|January 12th 2012 earthquake measuring 5.7 off Japan coast (usgs.gov/earthquakes)|
Wednesday, 2 November 2011
The Bounce: Mapping geophysical responses - updated
The inspiration for this short piece come from a very recent seminar given by Bill McGuire of the Aon Benfield Hazards Unit at UCL. My connection to the Benfield unit is Steve Edwards, a scientist and volcanologist whom I crossed paths with at the University of Greenwich and who is now the research development manager at Aon Benfield UCL Hazard Centre. I'm not going to any papers here so there will be no numbers, but Bill McGuire talked of the post-glacial response to climate change in geomorphology. The weight of the ice cap in the glacial age supressed the land for such a time and with such a weight that only now is the land responding and uplifting in relief of the melted mass. On the small scale, there are strike and slip movements in recovery that have seen small earthquakes occur in Cumbria for example in 2009, measuring 3.7 and previously in Dover in 1580 one occured at a magnitude of 5.5, scientists say a larger movement is long overdue. The epicentre of such responses is in Norway, in the UK we are on the periphery, but in Norway the ice mass was at the thickest and therefore the 'bounce' more prominent. The movement of the plates and the earth is generally up, or if there is a weakness then there is an angled move in that general direction. Where this differs from the Japan earthquake is that the plate boundary in Japan is convergent, therefore the energy starts leterally and results in a violent uplift as substrates buckle. What is interesting about the incidents of localised tremors in the UK is that the geomorphological structure is so varied as to limit the broad impact and make these occurances localised. We have friends in both Santiago and Tokyo who have seen many lives ruined by these tremors and we have great respect for their incredible resilience.