Science Faculty Colloquium: Continental deformation and seismic hazard - what are the rules?
Speaker: Prof Phillip England FRS (Professor of Geology, University of Oxford)
It has been recognised for over 40 years that the continents do not conform to the rules of plate tectonics. The oceanic parts of the earth are characterised by rigid plates that are thousands of kilometres in extent with deformation confined to narrow bands (10s of km wide) at their boundaries. In contrast, many continents contain regions of present-day deformation that extend hundreds or thousands of kilometres into their interiors. While the distribution of earthquakes (and the of associated hazards) is fairly well understood at plate boundaries, this understanding is missing in much of the continental interiors because there is no accepted physical model for the deformation of the continents. A range of mechanical models have been proposed to explain this deformation, but discriminating among them has been difficult because of the lack of reliable data. This state of affairs is of practical concern, because continental earthquakes account for over two thirds of all fatalities in earthquakes, and this problem is only going to get worse as billions of people move into vulnerable mega-cities. In this lecture I shall discuss recent measurements of deformation (mostly using GPS), in Asia, southern Europe, and New Zealand. These measurements show that the patterns of present-day deformation in the continents are consistent with the deformation of a very viscous non-linear fluid, and are inconsistent with the common belief that the continents consist of a set of small plates (often called micro-plates). I shall also discuss the implications of this result for the assessment of seismic hazard in the developing world.
All students and staff are welcome, and attendance is free. This event will, no doubt, be very well-attended, so please arrive early to get yourself a seat.
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