The great 1950 Assam Earthquake revisited: Field evidences of liquefaction and search for paleoseismic events

Abstract

Extensive field investigations were carried out for the first time in the meizoseismal area of the great 1950 Assam Earthquake aimed at exploring the paleoseismic history of the NE Indian region through documentation of liquefaction features and radiocarbon ( 14C) dating. Trenching at more than a dozen locations along the Burhi Dihing River valley and within the alluvial fans adjoining the Brahmaputra and Dibang Rivers resulted in the identification of more than a dozen very prominent liquefaction features (sand dykes, sills, sand blows etc.) as evidences of large to great earthquakes. 14C dating of the organic material associated with some of the features indicates a paleoseismic record of about 500 yrs archived by the sediments in this region. Compelling geological evidence(s) of the great 1950 earthquake are well constrained by 14C dating. Out of the two historically reported seismic events (1548 AD and 1697 AD) from this region, 14C dating could constrain the 1548 AD event though not distinctly. Further studies using combined 14C and OSL dating may better constrain the seismo-chronology of the study region.