Science Links Japan | Spatial Distribution of Seismic Scatterers beneath the Ou Backbone Range, Northeastern Japan, Estimated by Seismic Array Observations.

Spatial Distribution of Seismic Scatterers beneath the Ou Backbone Range, Northeastern Japan, Estimated by Seismic Array Observations.

Accession number;00A0320343

Title;Spatial Distribution of Seismic Scatterers beneath the Ou Backbone Range, Northeastern Japan, Estimated by Seismic Array Observations.

Author; ASANO YOICHI (Tohoku Univ., Grad. Sch.) UMINO NORIHITO (Tohoku Univ., Grad. Sch.) NAKAMURA AYAKO (Tohoku Univ., Grad. Sch.) OKADA TOMOMI (Tohoku Univ., Grad. Sch.) HORI SHUICHIRO (Tohoku Univ., Grad. Sch.) KONO TOSHIO (Tohoku Univ., Grad. Sch.) NIDA KOICHI (Tohoku Univ., Grad. Sch.) KOSUGA MASAHIRO (Hirosaki Univ., Fac. Sci. and Technol., JPN) HASEMI AKIKO (Yamagata Univ., Fac. of Sci.)

Journal Title;Journal of the Seismological Society of Japan. Second Series

Journal Code:G0931A

ISSN:0037-1114

VOL.52;NO.3;PAGE.379-394(1999)

Figure&Table&Reference;FIG.13, TBL.1, REF.28

Pub. Country;Japan

Language;Japanese

Abstract;Seismic array observations were made for about 3 months from July 28 to November 4, 1998 to estimate inhomogeneous structure of the crust and uppermost mantle beneath the Ou backbone range, which is one of the most seismically active areas in northeastern Japan. We deployed L-shaped small aperture seismic arrays at 13 locations in and around the range. Each array is composed of 16 seismometer stations with a 50 m separation and 3 sets of DAT recorders, which record 18-channel seismic signals continuously for about 4 weeks with a 100-Hz sampling. We recorded waveforms from 100 kg explosions detonated at 11 locations for the seismic refraction/reflection experiment of the 1998 Joint Seismic Observation of Tohoku. We also observed many earthquakes, including aftershocks of M 6.1 earthquake that occurred on September 3, 1998, in the northern edge of our array observation network. Both explosion and natural earthquake data recorded by the arrays are used to estimate a spatial distribution of seismic scatterers in the crust and uppermost mantle. We evaluated semblance coefficients and powers of seismograms to detect coherent wave trains with large amplitudes. Then the azimuth and slowness of these wave trains are converted to their source locations by assuming a single scattering in the model velocity structure. Estimated distribution of scatterers shows that most of them are distributed within the crust beneath the Ou backbone range. Particularly, concentrations of scatterers are seen around the fault planes and their deeper extensions of active faults bounding both at eastern and western edges of the backbone range and the fault plane of the September 3, 1998, earthquake of M 6.1. Some of the scatterers are also located around the S-wave reflectors (bright spots) detected by the previous study in the lower crust of this area. (author abst.)

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