Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by SUYEHIRO, K. Articles by SACKS, I. S. Search for Related Content GeoRef GeoRef Citation

P- and S-wave velocity anomalies associated with the subducting lithosphere determined from travel-time residuals in the Japan region

CARNEGIE INSTITUTION OF WASHINGTON DEPARTMENT OF TERRESTRIAL MAGNETISM, 5241 BROAD BRANCH ROAD, N.W., WASHINGTON, D.C. 20015

Abstract

Travel-time residuals of P and S waves from local deep earthquakes are used to apply geophysical constraints to the laterally heterogeneous structure associated with the Japan subduction zone. Theoretical residuals for two-dimensional upper mantle models that have high-velocity dipping slabs are calculated by applying Jacob's (1970) ray-tracing method. The forms of the spatial distribution of the observed and the calculated residuals are matched to determine the velocity contrasts across the asthenosphere and the subducting lithosphere boundary and a possible velocity structure inside the slab.

We find 5 ± 1 per cent for Vp contrast and 7 ± 2 per cent for Vs contrast. These contrasts cannot simply be explained by a temperature effect alone and it is likely that other mechanisms such as partial melting in the asthenosphere are required for the observed velocity change.

The data indicate that the subducting lithosphere can be modeled by a two-layer structure similar to that found for oceanic lithosphere (Shimamura and Asada, 1976) but with a smaller velocity contrast. Two-layer model calculations show that the subducting lithosphere is about 120 km thick. The upper layer of the slab is about 40 to 50 km thick and has about 1 per cent lower velocity than the underlying layer.

This article has been cited by other articles:

				S. J. HEARN and J. P. WEBB Relative teleseismic P residuals and upper mantle structure in eastern Queensland, Australia Bulletin of the Seismological Society of America, October 1, 1984; 74(5): 1661 - 1681. [Abstract] [PDF]

				J. LAWTON, C. FROHLICH, H. PULPAN, and G. V. LATHAM Earthquake activity at the Kodiak continental shelf, Alaska, determined by land and ocean bottom seismograph networks Bulletin of the Seismological Society of America, February 1, 1982; 72(1): 207 - 220. [Abstract] [PDF]