Abstract
A data set of 79 local events (0.7⩽Mw⩽3.7) occurred during February 2003 to May 2003, collected by a temporary network deployed in Kameng region of Arunachal Lesser Himalaya have been analyzed to study the source parameters and fmax. In this study Brune model that yield a fall-off of two beyond corner frequency along with high frequency diminution factor for frequencies greater than fmax represented by a Butterworth high-cut filter (Boore, 1983) has been considered. The software EQK_SRC_PARA (Kumar et al., 2012) has been used to estimate the spectral parameters namely: low frequency displacement spectral levels (Ω0), corner frequency (fc) above which spectrum decays with a rate of two, the high-cut frequency (fmax) above which the spectrum again decays and the rate of decay (N) above fmax. These spectral parameters are used to estimate source parameters, viz., seismic moments, source dimensions and stress drops and to develop scaling laws for the region. Seismic moments vary from 1.42×1017dyne-cm to 4.23×1021dyne-cm; the source radii vary from 88.7m to 931.5m. For 28 events, stress drops are less than 1bar and 51 events have stress drops between 1bar and 40bars. A scaling relation, M0 (dyne-cm)=2×1022fc-3.34 has been derived for earthquakes having seismic moments greater than 1.5×1019dyne-cm. The estimated values of fmax values by and large conform to the worldwide observations. Dependence of fmax on source sizes, focal depths, epicentral distances and recording sites has been studied on the basis of comparative dependency of fc and fmax. The fmax and fc show almost similar dependency to seismic moments which shows fmax is also due to source process and is independent of epicentral distances and focal depths. At different recording sites, the observed values of fmax show consistent increase with seismic moment. This reflects that the source is the main controlling factor rather than recording site conditions for the observed variation of fmax in the Kameng region.
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