Three-dimensional velocity structure beneath the Kanto district, Japan.

Velocity Structure Beneath the Hidaka Mountains in Hokkaido, Japan

“…This biased seismic activity differs from the seismic activity seen in typical subduction zones, where high seismic activity is observed in the high velocity material of the subducting lithosphere (HIRAHARA, 1977;HORIE and AKI, 1982;etc.). As discussed by ROECKER (1982) , high seismic activity in the LVZ might be caused by a brittle destruction of the subducted crust due to tectonic forces which may result in collision of the Kurile arc , Northeastern Japan arc, and the subducted Pacific plate .…”

“…Methods for estimating the velocity structure from high density seismic array measurements have been discussed by CROSSON (1976) and AKI and LEE (1976). These and other similar methods have been widely used to estimate the velocity structures of several regions (AKI et al, 1977;SATO, 1979;HORIE and SHIBUYA, 1979;HIRAHARA, 1977;HAWLEY et al, 1981;HORIE and AKI, 1982;ROECKER, 1982). As is well known, these methods require many arrival time data observed at an array of seismic stations located over the area in question.…”

Three-dimensional seismic structure of the crust and upper mantle beneath the orogenic belts in southern Hokkaido,Japan.

“…AKI and LEE (1976) developed a sophisticated method for determining laterally varying velocity structure from seismic array recordings of local earthquakes and applied this method to the Bear Valley area of Central California in the United States. HORIE and AKI (1979) have recently applied it on a larger scale, to the three-dimensional seismic structure beneath the Kanto district at around the junction between the Philippine Sea and the Pacific plates. This technique has been extensively used in the investigation of upper mantle heterogeneity, for example, in an arc-trench area such as Japan (HIRAHARA, 1977(HIRAHARA, , 1980.…”

Collision of Forearcs and Overlapped Deep Seismic Zone in the Transitional Zone Between the Northern Honshu and Kurile Arcs

“…AOKI (1974) defined the upward bending of the lithosphere beneath central Japan which is located at the arc-junction between the Izu-Bonin and northern Honshu arcs, based on the travel-time anomaly of the Kannikin event. HORIE and AKI (1982) however, examining the three-dimensional P-wave velocity structure and hypocenter distribution, suggested that the downward bending exists beneath the same arc-junction. Beneath the Hokkaido corner, the type of the disruption may be applicable to the deformation model as far as the existence of the overlapped deep seismic zone is considered.…”

“…It is expected that beneath the arc-junctions, the descending lithosphere must be deformed or disrupted because of surface area conservation of the lithosphere; that is, contractional displacement normal to the bisector of the arc-junction may be caused. For the deformation of the lithosphere, three possible types were presented by HORIE and AKI (1982); these are upward bending, downward bending, and disruption as shown in Fig. 7.…”