3-D seismic structure of the northeast India region and its implications for local and regional tectonics

Seismic b-Value and the Assessment of Ambient Stress in Northeast India

“…The seismological observatory network in northeast India was constructed jointly by the National Geophysical Research Institute (NGRI), Hyderabad, and the Regional Research Laboratory (RRL), Jorhat, in the 1980s (BHATTACHARYA et al, 2002;BHATTACH-ARYA and KAYAL, 2003;BHATTACHARYA et al, 2008), and has been recording local seismicity for more than two decades. The earthquake data used for the present study were collected from the earthquake catalogues published by the NGRI, Hyderabad, and RRL, Jorhat.…”

“…Although detailed investigations involving seismicity for the Shillong plateau as well as the whole of northeast India have been undertaken by several researchers (VERMA et al, 1976;MUKHOPADHYAY, 1984;KAYAL, 1987;KAYAL and ZHAO, 1998;RADHA KRISHNA and SANU, 2000;BILHAM and ENGLAND, 2001;BHATTACHARYA et al, 2008;STECKLER et al, 2008;KHAN et al, 2009), studies pertaining to the strength of the lithosphere and lithospheric-scale buckling are long-awaited for this convergent margin. Seismic b-values were analysed on a localised scale for appreciation of crustal heterogeneity (KAYAL, 1987;BHATTACHARYA et al, 2002, BHATTACHARYA andKAYAL, 2003;KHAN and CHAKRABORTY, 2007).…”

Scaling relations of moment magnitude, local magnitude, and duration magnitude for earthquakes originated in northeast India

“…The station parameters are given in Table 1. The hypocentral parameters are located by the HYPOCENTER location program of Lienert et al (1986) based on crustal velocity model of Bhattacharya et al (2008) and Baruah et al (2011). Uncertainties involved in the estimates of epicenters show that about 85 % of the events are located with an error of\2 km in depth and epicenter, and the error in origin times is of the order of 0.3 s. Duration magnitude (M D ) of these events are estimated in the range 3.0-4.96 (Lee et al 1972;Sitaram and Bora 2007).…”

“…where q = 2700 kg/m 3 is the average crustal density of the study area, ''v P '' is the average P-wave velocity as a function of depth (Bhattacharya et al 2008;Baruah et al 2011;Bora et al 2014), R is the source-to-receiver distance and R h/ is accounted for the radiation pattern of P-waves. The root mean square averages of radiation pattern coefficient R h/ = 0.52 is used for all the events in accordance with Boore and Boatwright (1984).…”

The 2009 Bhutan and Assam felt earthquakes (Mw6.3 and 5.1) at the Kopili fault in the northeast Himalaya region

“…The Kopili fault zone, approximately 300 km long and 50 km wide, separates the Shillong plateau and the Mikir massif by strike slip movement (figure 1), and it is identified as the most active fault in the Assam valley area (Kayal et al 2006, Bhattacharya et al 2008, 2010. The Shillong-Mikir massif are believed to be part of the Indian shield, and transported to the east by the Dauki fault (Evans 1964) (figure 1).…”