Quaternary Faulting Along the Median Tectonic Line in the Central Part of Shikoku

Okada, Atsumasa

doi:10.4157/grj.46.295

Cited by 52 publications

(50 citation statements)

References 2 publications

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“…to Kyushu (Figure 1). Geological studies indicate an average displacement rate of about 5-10 mm/yr [Okada, 1973], and it is hence recognized as one of the most active inland faults in Japan. In spite of the high rate suggested by neotectonic studies, no large earthquakes have been known at MTL for more than 1000 years.…”

Section: Interarc Collision In Japanmentioning

confidence: 99%

Crustal velocity field of southwest Japan: Subduction and arc‐arc collision

Miyazaki¹,

Heki²

2001

J. Geophys. Res.

366

410

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Abstract. We investigate crustal deformation in southwest Japan over a 3-year period revealed by a permanent dense Global Positioning System (GPS) array.Southwest Japan is a part of the Arnurian Plate, a microplate moving about 10 mm/yr toward the east with respect to the Eurasian Plate. It overrides the Philippine Sea Plate at the Nankai Trough and collides with the northeast Japan arc in the central part of Japan. In this paper we first derive GPS site velocities relative to the stable part of the Arnurian Plate in order to isolate signals of crustal deformation caused by the subduction and/or the collision. The velocity field has a conspicuous feature indicating the interseismic elastic loading by the Philippine Sea Plate slab at the Nankai Trough, characterized by the northwestward movements of points throughout the studied area. Their amplitudes are the largest at the Pacific coast and decay toward the Japan Sea coast with a subtle systematic shift of azimuths. A model assuming an elastic half-space, the convergence rate at the Nankai Trough based on a refined Euler vector, and the strength of the coupling inferred from a thermal model, could explain the velocity field in the western part of the studied area to a large extent. Those in the eastern part systematically deviate from them, and the residual components there show east-west shortening and north-south extension. This may represent crustal thickening and trenchward extrusion of crustal blocks caused by the collision between southwest and nor;heast Japan. This suggests that the collision between southwest and northeast Japan gives rise to not only crustal thickening but also trenchward extrusion of crustal block. A velocity contrast was found across the Median Tectonic Line, the largest inland active fault in Japan, but the current permanent GPS network is not dense enough for us to discuss its coupling depth.

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Section: Interarc Collision In Japanmentioning

confidence: 99%

Crustal velocity field of southwest Japan: Subduction and arc‐arc collision

Miyazaki¹,

Heki²

2001

J. Geophys. Res.

366

410

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“…12 (right), the Mikawa earthquake occurred just north of the Median Tectonic Line which runs through Mikawa Bay. Okada (1973) pointed out that several reverse faults whose western sides uplift as a hanging wall are present in the Inner Zone along the Median Tectonic Line in addition to the Mikawa earthquake Fig. 20.…”

Section: Relation To the 1944 Tonankai Earthquakementioning

confidence: 99%

Rupture Process of the 1945 Mikawa Earthquake as Determined from Strong Motion Records.

Kakehi

Iwata

1992

J,Phys,Earth

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“…The MTL is the largest tectonic line in southwestern Japan and is mainly composed of metamorphic rocks. In the present-day tectonic setting, geological studies have reported right-lateral strike-slip and extensional movements along the MTL on Kyushu Island (e.g., Okada 1980;Kodama 1994, 1999). An area transecting in the EW direction at the central part of Kyushu, which is located to the north of the MTL from the city of Beppu to the Unzen Volcano at Shimabara Peninsula, is called the Beppu-Shimabara graben (hereafter, B-U area) owing to the many normal faults around and between Beppu and Unzen.…”

Section: Introductionmentioning

confidence: 99%

Spatial heterogeneities in tectonic stress in Kyushu, Japan and their relation to a major shear zone

et al. 2015

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We investigated the spatial variation in the stress fields of Kyushu Island, southwestern Japan. Kyushu Island is characterized by active volcanoes (Aso, Unzen, Kirishima, and Sakurajima) and a shear zone (western extension of the median tectonic line). Shallow earthquakes frequently occur not only along active faults but also in the central region of the island, which is characterized by active volcanoes. We evaluated the focal mechanisms of the shallow earthquakes on Kyushu Island to determine the relative deviatoric stress field. Generally, the stress field was estimated by using the method proposed by Hardebeck and Michael (2006) for the strike-slip regime in this area. The minimum principal compression stress (σ3), with its near north-south trend, is dominant throughout the entire region. However, the σ 3 axes around the shear zone are rotated normal to the zone. This result is indicative of shear stress reduction at the zone and is consistent with the right-lateral fault behavior along the zone detected by a strain-rate field analysis with global positioning system data. Conversely, the stress field of the normal fault is dominant in the Beppu-Shimabara area, which is located in the central part of the island. This result and the direction of σ3 are consistent with the formation of a graben structure in the area.

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Quaternary Faulting Along the Median Tectonic Line in the Central Part of Shikoku

Cited by 52 publications

References 2 publications

Crustal velocity field of southwest Japan: Subduction and arc‐arc collision

Crustal velocity field of southwest Japan: Subduction and arc‐arc collision

Rupture Process of the 1945 Mikawa Earthquake as Determined from Strong Motion Records.

Spatial heterogeneities in tectonic stress in Kyushu, Japan and their relation to a major shear zone

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