Reassessing the earthquake hazard in Kerala based on the historical and current seismicity |
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Authors: | CP Rajendran Biju John K Sreekumari Kusala Rajendran |
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Institution: | (1) Centre for Earth Sciences, Indian Institute of Science, Bangalore, 560 012, India;(2) National Institute of Rock Mechanics, Champion Reefs, Kolar, 563 117, India;(3) Seismic Station, Kerala Forest Research Institute Campus, Thrissur, 680 653, India;(4) Centre for Earth Science Studies, Akkulam, Thiruvananthapuram, 695 031, India;(5) Geological Survey of India, Northern Region, Lucknow, 226 024, India |
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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 low-level 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 NNW-SSE 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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Keywords: | Seismic hazard Earthquakes Stable continental interiors Central Kerala |
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