3-D seismic structure of Kii Peninsula in southwest Japan: evidence for slab dehydration in the forearc

Salah, Mohamеd K.; Zhao, Dapeng

doi:10.1016/s0040-1951(03)00059-3

Cited by 88 publications

(49 citation statements)

References 38 publications

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“…Travel-time tomography analysis in the region has revealed 5 -6% low-velocity and high-Poissonratio anomalies exist within the slab mantle beneath the southern part of the Kii Peninsula [e.g., Honda and Nakanishi, 2003;Nakajima and Hasegawa, 2007a;Salah and Zhao, 2003]. The stations with overestimated dip angle are distributed within this region (Figure 10b).…”

Section: Possibility Of An Anisotropic Layermentioning

confidence: 96%

Structural features of the subducting slab beneath the Kii Peninsula, central Japan: Seismic evidence of slab segmentation, dehydration, and anisotropy

Shiomi¹,

Park²

2008

J. Geophys. Res.

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Seismic evidence of lithospheric slab segmentation, dehydration, and anisotropic rocks beneath the Kii Peninsula, central Japan, is detected with receiver function (RF) analyses. By stacking radial and transverse RFs with moveout perturbations, we estimate the downdip azimuth, dip angle, and depth of the slab Moho beneath each seismic station. Comparing the downdip azimuth to the slab convergence azimuth, we can classify the slab into three segments. The segments correspond to both the fault zones of past megathrust earthquakes and to the spatial distribution of intraslab seismicity. The slab Moho lies just above the intraslab seismicity in the southwestern Kii Peninsula. Slab Moho lies deeper at the eastern part of the peninsula, at the bottom of seismicity. This suggests that earthquakes occur only within the slab mantle under the southern Kii Peninsula. The dip angle of slab Moho becomes steeper at 40‐ to 50‐km depth, perhaps caused by dehydration transformation of basalt to eclogite. At some stations located in the western part of the Kii Peninsula, RF‐estimated dip angle of the interface is much steeper than that estimated by spatial trends in seismicity. Since the local seismicity distribution reflects well the larger‐scale geometry of the slab, the RF‐estimated dip angle may imply anisotropic wave speeds within strongly sheared and/or hydrated media around the slab Moho. These detailed features of the slab may be one key in distinguishing the source regions of megathrust earthquakes in the Nankai region.

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Section: Possibility Of An Anisotropic Layermentioning

confidence: 96%

Structural features of the subducting slab beneath the Kii Peninsula, central Japan: Seismic evidence of slab segmentation, dehydration, and anisotropy

Shiomi¹,

Park²

2008

J. Geophys. Res.

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“…This 1-D model assumption is valid if velocity discontinuities (like the Conrad and the Moho) are generally flat and lateral velocity variations are small. According to the previous studies (Tani, 2002;Kudo and Yamaoka, 2003;Salah and Zhao, 2003), Biwa Lake (see Fig. 1(b)) has a considerably different velocity structure from that of the surrounding areas.…”

Section: Methodsmentioning

confidence: 83%

“…Both Zhao et al (1992) and Salah and Zhao (2004) found no local structural variations beneath Biwa Lake perhaps due to the lower spatial resolution of their data sets. Salah and Zhao (2003) revealed lateral velocity variations of up to 5% beneath this area (Fig. 20).…”

Section: Discussionmentioning

confidence: 89%

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Waveform modelling of local earthquakes in southwest Japan

Abdelwahed

Zhao

2005

Earth Planet Sp

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The crustal structure beneath southwest Japan is investigated through waveform modellings of four local crustal earthquakes by using the generalized ray theory. High-quality seismograms recorded by the Hi-net seismic network are used. The focal mechanism solutions of the events used are estimated by using the first P-wave polarity data. Twenty-nine paths are used to characterize the crustal waveguide in SW Japan. Optimal 1-D velocity models for different paths are derived individually by waveform modelling. Synthetic tests are conducted to study the effects of different model parameters and to confirm the focal mechanism solutions. Modelling the waveforms individually is proven applicable for the heterogeneous regions. The resulted synthetics match the observed seismograms well. Considerable variations of the Conrad and Moho depths are found in the study area. The Conrad depth ranges from 14.8 to 19.7 km, and the Moho depth ranges from 28.4 to 33.4 km. Considerable variations in the crustal structure are found for the eastern portion of the study area where Biwa Lake lies. The effects of Biwa Lake on different paths are examined in detail.

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“…Poorly consolidated or fractured material will also exhibit high V P /V S values. Compared to the seismic velocity itself, Poisson's ratio is a better indicator of the content of fluids and/or magma (Kayal et al 2002;Takie 2002;Salah and Zhao 2003).…”

Section: Introductionmentioning

confidence: 99%

Relationships between geotectonic and seismodynamic characteristics of the crust in the Eastern Anatolia

Aydin

2015

Acta Geod Geophys

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The geotechnical lateral variations of the upper crust of the Eastern Anatolian were investigated using amplitude decay, Quality factor, seismic velocity and Poisson's ratio. The average Poisson's ratio was calculated as 0.2988 for the whole study area. Q P and Q S average quality factor were determined as 35 and 57, respectively and average d P and d S values were determined as 0.0149 and 0.0163 for the whole study area. The lowest Q S /Q P value 1.479 and the highest V P /V S value 1.194 are found at the Palu station. The highest V P /V S value, Poisson's ratio and quality factor rates were found in and around Kemaliye. The estimated Poisson's ratio values for the six stations ranged from 0.117 to 0.680 highlighting the regional differences in the seismodynamic of the crust. The entire study area is divided into different geotechnical regimes according to the lateral distributions of the seismodynamics properties. Study results showed once again that the fracture density and dimensions is associated with seismodynamics properties which are the changeable pressure ratios of the upper crust.

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3-D seismic structure of Kii Peninsula in southwest Japan: evidence for slab dehydration in the forearc

Cited by 88 publications

References 38 publications

Structural features of the subducting slab beneath the Kii Peninsula, central Japan: Seismic evidence of slab segmentation, dehydration, and anisotropy

Structural features of the subducting slab beneath the Kii Peninsula, central Japan: Seismic evidence of slab segmentation, dehydration, and anisotropy

Waveform modelling of local earthquakes in southwest Japan

Relationships between geotectonic and seismodynamic characteristics of the crust in the Eastern Anatolia

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