Source parameters and f max in lower Siang region of Arunachal lesser Himalaya
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ORIGINAL PAPER
Source parameters and f max in lower Siang region of Arunachal lesser Himalaya Rohtash Kumar & S. C. Gupta & Arjun Kumar & Himanshu Mittal
Received: 17 July 2013 / Accepted: 26 November 2013 # Saudi Society for Geosciences 2013
Abstract A data set of 60 local events (1.9≤M w ≤3.6) collected by a temporary digital network deployed in the Siang region of Arunachal Lesser Himalaya during July 2011 to Feburary 2012 is analysed to study the source parameters and f max. The software EQK_SRC_PARA (Kumar et al. in Int J Geosci 3(5):1142–1149, 2012) that considers Brune’s model with a high-frequency diminution factor (Boore in Bull Seismol Soc Am 73:1865–1894, 1983) has been used to estimate the spectral parameters namely: low-frequency displacement spectral level (Ω0), corner frequency (f c) and f max. These obtained spectral parameters are used to estimate source parameters, namely: seismic moment, source dimension and stress drop and to study the characteristics of f max in this region. Seismic moment varies from 6.13×1018 dyn-cm to 3.15×1021 dyn-cm; the source radii vary from about 175 to 357 m. The stress drops of these events vary from 0.2 to 56 bars and shows general increasing trend with increase in seismic moment. Various plots of both f c and f max with seismic moment, focal depth, epicentral distance and site showed the same amount of scatters and trends. From this study, it is found that f max has similar behavior as f c to seismic moment showing that it is also due to source process, and the same amount of scatter in both cut-off frequencies may be due to either source complexities or site effects or both. Both f c and f max seems independent of epicentral distance and focal depth. Relationships between f max and seismic moment and stress drop are obtained. R. Kumar : S. C. Gupta : A. Kumar (*) : H. Mittal Department of Earthquake Engineering, Indian Institute of Technology, Roorkee 247667, Uttarakhand, India e-mail: [email protected] R. Kumar e-mail: [email protected] S. C. Gupta e-mail: [email protected] H. Mittal e-mail: [email protected]
Keywords Source parameters . f max, Lower Siang . Arunachal Lesser Himalaya
Introduction Earthquake source parameters play an important role towards understanding the kinematic and dynamic properties of earthquake source as well as for understanding the seismotectonics of an area and hence for seismic hazard assessment. Earthquake source parameters are generally estimated from the radiated seismic wave-fields. Aki (1967) examined the dependence of the amplitude spectrum of seismic waves on source size on the basis of two dislocation models (ω3 model and ω2 model) of an earthquake source. The ω2 model gives a satisfactory agreement with such observations on the assumption of similarity, but the ω3 model does not. Brune (1970, 1971) modeled an earthquake source as a tangential stress pulse applied instantaneously to the interior of a dislocation surface. This model employs three independent parameters (moment, source dimension and fractional st
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