A new insight into seismic attenuation characteristics of Northwest Himalaya and its surrounding region: Implications to structural heterogeneities and earthquake hazards

Abstract

The frequency-dependent attenuation characteristics of P-waves (Qα), S-waves (Qβ) and coda waves (Qc) in north-west (NW) Himalaya and its surrounding region have been estimated using 515 micro to moderate earthquakes (2.5 ≤ Mw ≤ 5.0) recorded from January 2008 to November 2015 for a central frequency range (fc) varying from 1.5 to 12 Hz.Average attenuation relationships of Qc, Qα and Qβ found as: Qc = (126.94 ± 37.9)·f (1.122±0.06), Qα = (65.127 ± 5.7)·f(1.1261±0.03) and Qβ = (93.855 ± 3.05)·f(1.1145±0.01) for the region. It is found that the nature and extent of seismic attenuation are different for different seismotectonic belts consisted of various kinds of fault systems distributed into the Indo Gangetic Plain (IGP), the Sub Himalaya (SH), the Lesser Himalaya (LH) and the Higher Himalaya (HH) geotectonic segments beneath NW Himalaya and its surrounding region. Material property heterogeneity beneath the subsurface earth is playing an important role in influencing the degree of release of seismic energy in NW Himalaya and its surrounding region because of varying attenuative property in different geotectonic segments Q−1α,β,cHH<Q−1α,β,cIGP<Q−1α,β,cSH<Q−1α,β,cLH. This study may help in better understanding of structural heterogeneities that control the nature and extent of seismogenesis, which in turn may help in assessing seismic hazards through estimates of strong ground motion by computing earthquake source parameters. Our schematic model for NW Himalaya and its surrounding region shed an important light on attenuative characteristics of different tectonic blocks associated with both local and regional fault systems that dictate the source characteristics and potential of earthquake hazards of the region.