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Seismological evidence for anomalous structure of island arcs with special reference to the Japanese region
Author(s) -
Utsu Tokuji
Publication year - 1971
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/rg009i004p00839
Subject(s) - geology , seismology , island arc , crust , trench , tectonics , volcano , mantle (geology) , volcanic arc , plate tectonics , geophysics , subduction , oceanic crust , continental crust , arc (geometry) , geometry , chemistry , organic chemistry , layer (electronics) , mathematics
Evidence indicating lateral heterogeneity in the deep structure of island arcs has been collected from seismological literature. Abundant evidence from seismological studies in Japan during the last fifty years generally supports the large‐scale anomalous structure beneath this typical island‐arc region, i.e., the existence of a high‐ Q , high‐velocity zone about 100 km thick that dips from the vicinity of the trench beneath the arc to a depth of several hundred kilometers, and two low‐ Q , low‐velocity zones in the upper mantle on the inner (continental) and outer (oceanic) sides of this dipping zone. Most of the seismic activity is confined to this dipping zone and to the crust near and on the inner side of the volcanic belt. In other island‐arc regions, such as Kurile‐Kamchatka, Indonesia, Tonga‐Kermadec, and New Zealand, a number of seismological studies have indicated the existence of similar anomalous structure. At present, more detailed, more accurate determination of the configuration and physical parameters of these anomalous zones by seismological techniques is in progress, providing important information for understanding the global tectonic process and the origins of regional geophysical and geological features found in island‐arc regions.