Reassessing the earthquake hazard in Kerala based

Authors: CP Rajendran Biju John K Sreekumari Kusala Rajendran

Publish Date: 2009/06/14

Volume: 73, Issue: 6, Pages: 785-802

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Abstract

Given the lack of proper constraints in understanding earthquake mechanisms in the cratonic interiors and the general absence of good quality database here we reassess the seismic hazard in the province of Kerala a part of the •stable continental interior• based on an improved historical and instrumental database The temporal pattern of the current seismicity suggests that 60 of the microtremors in Kerala occurs with a time lag after the peak rainfall indicating that hydroseismicity may be a plausible model to explain the lowlevel seismicity in this region Further an increment in overall seismicity rate in the region in the recent years is explained as due to increased anthropogenic activities which includes changes in hydrological pathways as a consequence of rapid landscape changes Our analyses of the historical database eliminate a few events that are ascribed to this region this exercise has also led to identification of a few events not previously noted The improved historical database essentially suggests that the central midland region is more prone to seismic activity compared to other parts of Kerala This region appears to have generated larger number of significant earthquakes the most prominent being the multiple events doublets of 1856 and 1953 whose magnitudes are comparable to that of the 2000/2001 central Kerala events Occurrences of these historical events and the recent earthquakes and the local geology indicative of pervasive faulting as shown by widely distributed pseudotachylite veins suggest that the NNWSSE trending faults in central midland Kerala may host discrete potentially active sources that may be capable of generating light to moderate size earthquakes The frequency of earthquakes in central Kerala evident from the historical database requires that the seismic codes stipulated for this region are made mandatory

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