Double-planed structure of intermediatedepth seismic zone and thermal stress in the descending plate.

Hamaguchi, Hiroyuki; Goto, Kazuhiko; Suzuki, Ziro

doi:10.4294/jpe1952.31.329

Cited by 28 publications

(14 citation statements)

References 18 publications

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“…9. The main cause of these depth variations is probably thermal stress, which implies a similar regime to the thermal stress model for the intraslab earthquakes (Goto et al 1985;Hamaguchi et al 1983;Manea et al 2006). If a heat source is really located in the crust as pointed out by Yoshida et al (2011), the crust immediately above it warms and expands (Fig.…”

Section: Discussionmentioning

confidence: 75%

Complex microseismic activity and depth-dependent stress field changes in Wakayama, southwestern Japan

Maeda

Matsuzawa

Toda

et al. 2018

Earth Planets Space

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We examined the spatial relationship between seismicity and upper crustal structure in the Wakayama region, northwestern Kii Peninsula, Japan, by investigating microearthquake focal mechanisms and the local stress field. The focal mechanisms of most events studied fall into three categories: (1) normal faulting with N-S-oriented T-axes mainly occurring at shallow depths, (2) reverse faulting with E-W-oriented P-axes dominating at intermediate depths, and (3) strike-slip faulting with N-S-oriented T-axes and E-W-oriented P-axes mainly seen at greater depths. The stress field varies with depth: the shallow part is characterized by a strike-slip-type stress regime with N-S tension and E-W compression, while the deep part is characterized by an E-W compressional stress regime consistent with reverse faulting. The depth-dependent stress regime can be explained by thermal stress caused by a heat source, as expected from geophysical observations. Geologic faults, acting as weak planes, might contribute to generate shallow normal fault-type and deeper strike-slip fault-type microearthquakes.

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Section: Discussionmentioning

confidence: 75%

Complex microseismic activity and depth-dependent stress field changes in Wakayama, southwestern Japan

Maeda

Matsuzawa

Toda

et al. 2018

Earth Planets Space

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“…In some slabs, double seismic zones are observed at the depth range of 60-300 km, often having down-dip compressional (DDC) and down-dip tensional (DDT) stresses in the upper and lower zones, respectively. This suggests that stresses due to unbending (Engdahl and Scholz, 1977), sagging (Sleep, 1979), or thermal expansion (Hamaguchi et al, 1983) may be operating in the slab. However, these alone are not enough to explain the occurrence of such intermediate-depth events because the differential stresses are still too small compared with the high confining pressure.…”

Section: Introductionmentioning

confidence: 99%

Dehydration of serpentinized slab mantle: Seismic evidence from southwest Japan

et al. 2014

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“…The stress state of these slabs is generally characterized by down‐dip compression and down‐dip tension along the top and bottom layers of the double zones, respectively [e.g., Hasegawa et al , 1978a; Kawakatsu and Seno , 1983; Matsuzawa et al , 1986]. The origin of such a stress state has been discussed, and unbending of the slab [e.g., Engdahl and Scholz , 1977; Kawakatsu , 1986], thermoelastic stresses [ Fujita and Kanamori , 1981; Hamaguchi et al , 1983; Goto et al , 1985] and sagging of the subducted slab [ Sleep , 1979] have been proposed as possible mechanisms. On the other hand, the double seismic zones observed in Cape Mendocino [ Smith et al , 1993], Alaska [ Ratchkovsky et al , 1997], northeast Taiwan [ Kao and Rau , 1999], and New Zealand [ Eberhart‐Phillips and Reyners , 1997] are relatively shallow and have lateral compression in the shallow portion and down‐dip tension in the deeper portion both for the upper and lower planes.…”

Section: Introductionmentioning

confidence: 99%

Double seismic zone and dehydration embrittlement of the subducting slab

2003

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[1] Dehydration embrittlement of metamorphosed oceanic crust and mantle in the subducting slab may be responsible for the occurrence of intermediate-depth earthquakes. We explore the possibility that this hypothesis can explain the morphology of the double seismic zones observed in northeast Japan, southwest Japan, northeast Taiwan, northern Chile, Cape Mendocino, and eastern Aleutians. We calculate transient temperature structures of slabs based on geologically estimated subduction histories of these regions. We then determine dehydration loci of metamorphosed oceanic crust and serpentinized mantle using experimentally derived phase diagrams. The depth range of the dehydration loci of metamorphosed oceanic crust and serpentine is dependent on slab age. The dehydration loci of serpentine produce a double-layered structure. Because the upper dehydration loci of serpentine are mostly located in the wedge mantle above the slab, we regard the upper plane seismicity representing dehydration embrittlement in the oceanic crust, and we fix the slab geometry so that the upper plane seismicity is just below the upper surface of the slab. We find that the lower plane seismicity is located at the lower dehydration loci of serpentine, which indicates that the morphology of the double seismic zones is consistent with the dehydration embrittlement.INDEX TERMS: 7218 Seismology: Lithosphere and upper mantle; 7209 Seismology: Earthquake dynamics and mechanics; 7220 Seismology: Oceanic crust; KEYWORDS: double seismic zone, dehydration embrittlement, serpentine, oceanic crust, subducting plate Citation: Yamasaki, T., and T. Seno, Double seismic zone and dehydration embrittlement of the subducting slab,

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Double-planed structure of intermediatedepth seismic zone and thermal stress in the descending plate.

Cited by 28 publications

References 18 publications

Complex microseismic activity and depth-dependent stress field changes in Wakayama, southwestern Japan

Complex microseismic activity and depth-dependent stress field changes in Wakayama, southwestern Japan

Dehydration of serpentinized slab mantle: Seismic evidence from southwest Japan

Double seismic zone and dehydration embrittlement of the subducting slab

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