Probabilistic seismic hazard assessment of Himachal Pradesh and adjoining regions

Abstract

Seismically active Himachal Pradesh and adjoining regions comprising Himalayan orogenic belt with the experience of the great Kangra earthquake of 1905, has high potential for river valley projects. There are already operating hydropower projects, some under construction and a few more coming up. In view of this it is important to know the ground motion nature for various locales. The present study is about estimation of Peak Ground Acceleration (PGA) for the state of Himachal Pradesh and adjoining regions using probabilistic seismic hazard analysis (PSHA) approach. Standard procedure for PSHA has been adopted for this study and peak ground motion has been estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level considering two cases: (i) varying b-value for each source zone, (ii) constant b-value for each source zone. For 10% probability of exceedance in 50 years, the PGA values vary from 0.096 to 0.15 g and 0.09 to 0.26 g considering varying b-value, and constant b-value, respectively. In case of 2% probability of exceedance in 50 years, the PGA varies between 0.07 to 0.24 g considering varying b-values and 0.14 to 0.37 g considering constant b-values. Higher PGA values are observed in the southeast part considering varying b-values whereas the region situated around Kaurik Fault System (KFS) has shown higher PGA values in case of constant b-value.

Site-specific Probabilistic Seismic Hazard Map of Himachal Pradesh, India. Part II. Hazard Estimation

“…From the PGA values at class-D for 2475 year return period, the districts of Hamirpur, Bilaspur, Solan, Mandi, Shimla, Kullu, northern parts of Kangra, and the southern parts of Chamba exhibit nearly 35-65% more hazard levels than the districts of Una, Lahaul & Spiti, northern Chamba, eastern Sirmaur, and a small region in the southern part of Kullu. Most importantly, the seismic hazard of the region surrounding Bilaspur, Chamba, and Kullu are found to be the highest within the study region and hazard of this region is higher than the previous studies (NDMA 2011, Patil et al 2014.…”

“…Due to the site amplification effects, the values reported in this study are found to be higher in comparison with the values reported by NDMA (2011) for the same return period, whose PGA values presented for class A sites range from 0.05-0.12 g. Similarly, these values are higher than those reported by Parvez et al (2003), obtained by a deterministic approach (design ground acceleration ranges from 0.08-0.15 g). When compared with the case 1 (varying b value) estimates of Patil et al (2014) that range between 0.078-0.15 g, it can be seen that their values underestimates the hazard in this region. When compared with their case 2 (constant b value), the hazard is in the range of 0.12-0.26 g which shows higher estimates for the region except for the Bilaspur and Chamba region.…”

“…The review of earlier seismic hazard studies for this region (Khattri et al 1984, Bhatia et al 1999, Parvez et al 2003, Mahajan et al 2010, Patil et al 2014 indicates that the previous estimates are based on ground motion relations developed for entirely different geological regions. This issue was addressed by NDMA (2011) which presented ground motion relations for class A sites taking into account the regional geological and seismogenic characteristics of India.…”

Estimation of bedrock depth for a part of Garhwal Himalayas using two different geophysical techniques

“…1a, b below. The tectonic setup of the study area has been studied quite extensively and is easily available (Joshi and Mohan 2010;Patil et al 2014).…”

Probabilistic seismic hazard assessment of NW and central Himalayas and the adjoining region

“…It is important to carry out seismic hazard analysis of the region because of its high level of natural seismicity and the presence of segments of major longitudinal tectonic boundary thrusts, namely the Main Central Trust (MCT) and the Main Boundary Thrust (MBT) along with various neotectonic faults traversing through the areas. Several authors have attempted to estimate PSHA for the Indian subcontinent and for different parts of the country (e.g., Khattri et al 1984;Bhatia et al 1999;Mahajan et al 2010;Nath and Thingbaijam 2012;Patil et al 2014). Bhatia et al (1999) estimated expected PGA for the Himalayan region between 0.10 and 0.30 g with 10% probability of exceedance in 50 years.…”