Detailed seismic attenuation structure beneath Hokkaido, northeastern Japan: Arc-arc collision process, arc magmatism, and seismotectonics

Saeko Kita, Junichi Nakajima, Akira Hasegawa, Tomomi Okada, Kei Katsumata, Youichi Asano, Takeshi Kimura

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

In this study, we imaged a detailed seismic attenuation structure (frequency-independent Q-1) beneath Hokkaido, Japan, by merging waveform data from a dense permanent seismic network with those from a very dense temporary network. Corner frequency of each event used for t∗ estimation was determined by the S coda wave spectral ratio method. The seismic attenuation (Qp-1) structure is clearly imaged at depths down to about 120 km. For the fore-arc side of Hokkaido, high-Qp zones are imaged at depths of 10 to 80 km in the crust and mantle wedge above the Pacific slab. Low-Qp zones are clearly imaged in the mantle wedge beneath the back-arc areas of eastern and southern Hokkaido. These low-Qp zones, extending from deeper regions, extend to the Moho beneath volcanoes, the locations of which are consistent with those of seismic low-velocity regions. These results suggest that the mantle wedge upwelling flow occurs beneath Hokkaido, except in the area where there is a gap in the volcano chain. In contrast, an inhomogeneous seismic attenuation structure is clearly imaged beneath the Hokkaido corner. A broad low-Qp zone is located at depths of 0-60km to the west of the Hidaka main thrust. The location almost corresponds to that of the seismic low-velocity zone in the collision zone. The fault planes of the 1970M6.7 and 1982M7.1 earthquakes are located at the edges of this broad low-Qp zone. Observations in this study indicate that our findings contribute to understanding the detailed arc-arc collision process, magmatism, and seismotectonics beneath Hokkaido.

Original languageEnglish
Pages (from-to)6486-6511
Number of pages26
JournalJournal of Geophysical Research: Solid Earth
Volume119
Issue number8
DOIs
Publication statusPublished - 2014 Aug

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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