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We attempt to estimate the physical state of interplate coupling of subducting Philippine Sea plates in the central Japan by using seismic ACROSS (Kasahara et al., 2005). Sinusoidal seismic signals have been transmitting by the ACROSS source at Toki city in the central Japan since 2002. Here we describe the results of the long-based array experiments, which has been conducted with 10 seismic stations aligned along 40-75 km from the ACROSS source since 2004. We analyze the data in the frequency range of 10-20 Hz to obtain the transfer functions described as six elements of second-order tensor through dividing 3-component displacements by horizontal 2-component source. Several wave groups are noticeable around 12-16 and 17-23 seconds in the seismic records at 61-64 km from the source through stacking the data for about 20 days. Assuming a seismic velocity structure referring to the model of Kodaira et al. (2004), it is found the above-mentioned arrival times are close to the theoretical travel times of the PmP and from an upper boundary of the Philippine Sea plate at the depth of 20-40 km.
Note. Abstracts are published in author's edition
Last update: 06-Jul-2012 (11:44:54)