Life of an oceanic plate: Cooling time and assimilation time

Shiono, Kiyoji; Sugi, Noriko

doi:10.1016/0040-1951(85)90171-4

Cited by 32 publications

(15 citation statements)

References 37 publications

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“…Spreading ceased at 15 Ma, leaving the Kinan Seamounts marking the extinct spreading axis [Kobayashi and Nakada, 1978;Hibbard and Karig, 1990; Okino controlling a seismic activity along the subducting Philippine Sea Plate [Sugi and Uyeda, 1984;$hiono and $ugi, 1985]. $hiono and Sugi [1985] event, however, spread with time to the southwest along the coast and landward [Kanamori, 1972;Ando, 1975]. This larger area agrees with the dislocation determined from the geodetic and tsunami data [Ando, 1982].…”

Section: Tectonic Setting and Previous Geophysical Studiessupporting

confidence: 70%

Western Nankai Trough seismogenic zone: Results from a wide‐angle ocean bottom seismic survey

Kodaira¹,

Takahashi²,

Park³

et al. 2000

J. Geophys. Res.

104

113

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Abstract. The Nankai Trough, southwestern Japan, is recognized as a vigorous seismogenic zone with well-studied historic earthquakes. This paper presents results of a wide-angle ocean bottom seismographs (OBS) study at the western Nankai Trough seismogenic zone. The OBS data used were acquired on a profile (250 km long) across the presumed coseismic slip zone of the 1946 Nankaido earthquake (Ms=8.2). The main purpose of the seismic study is to obtain an entire crustal cross section of the seismogenic zone for the 1946 earthquake. The crustal model is characterized by a gentle sloping of subducting oceanic crust and thick overlying sedimentary wedge. P wave seismic velocities of the subducting oceanic crust show normal oceanic crustal velocities (Vp=5.0-5.6 km/s and 6.6-6.8 km/s in oceanic layers 2 and 3, respectively). The maximum thickness of the sedimentary wedge is 9 km at 70 km from the trough axis with Vp=3.4-4.6 km/s in the deeper part. The subducting oceanic crust traced down to 25 km depth shows that the subduction angle becomes steeper landward: 3.2øand 7.2 ø at 0-50 km and 50-100 km from the trough axis, respectively. The oceanic crust is smooth to the hypocenter zone, down to 40 km depth beneath Shikoku Island. Our crustal model shows that the downdip limit of the coseismic slip area does not extend to the deep end of the oceanic crust-island arc crust contact zone. Even though there is large uncertainty about the seaward limit of the coseismic slip zone, the crustal model clearly indicates that the updip limit of the coseismic slip zone extends beneath the young accretionary prism.

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Section: Tectonic Setting and Previous Geophysical Studiessupporting

confidence: 70%

Western Nankai Trough seismogenic zone: Results from a wide‐angle ocean bottom seismic survey

Kodaira¹,

Takahashi²,

Park³

et al. 2000

J. Geophys. Res.

104

113

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“…On the other hand, just in the east of the Kyushu-Palau ridge, where the age of the plate is the oldest, the length of the subducted plate is long and subcrustal earthquakes occur further inland region. From such observations, Shiono (1988) concluded that length of the subducted plate is related to thermal assimilation from the surrounding mantle: thermal assimilation occurs faster for a younger plate than for an older plate, resulting in shorter and longer lengths of the subducted plate, respectively (Shiono and Sugi, 1985). From these results, we suggest that the thickness of the Philippine Sea plate becomes thick as being away from the Kinan seamount chain toward the Kyushu-Palau ridge.…”

Section: Estimated Plate Thickness Of the Philippine Sea Platesupporting

confidence: 50%

Lateral variations of effective elastic thickness of the subducting Philippine Sea plate along the Nankai trough

Yoshioka

Ito

2014

Earth Planet Sp

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We investigated lateral variations of effective elastic thickness of the subducting Philippine Sea plate along the Nankai trough. For this purpose, we applied two-dimensional thin elastic plate bending theory to several profiles almost perpendicular to the trough axis, correcting the effect of thick marine sediments in the Shikoku Basin. The 15 topographic profiles were selected from 61 profiles and were fit to respective theoretical deflection curves by minimization of the L 1 norm. Classifying the Shikoku Basin into three regions, namely, the western, the middle, and the eastern regions, we obtained the results that the effective elastic plate thickness tends to decrease gradually from the east of the Ryukyu-Palau ridge to the Kinan seamount chain. This is consistent with heat flow data, seafloor age, formation process of the Shikoku Basin, length of the slab subducted from the Nankai trough, and spatial distribution of subcrustal earthquakes associated with subduction of the Philippine Sea plate.

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“…The volcanic front is not as clear as in NE Japan except for Kyushu and heat flow values are relatively high in the trench region (Yamano et al, 1984). These features are generally attributable to the subduction of the young and warm lithosphere of the Philippine Sea plate beneath the Eurasian plate (Shiono and Sugi, 1985). In addition the Pacific plate descends from the east beneath the Philippine Sea and Eurasian plates.…”

Section: Helium Isotopes In Chugoku and Shikoku Of Sw Japanmentioning

confidence: 94%

Geographical distribution of 3He/4He ratios and seismic tomography in Japan

Sano

Nakajima

2008

Geochem. J.

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The 3 He/ 4 He ratios (Ra) of natural gas, volcanic fluid, and groundwater are compiled in the Japanese Islands and their geographical distributions are discussed in the tectonic frame work of subduction zone together with preciselydetermined seismic velocity structures. In Northeastern (NE) Japan where typical island arc signatures are developed, there is a clear contrast of 3 He/ 4 He ratios perpendicular to the trench axis, low-Ra in the frontal arc and high-Ra in the volcanic arc. This may reflect the presence or absence of magma with high-Ra in the shallow crust. As a carrier of primordial helium, source melt may be generated in low-V zone of the wedge mantle by dehydration of Pacific slab at about 150 km deep and may flow upward sub-parallel to the slab, which is well constrained by S-wave velocity perturbation. In the Chugoku and Shikoku districts of Southwestern (SW) Japan, there is a geographical contrast of Ra similar to NE Japan except for the region at about 100 km from the volcanic front where medium-Ra was found. High-Ra observed in volcanic arc of the Chugoku district may be attributable to the mantle helium derived from the magma source generated below the Philippine Sea slab. Medium-Ra in the Shikoku district is explained by dehydration of the young slab with a moderate aging effect. These features are again consistent with the results of seismic tomography. In the Kinki district of SW Japan, anomalously high-Ra was observed in the frontal arc region that was called by "Kinki Spot". Since the high-Ra is located at much wider region from the volcanic front when compared with NE Japan, the melt generated below the Philippine Sea slab may penetrate into the fissure of the slab tear and may arrive at the shallow crust by upwelling flow.

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Life of an oceanic plate: Cooling time and assimilation time

Cited by 32 publications

References 37 publications

Western Nankai Trough seismogenic zone: Results from a wide‐angle ocean bottom seismic survey

Western Nankai Trough seismogenic zone: Results from a wide‐angle ocean bottom seismic survey

Lateral variations of effective elastic thickness of the subducting Philippine Sea plate along the Nankai trough

Geographical distribution of 3He/4He ratios and seismic tomography in Japan

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