Detailed plate boundary structure off northeast Japan coast

Takahashi, Narumi; Kodaira, Shuichi; Tsuru, Takeshi Go; Park, Jin Oh; Kaneda, Yasufumi; Kinoshita, Hajimu; Abe, Shintaro; Nishino, Minoru; Hino, Ryota

doi:10.1029/2000gl008501

Cited by 24 publications

(23 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The large value of d c may be consistent with the idea that plate boundary is a fairly matured fault composed by thick shear zone and d c is larger for the thicker shear zone width in direct shear experiments of gouge layer (Marone, 1998). Although existence of thick shear zone is not directly observed in subduction zone, low velocity layer is found on plate boundary in Japan trench area (Miura et al, 2003;Takahashi et al, 2000). So called subduction channel (Vannucchi et al, 2008) is also a candidate of substance for a large d c fault.…”

Section: Model Setup In Subduction Zonesupporting

confidence: 70%

Generation Mechanism of Giant Earthquakes in Subduction Zones with Smaller-Size Interplate Earthquakes During Interseismic Period

Hori¹,

Hyodo²,

Miyazaki³

2012

Earthquake Research and Analysis - Seismology, Seismotectonic and Earthquake Geology

View full text Add to dashboard Cite

Section: Model Setup In Subduction Zonesupporting

confidence: 70%

Generation Mechanism of Giant Earthquakes in Subduction Zones with Smaller-Size Interplate Earthquakes During Interseismic Period

Hori¹,

Hyodo²,

Miyazaki³

2012

Earthquake Research and Analysis - Seismology, Seismotectonic and Earthquake Geology

View full text Add to dashboard Cite

“…As previously shown, it is quite likely that a thin low‐velocity zone is present along the plate boundary at depths between ∼12–16 km, resulting in the observed high‐amplitude P2P phases. A thin low‐velocity zone along the plate boundary at a depth of 10–30 km has been considered to indicate the presence of fluid along the plate boundary [e.g., Takahashi et al , 2000; Fujie et al , 2002; Kodaira et al , 2002]. Considering the interpretation that the increase in velocity within oceanic layer 2 is caused by cementation of internal fractures due to the subduction process (as mentioned above), it seems reasonable to consider that the thin low‐velocity zone is a result of trapped fluid dewatered from the oceanic layer below.…”

Section: Discussionmentioning

confidence: 99%

Structural factors controlling the coseismic rupture zone of the 1973 Nemuro‐Oki earthquake, the southern Kuril Trench seismogenic zone

et al. 2004

Self Cite

View full text Add to dashboard Cite

[1] The Kuril Trench is an active seismogenic zone where historic great earthquakes have occurred repeatedly with temporal and spatial regularities. This paper presents the results of a wide-angle ocean bottom seismographic (OBS) survey across the coseismic rupture zone of the 1973 Nemuro-Oki earthquake (Mw = 7.8), together with thermal modeling. The main purpose of this study is to understand the crustal and thermal controls on the Kuril seismogenic zone. Revealing structures that can be controlling factors of a megathrust earthquake helps in estimating earthquake hazards. We focus specifically on the precise structure of the seismogenic interface. Our imaged subduction structure clearly indicates that the coseismic rupture of the 1973 event occurred between the subducting oceanic crust and the Kuril island arc crust at 15-30 km depth. A thermally determined updip limit of the seismic rupture (100°C) corresponds to the seismically determined updip limit (15 km depth). An analysis of amplitude variations of wide-angle reflections demonstrated a highly reflective plate interface immediately trenchward of the coseismic rupture zone (shallower than 15 km depth), while a weakly reflective interface is observed at the coseismic rupture zone. From the observed amplitude variation with offsets, a thin low-velocity layer (4.5 km/s) is observed at the top of the highly reflective interface. This suggests the presence of fluid, which would indicate weak coupling updip of the rupture zone. We also deduced, from these observations, that a weakly reflective interface in the coseismic slip zone represents a strongly coupled zone pending the next megathrust earthquake.

show abstract

“…A weak seismic coupling could be due to the presence of unconsolidated or partly consolidated sediments between crusts of the arc side of the oceanic [e.g., Hartog and Schwartz , 1996]. At the Japan trench seismogenic zone area, it is known that the seismic coupling is <20% [e.g., Pacheco et al , 1993] and a low‐velocity zone exists between the subducting oceanic crust and the forearc crust of the northeastern Japan arc [e.g., Takahashi et al , 2000; Miura et al , 2000]. On the other hand, Ito et al [1999] showed that an average back‐slip rate of the western Nankai trough area is 4 cm/yr and that the seismic interplate coupling is strong.…”

Section: Crustal Model and Discussionmentioning

confidence: 99%

Seismic structure of western end of the Nankai trough seismogenic zone

Takahashi¹,

Kodaira²,

Nakanishi³

et al. 2002

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

[1] In 1998 a seismic experiment along a 320-km-long profile using an air gun array and ocean bottom seismographs (OBSs) was collected in the on shore-offshore, forearc region of the western Nankai trough seismogenic zone, southwestern Japan. This area is outside the coseismic rupture area of the 1946 Nankaido earthquake (M s = 8.2). The main objectives of this paper are to clarify the P wave and the Poisson's ratio profile around the forearc region of southwestern Japan, and estimate differences between this area and the Nankaido coseismic rupture area. The P wave velocity model estimated by two-dimensional (2-D) ray tracing and travel time inversion indicates three units with distinctive velocity patterns. The lens-shaped unit has a maximum thickness of 5 km and velocity of 3.4-4.0 km/s. The underlying unit has velocity of 5.4-5.6 km/s, and its P wave velocity increases on land (V p = 6.2-6.4 km/s). The relative homogeneous unit with P wave velocity of 6.6-6.9 km/s exists just beneath secondary unit with P velocity of 5.4-5.6 km/s. The angle of subduction is $7°. We also obtained a Poisson's ratio of the crustal structure of the forearc region. The Poisson's ratio of the southern part of secondary unit is larger than that of the northern part. We conclude that these data indicate clay-rich metamorphic rocks plus oceanic basaltic rocks, rather than high-porosity materials, comprise the majority of the layer. We suggest that the region of high Poisson's ratio probably corresponds to underplating and the metamorphism of the clay-rich sediments and possibly the oceanic basalt just below the decollement.

show abstract

Detailed plate boundary structure off northeast Japan coast

Cited by 24 publications

References 11 publications

Generation Mechanism of Giant Earthquakes in Subduction Zones with Smaller-Size Interplate Earthquakes During Interseismic Period

Generation Mechanism of Giant Earthquakes in Subduction Zones with Smaller-Size Interplate Earthquakes During Interseismic Period

Structural factors controlling the coseismic rupture zone of the 1973 Nemuro‐Oki earthquake, the southern Kuril Trench seismogenic zone

Seismic structure of western end of the Nankai trough seismogenic zone

Contact Info

Product

Resources

About