Seismotectonic zones demarcation in the Shillong Plateau using the microearthquakes and radon emanation rate
The Shillong Plateau signifies the intense tectonic processes that the region has experienced during the Tertiary Indo-Tibetan and Indo- Burman collisions. An attempt has been made to study the microearthquake and radon emanation rate to understand and identify the seismotectonic zones. The microearthquake data was recorded along a network of seven temporary seismic stations. The epicentral map prepared using the microearthquake data indicates sparse seismic activity over the Shillong Plateau. The alignment of earthquake epicenters does indicate definite pattern of the activity disposition and hence the active fault zones. The calculated b-value over the Shillong Plateau is low which indicates asperity and the fact that the 'stress' is being built-up. Accordingly, along the few identified active crustal structures, time integrated and continuous radon monitoring was made using the LR 115 and Barasol detectors. The sites with anomalous radon concentration are demarcated as active fault zones or sensitive seismotectonic zones and are being monitored continuously using the Barasol detectors. The anomalous radon concentration may not indicate the magnitude of impending earthquake but it certainly can be used to spatially locate the earthquake preparation zones.
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