Seismic Scatterer Distribution near Focal Area of the 1931 Oguni Earthquake, Iwate Prefecture, Northeastern Japan, as Derived from P Coda Wave Observations of an Explosion by a Dense Seismic Array Network
Year: 1993
Type: article
Abstract: An explosion was fired near the focal area of the Oguni Earthquake with M 6.5 which occurred at Kawai, Iwate Prefecture, northern Honshu, Japan, in 1931. Distribution of seismic scatterers was studied by setting an extremely dense seismic array network around the focal area of this earthquake. The number of stations and the distance of separation between stations are 196 and 25m, respectively. In observed seismograms, we found a clear later phase coming from northwest while the explosion was fired to the south. The location of the reflector for the clear phase is determined by using arrival times of this phase. Depth, dip direction and dip angle of the reflector are about 6km, S 40°W and 60 degrees, respectively. The estimated reflector is located in the Hayachine tectonic zone and the strike of the reflector coincides with that of the tectonic zone. We determined locations of seismic scatterers by computing semblance values for every azimuth and incident angle at intervals of 5 degrees and for every time window at intervals of 0.3s. It is found that there exist many scatterers in the Hayachine tectonic zone, with strikes similar to that of the tectonic zone, and few scatterers in the area covered by granitic rock.
Institutions: Tohoku University, Hirosaki University
Language: English
Topic: Seismic Waves and Analysis
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W2606401044