<p>The Northeastern Region of India is one of the most seismically active and tectonically complex regions globally, situated at the convergent boundary of the Indian Plate, the Eurasian Plate, and the Burmese microplate. Reliable characterisation of seismic wave attenuation in this region is critical for seismic hazard assessment and regional ground-motion prediction. In this study, we estimate the frequency-dependent crustal quality factor of Lg waves for Northeast India using spectral amplitude decay of broadband waveforms from regional earthquakes. A total of 1,313 high-quality station–event records were analysed following rigorous quality-control criteria based on signal-to-noise ratio, epicentral distance, and waveform characteristics. A regional-average, frequency-dependent <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$Q_{\textrm{Lg}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>Q</mi> <mtext>Lg</mtext> </msub> </math></EquationSource> </InlineEquation> model was derived over the 0.5–8 Hz frequency range and fitted using a power-law relationship, yielding <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$Q_0 = 502 \pm 27$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>Q</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>502</mn> <mo>±</mo> <mn>27</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\eta = 0.80 \pm 0.05$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>η</mi> <mo>=</mo> <mn>0.80</mn> <mo>±</mo> <mn>0.05</mn> </mrow> </math></EquationSource> </InlineEquation>, indicative of moderate attenuation and strong frequency dependence. Residual and site-term behaviour indicate the presence of unresolved lateral heterogeneity and highlight the limitations of a single uniform attenuation model in a tectonically heterogeneous region. The resulting <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$Q_{\textrm{Lg}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>Q</mi> <mtext>Lg</mtext> </msub> </math></EquationSource> </InlineEquation> model provides a robust regional-average baseline for seismic hazard assessment, regional ground-motion modelling, and future attenuation studies in Northeast India.</p>

Lg wave attenuation characteristics in Northeast India

期刊论文
发表日期：

2026年4月21日

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Prasad Kasulanati,
Bijit Kumar Choudhury

摘要

The Northeastern Region of India is one of the most seismically active and tectonically complex regions globally, situated at the convergent boundary of the Indian Plate, the Eurasian Plate, and the Burmese microplate. Reliable characterisation of seismic wave attenuation in this region is critical for seismic hazard assessment and regional ground-motion prediction. In this study, we estimate the frequency-dependent crustal quality factor of Lg waves for Northeast India using spectral amplitude decay of broadband waveforms from regional earthquakes. A total of 1,313 high-quality station–event records were analysed following rigorous quality-control criteria based on signal-to-noise ratio, epicentral distance, and waveform characteristics. A regional-average, frequency-dependent $Q_{\textrm{Lg}}$ $Q_{Lg}$ model was derived over the 0.5–8 Hz frequency range and fitted using a power-law relationship, yielding $Q_0 = 502 \pm 27$ $Q_{0} = 502 \pm 27$ and $\eta = 0.80 \pm 0.05$ $η = 0.80 \pm 0.05$ , indicative of moderate attenuation and strong frequency dependence. Residual and site-term behaviour indicate the presence of unresolved lateral heterogeneity and highlight the limitations of a single uniform attenuation model in a tectonically heterogeneous region. The resulting $Q_{\textrm{Lg}}$ $Q_{Lg}$ model provides a robust regional-average baseline for seismic hazard assessment, regional ground-motion modelling, and future attenuation studies in Northeast India.