Seismic anisotropy in the wedge above the Philippine Sea slab beneath Kanto and southwest Japan derived from shear wave splitting

Salah, Mohamеd K.; Seno, Tetsuzo; Iidaka, Takashi

doi:10.1016/j.jseaes.2008.04.004

Cited by 15 publications

(29 citation statements)

References 46 publications

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“…Those that are sub-parallel to the trench have also been reported in New Zealand (Audoine et al, 2000) and the Shumagin Island section of the Aleutian (Yang et al, 1995). In addition, complex patterns of fast directions have been observed in northeastern (NE) Japan (Okada et al, 1995;Nakajima and Hasegawa, 2004), central Japan and the Kanto area (Fouch and Fischer, 1996;Hiramatsu et al, 1998;Salah et al, 2008), central South America (Polet et al, 2000), south central Alaska (Wiemer et al, 1999), the Lau backarc (Smith et al, 2001), Kamchatka (Levin et al, 2004) and in the north of New Zealand (Morley et al, 2006).…”

Section: Introductionmentioning

confidence: 77%

“…Similar splitting patterns in southwest Japan have also been reported by Long and van der Hilst (2005) using teleseismic data. Salah et al (2008) observed NW-SE and NE-SW fast directions in the wedge above the PHS slab. The splitting times are less than 0.4 s, which are smaller than those observed in this study.…”

Section: Observed Splitting In Southwest Japanmentioning

confidence: 86%

“…There is abundant intermediate-depth seismicity beneath the Kanto-Izu, and the Tokai-Kii Peninsula regions. Because both the Pacific and PHS plates subduct underneath the Kanto region, causing complex seismic activities in the upper mantle (e.g., Noguchi, 1998;Hori, 2006), some shallow events in this region might also occur in the subducting PHS slab (Hori, 2006; see also Salah et al, 2008). These possible events are excluded from the present analysis.…”

Section: Methodsmentioning

confidence: 99%

“…Iidaka and Obara (1995) detected a weak seismic anisotropy in this region (east of the volcanic front) from a large deep earthquake beneath Sakhalin Island with NE-SW and NW-SE main fast directions. Salah et al (2008) in their study of the mantle wedge anisotropy above the subducting PHS slab, observed NE-SW, NW-SE, and E-W fast polarization directions from shallow and intermediate-depth events occurring in the PHS and Pacific slabs in the Kanto area recorded at the Hi-net seismic stations. The area they studied corresponds to the shallower portion of the wedge above the PHS and Pacific slabs.…”

Section: Observed Splitting In the Kanto Areamentioning

confidence: 99%

“…Major features of these previous studies will be briefly explained in Section 4.3 to compare them with the main findings in this study. Recently, Salah et al (2008) conducted shear wave splitting measurements beneath central and southwest Japan from local shallow-and intermediatedepth earthquakes occurring in the subducting Philippine Sea (PHS) slab. The study also includes shallow events in the Pacific slab beneath Kanto.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Upper mantle anisotropy beneath central and southwest Japan: An insight into subduction-induced mantle flow

Salah

Seno

Iidaka

2008

Journal of Geodynamics

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Section: Introductionmentioning

confidence: 77%

Section: Observed Splitting In Southwest Japanmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Observed Splitting In the Kanto Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Upper mantle anisotropy beneath central and southwest Japan: An insight into subduction-induced mantle flow

Salah

Seno

Iidaka

2008

Journal of Geodynamics

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Seismic attenuation tomography of the source zone of the 2016 Kumamoto earthquake (M 7.3)

et al. 2017

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We study the three‐dimensional seismic attenuation (QP and QS) structure in the source area of the 2016 Kumamoto earthquake (M 7.3) by using 18,296 tP* and 29,668 tS* data from 742 local earthquakes recorded by a dense seismic network consisting of 112 stations deployed in Kyushu Island. Our results show that significant low‐Q (high‐attenuation) anomalies exist in the crust and mantle wedge beneath the volcanic front and back‐arc area, which reflect hot and wet zones caused by convective circulation in the mantle wedge and dehydration of the young Philippine Sea (PHS) slab. The 2016 Kumamoto earthquake occurred in a high‐Q and high‐velocity (high‐V) zone in the upper crust, which is surrounded and underlain by low‐Q and low‐V anomalies in the lower crust and upper mantle. These results suggest that the 2016 Kumamoto earthquake took place in a brittle seismogenic layer in the upper crust, but its rupture nucleation was affected by fluids and arc magma ascending from the mantle wedge. In addition, an obvious low‐Q zone is revealed in the fore‐arc mantle wedge, which reflects serpentinization of the fore‐arc mantle due to abundant fluids from the PHS slab dehydration.

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Mantle flow in subduction systems: The mantle wedge flow field and implications for wedge processes

2013

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[1] The mantle wedge above subducting slabs is associated with many important processes, including the transport of melt and volatiles. Our understanding of mantle wedge dynamics is incomplete, as the mantle flow field above subducting slabs remains poorly understood. Because seismic anisotropy is a consequence of deformation, measurements of shear wave splitting can constrain the geometry of mantle flow. In order to identify processes that make first-order contributions to the pattern of wedge flow, we have compiled a data set of local S splitting measurements from mantle wedges worldwide. There is a large amount of variability in splitting parameters, with average delay times ranging from~0.1 to 0.3 s up to~1.0-1.5 s and large variations in fast directions. We tested for relationships between splitting parameters and a variety of parameters related to subduction processes. We also explicitly tested the predictions made by 10 different models that have been proposed to explain splitting patterns in the mantle wedge. We find that no simple model can explain all of the trends observed in the global data set. Mantle wedge flow is likely controlled by a combination of downdip motion of the slab, trench migration, ambient mantle flow, small-scale convection, proximity to slab edges, and slab morphology, with the relative contributions of these in any given subduction system controlled by the subduction kinematics and mantle rheology. There is also a likely contribution from B-type olivine and/or serpentinite fabric in many subduction zones, governed by the local thermal structure and volatile distribution.

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Seismic anisotropy in the wedge above the Philippine Sea slab beneath Kanto and southwest Japan derived from shear wave splitting

Cited by 15 publications

References 46 publications

Upper mantle anisotropy beneath central and southwest Japan: An insight into subduction-induced mantle flow

Upper mantle anisotropy beneath central and southwest Japan: An insight into subduction-induced mantle flow

Seismic attenuation tomography of the source zone of the 2016 Kumamoto earthquake (M 7.3)

Mantle flow in subduction systems: The mantle wedge flow field and implications for wedge processes

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