This talk, bring me back to my 2nd year lecture of Natural Hazard in Seismic part of the course, glad I took the course and can use what I learnt then to understand and comprehend the talk. Basically, the speaker is highlighting the possibility of earthquake generation after the triggering event and the processes involved in that generation of the Earthquake using the data from Sierra Negra Volcano as example.
The nature of the dynamic triggering
The main question that I think people should listen to this talk to is
Which part of the earth is the most sensitive for the earthquake triggering and where is the perturbation of earthquake most likely to occur for of course better understanding and also better forecast of the earthquake.
Processes that cause the interaction between the earthquakes and volcano eruption is quite well known in sense that we know how exactly the stresses change through the earth,
1) Dynamic stress changes
2) Static stress changes
The record on whether stress increasing or decreasing after earthquake can be recorded, but the background of the stress is still not known and the area in which more susceptible of the stress changes is also can't be pin-point easily.
The dynamic stress changes as earthquake move away from the source of the earth quake govern by the surface wave which from the observation can last for few seconds or minutes, in very rare cases few hours.
In the allocated 30 minutes target time at Sierra Negra, the low frequency energy on seismographs, showing that arrival of big earthquake that happen with Rayleigh wave arrival earlier than surface wave with high amplitude with double dispersion. The amplitude gradually decreasing with time.
This high frequency energy must be generated locally and this is what correspond to the eathquake which trigger the wave. Earthquake is more likely to happen in the area with high dynamic stress changes.
The first ever local record of seismicity associated with an eruption at a volcano in the Galapagos
Rate of the earthquake in the area is increasing showing that the volcano is becoming more seismically active and continue to inflate. The volcano in other way, is approaching a likely eruption.
And hence why it is suitable for the area to be the main focus for investigatin the relationship between dynamic stress changes and earthquake triggering.
There is good possibilities to be able to witness several triggering event of the volcano with the dense distribution of seismometer that allows accurate eathquake locating process. Opening a window to see the mechanism of the earthquake and what is the interaction processes between the dynamic wave with the local stress from the volcano for better idea on what controlling the dynamic triggering and how to identify them
The logistic part
Galapagos Island is a hotspot for volcanos because they belong to Ecuador. Dominated by big basaltic shield volcanoes with large and deep caldera system. Started in April and arrived in the island after 48 hours.Some areas are quite remote and some have very thick vegetation.
I think this is very cool and interesting to participate in and the area sound very fun too!
Next post: Getting into the mechanical behaviour of sand with X-ray Tomography
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