Characteristics of seismic wave attenuation in the Kishtwar and its adjoining region of NW Himalaya

We investigate the attenuation characteristics of high frequency seismic waves in the Kishtwar and its adjoining region of NW Himalaya using 161 local earthquakes (M 2.1–5.7), recorded by a local network of seven Broad Band Seismic (BBS) stations. The extended coda normalization technique and the single backscattering method are used to study the attenuation characteristics of body and coda waves, respectively. The study shows that the attenuation quality factors for P-wave (Qα), S-wave (Qβ) and Coda wave (Qc) are strongly dependent on frequency and increase with the increase in central frequency. The average frequency-dependent relationship for Qα, Qβand Qc is found to be as Qα = (44 ± 7)f(1..01±0.91), Qβ = (71 ± 6)f(0.91±0.01) and Qc = (60 ± 4)f(1.06±0.04). The sites located on the western part of the study area exhibit higher attenuation (Q) compared with those in eastern part, suggesting that the eastern part of the study area is more heterogeneous than the western part. Variation of Qc with increasing lapse time suggests that the lower lithosphere is less heterogeneous, compared with the upper crust. We infer that the heterogeneity in the upper crust of Kishtwar area is primarily, due to the presence of highly fractured strata, dense network of joints and local faults, which mainly include splays of regional faults.