Receiver function images of the central Chugoku region in the Japanese
islands using Hi-net data
Ramesh, D. S.,
H. Kawakatsu, S. Watada, and X. Yuan
Earth Planets Space, 57, 271-280, 2005.
Abstract
Crustal configuration of the central Chugoku region with disposition of the Philippine Sea Plate (PHS) in
this area are investigated through the receiver function approach using short-period Hi-net data. Images of the
upper mantle discontinuities are also obtained. Restituted short-period receiver functions bring out discernible
variations in average composition of the crust and its thickness in the study region. The Vp/Vs values in the study
area are generally high, reaching values in excess of 1.85 at a few places. The central part of the study region
showing the highest Vp/Vs values is coincidentally a subregion of least seismicity, possibly bestowed with special
subsurface structure. Migrated receiver function images, both Ps and Pps images, unambiguously trace the NW
subducting PHS taking a steeper plunge in the northwest part of the Chugoku region reaching depths of 70 km
from its low dip disposition in the southeast. An excellent correlation of the subducting PHS with the hypocenters
is also seen. We demonstrate that short-period data after restitution and application of appropriate low pass filters
can indeed detect presence of the global 410-km and 660-km discontinuities and map their disposition reasonably
well. Our migrated receiver functions image the deflections in the 410-km and 660-km discontinuities in an
anti-correlated fashion on expected lines of Clapeyron slope predictions induced by subduction of the Pacific
plate (PAC) beneath Japanese islands, though PAC itself is feebly traced but shows good correlation with slab
seismicity.