Earthquake hazard assessments for the Tokyo Region are complicated by the trench–trench triple junction where the oceanic Philippine Sea Plate not only underthrusts a continental plate but is also being subducted by the Pacific Plate. Great thrust earthquakes and associated tsunamis are historically recognized hazards from the Continental/Philippine Sea (Sagami Trough) and Continental/Pacific (Japan Trench) plate boundaries but not from the Philippine Sea/Pacific (Izu–Bonin Trench) boundary alone. Here we employed a series of historical and hypothetical rupture models to explain the widespread distribution of geological evidence for an unusually large tsunami found along 50 km of coastline east of Tokyo. Dating to about 1,000 years ago, this inferred tsunami predates local written history by several hundred years. We found that the inland extent of its sand sheet is best explained, in computer simulations, by displacement on one of the three plate boundaries offshore of the Boso Peninsula, which corresponds to the triple junction. The minimum magnitude scenario capable of generating the inland extent of inundation involves displacement along the Philippine Sea/Pacific boundary megathrust. This plate-boundary fault adds another potential source for earthquakes in the Tokyo Region and tsunamis in the Pacific Ocean.
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Code for the Bayesian model can be accessed at https://github.com/andrewcparnell/sand_ages_pilarczyk.
Committee for Subduction Zone Earthquakes in Japan and Kuril Trenches (10th Meeting) [in Japanese] (Cabinet Office Japanese Government, 2005); http://www.bousai.go.jp/kaigirep/chuobou/senmon/nihonkaiko_chisimajishin/10/index.html
Takeuchi, H. et al. Survey of run-up height of Empo Boso-oki Earthquake Tsunami on the coast from Chiba Prefecture to Fukushima Prefecture (in Japanese with English abstract). Rekishi Zishin 22, 53–59 (2007).
Uchida, N., Nakajima, J., Hasegawa, A. & Matsuzawa, T. What controls interplate coupling? Evidence for abrupt change in coupling across a border between two overlying plates in the NE Japan subduction zone. Earth Planet. Sci. Lett. 283, 111–121 (2009).
Shishikura, M. History of the paleo-earthquakes along the Sagami Trough, central Japan: review of coastal paleo-seismological studies in the Kanto region. Episodes 37, 246–257 (2014).
Sawai, Y., Namegaya, Y., Okamura, Y., Satake, K. & Shishikura, M. Challenges of anticipating the 2011 Tohoku earthquake and tsunami using coastal geology. Geophys. Res. Lett. 39, L21309 (2012).
Ozawa, S. et al. Coseismic and postseismic slip of the 2011 magnitude-9 Tohoku-oki earthquake. Nature 475, 373–376 (2011).
Simons, M. et al. The 2011 magnitude 9.0 Tohoku-Oki earthquake: mosaicking the megathrust from seconds to centuries. Science 332, 1421–1425 (2011).
Satake, K., Fujii, Y., Harada, Y. & Namegaya, Y. Time and space distribution of coseismic slip of the 2011 Tohoku earthquake as inferred from tsunami waveform data. Bull. Seismol. Soc. Am. 103, 1473–1492 (2013).
Satake, K. Geological and historical evidence of irregular recurrent earthquakes in Japan. Philos. Trans. R. Soc. A 373, 20140375 (2015).
Sawai, Y., Namegaya, Y., Tamura, T., Nakashima, R. & Tanigawa, K. Shorter intervals between great earthquakes near Sendai: scour ponds and a sand layer attributable to AD 1454 overwash. Geophys. Res. Lett. 42, 4795–4800 (2015).
Tormann, T., Enescu, B., Woessner, J. & Wiemer, S. Randomness of megathrust earthquakes implied by rapid stress recovery after the Japan earthquake. Nat. Geosci. 8, 152–158 (2015).
Usami, T. et al. Materials for Comprehensive List of Destructive Earthquakes in Japan 599–2012 (in Japanese) (Univ. Tokyo Press, 2013).
Watanabe, H. Comprehensive List of Tsunamis to Hit the Japanese Islands (in Japanese) (Univ. Tokyo Press, 1998).
Yanagisawa, H. et al. Tsunami earthquake can occur elsewhere along the Japan Trench—historical and geological evidence for the 1677 earthquake and tsunami. J. Geophys. Res. Solid Earth. 121, 3504–3516 (2016).
Masuda, F., Fujiwara, O., Sakai, T. & Araya, T. Relative sea-level changes and co-seismic uplifts over six millennia, preserved in beach deposits of the Kujukuri strand plain, Pacific coast of the Boso Peninsula, Japan. J. Geogr. (Chigaku zasshi) 110, 650–664 (2001).
Tamura, T., Murakami, F., Nanayama, F., Watanabe, K. & Saito, Y. Ground-penetrating radar profiles of Holocene raised-beach deposits in the Kujukuri strand plain, Pacific coast of eastern Japan. Mar. Geol. 248, 11–27 (2008).
Monecke, K. et al. A 1,000-year sediment record of tsunami recurrence in northern Sumatra. Nature 455, 1232–1234 (2008).
Jankaew, K. et al. Medieval forewarning of the 2004 Indian Ocean tsunami in Thailand. Nature 455, 1228–1231 (2008).
Koyama, M. A review of historical seismology in Japan: analyses and proposals for next stage of study of historical documents. J. Geogr. 108, 346–369 (1999).
Komori, J., Shishikura, M., Ando, R. & Yokoyama, Y. History of the great Kanto earthquakes inferred from the ages of Holocene marine terraces revealed by a comprehensive drilling survey. Earth Planet. Sci. Lett. 471, 74–84 (2017).
Barlow, N. L. M. et al. Salt marshes as late Holocene tide gauges. Glob. Planet. Change 106, 90–110 (2013).
Igarashi, T. Catalog of small repeating earthquakes for the Japanese Islands. Earth Planets Space 72, 73 (2020).
Namegaya, Y. & Satake, K. Reexamination of the A.D. 869 Jogan earthquake size from tsunami deposit distribution, simulated flow depth, and velocity. Geophys. Res. Lett. 41, 2297–2303 (2014).
Fujii, Y., Satake, K., Sakai, S., Shinohara, M. & Kanazawa, T. Tsunami source of the 2011 off the Pacific coast of Tohoku Earthquake. Earth Planets Space 63, 815–820 (2011).
Wei, D. & Seno, T. in Mantle Dynamics and Plate Interaction in East Asia (eds Flower, M. et al.) 337–346 (American Geophysical Union, 1998).
Hirose, F., Nakajima, J. & Hasegawa, A. Three-dimensional velocity structure and configuration of the Philippine sea slab beneath Kanto district, central Japan, estimated by double-difference tomography. J. Seismol. Soc. Jpn 60, 123–138 (2008).
Nakajima, J. & Hasegawa, A. Anomalous low-viscosity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: reactivation of subducted fracture zone? Geophys. Res. Lett. 33, L16309 (2006).
Nakajima, J., Hirose, F. & Hasegawa, A. Seismotectonics beneath the Tokyo metropolitan area: effect of slab-slab contact and overlap on seismicity. J. Geophys. Res. 114, B08309 (2009).
Long-Term Evaluation of Subduction Zone Earthquakes around the Sagami Trough (The Headquarters for Earthquake Research Promotion, 2004); https://www.jishin.go.jp/main/chousa/kaikou_pdf/sagami.pdf
1:25,000 Tsunami Flood Area Overview Map Technical Report D1-No. 592 (Geospatial Information Authority of Japan, 2011).
Pilarczyk, J. E. et al. Microfossils from coastal environments as indicators of paleo-earthquakes, tsunamis and storms. Palaeogeogr. Palaeoclimatol. Palaeoecol. 413, 144–157 (2014).
Bronk Ramsey, C. Radiocarbon calibration and analysis of stratigraphy: the OxCal program. Radiocarbon 37, 425–430 (1995).
Bronk Ramsey, C. Development of the radiocarbon program OxCal. Radiocarbon 43, 355–363 (2001).
Bronk Ramsey, C. & Lee, S. Recent and planned developments of the program OxCal. Radiocarbon 55, 720–730 (2013).
Reimer, P. J. et al. IntCal13 and Marine13 radiocarbon age calibration curves 0–50,000 years cal bp. Radiocarbon 55, 1869–1887 (2013).
Haslett, J. & Parnell, A. A simple monotone process with application to radiocarbon-dated depth chronologies. J. R. Stat. Soc. C 57, 399–418 (2008).
Parnell, A., Haslett, J., Allen, J., Buck, C. & Huntley, B. A flexible approach to assessing synchroneity of past events using Bayesian reconstructions of sedimentation history. Quat. Sci. Rev. 27, 1872–1885 (2008).
Rubin, C. et al. Highly variable recurrence of tsunamis in the 7,400 years before the 2004 Indian Ocean tsunami. Nat. Commun. 8, 16019 (2017).
Robert, C. & Casella, G. Introducing Monte Carlo Methods with R (Springer, 2010).
Hyndman, R. hdrcde: Highest Density Regions and Conditional Density Estimation (pkgdown, 2018); http://pkg.robjhyndman.com/hdrcde
Wickham, H. Ggplot2: Elegant Graphics for Data Analysis (Springer, 2016).
Okada, Y. Surface deformation due to shear and tensile faults in a half-space. Bull. Seismol. Soc. Am. 75, 1135–1154 (1985).
Goto, C., Ogawa, Y., Shuto, N. & Imamura, F. IUGG/IOC Time Project, Numerical Method of Tsunami Simulation with the Leap-Frog Scheme IOC Manuals and Guides 35 (UNESCO, 1997).
Sella, G. F., Dixon, T. H. & Mao, A. REVEL, a model for recent plate velocities from space geodesy, J. Geophys. Res. B https://doi.org/10.1029/2000JB000033 (2002).
Tamura, T., Murakami, F. & Watanabe, K. Holocene beach deposits for assessing coastal uplift of the northeastern Boso Peninsula, Pacific coast of Japan. Quatern. Res. 74, 227–234 (2010).
Wessel, P., Smith, W. H. F., Scharroo, R., Luis, J. & Wobbe, F. Generic Mapping Tools: improved version released. EOS Trans. AGU 94, 409–410 (2013).
GEBCO Bathymetric Compilation Group The GEBCO_2020 Grid—A Continuous Terrain Model of the Global Oceans and Land (British Oceanographic Data Centre, 2020); https://doi.org/10.5285/a29c5465-b138-234d-e053-6c86abc040b9
We thank B. Atwater, K. Satake and K. Ioki for their comments on an earlier version of the manuscript. This work is a contribution to IGCP Project 725, was supported by the Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST) and in part by grants awarded to J.E.P. (National Science Foundation (EAR-1303881 and 1624612), Natural Sciences and Engineering Council of Canada (NSERC), Canada Research Chair (CRC) program and Japan Society for the Promotion of Science (JSPS) International Research Fellows (Geological Survey of Japan, AIST, PE14038)), A.C.P. (Science Foundation Ireland Career Development Award (17/CDA/4695), Investigator Award (16/IA/4520), Marine Research Programme funded by the Irish Government, co-financed by the European Regional Development Fund (Grant-Aid Agreement no. PBA/CC/18/01), European Union’s Horizon 2020 research and innovation programme under grant agreement no. 818144 and SFI Research Centre (16/RC/3872 and 12/RC/2289_P2)) and B.P.H. (Singapore Ministry of Education Academic Research Fund (MOE2019-T3-1-004), National Research Foundation Singapore and Singapore Ministry of Education, under the Research Centers of Excellence initiative). This work is Earth Observatory of Singapore contribution 382. CT scanning (Fig. ED2I) was performed under the cooperative research programme of the Center for Advanced Marine Core Research (CMCR), Kochi University (no. 17A008). C.H.V. publishes with the permission of the Executive Director British Geological Survey.
The authors declare no competing interests.
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a, Modelled inundation at Kujukuri relative to the position of sand B. Index map, showing geomorphology, position of tsunami deposits (sand B), and inundation area estimated from model 10 for all three field sites in Sosa, Hasunuma, and Ichinomiya (Supplementary Fig. 2). b, Modelled inundation at Sosa (north Kujukuri) relative to the position of sand B. Core locations at Sosa relative to inundation resulting from models 1 (red line), 5 (yellow shaded area), 9 (white shaded area), and 10 (sky blue shaded area). Sky blue areas bounded by a dashed line represent the location of past reservoirs or ponds that are evident in historical maps from the Meiji era (c. 1868–1922 CE). Photograph from the Geospatial Information Authority of Japan (GSI; https://maps.gsi.go.jp/development/ichiran.html). c, Stratigraphic evidence for a tsunami at Sosa (north Kujukuri). Photograph and stratigraphic log of core shown in b.
a, Modelled inundation at Kujukuri relative to the position of sand B. Index map, showing geomorphology, position of tsunami deposits (sand B), and inundation area estimated from model 10 for all three field sites in Sosa, Hasunuma, and Ichinomiya (Supplementary Fig. 2). b, Modelled inundation at Hasunuma (central Kujukuri) relative to the position of sand B. Core locations at Hasunuma relative to inundation resulting from models 1 (red line), 5 (yellow shaded area), 9 (white shaded area), and 10 (sky blue shaded area). Sky blue areas bounded by a dashed line represent the location of past reservoirs or ponds that are evident in historical maps from the Meiji era (c. 1868–1922 CE). Photograph from Geospatial Information Authority of Japan (GSI; https://maps.gsi.go.jp/development/ichiran.html). c–f Stratigraphic evidence for two tsunamis at Hasunuma (central Kujukuri). Detailed cross section of stratigraphy from transect shown in b. g-h, Stratigraphic evidence for two tsunamis at Hasunuma (central Kujukuri). Photograph and stratigraphic log of core shown in c. i, Stratigraphic evidence for two tsunamis at Hasunuma (central Kujukuri). Photograph, stratigraphic log, and CT image of core shown in b.
a, Modelled inundation at Kujukuri relative to the position of sand B. Index map, showing geomorphology, position of tsunami deposits (sand B), and inundation area estimated from model 10 for all three field sites in Sosa, Hasunuma, and Ichinomiya (Supplementary Fig. 2). b, Modelled inundation at Ichinomiya (south Kujukuri) relative to the position of sand B. Core locations at Ichinomiya relative to inundation resulting from models 1 (red line), 5 (yellow shaded area), 9 (white shaded area), and 10 (sky blue shaded area). Sky blue areas bounded by a dashed line represent the location of past reservoirs or ponds that are evident in historical maps from the Meiji era (c. 1868–1922 CE). Photograph from Geospatial Information Authority of Japan (GSI; https://maps.gsi.go.jp/development/ichiran.html). c, Stratigraphic evidence for two tsunamis at Ichinomiya (south Kujukuri). Detailed cross section of stratigraphy from transect shown in b. d, Stratigraphic evidence for up to three tsunamis at Ichinomiya (south Kujukuri). Photograph and stratigraphic log of core shown in b, c.
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Pilarczyk, J.E., Sawai, Y., Namegaya, Y. et al. A further source of Tokyo earthquakes and Pacific Ocean tsunamis. Nat. Geosci. 14, 796–800 (2021). https://doi.org/10.1038/s41561-021-00812-2