Real-time coverage of earthquake event — 42 km E of Noda, Japan — Pandita Data.
🌍 OPEN LIVE 3D EARTHQUAKE MAPA magnitude 5.6 earthquake struck 42 km east of Noda, Japan at 17:57 UTC on August 8, 2026, at a depth of 34 km. No tsunami warning was issued. The USGS PAGER alert remained green, indicating minimal expected impacts to structures and population.
This moderate-magnitude event occurred along Japan's most seismically active zone—the subduction interface where the Pacific Plate descends beneath the North American Plate at rates exceeding 8 cm per year. The rupture mechanics, depth, and location place this earthquake within the transition zone between shallow megathrust ruptures (which generate tsunamis) and deeper intermediate-depth seismicity. At 34 km depth, this event likely involved brittle failure within the subducting Pacific slab itself, rather than at the plate interface, explaining the absence of tsunami potential.
Eastern Honshu lies directly above the Japan Trench, where the Pacific Plate subducts at one of Earth's fastest rates. This region has generated the largest earthquakes on record—including the 2011 Tōhoku M9.1 megathrust event. The Noda area, in Chiba Prefecture, experiences frequent seismicity from both megathrust ruptures and intraslab earthquakes within the descending Pacific slab. Intraslab earthquakes like this August 8 event occur within the cold, brittle interior of the subducting plate, typically at depths of 30–200 km, and pose different hazards than shallow megathrust ruptures.
At magnitude 5.6, this earthquake released approximately 1.4 × 1020 joules of energy—equivalent to 33 kilotons of TNT. The 34 km depth classifies this as an intermediate-depth intraslab rupture. Such events radiate seismic energy efficiently through the cold, rigid slab material, meaning ground motion can be felt over larger distances than shallow earthquakes of the same magnitude. However, because the rupture occurred entirely within the downgoing slab (not at the plate interface), no vertical seafloor displacement occurred, and therefore no tsunami was generated.
Tsunamis require significant vertical displacement of the seafloor or water column. Intraslab earthquakes rupture horizontally within the descending plate, producing minimal seafloor motion. Only shallow megathrust ruptures (depths <30 km) at subduction zones generate dangerous tsunamis. The 2011 Tōhoku earthquake was a megathrust event at ~25 km depth; this August 2026 rupture occurred 9 km deeper, within the slab interior.
Chiba Prefecture, home to ~6.2 million people including eastern Tokyo suburbs, experienced moderate to light shaking. The USGS PAGER alert remained green, with expected structural damage rated minimal and fatalities unlikely. However, residents in nearby Noda (population ~150,000) and surrounding cities would have felt the earthquake as a strong jolt lasting 10–20 seconds. Given Japan's world-leading seismic building codes and earthquake early-warning systems, injuries and property damage are expected to be negligible. This event serves as a reminder that intermediate-depth subduction-zone earthquakes are a permanent feature of Japan's hazardscape and testing of early-warning infrastructure remains critical.