[S07-2] Hazard and risk assessment I

[S07-2-03] Joint project on seismic hazards in the Indo-Gangetic Plain, India: Results from Ground Motion Sensor network

^○Rajender Chadha¹, Kazuki Koketsu², Srinagesh Davuluri¹, Shri Krishna Singh³, Satoko Oki⁴, Srinivas Dakuri¹ (1.National Geophysical Research Institute Hyderabad, India, 2.Earthquake Research Institute, University of Tokyo, Tokyo, Japan, 3.Institute of Geophysics, UNAM, Mexico, 4.Keio University, Tokyo, Japan)

An Indo-Japanese “SATREPS-DISANET" project was jointly implemented by the Earthquake Research Institute, Tokyo and National Geophysical Research Institute, Hyderabad, India during 2010-15 in which a network of 26 Strong Motion Velocity meters was established in the Indo-Gangetic plains (IGP) to assess seismic hazard in the region. The Himalaya represent a continent-continent collision boundary and is the locale of four M>8.0 earthquakes in the past. The project was taken up to map shallow subsurface structure of the sediment filled fore land basin and to study seismic wave amplification to assess seismic hazard in the region and to develop ground motion prediction equations.

The network became operational from October 2012 and recorded two significant earthquakes, viz., the 2014 Bay of Bengal earthquake (Mw 6.1) and the 2015 Gorkha earthquake (Mw 7.9), as well as the larger aftershocks. The analyses of the data provide a glimpse of seismic-wave amplification in the IGP on a regional scale. During the 2014 Bay of Bengal earthquake, the PGA and PGV values in the IGP were up to 3 and 4 times the corresponding values on the adjacent hard sites, respectively. The observed SSRs in the IGP estimated from the data of the relatively deeper 2014 earthquake (depth between 60 and 80 km) recorded at far distances (975 ≤ Δ ≤ 1650 km) are found to be reasonably similar to those from the shallow Gorkha earthquake at closer distances (350 ≤ Δ ≤ 680 km). Details of sediments thickness estimation and shear wave velocity in the IGP highlighting the implication of seismic risk in the region are presented. A passing remark on the outreach activities undertaken under the joint project will be made.