Structural investigation and characterization of active faults in Kala Amb Dehradun belt Northwestern Himalaya significance for paleoseismological studies

Abstract

Due to ongoing continent-continent collision between Indian and Eurasian plates Himalaya is prone to large-scale seismic hazard. A reliable seismic hazard assessment is very necessary in the region where population is growing exponentially. The knowledge of active fault distribution and paleoseismology have recently emerged as an important tool for understanding earthquake recurrence patterns in earthquake prone regions of the world. In the present work I have mapped active faults in the region between Kala Amb and Dehradun in northwest Himalaya with the help of high resolution Cartosat-I satellite data and attempted paleo-seismological studies at two locations. The latest tectonic activity along Himalayan Frontal Thrust(HFT) in the Nahan Salient is bracketed between 3.8 Ka. and 0.706 Ka. B.P which indicates the active nature of the fault. The geological fault slip rate along HFT determined using uplifted Quaternary River terraces in the Nahan Salient amounts to 12.8 mm/yr. which indicates a slip deficit of ~9m has been accumulated since 0.706 ka BP along HFT which can trigger a large magnitude earthquake in the region. The paleoseismic study along Yamuna Tear fault in Dehra Dun, using OSL ages shows the evidence of paleoseismic event between A.D. 1043-1141. The Yamuna Tear Fault is a structural discontinuity within Dehra Dun and indicates differential movement between two tectonic blocks. Therefore, the fault may have acted as a lateral boundary for the paleoseismic ruptures. The present study contributes new information towards the refinement of seismic hazard assessment studies in the Himalaya. newline