have to analyse the subsurface untik they have the estimated reserve of the reservoir, this pre-analysis should be done to minimize the risk and cost of petroleum production.

@ Gabriel Szabo/ Guzelian

The most common geophysical method used in petroleum exploration is seismic reflection/reflection seismology methof. This method make use of rock Acoustic Impedance (AI), which is the product of velocity and density . Seismic reflection will show response if there is a change in AI (which is can be caused by change of lithology). The greater the contrast between the top and bottom layer acoustic impedance, the greater the amplitude of the seismogram.

In seismic reflection method, seismic attributes can be analyzed then mapped to interpret subsurface condition. An example of seismic attribute is amplitude. Amplitude could detect hydrocarbon presence directly, so they often referred as DHI (Direct Hydrocarbon Indicator). Here are types of DHI that we could make use of to locate hydrocarbon.

Bright Spot Bright spot is anindocator that can be easily observed in seismic section as an isolated high amplitude traces. This mark can be associated with hydrocarbon accumulation, this increase of amplitude caused by impedance contrast between hydrocarbon or other fluid saturated rock strata and overlying rock strata.

appears in contact point between water and hydrocarbon and always appear as strong reflector with positive value of reflection coefficient. This flat shape could be easily distinguished in seismic section because this flat shape will stand out in surrounding dipping reflectors. Gas-Oil contact and Water- Oil contact always have positive reflection coefficient. Figure 2. Figure 1. Bright spot in seismic section

Water saturated sandstone propagates seismic wave slower than shale. This contrast will increase if that sandstone is saturated by oil or gas. As a result, negative reflectivity gains more amplitude and creating bright spot. Need to keep in mind that bright spot not only caused by hydocarbon, it could be caused by other case, for example is a large porosity water saturated sandstone.

Figure 2. Geological condition that caused the flatspot effect in seismic section

If sandstone reservoir contains oil and gas, in its seismic image we will discover two flat spots, one is from GOC and another one is from OWC. (Figure 3).

Flat Spot Flat spot is an another DHI that appears as an image of horizontal reflector in seismic image. Flat spot appears if there is a contact between diferent types of fluid, it also appears as an isolated anomaly whereas the surrounding reflector in fact is not horizontal. Flat spot is not an amplitude anomaly. Flat spot will come out when hydrocarbon saturated sandstone with low AI lays over water saturated sandstone with high AI. (Figure 2) Flat spot

Figure 3. Seismic section that shows two flatspots. The first is caused by gas-oil contact. The second is caused by oil-water contact

Polarity Reversal

Dim Spot

Polarity reversal happens when water saturated sandstone has higher impedance than shale that is located over the hydrocarbon saturated sandstone, but the hydrocarbon saturated sandstone has the lowest AI between three of those, so impedance contrast will be more significant between water-hydrocarbon than shale-hydrocarbon. Change in impedance from positive to negative will cause seismic polarity reversal that inverted from SEG normal convention.

Dim spot is an amplitude anomaly that shows low amplitude, this anomaly indicates presence of hydrocarbon. Dim spot is a product of decreasing in AI when hydrocarbon, which has low AI, replaces water in porous reservoir, which has high AI.

Figure 6. Rock impedance causes dim spot

Figure 4. Rock impedance causes inversed polarity

Figure 5. Seismic section of inversed polarity

Figure 7. Seismic section of dim spot

With the presence of these indicators, surely it will ease us to find the location of hydrocarbon in the subsurface. But these indicators still bear their own uncertainty, hence seismic data analysis should not be the only guide in terms of petroleum exploration, it should be integrated with the regional geological settings in the area of interest.

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HIMA TG “TERRA” ITB INSTITUT TEKNOLOGI BANDUNG