Premium
S‐wave energy estimation of small‐earthquakes in the western Nagano region, Japan
Author(s) -
Matsuzawa Takanori,
Takeo Minoru,
Ide Satoshi,
Iio Yoshihisa,
Ito Hisao,
Imanishi Kazutoshi,
Horiuchi Shigeki
Publication year - 2004
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 - 10.1029/2003gl018445
Subject(s) - attenuation , seismology , seismic moment , geology , inversion (geology) , energy (signal processing) , moment (physics) , frequency domain , physics , optics , fault (geology) , mathematics , mathematical analysis , classical mechanics , quantum mechanics , tectonics
We estimate the S‐wave energy radiated by nine small earthquakes (M W 1.2–2.4) that occurred in the western Nagano region, Japan. First, we obtain the S‐wave energy radiated by 156 earthquakes (M W 0.8–2.6) below 60 Hz in the frequency domain. We separate the radiated energy spectra and the site amplification functions using a least squares inversion method including corrections for the S‐wave radiation pattern at the source and the attenuation along the path. Then, we assume an ω 2 ‐model to determine the corner frequencies for the nine earthquakes by using an empirical Green's function (EGF) method to remove the site and attenuation effects. Using the obtained corner frequencies, we then calculate radiated energy using these source models above 60 Hz. Our result indicates that the ratio of the seismic moment and S‐wave energy is between 8 × 10 −6 and 7 × 10 −5 .