10:45 AM - 11:00 AM
[SSS26-06] The one dimensional S-wave velocity structure inversion using Rayleigh admittance
Keywords:S-wave velocity structure, seafloor observation
We used the Rayleigh wave records of earthquakes with magnitude greater than 6.5 and within an epicentral distance of 30º. At each station, the velocity seismogram was converted to the displacement seismogram by removing the instrument response. The pressure record observed by the differential pressure gauge was used in this study because of a high resolution of the pressure observation. In the frequency domain, we estimated the amplitude transfer functions of displacement/pressure for each event, smoothed it using a Parzen window with a frequency band of 0.01 Hz, and stacked them over all of the used events. For inversion, we employed a simulated annealing technique to estimate one-dimensional S-wave velocity structure, in which the predicted admittance was calculated through a software of DISPER80 (Saito, 1988).
Because we used a broad frequency range (0.03–0.15 Hz), the velocity structure down to 10–20 km depths could be estimated. In particular, at depths from the seafloor to 5 km, the error of the estimated velocity was small compared with those at deeper depths. At some sites, it seems that the obtained S-wave velocity structure shows a low velocity layer within the accretionary prism. In the presentation, we will show other characteristics of the obtained velocity structures.