Suruga Trough

Suruga Trough
Name	Suruga Trough
Location	Pacific Ocean
Type	Trough
Countries	Japan

Suruga Trough is a submarine trough located off the coast of Honshū in Japan, marking a major structural boundary between the Philippine Sea Plate and the Eurasian Plate. It forms part of a complex convergent margin that includes nearby features such as the Nankai Trough, Izu Peninsula, and Sagami Bay, and is associated with frequent seismicity and tsunami generation. The trough has been studied by numerous institutions including the Japan Agency for Marine-Earth Science and Technology, University of Tokyo, and international collaborations involving the United States Geological Survey and Geological Survey of Japan.

Geography and Morphology

The trough lies off the coast of central Honshū near cities such as Shizuoka (city), Atami, and Numazu and is adjacent to the Izu–Bonin–Mariana Arc and the Philippine Sea Plate margin, connecting to the larger Nankai Trough along the Sagami Trough corridor. Bathymetric mapping by vessels like RV Mirai and surveys from the Japan Marine Science and Technology Center reveal a steep trench-like depression, submarine terraces, and active submarine canyons oriented towards the Pacific Ocean. The morphology is influenced by accretionary prisms and forearc basins that link to onshore geomorphology of the Izu Peninsula and the Akaishi Mountains, with shelf breaks near the Suruga Bay coastline and submarine fans extending seaward.

Tectonic Setting and Geology

The trough overlies the plate interface where the Philippine Sea Plate subducts beneath the Eurasian Plate along a convergent margin that includes the Nankai megathrust system, the Sagami Trough, and the Izu collision zone. Geological investigations integrate data from the Integrated Ocean Drilling Program, geological mapping by the Geological Survey of Japan, and seismic reflection profiles from research cruises conducted by JAMSTEC and teams from the University of Tokyo. The stratigraphy includes accreted sediments, mélanges, and uplifted seamounts connected to the Izu–Bonin arc; igneous activity relates to arc volcanism manifested by features like Mount Fuji and submarine volcanic edifices. Tectonic models reference interactions with fracture zones such as the Japan Trench and regional structures including the Median Tectonic Line and the Fossa Magna.

Seismicity and Earthquake History

The trough is part of a high-rate seismic zone with historical earthquakes documented by national archives alongside global catalogs maintained by the USGS, International Seismological Centre, and the Japan Meteorological Agency. Notable regional seismic events involve rupture segments associated with the Nankai earthquakes, the Ansei Edo earthquake era records, and instrumental records from networks like the Hi-net and K-NET. Paleoseismology and turbidite records studied by teams from University of Tokyo, Hokkaido University, and Kyoto University indicate repeated megathrust earthquakes and slow-slip events also observed by the Global Navigation Satellite System and the Dense Oceanfloor Network System for Earthquakes and Tsunamis. Seismic tomography studies by researchers at Tohoku University and Scripps Institution of Oceanography image complex plate geometry and locked-to-creeping transitions controlling rupture propagation.

Tsunami Hazard and Risk

Historical tsunami catalogs curated by the Japan Meteorological Agency and modeled by groups at Port and Airport Research Institute and Pacific Tsunami Warning Center show the trough can generate local tsunamis affecting ports including Shimizu Port, Numazu Port, and Atami Port as well as broader impacts along the Pacific coast of Honshu and distant effects recorded at Hawaii and California in some scenarios. Tsunami hazard assessment employs inland inundation models developed by the National Research Institute for Earth Science and Disaster Resilience, probabilistic seismic hazard analysis techniques used by the Cabinet Office (Japan), and scenario planning from multinational collaborations with the UNESCO Intergovernmental Oceanographic Commission. Warning and mitigation rely on networks such as the Japan Meteorological Agency tsunami warning system, local disaster management offices in Shizuoka Prefecture, and evacuation planning informed by historical events like the 1707 Hōei earthquake.

Marine Ecosystems and Sedimentology

Sediment cores recovered by expeditions from JAMSTEC, the Ocean Drilling Program, and universities reveal turbidites, hemipelagic sediments, and organic-rich layers that record earthquake and tsunami depositional events; bioturbation and benthic assemblages reflect influences from currents tied to the Kuroshio Current and regional productivity regimes. Marine biodiversity surveys by institutions such as the National Institute for Environmental Studies and the Tokyo University of Marine Science and Technology document communities of demersal fishes, chemosynthetic organisms near cold seeps, and benthic invertebrates influenced by sediment fluxes from rivers like the Fuji River and Kamo River. Sedimentology integrates research on slope stability, submarine landslides, and gas hydrate indicators studied by teams at National Institute of Advanced Industrial Science and Technology and international partners including Lamont–Doherty Earth Observatory.

Human Impacts and Monitoring

The coastal population centers of Shizuoka Prefecture and tourism hubs such as Atami and Izu Peninsula rely on infrastructure—ports, highways, and railways like the Tōkaidō Main Line—that are vulnerable to seismic and tsunami hazards originating from the trough. Monitoring and research are coordinated by agencies including JAMSTEC, the Japan Meteorological Agency, the Cabinet Office (Japan), and international partners such as the USGS and IOC/UNESCO, employing ocean-bottom seismometers, GPS networks like GEONET, and real-time tsunami buoys from the DART system. Disaster preparedness involves local governments, the Ministry of Land, Infrastructure, Transport and Tourism, university outreach programs from University of Tokyo and Shizuoka University, and community drills supported by the Japanese Red Cross Society and non-governmental organizations.

Category:Geology of Japan Category:Oceanic trenches Category:Seismic zones