When continents collide: Active deformation and seismic hazard

Since 1900, 35 earthquakes worldwide have each killed at least 10,000 people. Of these, 26 were in the Alpine-Himalayan seismic belt – a broad “crumple zone” where the African, Arabian and Indian tectonic plates collide with Europe and Asia. Most of these deadly earthquakes were caused by the rupture of faults that had not previously been identified.

CGS scientist Tim Wright is Professor of Satellite Geodesy at the University of Leeds and Director of the Natural Environment Research Council’s Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET). His work has been at the forefront of developing the use of satellite radar for measuring tectonic and volcanic deformation.

Tim was recently invited to present a guest lecture at the Geological Society on his work trying to understand the nature of seismic hazard within the Alpine-Himalayan region.

You can follow Tim on twitter: @timwright_leeds

Tweets from Wegener 2014

Here are some of the highlight tweets from the Wegener 2014 conference held at the School of Earth and Environment, University of Leeds, UK. Find all the tweets at #wegener2014.

ICTP Earthquake Tectonics and Hazards on the Continents Workshop

During the last two weeks of June I had the good opportunity to attend the Earthquake Tectonics and Hazards on the Continents workshop at the International Centre for Theoretical Physics (ICTP) in Trieste, Italy.

The workshop was organised as part of the Earthquakes without Frontiers (EwF) project which is a large multidisciplinary project involving CGS academics in Leeds and other national and international collaborators.

James Jackson (University of Cambridge) introduced the workshop by highlighting the central theme for the event: Our understanding of earthquake hazards is directly related to our understanding of earthquakes.  In other words, the more we understand about earthquakes and their tectonic settings, the more we will understand the hazards they present.

Most cumulative deaths are from continental earthquakes between magnitudes 6.5-8.
Source: Roger Bilham

The workshop material was broadly split up into two week blocks, with the first week focused on the basics of continental tectonics and the techniques used to study the behaviour of the Earth. Topics covered included an introduction to earthquake source seismology, the relationship between active tectonics and lithospheric structure, earthquake/fault scaling laws, stress and strain, InSAR, focal mechanisms and the geomorphic expression of strike-slip, normal and reverse faults.

For me, the most important aspect of the first week was highlighted by Steve Wesnousky (University of Nevada) in his talk on earthquake scaling laws. The empirical scaling laws derived from basic observations indicate that there are (as Steve likes to put it), Rules of the Game. The general behaviour of faults and earthquakes can be estimated knowing certain parameters. For example, if we know the length and width of a fault  we can estimate the maximum magnitude earthquake that fault can generate. This is a very powerful concept and one that is central to our understanding of earthquake hazards.

One of the key learning goals for the first week was to be able to recognise active faults from aerial photos or satellite imagery.
Source: Steve Wesnousky

The second week consisted of detailed case studies of different regions and applications of the techniques studied in the previous week. The main focus was in regions along the Alpine-Himalayan mountain belt, central Asia, central and western America and the Afar region.

One of the main points from this week was that earthquakes are unpredictable! Some of the deadliest earthquakes in the past century occurred on faults we didn’t even know existed! This highlights the importance of identification and measurement of slip rates and recurrence intervals of known and unknown active faults.

CGS academic Tim Wright describing how InSAR can be used to study earthquake deformation.

It is understandable that due to the varied approaches at modelling and interpreting observations that some academics will not agree with the approach of others. Scientists by nature are critical people and this is an important aspect in the work we do. We had a brief glimpse of one such topic where it was clear some academics prefered interpreting GPS data using block models while others preferred a viscous modelling approach. I will not go into a discussion of their their relative pros and cons in this post.

The workshop ended with a day discussing how scientists can turn their science into policy which will directly affect people’s lives and livelihoods. We had some very inspiring case studies from Kyrgyzstan (by Kanatbek Abdrakhmatov), Tehran (by Morteza Talebian) and the recent L’Aquila case in Italy (by Giulio Selvaggi).

Many thanks to the organisers for bringing people from all around the world and from different backgrounds together to study this important subject. I think everyone will agree that it was a highly successful event.

All the teaching material from the workshop are available to download for free at: http://cdsagenda5.ictp.trieste.it/full_display.php?ida=a12186

This is a fantastic resource and one that hopefully many will make good use of.

Also read up on the workshop tweets at the event hashtag: #ICTPTectonics

Ekbal

Workshop group photo.