Simple assessment of shallow velocity structures with small-scale microtremor arrays: interval-averaged S-wave velocities
Ikuo Cho 1 3 Atsushi Urabe 2 Tsutomu Nakazawa 1 Yoshiki Sato 1 Kentaro Sakata 11 Geological Survey of Japan, AIST, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan.
2 Research Institute for Natural Hazards and Disaster Recovery, Niigata University, 8050 Ikarashi 2-no-cho, Niigata 950-2181, Japan.
3 Corresponding author. Email: ikuo-chou@aist.go.jp
Exploration Geophysics 49(6) 922-927 https://doi.org/10.1071/EG18020
Submitted: 11 February 2018 Accepted: 18 February 2018 Published: 20 April 2018
Journal compilation © ASEG 2018 Open Access CC BY-NC-ND
Abstract
This article describes a method for processing microtremor records from a small-scale seismic array that allows interval-averaged S-wave velocities to be estimated for 10-m depth ranges down to a depth of 30 m. The method was applied to microtremor data obtained in the town of Mashiki, Kumamoto Prefecture, Japan, and the analysis results were evaluated through a comparison with available PS logs and sections obtained by surface-wave methods. It turned out that the interval-averaged S-wave velocity estimates may be subject to errors of up to 20–30% in absolute values, but it was shown that the method can help evaluate relative spatial variations in those S-wave velocities. In view of the simplicity of analysis, the analyser-independent nature of the results and the limitations of analysis accuracy, the interval-averaged S-wave velocity estimation method presented here could be used as an effective tool for the preliminary analysis of microtremor data from small-scale seismic arrays.
Key words: arrays, exploration methodologies, noise, passive, shallow, surface wave, velocity.
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