[SCG48-P08] Constraining S Wave Velocity of the Source Region of Shallow Very Low-Frequency Earthquakes
Keywords:shallow very low frequency earthquake, seismic velocity structure, ocean bottom seismometer, bayesian analysis
Recent achievements by the authors may help overcome this issue. Akuhara et al. (2019) developed a robust technique to estimate Green's functions of receiver side structures from offshore seismograms, which are typically ill-conditioned due to water reverberations. Tonegawa et al. (2017) inverted Rayleigh wave admittance (i.e., a ratio of ground displacement to hydraulic pressure) for shallow S wave velocity structures beneath DONET seafloor observatories at the Nankai Trough subduction zone. Their velocity models show low-velocity zones that characterize the source regions of shallow VLFEs. However, a smoothing constraint imposed on the models renders their interpretation somewhat difficult.
This study presents preliminary results from transdimensional inversion of receiver-side Green's function estimated by the method of Akuhara et al. (2019), where we adopt a prior constraint by the velocity models of Tonegawa et al. (2017). Complementary to the Rayleigh admittance, the Green's function approach is sensitive to velocity contrasts and thus will offer an improved resolution.