Three-dimensional plate geometry and P-wave velocity models of the subduction zone in SW Japan: Implications for seismogenesis

Nakanishi, Ayako; Takahashi, Narumi; Yamamoto, Yojiro; Takahashi, Tsutomu; Citak, Seckin; Nakamura, Takeshi; Obana, Koichiro; Kodaira, Shuichi; Kaneda, Yasufumi

doi:10.1130/2018.2534(04)

Cited by 41 publications

(78 citation statements)

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“…The M7-class interplate earthquakes that were detected by the Japan Meteorological Agency since 1923 are indicated by the red stars. The iso-depths on the plate boundary (Nakanishi et al, 2018) are shown by the dashed purple contours (5-km interval). The black circles indicate the source distribution of shallow low-frequency tremor (Yamashita et al, 2015).…”

Section: Resultsmentioning

confidence: 99%

“…The parameters of each subfault in the model are summarized in Table 1. The depth and dip angles of the subfaults were determined using a plate boundary model (Nakanishi et al, 2018) that was obtained by compiling the structural data from offshore surveys. The slip amount in the model, which was determined by a trial-and-error process during the tsunami simulations, was set to be larger at shallower depths.…”

Section: Revised Fault Model For the 1662 Hyuga-nada Earthquakementioning

confidence: 99%

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Reconsideration of the Source Model for the 1662 Hyuga-nada Earthquake

Yamashita

Ioki

Kase

2020

Preprint

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Abstract The 1662 Hyuga-nada Earthquake is one of the largest earthquakes to have occurred in the Hyuga-nada region, Southwest Japan, rupturing the western part of the Nankai Trough subduction zone. Strong ground motion and a large tsunami with an estimated height of at least 4–5 m were reported along the coast of Miyazaki Prefecture, Kyushu Island, with extensive damage reported across this region. Therefore, developing a more complete picture of the 1662 Hyuga-nada Earthquake will improve our understanding of tsunami risk along the Pacific coast of Southwest Japan. Here we use the most recent geophysical data from the region to propose a novel source model for the 1662 Hyuga-nada Earthquake that incorporates our current understanding of the interactions between slow earthquakes and great earthquakes. The source area in our proposed model extends from the focal region of recurrent M7-class interplate earthquakes to the region of slow earthquakes that occur at relatively shallow depths along the plate boundary. Tsunami simulations indicate that the predicted coastal tsunami heights are broadly compatible with previously reported tsunami heights. This new model suggests that the 1662 Hyuga-nada Earthquake was probably a M8-class earthquake, and that previous magnitude determinations may have underestimated the strength of this historic earthquake. However, the model uncertainty remains large, and the calculated tsunami heights for the southern coast of Miyazaki Prefecture are very high. We suggest that future verification, including an analysis of tsunami-related deposits along the coast, will be important to more accurately determine the source area of the 1662 Hyuga-nada Earthquake.

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Section: Resultsmentioning

confidence: 99%

Section: Revised Fault Model For the 1662 Hyuga-nada Earthquakementioning

confidence: 99%

Reconsideration of the Source Model for the 1662 Hyuga-nada Earthquake

Yamashita

Ioki

Kase

2020

Preprint

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“…c 2D plate geometry model (Kodaira et al 2000). d 3D plate geometry model (Nakanishi et al 2018). e Hypocenter distributions (Akuhara et al 2013) geometry models, the depth to the top of the plate is represented as lines connecting the plate depths (Fig.…”

Section: Converting Equal-interval Data To Kmlmentioning

confidence: 99%

“…The 250-m equal-interval data are provided in a vertical section beneath the user-specified profile for 3D seismic velocity models or in a rectangular parallelepiped under the user-specified search region for 3D plate geometry models. For 2D seismic velocity and Nakajima and Hasegawa (2007), the 3D plate geometry model from Nakanishi et al (2018), the 2D plate geometry and seismic velocity models from Kodaira et al (2006), and the hypocentral distribution from Akuhara et al (2013). The green rectangle on the Earth's surface shows the userdefined search area.…”

Section: Use Of 250-m Equal-interval Gridded Datamentioning

confidence: 99%

“…Therefore, the database can simultaneously visualize several seismic structure models, regardless of the model types. Figure 5 shows a visual comparison of 3D plate geometry (Nakanishi et al 2018) and seismic velocity models (Nakajima and Hasegawa 2007), 2D plate geometry and seismic velocity models (Kodaira et al 2006), and hypocentral distributions (Akuhara et al 2013). Differences between the 3D plate geometry model, 3D seismic velocity model, and hypocenters are notable at greater depths; for example, hypocenters located at the subducting slab interface are consistently deeper than the top of the slab in the 3D plate geometry model.…”

Section: Visualization Of Seismic Structure Modelsmentioning

confidence: 99%

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Development of a database and visualization system integrating various models of seismic velocity structure and subducting plate geometry around Japan

Yamagishi

Nakanishi

Miura

et al. 2018

Prog Earth Planet Sci

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To estimate strong ground motions caused by future earthquakes in Japan and to more accurately predict seismic hazards and tsunamis, it is necessary to accurately model the geometry of the subducting plate and the seismic velocity structure around Japan, particularly in offshore areas. Although various seismic velocity structure and plate boundary models have been proposed around Japan, they are all managed individually and differ in extent, data type, and format. Ensuring consistency among those models requires knowledge of their spatial distribution around the subduction zones of Japan. Here, we describe a database system to store and serve various velocity structure and plate geometry datasets from around Japan. Seismic structure models in this database include 3D seismic velocity models obtained by seismic tomography, 3D plate geometry models, 2D seismic velocity structure models, 2D plate geometry models obtained by offshore seismic surveys, and hypocenter distributions determined by offshore observations and the Japan Meteorological Agency. Using this database (currently available only in Japanese), users can obtain data from several structural models at once in the form of the original model data, equal-interval gridded data in a text file, and Keyhole Markup Language (KML) data. Users can grasp the distributions of all available seismic models and hypocenters using a web-based interface, simultaneously view various models and hypocenters as KML output files in Google Earth, and easily and freely handle the structural models in a selected area of interest using the gridded text-file output data. This system will be useful in creating more accurate models of the geometries of the subducting plate and the seismic velocity structure around Japan.

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Modelling temporal changes in the gravity field in the Nankai Trough subduction zone, Japan

Vassvåg¹

2021

Preprint

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The Nankai trough subduction zone off southwest Japan is prone to large earthquakes, causing tsunamis and great damages to the nearby islands. Linking the sources of these earthquakes to asperities along the plate interface is of great importance in monitoring earthquake and tsunami activity at the subduction zone. However, the location of asperities near the trough axis at the Nankai trough are not well constrained. During the interseismic period between megathrust earthquakes, shallow slow earthquakes occurring along the interface are messengers of the stress distribution outside of these asperities. They occur on areas were fluid migration on the interface leads to loosely coupled regions. Through gravity measurements, small changes in subsurface density caused by this fluid migration can be detected. These changes can be observed through time-lapse gravimetric surveys at the seafloor, allowing for detailed mapping of these gravity anomalies.In addition, I wish to thank my parents, Theresa and Sigbjørn, and my sisters, Monique and Sarita, for always being supportive and for providing helpful advice. In particular, thank you for taking the time to proofread all these pages.Last, but not least, thanks to my friends for their companionship and for being there when I needed to unwind during the last year of my studies. I would also like to give warm thanks to my classmates for five and a half years of their company, in particular Vilde and Regine for making my time in Bergen "the best".

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Three-dimensional plate geometry and P-wave velocity models of the subduction zone in SW Japan: Implications for seismogenesis

Cited by 41 publications

References 0 publications

Reconsideration of the Source Model for the 1662 Hyuga-nada Earthquake

Reconsideration of the Source Model for the 1662 Hyuga-nada Earthquake

Development of a database and visualization system integrating various models of seismic velocity structure and subducting plate geometry around Japan

Modelling temporal changes in the gravity field in the Nankai Trough subduction zone, Japan

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