Regional seismicity and on‐land deformation in the Ryukyu arc: Implications for the kinematics of opening of the Okinawa Trough

Fournier, Marc; Fabbri, Olivier; Angelier, Jacques; Cadet, Jean-Paul

doi:10.1029/2001jb900010

Cited by 50 publications

(33 citation statements)

References 55 publications

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“…For studies of the crustal structure of the Ryukyu arc and the adjacent oceanic regions we refer to Iwasaki et al (1990) and Wang et al (2004). Analyses of earthquake focal mechanisms and fault geometries (e.g., McCaffrey, 1996;Fournier et al, 2001;Kubo and Fukuyama, 2003) suggest the existence of localized regions of arc-parallel extension along the arc, but it is unclear to what degree, if any, extension in the crust is coupled to deformation in the mantle.…”

Section: Tectonics Of the Ryukyu Arcmentioning

confidence: 99%

Shear wave splitting from local events beneath the Ryukyu arc: Trench-parallel anisotropy in the mantle wedge

Long

Hilst

2006

Physics of the Earth and Planetary Interiors

141

148

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We present shear wave splitting measurements from local slab earthquakes at eight seismic stations of the Japanese F-net array located in the Ryukyu arc. We obtained high-quality splitting measurements for 70 event-station pairs and found that the majority of the measured fast directions were parallel to the strike of the trench and perpendicular to the convergence direction. Splitting times for individual measurements ranged from 0.25 to 2 s; most values were between 0.75 and 1.25 s. Both the fast directions and the split times were similar to results for teleseismic S(K)KS and S wave splitting at the same stations, which suggests that the anisotropy is located in the mantle wedge above the slab. We considered several mantle deformation scenarios that would result in predominantly trench-parallel fast directions, and concluded that for the Ryukyu subduction system the most likely explanation for the observations is corner flow in the mantle wedge combined with B-type olivine fabric. In this model, the flow direction in the wedge is perpendicular to the trench, but the fast axes of olivine crystals tend to align perpendicular to the flow direction, resulting in trench-parallel shear wave splitting.

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Section: Tectonics Of the Ryukyu Arcmentioning

confidence: 99%

Shear wave splitting from local events beneath the Ryukyu arc: Trench-parallel anisotropy in the mantle wedge

Long

Hilst

2006

Physics of the Earth and Planetary Interiors

141

148

View full text Add to dashboard Cite

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“…1(a)). Normal faulting is a common tensional process evidenced by seismic reflection data (Sibuet et al, 1998) and focal mechanism analyses (Fournier et al, 2001;Kao and Jian, 2001;Kubo and Fukuyama, 2003). In the southern OT, the volcanic front of the Ryukyu subduction zone is located within the backarc basin (Sibuet et al, 1998;Wang et al, 2000) ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Spatial variations in the frequency-magnitude distribution of earthquakes in the southwestern Okinawa Trough

et al. 2007

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The relations between the frequency of occurrence and the magnitude of earthquakes are established in the southern Okinawa Trough for 2823 relocated earthquakes recorded during a passive ocean bottom seismometer experiment. Three high b-values areas are identified: (1) for an area offshore of the Ilan Plain, south of the andesitic Kueishantao Island from a depth of 50 km to the surface, thereby confirming the subduction component of the island andesites; (2) for a body lying along the 123.3• E meridian at depths ranging from 0 to 50 km that may reflect the high temperature inflow rising up from a slab tear; (3) for a third cylindrical body about 15 km in diameter beneath the Cross Backarc Volcanic Trail, at depths ranging from 0 to 15 km. This anomaly might be related to the presence of a magma chamber at the base of the crust already evidenced by tomographic and geochemical results. The high b-values are generally linked to magmatic and geothermal activities, although most of the seismicity is linked to normal faulting processes in the southern Okinawa Trough.

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“…In addition, a positive magnetic anomaly was observed over the chains of small volcanic knolls (arrows in Figure 2b), suggesting the presence of igneous rocks beneath the seafloor, which may correspond to magmatic bodies of ancient volcanoes (Figures 2b and 3a). These small volcanic knolls belong to the V-series, and the orientations of these chains appear to be related to previous tectonic extensions (Fournier et al 2001). …”

Section: Recent Volcanic Frontmentioning

confidence: 97%

“…The Okinawa Trough is generally interpreted as being in the early stage of rifting (e.g., Sibuet et al 1987Sibuet et al , 1995Sibuet et al , 1998Miki 1995;Shinjo et al 1999;Fournier et al 2001;Hsu et al 2001;Fabbri et al 2004;Lin et al 2005). We have divided the Okinawa Trough into northern, central, and southern regions corresponding to the divisions of the Ryukyu Arc (Konishi 1965) (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Detailed bathymetry and magnetic anomaly in the Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after approximately 2.1 Ma

et al. 2014

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Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed approximately 20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least approximately 2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

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Regional seismicity and on‐land deformation in the Ryukyu arc: Implications for the kinematics of opening of the Okinawa Trough

Cited by 50 publications

References 55 publications

Shear wave splitting from local events beneath the Ryukyu arc: Trench-parallel anisotropy in the mantle wedge

Shear wave splitting from local events beneath the Ryukyu arc: Trench-parallel anisotropy in the mantle wedge

Spatial variations in the frequency-magnitude distribution of earthquakes in the southwestern Okinawa Trough

Detailed bathymetry and magnetic anomaly in the Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after approximately 2.1 Ma

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