Thermal–petrological controls on the location of earthquakes within subducting plates

Abers, G. A.; Nakajima, Jun; Keken, Peter E. van; Kita, S.; Hacker, Bradley R.

doi:10.1016/j.epsl.2013.03.022

Cited by 158 publications

(165 citation statements)

References 79 publications

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“…The simplest explanation for this correlation is that intermediate-depth seismicity is not possible at low water content in the downgoing oceanic crust. A similar correspondence between upper-plane seismicity and the blueschist-out dehydration boundary is suggested in Alaska (Abers et al, 2006;Abers et al, 2012) although intriguingly in this subduction zone the seismicity tends to align with the predicted boundary, rather than just delimit it.…”

Section: Discussionmentioning

confidence: 71%

“…1; Tanaka et al, 2004). The correlation between the predicted blueschistout boundary and the cessation of seismicity is even more intriguing since the eclogite that forms still contains signifi- Kita et al (2006) and Abers et al (2012). The earthquakes from 120 km wide box shown in the insert are projected on the center cross section, normal to the trench.…”

Section: Introductionmentioning

confidence: 99%

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Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

2012

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Abstract. The cause of intermediate-depth (> 40 km) seismicity in subduction zones is not well understood. The viability of proposed mechanisms, which include dehydration embrittlement, shear instabilities and the presence of fluids in general, depends significantly on local conditions, including pressure, temperature and composition. The wellinstrumented and well-studied subduction zone below Northern Japan (Tohoku and Hokkaido) provides an excellent testing ground to study the conditions under which intermediatedepth seismicity occurs. This study combines new finite element models that predict the dynamics and thermal structure of the Japan subduction system with a high-precision hypocenter data base. The upper plane of seismicity is principally contained in the crustal portion of the subducting slab and appears to thin and deepen within the crust at depths > 80 km. The disappearance of seismicity overlaps in most of the region with the predicted phase change of blueschist to hydrous eclogite, which forms a major dehydration front in the crust. The correlation between the thermally predicted blueschist-out boundary and the disappearance of seismicity breaks down in the transition from the northern Japan to Kurile arc below western Hokkaido. Adjusted models that take into account the seismically imaged modified upper mantle structure in this region fail to adequately recover the correlation that is seen below Tohoku and eastern Hokkaido. We conclude that the thermal structure below Western Hokkaido is significantly affected by timedependent, 3-D dynamics of the slab. This study generally supports the role of fluids in the generation of intermediatedepth seismicity.

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Section: Discussionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

2012

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“…Therefore, they likely represent subducting crust with thicknesses of about 7 km rather than sedimentary layers with thicknesses of 0.5 km (e.g., Martin et al 2003;Abers 2005). Shiina et al (2013) showed the existence of free water in the crust at depths of 60 to 90 km beneath northeastern Japan, which is consistent with depths of dehydration reactions of hydrous minerals (Abers et al 2013) and concentrated seismicity in the crust (Kita et al 2006). Although the obtained velocity at the eastern part of Hokkaido was slightly higher than that in northeastern Japan (Figure 7b), which may be associated with the apparent high velocity due to faultinduced anisotropy, the value is still lower than that expected for hydrated compositions of the crust even with anisotropy of 2% to 3% (Fujimoto et al 2010).…”

Section: P-wave Velocity In the Subducting Crustmentioning

confidence: 64%

“…The increase in velocity in the crust appears to be correlated with an abrupt decrease in seismic activity beyond a depth range of the upper plane seismic belt that is defined as a concentrated crustal seismicity at depths of 70 to 90 km (Kita et al 2006). This phenomenon suggests that earthquakes in the crust are facilitated as a result of substantial pore fluid generated by dehydration reactions to eclogite from hydrous minerals (e.g., Abers et al 2013). Therefore, investigations of the locations of which hydrous minerals are hosted and dehydration reaction occurs are important for understanding ongoing metamorphism and the resultant processes in subduction zones.…”

Section: Introductionmentioning

confidence: 95%

Guided wave observations and evidence for the low-velocity subducting crust beneath Hokkaido, northern Japan

et al. 2014

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At the western side of the Hidaka Mountain range in Hokkaido, we identify a clear later phase in seismograms for earthquakes occurring at the uppermost part of the Pacific slab beneath the eastern Hokkaido. The later phase is observed after P-wave arrivals and has a larger amplitude than the P wave. In this study, we investigate the origin of the later phase from seismic wave observations and two-dimensional numerical modeling of wave fields and interpret it as a guided P wave propagating in the low-velocity subducting crust of the Pacific plate. In addition, the results of our numerical modeling suggest that the low-velocity subducting crust is in contact with a low-velocity material beneath the Hidaka Mountain range. Based on our interpretation for the later phase, we estimate P-wave velocity in the subducting crust beneath the eastern part of Hokkaido by using the differences in the later phase travel times and obtain velocities of 6.8 to 7.5 km/s at depths of 50 to 80 km. The obtained P-wave velocity is lower than the expected value based on fully hydrated mid-ocean ridge basalt (MORB) materials, suggesting that hydrous minerals are hosted in the subducting crust and aqueous fluids may co-exist down to depths of at least 80 km.

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“…The subducted oceanic crust is revealed at the top of subducting slabs under many regions, and has a thickness of < 10 km (e.g., Hori et al 1985;Matsuzawa et al 1986;Abers and Sarker 1996;Martin et al 2003;Abers 2005;Xia et al 2008;Abe et al 2013;Shiina et al 2013). Tomographic images also show velocity variations within the subducting slabs, which may be associated with the inhomogeneous distribution of intraslab earthquakes (e.g., Zhao et al 1992Zhao et al , 2002Nakajima et al 2001;Peacock 2001;Mishra and Zhao 2004;Kita et al 2006;Hasegawa et al 2009;Huang et al 2011a;Abers et al 2013). Forward-modeling of deep-earthquake travel times and receiver-function studies revealed a thin low-V zone within the subducting Pacific slab in the mantle transition zone (410-660 km depth), which may reflect a metastable olivine wedge probably associated with the generation of deep-focus earthquakes (e.g., Iidaka and Suetsugu 1992;Kaneshima et al 2007;Jiang et al 2008;Jiang and Zhao 2011;Kawakatsu and Yoshioka 2011).…”

Section: Subducting Slabsmentioning

confidence: 96%

Subduction Zone Tomography

Zhao

2015

Multiscale Seismic Tomography

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In this chapter, we review recent seismic tomography studies of subduction zones and new insights into arc magmatism, seismotectonics and subduction dynamics. Seismic velocity and attenuation tomography clearly reveals subducting slabs as high-velocity and low-attenuation zones, where intermediate-depth and deep earthquakes occur. In the crust and upper-mantle wedge, low-velocity (low-V) and high-attenuation (low-Q) anomalies are revealed beneath arc and back-arc volcanoes, and they extend to a deeper portion of the mantle wedge, indicating that the low-V and low-Q anomalies reflect source zones of arc magmatism and volcanism which are caused by corner flow in the mantle wedge and fluids from slab dehydration. P-wave anisotropy tomography and shear-wave splitting measurements also provide important constraints on mantle flows and dynamics in subduction zones.

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Thermal–petrological controls on the location of earthquakes within subducting plates

Cited by 158 publications

References 79 publications

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

Guided wave observations and evidence for the low-velocity subducting crust beneath Hokkaido, northern Japan

Subduction Zone Tomography

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