• journal_title：Bulletin of the Seismological Society of America
• Contributor：Dipok K. Bora ; Saurabh Baruah ; Rajib Biswas ; Naba Kumar Gogoi
• Publisher：Seismological Society of America
• Date：2013-02-01
• Format：text/html
• Language：en
• Identifier：10.1785/0120120095
• journal_abbrev：Bulletin of the Seismological Society of America
• issn：0037-1106
• volume：103
• issue：1
• firstpage：437
• section：Articles

We estimate the source parameters (seismic moment, source radius, stress drop, and source displacement) and scaling laws for local earthquakes that occurred in the Shillong–Mikir plateau, Assam Valley, and Arunachal Himalaya in northeast India during 2001–2008. The source parameters were determined using the spectral analysis of P waves from the vertical component seismograms, after correction for attenuation. Seismic moments are observed within the range from 9.51×10¹² to ; stress drop ranges from 4×10⁵ to 9×10⁷  Pa for the Brune model and 7×10⁵ to 1×10⁸  Pa for the Madariaga model. Seismic events in this study are prominent with an average stress drop of 0.1–10 MPa. The effect of site geology may be a contributing factor for such a variation in stress drop. Source dimensions are, however, found to be smaller within the major part of the plateau. It is suggested that local earthquakes in the region are associated with a brittle shear‐failure mechanism on fault segments and/or the presence of weakened zones, and earthquakes are triggered by low deviatoric stress. Empirical relations between M_w–M_L and M₀–M_L are developed leading to the future prediction of calibration coefficients for the local earthquakes in the Shillong–Mikir plateau and its adjoining region.

Online Material: Tables of source parameters.