Characterization of Source Parameters and Some Empirical Relations between Them for Kachchh Region, Gujarat, India: Implication of January 26, 2001 Bhuj Earthquake and Its Aftershock Sequence

Abstract

Study of source parameters of small to moderate and large earthquakes is important to understand the differences and similarities between dynamic ruptures of different earthquakes and clarifying the scaling relations. In the present study, we have characterized source parameters and presented new and revised empirical relationships between various source parameters for Kachchh region of Gujarat, India to facilitate to draw first-order conclusions regarding the trends in the region. We have studied total 202 aftershocks of shallow-focus (hypo central depth less than 40 km) and moderate magnitude recorded over the Kachchh region during January 2001 to December 2012 by different seismological observatories of India Meteorological Department. We have adopted the spectral technique for source parameter estimation, where S-wave displacement spectra are considered and applied Fast Fourier Transform (FFT) to compute displacement spectra. We have followed the Brune’s source model for our estimation and the estimated values of source parameters show close approximation to the global values. While derived empirical relations between different source parameters, they demonstrate direct or inverse proportion to linear or power scale. Interrelation between seismic moment, rupture parameters, corner frequency and radiated seismic energy can be summarized as , , and E R μ M 0 and E R μ M w for our analysis . Stress drop distribution over the Kachchh region is very scattered and due to its peculiar behavior, it is difficult to derive its empirical relation with other source parameters. Sufficient accuracy on measuring source parameters like corner frequency stress drop, rupture dimensions, radiated seismic energy etc. helps to understand earthquake processes in the region. This is the first ever attempt to establish empirical relation between different source parameters for Kachchh region for longer aftershock sequence and they are useful to assess future earthquake potential over the region.