1,2,6,- 1GFZ Helmholtz Centre for Geosciences, Section of Earth Surface Process Modelling, Germany (luca.malatesta@gfz-potsdam.de)
- 2Tono Geoscience Center, Japan Atomic Energy Agency, Gifu, Japan
- 3Geosciences Rennes, University of Rennes 1, Rennes 35042, France
- 4Leibniz Institute for Applied Geophysics, Hannover 30655, Germany
- 5Department of Geography, Tokyo Metropolitan University, Hachioji, 192-0364, Japan
- 6Disaster Prevention Research Institute, Kyoto University, Kyoto, 611-0011, Japan
- 7Department of Earth Science, Tohoku University, Sendai, 980-8578, Japan
- 8Research Institute for Natural Hazards and Disaster Recovery, Niigata University, Niigata, 950-2181, Japan
- 9Center for Education and Research of Disaster Risk Reduction and Redesign, Oita University, Oita, 870-1192, Japan
On January 1st, 2024, the Mw 7.5 Noto Peninsula earthquake ruptured on a series of coastal offshore reverse faults in the back arc of central Japan. Closest to the rupture, in the northwest, the coastal rocks uplifted as much as 4.4 m (Fukushima Yo et al., 2024). The coastline accordingly moved seaward by up to 200 m creating new wide bedrock platforms. Recent Holocene terraces mapped along the northern coast (Shishikura et al., 2020), where coseismic uplift was greatest on January 1st 2024, suggest similar past ruptures. Many of the ruptured faults follow the coast at a depth of ca. 60 m below modern sea level. This is the average elevation of sea level over the last 500 kyr, and strongly suggests that these faults define the extent of the continental domain.
The Peninsula itself hosts 4767 unique mapped terraces ranging in age from Holocene to 1.02 Ma (Ota and Hirakawa, 1979, Koike and Machida, 2001). The terraces associated with the last two interglacial high stands (ca. 120 and 234 ka) record a tectonic SE-tilting similar to that of the Mw 7.5 earthquake. Older terraces all record a spatially uniform rate of uplift across the Peninsula. The landscape itself does not appear to be equilibrated to this gradient in uplift, with a seemingly disconnected fluvial geometry. We conclude that the faults that caused the most recent earthquake became the dominant structures on the Peninsula around 250 ka and that the Peninsula is in a state of transient equilibration.
80 km northeast of the Noto Peninsula lies the Island of Sado. The Island is made of two mountain ranges oriented SW-NE along the main tectonic lineation of the back arc, roughly parallel to the northern coast of Noto Peninsula. The marine terraces of the northern range, Oosado, record a strong southeast tilting synchronous and similar to that observed on the Noto Peninsula. The landscape morphology is not equilibrated to this pattern of deformation either. Earlier work by Ota et al., (1992) suggested that the tilt is driven by a fault lying just offshore of the Oosado coast. Closer inspection of the bathymetry reveals a ramp at around -60 m reflecting a geometry similar to the Noto Peninsula. The lessons from the Noto Peninsula earthquake can be applied to Sado Island where information about the seismic cycle is lacking. It confirms the hypothesis of Ota et al. (1992) and highlights a potential seismogenic source close to the shore.
Koike, K., & Machida, H. (2001). Atlas of Quaternary… Tokyo: University of Tokyo Press.
Ota, Y., & Hirakawa, K. (1979). Marine terraces and… Geographical Review of Japan, 52(4), 169–189.
Ota, Y., Miyawaki, A., & Shiomi, M. (1992). Active Faults on Sado Island… Journal of Geography (Chigaku Zasshi), 101(3), 205–224.
Shishikura, M., Echigo, T., & Namegaya, Y. (2020). Activity of the off-shore… Active Fault Research, 53, 33–49.
How to cite: Malatesta, L. C., Sueoka, S., Weiss, N.-M., Gailleton, B., Tsukamoto, S., Ishimura, D., Nishimura, T., Takahashi, N., Kataoka, K., Komatsu, T., and Iwasa, Y.: Active faults and coastal landscapes in the back arc of Central Japan, lessons from the Mw 7.5 Noto Peninsula earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11196, https://doi.org/10.5194/egusphere-egu25-11196, 2025.
