Configuration of the Moho discontinuity beneath the Japanese Islands derived from three-dimensional seismic tomography

Matsubara, Makoto; Satō, Hiroshi; Ishiyama, Tatsuya; Horne, Anne Van

doi:10.1016/j.tecto.2016.11.025

Cited by 43 publications

(35 citation statements)

References 58 publications

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“…In other words, the hypocenters are separated into a shallow spot at a depth of 10-15 km and a deep spot at a depth of 20-27 km, while the hypocenters of DLF earthquakes in most of the other volcanoes have continuous distributions in the vertical direction according to the JMA catalog. Both spots are above the Moho discontinuity in the Kirishima volcanoes at the depth of approximately 30 km here (Matsubara et al, 2017).…”

Section: Methodsmentioning

confidence: 78%

Deep Low‐Frequency Earthquakes Associated With the Eruptions of Shinmoe‐dake in KirishimaVolcanoes

et al. 2019

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Deep low‐frequency (DLF) earthquakes occur beneath the Kirishima volcanoes in southwest Japan at depths of 10–30 km. In this study, we aim to reveal the relationship between DLF earthquakes and volcanic activity including eruptions by relocating the hypocenters of the earthquakes using the network correlation coefficient method and detecting the earthquakes comprehensively using the matched filter technique. Hypocenters of DLF earthquakes are found to be concentrated in some separated small clusters within depths of 10–15 and 20–27 km. Activation of deeper DLF earthquakes had been observed for approximately 2 years from December 2009, during which various styles of eruptions occurred. Such a 2‐year increase in DLF seismicity was well correlated with crustal deformation because of the volume change of a magma reservoir. The waveforms and hypocenters of DLF earthquakes during the activation period were different from those during other time periods. The activated DLF earthquakes mostly had low dominant frequencies and were located in four deeper clusters. The activation of each cluster was switched 3 times at the transition of the eruption styles. These results suggest that DLF earthquakes might occur near magma sills and could be triggered by fluid flow in the changing paths by complex eruption processes. In addition, the waveforms and hypocenters of DLF earthquakes associated with the 2018 eruptions are different from those associated with the 2011 eruptions. The fluid paths of the 2018 eruptions might be different from those of the 2011 eruptions.

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Section: Methodsmentioning

confidence: 78%

Deep Low‐Frequency Earthquakes Associated With the Eruptions of Shinmoe‐dake in KirishimaVolcanoes

et al. 2019

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“…A large white circle is a hypocenter of the main shock determined by the present study. The Moho byMatsubara et al (2017b) is shown by yellow circles. White circles show the top of the Pacific Plate by…”

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confidence: 99%

Structural heterogeneity in and around the fold-and-thrust belt of the Hidaka Collision zone, Hokkaido, Japan and its relationship to the aftershock activity of the 2018 Hokkaido Eastern Iburi Earthquake

Iwasaki

Tsumura

Ito

et al. 2019

Earth Planets Space

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The Hokkaido Eastern Iburi Earthquake (M = 6.7) occurred on Sep. 6, 2018 in the southern part of Central Hokkaido, Japan. Since Paleogene, this region has experienced the dextral oblique transpression between the Eurasia and North American (Okhotsk) Plates and the subsequent collision between the Northeast Japan Arc and the Kuril Arc due to the oblique subduction of the Pacific Plate. This earthquake occurred beneath the foreland fold-and-thrust belt of the Hidaka Collision zone developed by the collision process, and is characterized by its deep focal depth (~ 37 km) and complicated rupture process. The reanalyses of controlled source seismic data collected in the 1998-2000 Hokkaido Transect Project revealed the detailed structure beneath the fold-and-thrust belt, and its relationship with the aftershock activity of this earthquake. Our reflection processing using the CRS/MDRS stacking method imaged for the first time the lower crust and uppermost mantle structures of the Northeast Japan Arc underthrust beneath a thick (~ 5-10 km) sedimentary package of the fold-and-thrust belt. Based on the analysis of the refraction/wideangle reflection data, the total thickness of this Northeast Japan Arc crust is only 16-22 km. The Moho is at depths of 26-28 km in the source region of the Hokkaido Eastern Iburi Earthquake. Our hypocenter determination using a 3D structure model shows that most of the aftershocks are distributed in a depth range of 7-45 km with steep geometry facing to the east. The seismic activity is quite low within the thick sediments of the fold-thrust belt, from which we find no indication on the relationship of this event with the shallow (< 10-15 km) and rather flat active faults developed in the fold-and-thrust belt. On the other hand, a number of aftershocks are distributed below the Moho. This high activity may be caused by the cold crust delaminated from the Kuril Arc side by the arc-arc collision, which prevents the thermal circulation and cools the forearc uppermost mantle to generate an environment more favorable for brittle fracture. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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“…This suggests that the brittle part may have extended to that depth in the source region. Note that the Moho depth in the source region has been estimated to be 32-34 km (Katsumata 2010, Matsubara et al 2017. The centroid depth of the Global CMT solution is 31 km, which is approximately 9 km deeper than the depth of the large slip in our model.…”

Section: Discussionmentioning

confidence: 69%

Rupture process of the 2018 Hokkaido Eastern Iburi earthquake derived from strong motion and geodetic data

Kobayashi

Koketsu

2019

Earth Planets Space

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The source rupture process of the 2018 Hokkaido Eastern Iburi earthquake was investigated by performing a joint inversion analysis using the strong motion and geodetic data. A fault model that consists of two fault planes was constructed by considering the relocated aftershock distribution and the focal mechanisms. The inversion result showed that the large slip occurred at approximately 22 km depth, which was much shallower than the hypocentral depth. Our results showed that the rupture initiated on the minor fault plane around the hypocenter and the major fault plane started to rupture 4-6 s after the rupture initiation. Although the shape of the minor fault plane has not been clearly determined, the major fault plane appears to be high-angle, east-dipping. An additional inversion with only the major fault plane showed that the strong ground motion near the source was mainly generated from the major fault plane. The total seismic moment estimated by the inversion with the two fault-plane model was 1.1 × 10 19 Nm, which yielded an M w of 6.6. Using the inversion result of the two fault-plane model, we simulated the ground surface and borehole waveforms at strong motion station IBUH03 where the large velocity pulse was observed on the ground surface. The simulations suggest that this large velocity pulse was generated from the combination of the large slip of the source and large site amplification of the velocity structure between the ground surface and borehole seismometers.

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Configuration of the Moho discontinuity beneath the Japanese Islands derived from three-dimensional seismic tomography

Cited by 43 publications

References 58 publications

Deep Low‐Frequency Earthquakes Associated With the Eruptions of Shinmoe‐dake in KirishimaVolcanoes

Deep Low‐Frequency Earthquakes Associated With the Eruptions of Shinmoe‐dake in KirishimaVolcanoes

Structural heterogeneity in and around the fold-and-thrust belt of the Hidaka Collision zone, Hokkaido, Japan and its relationship to the aftershock activity of the 2018 Hokkaido Eastern Iburi Earthquake

Rupture process of the 2018 Hokkaido Eastern Iburi earthquake derived from strong motion and geodetic data

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