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Understanding Extreme Geohazards: The Science of the Disaster Risk Management Cycle
European Science Foundation Conference
November 28 to December 1, 2011, Sant Feliu de Guixols, Spain
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Session 5 “Predicting increased risks for extreme hazards: volcanoes and
landslides.”
Discussion: “How safe are sleeping volcanoes?”
Roger Urgeles Esclasans
Most of the open questions I refer to here are related to submarine landslides, but some may apply to volcanic settings too:
- Submarine landslides are events of extremely large magnitude (1-2
orders of magnitude larger than their subaerial counterparts). Yet
the largest events occur at very low recurrence rates. Risk is
approximated using the formula: Risk = Hazard x Vulnerability that
can be approximated by: Risk = P of Occurrence (Hazard ) x
Consequences. For many extreme events the probability of occurrence
is very small but the consequences might be very large therefore we
approach a problem of the type: Risk ~ 0 x infinite. How can we
estimate the risk in such situations?
- Earthquakes occur over delimited areas that can be readily
identified by faults, while submarine landslides may occur anywhere
on continental margins with little diagnostic features. Monitoring
provides early warning capabilities and insights on the problem
under study. Are there areas that are well suited for monitoring of
submarine landslides? Are there tools to monitor submarine slope
activity over wide areas? What parameters should be monitored to
predict the timing of failure of a submarine slope?
- During the last 2-3 decades bottom waters in Arctic environments
have increased temperatures by up to 1oC due to climate change.
Methane plumes rising from the sea floor have also been detected in
these areas, at the place where gas hydrates occur. While it is not
clear whether these plumes result from a methane background flux,
these facts open new questions with regard to the stability of
Arctic submarine slopes: How rapid those temperature increases
diffuse below sea floor? How this affects methane hydrate
dissociation and dissolution? How fast ensuing pore pressure
dissipates? What is the slope stability of these regions?
- What could be a submarine landslide extreme geohazard study site?
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