Temporal change in P-wave scatterer distribution associated with the M6.1 earthquake near Iwate volcano, Northeastern Japan

Abstract

Temporal variation of the scatterer distribution has been detected around the focal area of an M6.1 earthquake, northeastern Japan, by applying semblance analysis to seismic array data. The variation was found in slant-stacked waveforms of two explosions detonated just above the focal area one month before and two months after the M6.1 earthquake. According to geodetic observations, a pressure source that might be a magma reservoir exists beneath this region and its location changed during the observation period. Slant-stacked waveforms are slightly different for the two explosions. The difference suggests that a scatterer contributing to the coda part is shifted towards the east and to greater depths only after three months. In this region, seismic and volcanic activity was very active during the interval between the two explosions. The volcanic activity of Mt Iwate just north of the M6.1 earthquake, which started several months beforehand, continued during this period. It may be considered that scatterer change relates to seismic and/or volcanic activity in the studied area.