Estimation of source parameters and scaling relations for local earthquakes of Lohit Valley in Arunachal Himalaya, Northeast India

Abstract

We estimate the source parameters (stress drop, corner frequency, source radius and scalar seismic moment) for local earthquakes that occurred during 2007–2008 in the Lohit Valley, Arunachal Himalaya in northeast India. The source parameters of 33 selected earthquakes (2.0 ≤ ML ≤ 4.4) are estimated by spectral analysis of P‐waves of the vertical component. The results are authenticated further by spectral analysis of S‐waves of horizontal component seismograms. Both P‐ and S‐wave spectral analyses show comparable results. The earthquakes' seismic moment varies from 2.66 × 1012 to 1.16 × 1015 N.m. The estimates of stress drop and source radius range from ~0.145 to 31.85 bar and ~242 to 647 m, respectively. The majority of the earthquakes show a low‐stress drop (≤10 bar). We interpret that the low‐stress drop is plausibly due to the presence of creeping patches in the thrust sheets in the study area within the upper ~10 km depth, which is not able to withstand much stress and release it in the forms of micro‐earthquakes. The scaling relations have been developed between important source parameters (ML, Mw, M0, ∆σ, and fc), which can serve as useful inputs for the assessment of earthquake hazards in the region.