Earthquake Swarm Activities after Rains in Peninsular India and a Case Study from Jamnagar

Abstract

About 200 shocks were felt and over 50 of M-2 to 4 were located south of Jamnagar in 2006 and same number was felt/located again in 2007 with blast like subterranean sounds soon after heavy rains. Most of the shocks have shallow focal depth of less than 10 km. Some of the tremors have caused cracks in a few houses. During September-October 2006 tremors were confined withm 5 km of Khankotda village which is about 30 km SE of Jamnagar. During August-September 2007 the activity had spread northward up to Jamnagar. Some shocks have occurred about 20-25 km west of this trend faults/lineaments/dykes in the area are studied to identify the causative feature for the tremors. The rainfall data of the district and water level data of nearby observation wells are studied to see any possible relationship with earthquake activity. Data of about hundred cases of swarm type of earthquake sequences in the peninsular India in last several decades are compiled to study their characteristics vis-a-vis monsoons.