Downhole distributed acoustic sensing reveals the wavefield structure of the coastal microseisms

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Authors

Stanislav Glubokovskikh, Roman Pevzner , Evgenii Sidenko , Konstantin Tertyshnikov, Boris Gurevich , Sergey Shatalin , Alexey Slunyaev, Efim Pelinovsky 

Abstract

Ocean-generated seismic waves are omnipresent in passive seismic records around the world and present both a challenge for earthquakes observations and an input signal for interferometric methods for characterisation of the Earth's interior. Understanding of these waves requires the knowledge of the depth-dependence of the oceanic noise at the transition into continent. To this end, we examine 80 days of continuous acquisition with Distributed Acoustic Sensor (DAS) system deployed in two deep boreholes near the south-eastern coast of Australia. The data has excellent Signal-to-Noise Ratio (SNR) in a range from 0.03Hz to over 100Hz. By analysing the seismograms and correlation with wave climate, the DAS response are confidently decomposed into the microseisms generated by swell from remote storms (~0.15Hz) and local winds (between 0.3Hz and 2Hz), and strong body waves energy from large surf break at the coast (from 2Hz to 20Hz). The depth dependence of the microseims allows for robust normal modes analysis of the Rayleigh waves with only one borehole. The results of this analysis agree with the data from conventional dense seismological arrays. Overall, we found that the link between the amplitudes at each channel along the borehole and wave climate is so strong and stable that with sufficient amount of training data, the passive seismic records on downhole DAS may be used for high-precision monitoring of both formations surrounding the borehole and remote storms in the ocean.

DOI

https://doi.org/10.31223/X5W30H

Subjects

Engineering, Physical Sciences and Mathematics

Keywords

Oceanic microseisms, Ambient Seismology

Dates

Published: 2020-10-21 09:30

Last Updated: 2020-10-21 16:30

License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
NONE

Data Availability (Reason not available):
The data belongs to the CO2CRC Ltd. It will be made available after the manuscript will have accepted for the publication by EPSL.

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