Lapse time and frequency-dependent attenuation characteristics of coda waves in the Northwestern Himalayas |
| |
| Authors: | S Mukhopadhyay C Tyagi |
| |
| Institution: | (1) Department of Earth Sciences, IIT Roorkee, Roorkee, 247667 Uttaranchal, India |
| |
| Abstract: | We analyzed the local earthquakes waveform recorded on a broadband seismic network in the northwestern Himalayan Region to
compute lapse time and frequency dependence of coda Q (Q
c). The observed Q
c values increase with increasing lapse time at all frequency bands. The increase in Q
c values with lapse time is attributed to an increase in Q
c with depth. This implies that attenuation decreases with increasing depth. The approximate radius of medium contributing
to coda generation varies from 55 to 130 km. By comparing the Q
c values with those from other regions of the world, we find that they are similar to those obtained from tectonically active
regions. The estimated Q
c values show a frequency-dependent relationship, Q
c = Q
0
f
n
, where Q
0 is Q
c at 1 Hz and n represents degree of frequency dependence. They represent the level of heterogeneity and tectonic activity in an area. Our
results show that northwest Himalayas are highly heterogeneous and tectonically very active. Q
0 increases from 113 ± 7 to 243 ± 10 and n decreases from 1.01 ± 0.05 to 0.85 ± 0.03 when lapse time increases from 30 to 70 s. As larger time window sees the effect
of deeper part of the Earth, it is concluded that Q
0 increases and n decreases with increasing depth; i.e., heterogeneity decreases with depth in the study area. |
| |
| Keywords: | Q c lapse time frequency attenuation characteristics northwest Himalayas |
| 本文献已被 SpringerLink 等数据库收录！ |
|
