Improved 3‐D <i>P</i> Wave Azimuthal Anisotropy Structure Beneath the Tokyo Metropolitan Area, Japan: New Interpretations of the Dual Subduction System Revealed by Seismic Anisotropy

Ishise, Motoko; Kato, Aitaro; Sakai, Shin’ichi; Nakagawa, Shigeki; Hirata, Naoshi

doi:10.1029/2020jb021194

Cited by 8 publications

(22 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“… (a) A schematic image indicating the subsurface structure beneath the E‐W section, corresponding to the dashed black line shown in Figure 6. The black line indicates the Moho detected using our receiver function analysis and the analysis of seismic tomography (Ishise et al., 2021). The green and orange lines indicate the upper surface of the Philippine Sea Plate identified by Nakajima et al.…”

Section: Discussionmentioning

confidence: 99%

“…The analysis by Ishise et al. (2021) elucidated the P‐wave velocity and its anisotropic properties. Unfortunately, it did not contain an S‐wave velocity distribution and did not cover the entirety of our study region.…”

Section: Discussionmentioning

confidence: 99%

“…Small and large black squares indicate prominent positive peaks, with large squares denoting peaks that we interpreted as corresponding to a common pervasive discontinuity. Open circles indicate the lower boundary of the layer that has a P-wave velocity of 7.5-7.7 km/s based on seismic tomography (Ishise et al, 2021). Green lines indicate the upper boundary of the Philippine Sea Plate, as estimated by Hirose et al (2008aHirose et al ( , 2008b and Nakajima et al (2009).…”

Section: Interpretation Of the Discontinuitymentioning

confidence: 99%

See 2 more Smart Citations

Relationship Between Crustal Structure and Plate Convergence Around the Izu Collision Zone in Central Japan

et al. 2023

Self Cite

View full text Add to dashboard Cite

The Izu collision zone is located in the northernmost part of the Izu Peninsula of central Japan (Figure 1). Active volcanoes (Mt. Fuji and Hakone) are located around the collision zone and belong to the southward-extending Izu-Bonin volcanic arc (Figure 1a). Around the collision zone, the Philippine Sea Plate moves northwest at 30-40 mm per year (Seno et al., 1993). In the past, the Philippine Sea Plate was subducting beneath central Japan; however, a buoyant aseismic ridge began to collide with the continental plate ∼20 Ma, resulting in a northward convex bend of its northern margin (Matsuda, 1978). During convergence, the Koma, Misaka, Tanzawa, and Izu Peninsula terranes (Figure 1b), which belonged to the Philippine Sea Plate, sequentially collided with the continental plate (Aoike, 1999). However, no such collided terranes have been identified at the northern margin of the Philippine Sea Plate, except for the Izu collision zone, and the plate is assumed to be subducting through the Nankai and Sagami troughs (Figure 1).Convergence between the two plates at the two subduction zones on either side of the collision zone causes slips at the subsurface plate interface. Repeated megathrust earthquakes along the Nankai and Sagami troughs (Ando, 1975;Kanda & Takemura, 2007) correspond to intermittent slips. The asperities of two megathrust earthquakes (the Kanto and Tokai earthquakes) are shown in Figure 1b.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Interpretation Of the Discontinuitymentioning

confidence: 99%

See 1 more Smart Citation

Relationship Between Crustal Structure and Plate Convergence Around the Izu Collision Zone in Central Japan

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…These results agree with our estimations that the tremor signals radiated from the deep part beneath the Hakone volcano, and propagated with the S-wave velocity. Ishise et al (2021) estimated that the depth of Moho discontinuity beneath the Hakone volcano is approximately 40 km using the anisotropic tomography method. These results suggest that the tremor signal radiated around the depth level of the uppermost mantle or lower crust.…”

Section: Discussionmentioning

confidence: 99%

Harmonic tremor from the deep part of Hakone volcano

Yukutake

Honda

Ukawa

et al. 2022

Earth Planets Space

View full text Add to dashboard Cite

The feeding system of magmatic fluid from the volcanic root to a shallow magma reservoir remains a poorly understood issue. Seismic events, including volcanic tremors and low-frequency earthquakes, in a deep part beneath volcanos are key observations for understanding the feeding system at the depth. Although deep low-frequency (DLF) earthquakes beneath volcanos have been recognized universally through dense seismic observations, volcanic tremors with harmonic frequency components originating at volcanic roots have rarely been observed. Here, we report the observation of a harmonic volcanic tremor event that occurred beneath the Hakone volcano on May 26, 2019. The tremor signal continued for approximately 10 min and was recognized at seismic stations 90 km away from the Hakone volcano. The apparent velocity of the tremor wave train is 5 km/s, corresponding to the S-wave velocity of the lower crust beneath the Hakone volcano. The frequency components varied with time. In the initial part of the tremor signal, a spectrum had a broad peak of around 1.2 Hz, whereas the tremor became harmonic with a sharp fundamental peak at 0.98 Hz in the latter part, increasing its amplitude. We estimated the source location of the volcanic tremor using the relative arrival times of the waveform envelope. The optimal source locations were estimated at a deep extension of the hypocenter distribution of the DLF earthquakes beneath the Hakone volcano, around the depth level of Moho discontinuity. The DLF earthquakes were activated immediately before the onset time of the volcanic tremor and continued for several months. The harmonic volcanic tremor may have been generated by the migration of magmatic fluid in the volcano’s deep region. Graphical Abstract

show abstract

“…In the past one and a half decades, a number of researchers have used the AAN tomographic methods to study the 3-D Vp structure and dynamics of many subduction zones, including New Zealand (Eberhart-Phillips and Henderson 2004; Eberhart-Phillips and Reyners 2009), NE Japan (Wang and Zhao 2008;Cheng et al 2011;Ishise et al 2018Ishise et al , 2021, SW Japan (Ishise and Oda 2008;Wang and Zhao 2012, 2013), South Kuril (Koulakov et al 2015aNiu et al 2016;Gou et al 2019b;Liu et al 2013), NW Pacific (Wei et al 2015;Ma et al 2019;Liang et al 2022), Taiwan-Philippine (Koulakov et al 2015b;Zhao 2019, 2021a), SE Asia (Koulakov et al 2009;Hua et al 2022;Wei et al 2022), Alaska (Tian and Zhao 2012;Gou et al 2019a), Cascadia (Zhao and Hua 2021), Central America (Rabbel et al 2011), Chile (Huang et al 2019), the Eastern Mediterranean and Middle East (Wei et al 2019), and Alps (Hua et al 2017;Rappisi et al 2022).…”

mentioning

confidence: 99%

Seismic Anisotropy Tomography and Mantle Dynamics

et al. 2023

View full text Add to dashboard Cite

Seismic anisotropy tomography is the updated geophysical imaging technology that can reveal 3-D variations of both structural heterogeneity and seismic anisotropy, providing unique constraints on geodynamic processes in the Earth’s crust and mantle. Here we introduce recent advances in the theory and application of seismic anisotropy tomography, thanks to abundant and high-quality data sets recorded by dense seismic networks deployed in many regions in the past decades. Applications of the novel techniques led to new discoveries in the 3-D structure and dynamics of subduction zones and continental regions. The most significant findings are constraints on seismic anisotropy in the subducting slabs. Fast-velocity directions (FVDs) of azimuthal anisotropy in the slabs are generally trench-parallel, reflecting fossil lattice-preferred orientation of aligned anisotropic minerals and/or shape-preferred orientation due to transform faults produced at the mid-ocean ridge and intraslab hydrated faults formed at the outer-rise area near the oceanic trench. The slab deformation may play an important role in both mantle flow and intraslab fabric. Trench-parallel anisotropy in the forearc has been widely observed by shear-wave splitting measurements, which may result, at least partly, from the intraslab deformation due to outer-rise yielding of the incoming oceanic plate. In the mantle wedge beneath the volcanic front and back-arc areas, FVDs are trench-normal, reflecting subduction-driven corner flows. Trench-normal FVDs are also revealed in the subslab mantle, which may reflect asthenospheric shear deformation caused by the overlying slab subduction. Toroidal mantle flow is observed in and around a slab edge or slab window. Significant azimuthal and radial anisotropies occur in the big mantle wedge beneath East Asia, reflecting hot and wet upwelling flows as well as horizontal flows associated with deep subduction of the western Pacific plate and its stagnation in the mantle transition zone. The geodynamic processes in the big mantle wedge have caused craton destruction, back-arc spreading, and intraplate seismic and volcanic activities. Ductile flow in the middle-lower crust is clearly revealed as prominent seismic anisotropy beneath the Tibetan Plateau, which affects the generation of large crustal earthquakes and mountain buildings.

show abstract

Improved 3‐D P Wave Azimuthal Anisotropy Structure Beneath the Tokyo Metropolitan Area, Japan: New Interpretations of the Dual Subduction System Revealed by Seismic Anisotropy

Cited by 8 publications

References 40 publications

Relationship Between Crustal Structure and Plate Convergence Around the Izu Collision Zone in Central Japan

Relationship Between Crustal Structure and Plate Convergence Around the Izu Collision Zone in Central Japan

Harmonic tremor from the deep part of Hakone volcano

Seismic Anisotropy Tomography and Mantle Dynamics

Contact Info

Product

Resources

About