Characterizing ambient noise sources and their directionality using beamforming of data recorded by the Gujarat, India seismic network
Abstract
Extraction of green's functions using ambient noise and high resolution imaging of the crustal structure has gained prominence in the recent past. However, deciphering the distribution of ambient noise sources and their energy level play a vital role in determining the quality of the green's functions and understand the constraints imposed by non-uniform source directionality on the estimated crustal velocities. In this study, we analyze the spatial variation of the energy of primary and secondary microseisms, and their directionality, using continuous data recorded by a 44 station seismic network in Gujarat, India, during 2015-2016. The probabilistic power spectral density (PPSD) and frequency domain beam forming methods are utilized for this purpose. Analysis of PPSD suggests that the spectral energies at short period are nearly close to the mean global average where as at the longer periods the spectral energies are close to the global maximum. In addition, sources in the coastal region of southern part of Gujarat show higher energies, those in the northern side being close to the global mean. In addition, the level of noise from the region with multiple faults in the north-west direction appears very high. Beamforming revealed primary micro seismic sources that are azimuthally well distributed, with comparatively low energies in the south east (SE) direction. However, the secondary micro seismic sources seem to be randomly distributed around the region. Both the primary and secondary microseisms have higher spectral power in the SE direction. However, the lower energies of sources in the SE direction could possibly be explained in terms of suppression/scattering of the noise signal by the geological faults and subsurface material. A synthesis of source directionality and the average spatial ambient noise levels revealed significant role of regional faults in altering the incoming source energies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S23C0652B
- Keywords:
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- 7212 Earthquake ground motions and engineering seismology;
- SEISMOLOGY;
- 7219 Seismic monitoring and test-ban treaty verification;
- SEISMOLOGY;
- 7255 Surface waves and free oscillations;
- SEISMOLOGY;
- 7270 Tomography;
- SEISMOLOGY