Detection of the subducting crust of oceanic plates beneath the Kanto district, Japan

Ohmi, Shiro; Hurukawa, Nobuo

doi:10.1016/0040-1951(95)00150-6

Cited by 20 publications

(27 citation statements)

References 26 publications

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“…Causing more than 100,000 fatalities, the Great Kanto earthquake of 1923 serves as a reminder to the severity of these events [Takemura, 2003]. Recent geophysical studies in Japan have confirmed and refined the subsurface geometry under Tokyo of the causative fault of the 1923 M8 earthquake and confirmed it as the megathrust at the interface of the Philippine Sea (PHS) and the Eurasian plates (EUR) [Ishida, 1992;Ohmi and Hurukawa, 1996;Ohmi and Hori, 2000;Matsubara et al, 2005]; based on this model the government of Japan issued in 2005 a long term forecast that a M $ 7 earthquake has a 70% probability to occur within 30 years in the Kanto region [Tsumura, 2005]. Deciphering the seismic hazards of possible future megathrust events requires major effort [Kobayashi and Koketsu, 2005;Tsumura, 2005].…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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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“…However, it is di¤cult to distinguish the boundary from our results since the total estimation error is comparable to the thickness of the oceanic crust shown in Ohmi & Hurukawa (1996). However, it is di¤cult to distinguish the boundary from our results since the total estimation error is comparable to the thickness of the oceanic crust shown in Ohmi & Hurukawa (1996).…”

Section: Comparison With the Tomography Resultsmentioning

confidence: 59%

“…Ohmi & Hurukawa (1996) showed considerable lateral heterogeneity above the PAC plate in the Kanto district. They concluded that the heterogeneity is mainly derived from the existence of the PHS plate.…”

Section: Estimation Error Of the Interface Due To Lateral Heterogeneitymentioning

confidence: 98%

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Seismic wave conversion near the upper boundary of the Pacific plate beneath the Kanto district, Japan

Ohmi¹,

Hori

2000

Geophys. J. Int.

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Summary A detailed structure of the Pacific plate beneath the Kanto district, Japan, was studied by the use of conspicuous SP converted waves that are generated near the upper boundary of the Pacific plate. These SP waves are observed for earthquakes occurring in the lower plane of the double seismic zone of the subducted Pacific plate. The location of the conversion interface is estimated by inverting the observed TSP−P times. 293 seismic traces recorded at 42 stations for 49 earthquakes are used for analysis. The conversion interface is located above the upper seismic plane of the double seismic zone and is equivalent to the upper boundary of the Pacific plate within the estimated uncertainty. In general, the conversion interface coincides well with the zone of low‐angle thrust‐fault‐type earthquakes in the entire area studied. Comparison with the result of 3‐D tomographic inversion reveals that the conversion interface is probably located in the low‐velocity layer on the top of the Pacific plate, which is interpreted as the oceanic crust of the Pacific plate.

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“…There are lateral structural variations of the Philippine Sea plate around Izu-Bonin arc that is located at south of the Kanto region (e.g., Kodaira et al 2007). Ohmi and Hurukawa (1996) also pointed out that the shallow crustal layer of the Philippine Sea Plate might be the crust of the subducting Izu-Bonin arc. This issue, including our interpretation of velocity increase in the low-velocity layer, is still open question and should be examined in the future.…”

Section: Dehydration Reactions In the Uppermost Oceanic Crust Of The mentioning

confidence: 99%

Velocity increase in the uppermost oceanic crust of subducting Philippine Sea plate beneath the Kanto region due to dehydration inferred from high-frequency trapped P waves

2015

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To investigate the detailed structural properties of the oceanic crust of subducting oceanic plate, we analyzed high-frequency (1 to 16 Hz) trapped P waves during earthquakes that occurred near the oceanic crust of the Philippine Sea plate. The distinct trapped P waves observed by the dense seismic network of the Kanto-Tokai region, Japan, did not show any apparent peak delay and frequency-dependent dispersion. These observations suggested that the oceanic crust around the source depths was characterized by a homogeneous velocity structure, rather than an inhomogeneous multiple-layered structure. This interpretation was examined by finite difference method simulations of seismic wave propagation using possible velocity structure models. The simulations demonstrated that a uniform velocity oceanic crust of the subducting Philippine Sea plate, which may result from the velocity increase in this layer at 30 to 40 km depth due to metamorphic-dehydration reactions, effectively trapped seismic energy as a short-distance waveguide and developed distinct pulse-like trapped P waves.

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Detection of the subducting crust of oceanic plates beneath the Kanto district, Japan

Cited by 20 publications

References 26 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

Seismic wave conversion near the upper boundary of the Pacific plate beneath the Kanto district, Japan

Velocity increase in the uppermost oceanic crust of subducting Philippine Sea plate beneath the Kanto region due to dehydration inferred from high-frequency trapped P waves

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