Temporal change of seismic structure around Iwate volcano inferred from waveform correlation analysis of similar earthquakes

We investigate the temporal change of crustal structure around Iwate volcano, northeastern Japan, using calculations of the cross-correlation coefficients of P- and S-waves of pairs of similar earthquakes that occurred between 1995-2002 at the subducting Pacific Plate boundary. While large coefficients are observed at most stations throughout the period, two stations located on the southwestern slope of Iwate volcano exhibit small S-wave coefficients. The coefficients at these two stations decreased remarkably from 1998, corresponding to a period of significant volcanic activity and an M6.1 earthquake. Since 2000, the coefficients have recovered gradually, suggesting their correlation with the activity of Iwate volcano. The coefficients of P-waves at these stations are large compared to those of S-waves, suggesting that temporal change in the crustal structure beneath these stations occurred in elastic properties to which S-waves are sensitive, such as rigidity, related to magmatic and/or seismic activity in and around the volcano.