High-frequency coda wave attenuation in the Mid and Far-Western region of the Nepal Himalaya

Abstract

In this study, we utilized the vertical components seismograms of 111 local earthquakes (Ml 2.5-5.5) recorded at fourteen stations by the HiKNet network, to present the first-ever estimate of the high-frequency coda waves attenuation in the Mid and Far-Western region of Nepal Himalaya. The inverse of coda wave attenuation, Q_c (quality factor) is estimated at eight central frequencies of 1.5, 3.0, 6.0, 9.0, 12.0, 15.0, 18.0, and 21.0 Hz through 30 s coda window length by using the single back-scattering model. Our findings are expressed in terms of the (Q_c) quality factor, showing a clear frequency-dependent power relation, Q_c (f) = Q₀ f ⁿ   where Q₀ is Q_c at 1 Hz, f is the frequency and n represents the degree of frequency dependence. The estimated average quality factor (Intrinsic and scattering quality factor) of all these seismic stations was obtained asat 30 s coda window length, which represents the highly heterogeneous and seismo-tectonically active region. The relatively lower quality factor (Q_c) value was obtained around Bajhang compared to the Mugu and Dailekh seismic belts. The Q₀ and n obtained in this study are consistent with previous research in the Central Region of the Nepal Himalaya and results with similar tectonic settings from other seismically active regions.