oa S-wave Anisotropy Analysis by Seismic interferometry Applied to Seismic Data Observed by DONET Observatories in the Nankai Trough

Seismic interferometry is an evolutionary new technique in seismic data processing field to obtain virtual shot records. We apply seismic interferometry to earthquake dataset acquired by DONET seafloor seismometers deployed in the Nankai Trough area. We use two horizontal components of seismometer to obtain virtual shot record. We expect that the two horizontal components are dominated by S-wave component. Therefore, the obtained virtual shot record should reflect the subseafloor S-wave velocity structure in the shallow part of the plate subduction zone. We then estimated direction of S-wave anisotropy from Alford rotation applied to obtained virtual shot records. Results show that the estimated directions of S-wave anisotropy are corresponding to the direction of principal share stress estimated from other methods, such as the borehole breakout analysis conducted in the IODP borehole sites, which are located near DONET observatories. Our results imply that seismic interferometry can be used as powerful tool to estimate S-wave anisotropy to monitor stress accumulation process which is underway in the plate subduction seismogenic zone.