New Study Reveals Tsunamigenic Fault Structures in 2024 Noto Peninsula Earthquake

The 2024 Noto Peninsula earthquake stands as one of Japan's most devastating seismic events in recent decades, striking on January 1 with a magnitude of 7.6. Centered off the northern coast of Ishikawa Prefecture, this reverse-fault earthquake unleashed powerful shaking, widespread landslides, raging fires, and a tsunami that battered coastal communities. The disaster claimed over 480 lives, including both direct casualties from the quake and subsequent disaster-related deaths, injured thousands more, and left more than 180,000 buildings damaged or destroyed across multiple prefectures. The tsunami, reaching heights exceeding 5 meters in some areas, exacerbated the destruction, flooding low-lying regions and complicating rescue efforts amid ongoing aftershocks.

In the aftermath, Japanese researchers mobilized swiftly, conducting rapid-response surveys to unravel the subsurface mechanics behind the event. A groundbreaking study published today in Scientific Reports, a Nature journal, provides the first detailed imaging of tsunamigenic fault structures within the rupture zone. Led by Jin-Oh Park from the University of Tokyo's Atmosphere and Ocean Research Institute (AORI), the research highlights complex fault geometries that amplified seafloor uplift, fueling the destructive waves.

Tracing the Roots: Pre-Earthquake Fault Awareness in Japan

Prior to 2024, the Noto Peninsula region was known for its active tectonics within Japan's back-arc basin of the Sea of Japan. Government-led initiatives, including the Japan Sea Earthquake and Tsunami Research Project (JSPJ) and surveys by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), had mapped potential offshore faults. These efforts identified multiple reverse faults dipping southeastward along the northern peninsula coast, capable of generating magnitude 7+ quakes and tsunamis.

Seismic swarms had rattled the area for years, peaking in late 2023, signaling stress buildup. Historical precedents, like the 2007 Noto Hanto earthquake (Mw 6.7), ruptured nearby segments, underscoring the segmented nature of the fault system. Academic institutions played a pivotal role in these preparatory studies, with the University of Tokyo's Earthquake Research Institute (ERI) contributing fault models through waveform analysis and geodetic data.

Methodology: Rapid Seismic Imaging Post-Quake

The new research exemplifies Japan's world-class capacity for post-disaster scientific response. Just two months after the quake, aboard the research vessel R/V Hakuho-maru, scientists from the University of Tokyo's AORI and collaborators deployed high-resolution multichannel seismic (MCS) reflection surveys. Equipped with GI guns and a 1,200-meter 48-channel streamer, they acquired data along key transects off the northeastern Noto coast.

Advanced processing— including pre-stack depth migration (PSDM) with velocity model refinement—yielded unprecedented images of shallow crustal structures down to 2 kilometers depth. Coupled with tsunami numerical modeling using JAGURS software, which solves nonlinear Boussinesq equations on a 50-meter grid, the team validated fault slips against observed wave heights at tide gauges. This interdisciplinary approach, blending geophysics, oceanography, and computational modeling, showcases the rigor of Japanese higher education in earth sciences.

Discovering the Large Deformation Zone: A Tsunami Generator

Central to the findings is the Large Deformation Zone (LDZ), a 2.5–3.8 km wide, 30 km long band of intensely deformed strata spanning subfaults NT4 and NT5. Seismic profiles reveal steeply southeast-dipping reverse faults (50°–75°), forming flower-like structures with pop-up blocks elevating the seafloor by up to 70 meters cumulatively. Branching faults hint at strike-slip components, complicating rupture dynamics.

These structures, shallow extensions of deeper listric seismogenic faults from back-arc rifting inversion, slipped 6–7 meters during the event, producing 3 meters of uplift. This vertical displacement displaced seawater, launching the initial tsunami. Simulations confirm this matches observations, with Aida indices indicating high fidelity (K=0.95–1.05).

Contrasting Fault Behaviors: Northwest-Dipping Segments

Not all faults participated equally. Northwest-dipping reverse faults (50°–55°) in NT2–NT3 regions showed evidence of past activity—fault scarps up to 110 meters high and tilted strata—but minimal 2024 slip (0–1 meter). Aftershocks, including a Mw 6.1, cluster here, suggesting locked stress for potential future ruptures up to Mw 7.8, as warned by Japan's Earthquake Research Committee.

This asymmetry explains why tsunami energy focused northeastward, while southwestern areas saw less impact. The study underscores how fault orientation and prior stressing influence participation in multi-segment ruptures.

Photo by Artem Beliaikin on Unsplash

University of Tokyo: Epicenter of Seismological Excellence

The University of Tokyo, Japan's premier institution for earth sciences, spearheaded this discovery. AORI's Jin-Oh Park, an expert in subduction dynamics, coordinated the seismic survey, leveraging UTokyo's fleet and expertise. ERI's Kenji Satake, in an earlier companion study, mapped slip distributions using tsunami waveforms and GNSS data, pinpointing 3–3.5 meter slips on NT4–NT6 subfaults.Details of Satake's model.

UTokyo's dual institutes exemplify integrated research: AORI focuses on marine geophysics, ERI on seismology. Their alumni dominate Japan's disaster mitigation agencies, training generations in fault imaging and hazard assessment.

Collaborative Power: Chuo University and JAMSTEC

Chuo University's Graduate School of Science and Engineering contributed tsunami modeling expertise via Taro Arikawa and Tomoya Kurihara, refining simulations to isolate LDZ effects. JAMSTEC, Japan's marine research powerhouse, provided vessel support and researchers like Gou Fujie and Kentaro Imai, whose ocean-bottom observatories informed fault depths.

Such partnerships highlight Japan's academic ecosystem, where national labs and universities co-drive breakthroughs. Geoscience Enterprise Inc. added industry perspective on data processing.

Enhancing Tsunami Forecasting and Mitigation

By linking shallow faults to tsunami sources, the study refines models for back-arc settings. Traditional simulations underestimated waves at distant Niigata and Sado Island; incorporating LDZ uplift improves predictions. This informs updates to Japan's tsunami hazard maps, emphasizing multi-fault scenarios.

For coastal engineering, it stresses resilient designs against near-field tsunamis from shallow ruptures. Universities now integrate these insights into curricula, preparing students for advanced modeling tools.

Future Risks and Ongoing Monitoring

The northwest faults remain a concern, with government alerts for M7+ events. Low recent activity northeastward suggests tapering risk, but 3D imaging and drilling are recommended. UTokyo and JAMSTEC plan follow-ups, monitoring aftershocks and fluids for precursors.

This positions Japanese academia at the vanguard of 'slow-to-fast' earthquake physics, blending geodesy, seismology, and AI for early warnings.

Careers in Seismology: Opportunities at Japanese Universities

Japan's top institutions seek experts in fault tectonics and tsunami dynamics. UTokyo's AORI and ERI offer professor and research positions, fostering international collaborations. Chuo University expands coastal engineering programs, while JAMSTEC recruits postdocs for marine surveys. These roles blend fieldwork, computation, and policy impact, ideal for PhD holders passionate about disaster science.

With rising global seismic risks, demand surges for graduates skilled in PSDM and Boussinesq modeling.

Photo by Roman Kraft on Unsplash

This landmark research not only demystifies the 2024 catastrophe but fortifies Japan's defenses against future threats. Collaborative efforts by University of Tokyo, Chuo University, and partners exemplify higher education's vital role in safeguarding society. As monitoring continues, these insights promise safer coasts and inspired careers in geohazards.