Volcano Seismology

VOLCANO SEISMOLOGY

Seismic activity will be inevitable as volcanoes are ready to erupt. There are those volcanoes where you'll see seismic activity around all the time, so only an increase in seismic activity will detect an eruption. You will see three types of earthquakes around a volcano:

1. Short-period earthquakes – these are similar to fault-generated earthquake activity. Brittle rock fragments in places and magma gets forced upward. These create A-waves or what are called VT events.

2. Long-period earthquakes – these mean that there is a lot of gas inside the chamber and sound like clanging in your plumbing sometimes. These acoustictype vibrations are called B waves or long-period resonance waves.

3. Harmonic tremors – these occur when magma pushes up against rock underneath the crust. Animals can feel them as buzzing or humming beneath their feet.

Gas emissions can indicate an upcoming eruption. These gases escape near the volcano. Much of it is sulfur dioxide, which is a major herald to an upcoming volcanic blast. Mount Pinatubo had this type of activity just before it erupted in 1991.

You can also measure areas of swelling where magma is building up. This increase in swelling was seen in Mount St Helens before it erupted. The north face was bulging detectably before the eruption. Normally, the ground deforms in ways only detectable by sophisticated equipment used by volcano experts. In Hawaii, you can literally see the magma moving just under a shallow surface.

You can measure the temperature of the ground with thermal monitoring to see if it is heating up. Satellites use infrared imaging, while others use the temperature of hot springs or fumaroles to see if things are heating up near a volcano. Hydraulic equipment can be used to measure the temperature and gas pressures deep within the earth. If you see increased sediment in a river near a volcano, it can be coming from the volcano just about to erupt.

Remote sensing is possible to measure eruption clouds above a volcano or to see how much carbon dioxide or sulfur dioxide is found in the atmosphere. Hot spots can be seen using remote thermal sensing as well. You also don't have to be near a volcano to detect its geometric changes or to see if there are variations in forest growth before an eruption. Remote monitoring can detect sound using sensors that are triangulated to find out where the eruption is likely.