Existence of low-velocity zones under the source areas of the 2004 Chuetsu and 2007 Chuetsu-oki earthquakes inferred from travel-time tomography

DOI PDF Web Site Web Site 被引用文献8件 参考文献16件 オープンアクセス

書誌事項

公開日
2008-11
権利情報
  • https://creativecommons.org/licenses/by/4.0/
  • https://creativecommons.org/licenses/by/4.0/
DOI
  • 10.1186/bf03353148
公開者
Springer Science and Business Media LLC

説明

<jats:title>Abstract</jats:title><jats:p>Travel-time tomography reveals the presence of highly heterogeneous seismic velocity structures around the source areas of the 2004 Chuetsu and 2007 Chuetsu-oki earthquakes. A prominent low-velocity zone present below the Moho under the source areas of the two events is probably formed by fluids being conveyed through a small-scale upwelling in the mantle wedge. A low-velocity zone distributed in the lower crust below each source area is attributable to fluids supplied from the uppermost mantle to the source area. Since this region with these two source areas is exceptional in that the low-velocity zone is distributed in the uppermost mantle but no Quaternary volcanoes are formed at the surface, a relatively large amount of fluids may be stored below the source areas. These localized fluids may have reduced the strength in the lower crust as well as in the fault zones in the upper crust and, consequently, have promoted a brittle failure in the seismogenic layer. Relocated hypocenters of aftershocks of the two events become several kilometers shallower than the original locations determined by the Japan Meteorological Agency, suggesting the importance of using the three-dimensional velocity model in locating the hypocenter.</jats:p>

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