TY - JOUR

T1 - High resolution Q-1 estimation based on extension of coda normalization method and its application to P-wave attenuation structure in the aftershock area of the 2005 West Off Fukuoka Prefecture Earthquake (M7.0)

AU - Matsumoto, S.

AU - Uehira, K.

AU - Watanabe, A.

AU - Goto, K.

AU - Iio, Y.

AU - Hirata, N.

AU - Okada, T.

AU - Takahashi, H.

AU - Shimizu, H.

AU - Shinohara, M.

AU - Kanazawa, T.

PY - 2009/11

Y1 - 2009/11

N2 - We developed a method for estimating the seismic-wave attenuation (1/Q) in a seismically active region such as an aftershock area. To estimate the attenuation factor between two adjacent hypocentres, we employed two seismograms recorded at a station and calculate the ratio between two power spectra of direct waves normalized by those in the coda for both the events. The coda normalization of the spectrum and the ratio between the two events minimize the possible influences of sources, sites, instruments and attenuation from the station to the hypocentral area. The 1/Q value can be estimated from the variation of the ratios of event pairs calculated at many stations for various traveltime differences between the even pairs. This method involves double-difference (DD) estimation from the logarithmic power spectra for estimating the 1/Q structure, employing a concept similar to the recently developed 'DD tomography' for velocity structures. We applied this method to the aftershock area of the 2005 West Off Fukuoka Prefecture Earthquake (M7.0) in order to investigate the 1/Q structure of P waves. By using the spectra of the seismograms of 1781 events recorded at a dense seismic network deployed around the aftershock area, we obtained the spatial variation of the 1/Q value in this region. The 1/Q distribution thereby obtained suggests that there exists a high-attenuation region around the edge of the main shock fault, which could correspond to the segment boundary between the earthquake fault and the adjacent faults. In addition, we found that the initiation points of the main shock and aftershocks were located in a low-attenuation region.

AB - We developed a method for estimating the seismic-wave attenuation (1/Q) in a seismically active region such as an aftershock area. To estimate the attenuation factor between two adjacent hypocentres, we employed two seismograms recorded at a station and calculate the ratio between two power spectra of direct waves normalized by those in the coda for both the events. The coda normalization of the spectrum and the ratio between the two events minimize the possible influences of sources, sites, instruments and attenuation from the station to the hypocentral area. The 1/Q value can be estimated from the variation of the ratios of event pairs calculated at many stations for various traveltime differences between the even pairs. This method involves double-difference (DD) estimation from the logarithmic power spectra for estimating the 1/Q structure, employing a concept similar to the recently developed 'DD tomography' for velocity structures. We applied this method to the aftershock area of the 2005 West Off Fukuoka Prefecture Earthquake (M7.0) in order to investigate the 1/Q structure of P waves. By using the spectra of the seismograms of 1781 events recorded at a dense seismic network deployed around the aftershock area, we obtained the spatial variation of the 1/Q value in this region. The 1/Q distribution thereby obtained suggests that there exists a high-attenuation region around the edge of the main shock fault, which could correspond to the segment boundary between the earthquake fault and the adjacent faults. In addition, we found that the initiation points of the main shock and aftershocks were located in a low-attenuation region.

KW - Body waves

KW - Seismic attenuation

KW - Seismic tomography

KW - Wave scattering and diffraction

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U2 - 10.1111/j.1365-246X.2009.04313.x

DO - 10.1111/j.1365-246X.2009.04313.x

M3 - Article

AN - SCOPUS:70350367413

VL - 179

SP - 1039

EP - 1054

JO - Geophysical Journal International

JF - Geophysical Journal International

SN - 0956-540X

IS - 2

ER -