Earthquake Source Fault Beneath Tokyo

Satō, Hiroshi; Hirata, Naoshi; Koketsu, Kazuki; Okaya, D. A.; Abe, Susumu; Kobayashi, Reiji; Matsubara, Makoto; Iwasaki, Takaya; Ito, Tomohiro; Ikawa, Takeshi; Kawanaka, Taku; Kasahara, Keiji; Harder, S. H.

doi:10.1126/science.1110489

Cited by 130 publications

(106 citation statements)

References 15 publications

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“…If PHS subduction does take place here it is not clearly expressed either in terms of a dipping seismic zone in the upper mantle or a continuous positive velocity anomaly. But recent seismic imaging profiles indicate shallow thrust faulting possibly associated with PHS subduction [Sato et al, 2005]. The lack of a Wadati-Benioff zone in this area (Figure 3 Profile #4) can perhaps be explained by the elevated thermal state in the zone due to subduction of the Izu-Bonin arc-related volcanic ridge.…”

Section: Discussionmentioning

confidence: 99%

“…This zone has typical megathrust structure at shallow levels [Sato et al, 2005] but because its slab toe begins to engage PAC an elevated level of seismicity develops updip within its slab as well. In Zone A, PHS encounters PAC at fairly shallow depths (50 -70 km) in the wedge between EUR and PAC.…”

Section: Discussionmentioning

confidence: 99%

“…Although globally not common, isolated cases exist where subducting plates come into contact, for example, in Espanola [Dolan et al, 1998] and in Ontong-Java [Mann and Taira, 2004]; but the interaction of PHS and PAC under Kanto is clearly more extensive and better delineated [Noguchi, 1998;Sekiguchi, 2001;Sato et al, 2005]. The PHS moved in a northerly direction until about 2 my ago [Seno and Maruyama, 1984] or as recent as 1 my [Yamaji, 2000] when it changed to a WNW direction.…”

Section: Introductionmentioning

confidence: 99%

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Interaction between two subducting plates under Tokyo and its possible effects on seismic hazards

Okaya

Sato

et al. 2007

Geophysical Research Letters

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Underneath metropolitan Tokyo the Philippine Sea plate (PHS) subducts to the north on top of the westward subducting Pacific plate (PAC). New, relatively high‐resolution tomography images the PHS as a well‐defined subduction zone under western Kanto Plain. As PAC shoals under eastern Kanto, the PHS lithosphere is being thrusted into an increasingly tighter space of the PAC‐Eurasian mantle wedge. As a result, zones of enhanced seismicity appear under eastern Kanto at the top of PHS, internal to PHS and also at its contact with PAC. These zones are located at depths greater than the causative fault of the disastrous 1923 Great Tokyo “megathrust” earthquake, in the vicinity of several well‐located historical, damaging (M6 and M7) earthquakes. Thus a rather unique interaction between subducting plates under Tokyo may account for additional seismic hazards in metropolitan Tokyo.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Interaction between two subducting plates under Tokyo and its possible effects on seismic hazards

Okaya

Sato

et al. 2007

Geophysical Research Letters

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“…Slow slip events and devastating earthquakes such as the 1923 Kanto earthquake associated with the subduction of the PHS were known in the region off Boso-peninsula (e.g. Sato et al, 2005;Ozawa et al, 2007). In order to analyze these The bathymetric contour interval is 1000 m. The inset shows the plate boundaries and survey area.…”

Section: Introductionmentioning

confidence: 99%

P-wave velocity structure in the southernmost source region of the 2011 Tohoku earthquakes, off the Boso Peninsula, deduced by an ocean bottom seismographic survey

et al. 2012

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We present the result of a seismic experiment conducted using ocean bottom seismometers and controlled sources in the region off Ibaraki and the Boso Peninsula. This region is the southern edge of the rupture zone of the 2011 off the Pacific coast of Tohoku Earthquake. We estimated the P-wave seismic velocity structure beneath the profile using a 2-D ray-tracing method. The crustal structure in the southern area is more heterogeneous than that of the northern area. This heterogeneity is thought to be related with subducting the Philippine Sea plate (PHS). The plate boundary between the landward plate and the Pacific plate (PAC) is positioned at depths of 20 km at a distance of 170 km from the southern end of the profile. The subducting PHS is imaged on the southern part of the profile. However, we could not obtain a distinct image of the contact zone of PHS and PAC. The contact zone of PHS and PAC is estimated to have a large heterogeneity resulting from strong deformation due to the collision of the two plates. We infer that the termination of the rupture, and the large afterslip in the collision region, are caused by this strong heterogeneity.

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“…Several tectonic faults, such as the Tonoki-Aikawa Tectonic Line and the Kozu-Matsuda Fault have developed around the area (e.g., Taira et al, 1998;Arai et al, 2009). The configuration of the subducting PHS plate in and around this region has been estimated based on the hypocenter distribution, S-P converted waves, seismic velocity tomography, and the seismic profile (e.g., Ishida, 1992;Iidaka et al, 1990;Tsumura et al, 1993;Matsubara et al, 2005;Sato et al, 2005). Kobayashi and Koketsu (2005) estimated that the rupture of the 1923 great Kanto earthquake extended to the region beneath the Tanzawa Mountains.…”

Section: Introductionmentioning

confidence: 99%

Seismotectonics in the Tanzawa Mountains area in the Izu-Honshu collision zone of central Japan, as revealed by precisely determined hypocenters and focal mechanisms

et al. 2012

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We investigate the detailed distribution of hypocenters and focal mechanisms beneath the Tanzawa Mountains, central Japan, where the Izu-Bonin arc has collided into the central part of the Honshu arc. Remarkable differences are found to exist between the hypocenter distributions in the western and eastern parts. The hypocenters of earthquakes in the eastern part tend to be distributed in a horizontal zone, whereas those in the western part are distributed in a volume. The focal mechanisms in the eastern part are right-lateral reverse faulting mechanisms, and one of the nodal planes is consistent with the geometry of the Philippine Sea (PHS) plate in the region. These results suggest that most earthquakes in the eastern part occur along the upper surface of the subducting PHS plate. In contrast, the focal mechanisms in the western part, especially deep in the western part, exhibit a different feature. The stress states in these two regions are found to be significantly different. The maximum and minimum principal stress axes in the eastern part are slightly inclined, whereas those in the western part are oriented in approximately the vertical and horizontal directions, respectively. The stress field in the eastern part may be caused by a slab pull force induced from the deeper part of the subducted plate.

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Earthquake Source Fault Beneath Tokyo

Cited by 130 publications

References 15 publications

Interaction between two subducting plates under Tokyo and its possible effects on seismic hazards

Interaction between two subducting plates under Tokyo and its possible effects on seismic hazards

P-wave velocity structure in the southernmost source region of the 2011 Tohoku earthquakes, off the Boso Peninsula, deduced by an ocean bottom seismographic survey

Seismotectonics in the Tanzawa Mountains area in the Izu-Honshu collision zone of central Japan, as revealed by precisely determined hypocenters and focal mechanisms

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