Widespread Geologic Evidence of a large Paleoseismic event near the Meizoseismal Area of the 1993 Latur Earthquake, Deccan Shield, India

Abstract

The occurrence of large to major earthquakes in Stable Continental Regions (SCR) is a rare phenomenon, generally associated with very long recurrence periods. The deadly seismic event (M-6.3) of 30th September 1993 in Latur district, Maharashtra, and the Jabalpur earthquake of 1999 (M 6.1), central India, challenge the earlier assumptions of the aseismic nature of the Deccan shield of India. Lack of historic seismic records for this region and the recent debate about the reactivation of a pre-existing fault in the basement beneath Deccan traps as the causative source for the 1993 Latur earthquake, led us to investigate the paleoseismicity of Latur, Osmanabad region. We present geological evidences, obtained from three sites, 60 km apart, of a paleoseismic event that took place during 190 BC-410 AD in the meizoseismal area of the 1993 Latur earthquake. The paleoseismic signatures like faults and liquefaction features (such as flame structures) are identified in four trenches made in the alluvial deposits of Tirna and Manjira river valleys. The timing of the paleoseismic signatures is constrained by radiocarbon dating of a number of organic samples from trenches at three sites, as well as through archaeological artifacts found in and around the disturbed horizon in one of the sites. The observed stratigraphic relations and concurrent 14 C dates strongly suggest that the observed paleoseismic features resulted from a single prehistoric seismic event, the magnitude of which could be inferred to be greater than that of the 1993 Latur earthquake.