Overview

Three-dimensional plate geometry model from the Nankai Trough to the Ryukyu Trench was constructed mainly from offshore seismic survey and observation results (Ref. 1), as part of the MEXT project “Research project for compound disaster mitigation on the great earthquakes and tsunamis around the Nankai Trough region” (FY2015–2019) and seismic tomography results (Ref. 5, 6). The model was later revised and updated using newly published results along five survey lines (ECr5, ECr6, ECr7, ECr11, ECr16) (Ref. 2). Both the original and updated models are presented here.

Important Notes for Use

• Accuracy and Reliability of the model is spatially heterogeneous.
• Spatial resolution depends on the accuracy of each seismic survey and tomography analysis, and therefore differs by survey line and observation area.
• The model is considered reliable from the trench axis to the west about depths of approximately 50–60 km considering the reliability of tomography results (Ref. 5, 6).
• Reliability in the middle Ryukyu Trench region is significantly low due to limited seismic study results.
• Details of the model construction method are provided in Reference (7).

Usage Procedures

1. Check JAMSTEC’s Data Policies, Basic Policy on the Protection of Personal Information, and Site Policy before using this model.

2. After agreeing to these policies, request the model data through the Data Request form

3. If you will use the models for research presentations, request through the Inquiry form in advance, and refer this site and DOI shown as below.

4. Redistribution of provided documents and data files is prohibited.

5. Again, please follow the Policies shown at 1.



DOI

JAMSTEC (2021) Subduction Philippine Sea plate geometry. JAMSTEC. doi:10.17596/0002217



Reference

(1) Annual Report of “Research project for compound disaster mitigation on the great earthquakes and tsunamis around the Nankai Trough region” (FY2019), 2020. (in Japanese)



(2) Nishizawa, A., Kaneda, K., Oikawa, M., Horiuchi, D., Fujioka Y., and Okada, C., Variation in velocity distribution along the Ryukyu(Nansei-Shoto) Trench subduction zone at the northwestern end of the Philippine Sea plate, Earth Planets and Space, 69, no.86, 2017, doi:10.1186/s40623-017-0674-7



(3) Arai, R., Takahashi, T., Kodaira, S., Kaiho, Y., Nakanishi, A., Fujie, G., Nakamura, Y., Yamamoto, Y., Ishihara, Y., Miura, S., and Kaneda, Y. , Structure of the tsunamigenic plate boundary and low-frequency earthquakes in the southern Ryukyu Trench, Nature communications, 2016, 7, 12255, doi:10.1038/ncomms12255



(4) Arai, R., Kodaira, S., Yamada, T., Takahashi, T., Miura, S., Kaneda, Y., Nishizawa, A., and Oikawa M., Subduction of thick oceanic plateau and high-angle normal-fault earthquakes intersecting the slab, Geophysical Research Letters, 2017, 44, p. 6109-6115, doi: 10.1002/2017GL073789



(5) Yamamoto, Y., Takahashi, T., Ishihara, Y., Kaiho, Y., Arai, R., Obana, K., Nakanishi, A., Miura, S., Kodaira S., and Kaneda, Y., Modeling the Geometry of Plate Boundary and Seismic Structure in the Southern Ryukyu Trench Subduction Zone, Japan, Using Amphibious Seismic Observations, J. Geophys. Res. Solid Earth, 2018, 123, 2, p.1793-1809, doi:10.1002/2017JB015330



(6) Yamamoto, Y., Takahashi,T., Ishihara, Y., Obana, K., Miura, S., Kodaira, S., and Kaneda, Y., Plate geometry model and seismicity in the northern Ryukyu subduction zone, Japan, deduced from amphibious seismic observations, Earth and Planetary Science Letters, 2020, 536, 116143, doi:10.1016/j.epsl.2020.116143



(7) Nakanishi, A., Takahashi, N., Yamamoto, Y., Takahashi, T., Citak, S. O., Nakamura, T., Obana, K, Kodaira, S., and Kaneda, Y., Three-dimensional plate geometry and P-wave velocity models of the subduction zone in SW Japan: Implications for seismogenesis, The Geological Society of America Special Paper , 2018, 534, 4, doi:10.1130/2018.2534(04)



(8) Kodaira, S., Iwasaki, T., Urabe, T., Kanazawa, T., Egloff, F., Makris, J., and Shimamura, H., Crustal structure across the middle Ryukyu trench obtained from ocean bottom seismographic data, Tectonophysics, 263, 1-4, p39-60, 1996, doi:10.1016/S0040-1951(96)00025-X