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A RAPID REPORT ON THE M 7.5 LAMJUNG, NEPAL EARTHQUAKE OF 25APRIL 2015 INCLUDING OBSERVATIONS/COMMENTS ON EARTHQUAKE EFFECTS IN LUCKNOW, U.P. and BIHAR, INDIA. (Data source: http://earthquake.usgs.gov/earthquakes/eventpage/us20002926#general_summary accessed on 25 April, 2015)
BY: Rafi Ahmad, Fellow Mona GeoInformatics Institute, University of the West Indies at Mona, Jamaica. The M7.5 Lamjung, Nepal earthquake of 25th April 2015, 11.45am, with a focal depth of 11.87km was a shallow earthquake event that was felt all over the North India. It is safe to say that the temblor was experienced by almost everyone in the city of Lucknow. Suddenly, after having had an impressive introduction without a prior warning, the citizenry wanted to know “earthquakes”. An opportunity presented itself for engaging in disaster risk reduction talk and that there are ways and means of avoiding damage and being safe. The purpose of this rapid report is to inform on the earthquake parameters, how to deal with the event based on credible data, and lessons that may be learnt from past earthquakes, also, use of scientific advancements to protect lives and property. The rapid reports are posted within 6-12 hours. In this report, we first present observation made in Lucknow followed by lessons learned from historical account of significant earthquakes felt in UP and Bihar, damage account 15 January 1934 Eastern Nepal [Bihar-1934], the science of the Nepal earthquake, a shake map to give an idea of anticipated damage for rescue and relief and finally USGS’s Did you feel it (dyfi) map to share the extent of earthquake effects. 1. PERSONAL OBSERVATIONS AT LUCKNOW( Lat/Long: 260 50’ N/ 800 54’ E), U.P., India). Lucknow is situated on the Alluvium (geologically called Varanasi Alluvium, Middle to Late Pleistocene) of the Gomti River system. First shock: felt at 11.42 am (IST) - moderately felt for about 5 seconds; Felt my chair is shaking; hanging electrical fixtures “to-fro” movement; appeared E to W; Nasima felt her bed is shaking; windows rattle; everyone in the neighbourhood felt pronounced shaking and were alarmed; came out of rooms; it was not a panicky situation. Intensity III-IV on the Modified Mercalli Intensity scale Second shock: felt at 11.43 am (IST) - weakly felt for about 2 seconds
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Felt my chair is shaking; hanging electrical fixtures “to-fro� movement. Intensity III on the Modified Mercalli Intensity scale Third shock, appears as an after-shock: felt at 12.16 pm (IST) - weak, felt for about 1 second. Felt my chair is shaking. Intensity II on the Modified Mercalli Intensity scale 2. A Historical account of significant earthquakes felt in UP and Bihar I have reproduced below a summary of 15 January 1934 Eastern Nepal_Bihar earthquake. Please note that the damage reported today has occurred in the same places as it was reported in 1934. The 1934 account appears to be that for 25th April 2015. Lessons for protection of lives and property from earthquakes: Although it is impossible to predict earthquakes but a study of nature of damage and places where it occurred allows us to avoid vulnerable areas and put in place measures to build better buildings, also retrofit weak buildings. The vulnerable areas are places of alluvial soils in the flood plains of rivers. When such a substrate is loaded with earthquake waves the soils loose strength and tends to flow. This is known as liquefaction process. Buildings built on these soils without adequate protection invariably suffer damage due to foundation failure, tilting. Other effects include: embankment damage, railway lines may twist, sand and water ejected, changes to ground water levels, springs/wells may go dry or increase flow. Most of the damage reported today, 25 April 2015 at least in UP and Bihar has occurred in the areas where alluvial soils occur with a high liquefaction potential. The lesson here is to learn from the past, invest in pro-active measures for disaster risk reduction. As far as shaking from earthquake is concerned, we have to make sure that the water storage tanks that mark the skyline of practically all the communities are designed as per seismic safety standards.
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I have reproduced below a map from Pandey and Molnar (1988) showing areas affected by liquefaction in 1934 to compare with damage areas in the wake of today’s earthquake (25th April 2015). It is no surprise that areas north of the Ganga river are reporting significant damage.
3. Damage Account 15 January 1934: Eastern Nepal [BIHAR-1934-A] What is common to the North Indian cities reporting damage in 1934 and 2015? They are all located in the Indo-Gangetic plain. The substrates of most of these cities make them vulnerable to the process of liquefaction following loading from earthquake vibrations. It is strict adherence to engineering-geological investigations and building codes that guarantees a safe built environment. “At least 8,519 people were killed in Nepal (Pandey and Molnar, 1988) along with 7,253 deaths in adjoining parts of India (Dunn et al., 1939). EMS intensities of 9 were assigned to Bagmati, Harisidhi and Khokna where destruction was “100 per cent” and such that “streets and alley-ways were completely blocked and their former alignments were often impossible to discern” (Dunn et al., 1939). About 70% of the town of Bhatgaon was destroyed (ibid.). Molnar (1988) interpreted the phrase “reduced to hell” to mean complete destruction from Rana (1935) who used it when detailing the destruction of private houses, a granary, a government storehouse, as well as all the houses in a villages.
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This study assigns EMS 9 to this term along with brief descriptions of damage from Bhojpur and Namche Bazaar. Extensive damage and landslides occurred in the mountains of eastern Nepal including at Biratnagar, Namche Bazaar, Kathmandu and Patan (Pandey and Molnar, 1988). Serious damage and widespread liquefaction occurred in parts of Bihar, India, including at Laheria Serai, Motihari, Munger, Muzaffarpur and Samastipur (Dunn et al., 1939). Minor damage also occurred in the adjoining Indian states of Chhattisgarh, Madhya Pradesh, Jharkhand, Orissa, Sikkim, West Bengal and Uttar Pradesh (ibid.). Damage was reported from several important cities and towns in the region such as Allahabad, Darjeeling, Gaya, Gorakhpur, Hazaribagh, Kanpur, Kathmandu, Lucknow, Patna, Ranchi, Raniganj and Varanasi (ibid.). The earthquake was felt throughout the subcontinent as far as Barmer, Chittagong, Lahore, Khairpur, Mumbai, Surat, Vishakhapatnam and Tiruvottiur as well as in parts of China and Burma (ibid.). Seismic seiches were generated by this earthquake in Andhra Pradesh, Karnataka, Maharashtra (ibid.) and as far as Kerala, where boats capsized on Lake Vembanad (Statesman. 1934. January 16–January 30). The temperature of hot springs at Anhoni near Mahuljhir in Madhya Pradesh and Sohna in Haryana are also thought to have risen (Dunn et al., 1939).� Source: Stacey Martin and Walter Szeliga 4. THE SCIENCE OF THE NEPAL EARTHQUAKE from http://earthquake.usgs.gov/earthquakes/eventpage/us20002926#general_summary (accessed on 25 April, 2015) Origin: M7.5 - 35km E of Lamjung, Nepal 7.5Mag; mwbType; 11.87km Depth; Preliminary Data on Faulting mechanism (from USGS): The type of fault movement related to this earthquake:
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Body-wave Moment Tensor (Mwb) Nodal Planes Plane
Strike
Dip
Rake
NP1
261°
85°
167°
NP2
353°
77°
5°
Focal plane solution prepared by USGS suggests slip on a strike-slip fault in the area.
Historical seismicity: “Examples of significant earthquakes, in this densely populated region, caused by reverse slip movement include the 1934 M8.1 Bihar, the 1905 M7.5 Kangra and the 2005 M7.6 Kashmir earthquakes. The latter two resulted in the highest death tolls for Himalaya earthquakes seen to date, together killing over 100,000 people and leaving millions homeless. The largest instrumentally recorded Himalaya earthquake occurred on 15th August 1950 in Assam, eastern India. This M8.6 right-lateral, strike-slip, earthquake was widely felt over a broad area of central Asia, causing extensive damage to villages in the epicentral region”. From USGS. 5. SHAKE MAP: gives an idea of anticipated damage for rescue and relief. http://earthquake.usgs.gov/earthquakes/eventpage/us20002926#impact_shakemap Epicentral area: According to the shake map the epicentral area appears to have experienced intensities at VII-VIII level. These will be revised as field data become available. Severe shaking is expected leading to heavy- violent damage corresponding to Peak Acc. at 40%g and a Peak vel. at 41cm/s.
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Earthquake-induced landslides are expected to occur in the hilly terrain. In neighbouring India: significant damage may occur in Bihar (border area with Nepal, as far as Salimpur and Muzaffarpur area) and Uttar Paradesh (Gorakhpur area). These areas are situated on geologically young alluvial soils and flood plains of major rivers. Significant damage, accompanied by liquefaction, have been reported in previous earthquakes.
6. DID YOU FEEL IT (DYFI): USGS prepares a community internet intensity map copied below. According to this map some areas in Nepal have experienced violent shaking which has resulted in heavy damage. In Lucknow and Kanpur, shaking intensity was at levels III-IV, weak to light. Hence general damage scenario is very light. This is the level of shaking which I have felt during the passage of the earthquake.
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