Quantifying Regional Body-wave attenuation in a seismic prone zone of northeast India

TL;DR

This study quantifies how seismic waves attenuate in northeast India's Kopili region, revealing frequency-dependent behavior and heterogeneity, which are crucial for seismic hazard assessment.

Contribution

It introduces a modified coda normalization method to accurately measure frequency-dependent body wave attenuation in a seismic prone zone.

Findings

Q_P^{-1} and Q_S^{-1} show strong frequency dependence.

Q_P^{-1}/Q_S^{-1} ratio exceeds unity across frequencies.

Results indicate significant heterogeneity and seismic activity.

Abstract

We evaluated the body wave attenuation parameter in Kopili region of northeast India. Using the modified algorithm of coda normalization method, we delineated frequency-dependent attenuation for both P and S waves. Taking more than 300 seismograms as input, we comprehensively studied microearthquake spectra in the frequency range of 1.5 to 12 Hz. The estimated values of $Q_P^{-1}$ and $Q_S^{-1}$ show strong frequency dependence. The relationships emerge to be $Q_P^{-1}=(23.8\pm 6)\times10^{-3}f^{-1.2\pm 0.008}$ and $Q_S^{-1}=(10.2\pm 2)\times10^{-3}f^{-1.3\pm 0.02}$, respectively. The ratio $Q_P^{-1}/Q_S^{-1}$ is found to be larger than unity for the entire frequency band which implies profound seismic activity and macroscale heterogeneity prevailing in the region. The study may act as the building block towards determination of source parameter and hazard related studies in the region.