Liquefaction and fluidization of lacustrine deposits from Lahaul-Spiti and Ladakh Himalaya: Geological evidences of paleoseismicity along active fault zone

Abstract

Soft-sediment deformational structures are important diagnostic features of paleoseismic studies. These seismites result from local vigorous fluidization and hydroplastic deformation formed during liquefaction as a direct consequence of permanent deformation of ground surface due to earthquakes of large magnitude. The region of eastern Ladakh, Spiti Basin and the upper Sutlej River basin record a concentration of earthquakes in a well defined NE-trending seismic zone sub-parallel to the strike of Leo-Pargil Horst and the Kaurik-Chango Fault Zone. Soft-sediment deformational studies of the fluvial and fluvio-lacustrine sequences near Sumdo village, along Sangla valley of Himachal Pradesh and near Saspol village of Ladakh indicate that the Kaurik-Chango Fault Zone is a seismogenic fault causing liquefaction and fluidization as the consequence of earthquake activity in the past. Thermal Luminescence (TL) date of the deformational structures near the Sumdo village constrains the paleoseismic activities of large magnitude between 90,000 years (third activity) to 26,000 years (last geological evidence) with a recurrence interval of approximately 10,000 years during the Quaternary period.