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Enhanced detection capability of non‐volcanic tremor using a 3‐level vertical seismic array network, VA‐net, in southwest Japan
Author(s) -
Imanishi Kazutoshi,
Takeda Naoto,
Kuwahara Yasuto,
Koizumi Naoji
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl049071
Subject(s) - geology , seismology , seismic array , seismic noise , volcano , noise (video) , geodesy , acoustics , computer science , physics , artificial intelligence , image (mathematics)
This study evaluates a method that enhances detection of non‐volcanic low frequency tremor (NVT) using VA‐net, a 3‐level vertical seismic array network that was recently constructed in southwest Japan. The method employs semblance analysis for continuous vertical array records and calculates semblance coefficients as a function of time and apparent vertical velocity. The sign of the best apparent velocity provides information about propagation direction, either upward or downward, allowing easy discrimination between seismic signals of natural origin and unwanted noise such as man‐made vibrations. We applied the method to a NVT episode that occurred beneath the Kii Peninsula during November 2008, to demonstrate that NVT signals can be detected using only the 3‐level array. Furthermore, we demonstrate that the method enables us to detect minor NVT activity which is not detected by a conventional envelope cross‐correlation method, resulting in a dramatic improvement in detection capability.