A Probabilistic Seismic Hazard Analysis of Northeast India

Abstract

Seismic hazard maps have been prepared for Northeast India based on the uniform hazard response spectra for absolute acceleration at stiff sites. An approach that is free from regionalizing the seismotectonic sources has been proposed for performing the hazard analysis. Also, a new attenuation model for pseudo-spectral velocity scaling has been developed by using 261 recorded accelerograms in Northeast India. In the present study, the entire area of Northeast India has been divided into 0.1° grid size, and the hazard level has been assessed for each node of this grid by considering the seismicity within a 300-km radius around the node. Using the past earthquake data, the seismicity for the area around each node has been evaluated by defining a and b values of the Gutenberg-Richter recurrence relationship, while accounting for the incompleteness of the earthquake catalogue. To consider the spatial distribution of seismicity around each node, a spatially smoothed probability distribution function of the observed epicentral distances has been used. Uniform hazard contours for pseudo-spectral acceleration as the hazard parameter have been obtained for an exposure time of 100 years and for 50% confidence level at different natural periods for both horizontal and vertical components of ground motion. The trends reflected by these contours are broadly consistent with the major seismotectonic features in the region.

A New Insight into Probabilistic Seismic Hazard Analysis for Central India

“…The design value is the ground-motion level that corresponds to a preselected design return period (BOMMER et al, 2000). The PSHA is able to reflect the actual hazard level due to earthquakes along with bigger and smaller events, which are also important in hazard estimation due to their higher occurrence rates (DAS et al, 2006). The PSHA is able to correctly reflect the actual knowledge of seismicity (OROZOVA and SUHADOLC, 1999) and calculates the rate at which different levels of ground motion are exceeded at the site by considering the effects of all possible combinations of magnitude-distance scenarios.…”

“…The goal of PSHA is to quantify the rate or probability of exceeding various ground motion levels at a site or a map of sites given all possible earthquakes (FRANKEL, 1995). CORNELL (1968) first formalized the numerical/analytical approach to PSHA and its computer code was developed by MCGUIRE (1976MCGUIRE ( , 1978 and ALGERMIS- SEN and PERKINS (1976 BHATIA et al (1999), SEEBER et al (1999), IYENGAR and GHOSH (2004), JAISWAL and SINHA (2007), RAGHUKANTH and IYENGAR (2006), DAS et al (2006), etc. This PSHA approach is widely used to estimate seismic-design loads for engineering purposes.…”

Seismic performance of reinforced concrete building in Guwahati city, northeast India

“…The annual occurrence rate of earthquakes, n(M j R i ), is obtained by spatially distributing the seismicity calculated from GutenbergRichter relationship. The detail of the procedure followed here is well explained in Das et al [13].…”

“…There are several studies on attenuation model for this part of India and an excellent review for peak ground motion predictions for rock sites in India is worth mentioning [14] in this regard. For the present study, the attenuation model proposed by Das et al [13] is adopted. Quantity n(M j R i ) in Eq.…”

“…The methodology proposed by Das et al [13] is adopted here for PSHA. Seismicity within 300 km radius from the site is considered.…”