We investigated sedimentary thickness and shear wave velocity structure in the western
part of the Indo-Gangetic Plain (Punjab and Haryana Plain) and adjoining Siwalik Himalaya
with the help of receiver function inversion at 20 broad-band seismological stations.
This region is one of the most seismically vulnerable zones of the world due to the
presence of thick surface sediments in the foreland basin that can amplify seismic
waves and cause huge damage due to the earthquakes of the Himalaya. The study reveals
a progressive thickening of sediments from southwest to northeast. The basement depth
varies from similar to 1.5 to 1.7 km in the Central Alluvium Plain, similar to 1.8
to 2.8 km in the Zone of Terminal Fans, and attains a maximum of similar to 3.8 km
near the Himalayan Frontal Thrust. The inverted models show the presence of soft alluvial
with extremely low Vs (< 0.5 km s(-1)) and high Vp/Vs (similar to 2.5-3.0) at the
top similar to 400-700 m of the surface at most of the stations. A comparatively higher
velocity of surface sediments observed at northern stations suggests the presence
of compact sediments at the surface. The layered sedimentary structure revealed by
the S-wave velocity models supports the previous geophysical investigations using
borehole data. The velocity-depth structure obtained in this study is important for
evaluating the seismic hazard of the densely populated urban areas spread over this
region.
