Source Parameters and Scaling Relation for Local Earthquakes in the Garhwal and Kumaun Himalaya, India

Yuvraj Borkar, Ashwani Kumar, S. C. Gupta, Arjun Kumar

Abstract


Earthquake source parameters provide great deal of information about the characteristics of earthquake source. Parameters such as stress drop, corner frequency, and fmax have applications in the estimation of strong ground motion. In the present study source parameters of 107 local events (0.1≤ML≤3.5), have been estimated using software EQK_SRC_PARA. Epicenters of majority of events are distributed along the trace of MCT between Barkot and Chamoli. Few events occurred in the Higher Himalaya to the northwest of Barkot and also in the Sub Himalaya. Seismic moments, Source radii, and Stress drops span the range from 3.03 x 1017 dyne-cm to 2.75 x 1021 dyne-cm, 111.7 m to 314.4 m, and 0.01 bars to 40 bars respectively. Maximum observed stress drops are associated with the events located at a distance of about 25 km in the west of epicenter of the Chamoli earthquake. Events with stress drops between 5 bar and 40 bars occurs at a depth of about 15 km. Stress drop increases with seismic moment for events with seismic moments above 1 x 1019 dyne-cm, and follows the relation: Δσ (bars) = 6x10-16 M00.8. A scaling law M0fc2.7 =5.0 x 1013 N-m/sec2.7 between seismic moment and corner frequency (1.0<Mw<3.3) has been developed for the region. Almost similar trend between fc and fmax with seismic moment has been observed and fc and fmax follow the empirical relation: fmax = 3 fc -2.6 for the region. Consistency in the fc and fmax which decreases with seismic moment has confirmed the stochastic nature of high frequency ground motion in the Garhwal and Kumaun Himalaya.

 


Keywords


Source Parameters, Stress Drop, Chamoli, Garhwal and Kumaun Himalaya, fmax

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