Estimation of source parameters and scaling relationship of the local earthquakes in the Central Seismic gap NW Himalaya, India

Abstract

In the past decade, the seismicity in the Garhwal Himalayas has been recorded by eight three-component broadband seismographs (BBS) deployed all along the Garhwal Himalayan Seismic Belt (GHSB). In this study, we estimated the source parameters of 52 local earthquakes of M_w1.5–3.3 using a 3-month seismicity catalog and the recordings of the broadband seismographs in a shear wave spectral inversion. This iterative technique is based on Brune’s (1970) ω-square circular source spectral model. The modeled source parameters, including corner frequency (fc), source- radius (r), stress drop (Δσ), seismic moment (Mo), and moment magnitude (Mw), varied in the ranges of 1.3–11.58 Hz, 117.6–1054.4 m, 0.004–36 bar, 2.83E+11–1.33E+14 N-m, and 1.5–3.3 respectively. The highest computed stress drop (Δσ max) is 36 bar, while the lowest computed stress drop (Δσ min) is 0.004 bar for events of M_w 2.84 and M_w 1.81, respectively. The scaling relation between fc and Mo is obtained as Mo = Afc^−2.6 N-m/s³ where, (A = 4 × 10¹³) N-m/s³, while between Mo and Δσ the relation is found to be as log (Δσ) = 0.605 log (Mo)-17.35 and Mo vs. radius, Mo = Br^1.24. where (B = 3 × 10⁹). The relation between Mw and Mo is obtained as Mo = C Mw^7.51, where (C = 1 × 10¹⁰) and other relations are obtained as follows: (Δσ) = D Mw^4.7894 where (D = 0.0268), fc = E r^−0.948 where (E = 1102.7), Depth (d) = F (Δσ)^−0.111. (F = 9.699). The estimation of earthquakes source parameters through waveform spectrum is an important component for the study of seismogenesis and obtaining scaling relations is crucial for understanding the seismic hazard assessment. The scaling relations are used to develop ground motion prediction equations (GMPEs) that relate earthquake source parameters to ground shaking characteristics (e.g., peak ground acceleration, spectral acceleration). The significant result is that our modelling indicates a scaling relationship between Mo and fc suggesting Mo fc^2.6 ∝ Constant for Garhwal Himalaya based on local earthquakes of Mw 1.5 to 3.3. These scaling relationships derived from our current study could enhance earthquake hazard modelling for the Garhwal Himalayan region. This, in turn, could allow earthquake engineers to construct more resilient buildings in the area.