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Published October 30, 1994 | metadata_only
Journal Article

Teleseismic evidence for lateral heterogeneities in the northeastern Japan arc


We have measured and analyzed 4211 P wave first-arrival times from 100 teleseismic events recorded by 67 high-sensitivity seismic stations in the northeastern Japan arc. The relative travel time residuals show regional variations of about 1.6 s. The mean relative residuals averaged for all 100 events produce a spatial pattern of early arrivals at stations near the Pacific coast and delayed arrivals in the central part of the island arc and along the Japan Sea coast. Large delayed arrivals are observed at stations in volcanic areas. This pattern is generally consistent with the heat flow distribution and the major structural features that have been determined by local and regional earthquake studies. Large early arrivals appear in northern Kanto and southern Tohoku for the rays from the teleseismic events in the southwestern direction. Using a simple and plausible model of plate subduction, we have shown that this anomalous pattern can be explained by the change of the geometry of the subducting Pacific plate beneath Kanto. The observed teleseismic residual distributions can be explained with a 3-D velocity model which includes the high-velocity subducting Pacific plate and low-velocity anomalies in the crust and mantle wedge beneath active volcanoes, suggesting that the 3-D model represents well the velocity structure in this region. These teleseismic observations provide a new piece of information on the significant lateral heterogeneities of seismic velocity structure in the northeastern Japan arc.

Additional Information

© 1994 Published by Elsevier B.V. Received 3 November 1993, Accepted 24 May 1994. We thank the staff members of the seismic networks of Hokkaido University, Hirosaki University, and University of Tokyo, for allowing us to use the teleseismic data recorded at some of their stations. We benefited from helpful discussions with H. Kanamori, D.L. Anderson and K. Aki. J. Vidale, D. Christensen and two anonymous reviewers carefully read the manuscript and provided helpful comments. The first author (DZ) has been supported by a research fellowship of the Southern California Earthquake Center and the Texaco Research Fellowship of the California Institute of Technology. Contribution No. 5327, Division of Geological and Planetary Sciences, California Institute of Technology.

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August 20, 2023
August 20, 2023