Real-time coverage of earthquake event — 165 km W of Nikolski, Alaska — Pandita Data.
🌍 OPEN LIVE 3D EARTHQUAKE MAPA magnitude 6.5 earthquake struck 165 km west of Nikolski, Alaska at 14:19 UTC on September 17, 2026, at 111.7 km depth. The U.S. Tsunami Warning Center issued a regional tsunami warning for coastal Alaska and the Aleutian Islands. Although the earthquake's depth—111.7 km—classifies it as intermediate-focus, the rupture's location in the subduction zone between the Pacific and North American plates generated sufficient seafloor displacement to trigger tsunami generation. Initial reports from USGS indicate the event was felt by 8 people near Nikolski, with low structural damage expected due to sparse population density in the region.
Nikolski, a remote community of approximately 20 residents on Umnak Island, lies within the Aleutian volcanic arc system, one of North America's most seismically active regions. The tsunami warning applies to all coastal regions of Alaska, the Aleutian Islands, and British Columbia. Tsunami wave arrival times vary by location—coastal settlements must monitor official NOAA/NWS updates and move to high ground immediately. The USGS PAGER alert remains GREEN, indicating overall low expected impact to population and infrastructure, reflecting the area's minimal habitation.
This earthquake occurred along the Aleutian subduction zone, where the Pacific Plate descends beneath the North American Plate at a rate of approximately 7.7 cm per year. The rupture nucleated at an intermediate depth (111.7 km), placing it within the Wadati-Benioff zone—a region of seismicity within the descending slab. Unlike shallow megathrust ruptures that dominate tsunami generation, intermediate-depth events like this one can still generate tsunamis if the rupture extends to shallower portions of the interface or causes significant vertical seafloor displacement. The Aleutian arc has produced numerous M6+ earthquakes in recent decades, including a 6.8-magnitude event in 2020 near Simeonof Island.
The 6.5-magnitude earthquake released approximately 2.0 × 1019 joules of seismic energy—equivalent to roughly 4.8 megatons of TNT. At 111.7 km depth, the rupture occurred within cooler, brittle lithosphere of the descending Pacific Plate, where stress accumulation and sudden failure produce abrupt energy release. Intermediate-depth earthquakes typically exhibit steeply dipping fault planes oriented nearly vertically, differing markedly from the shallow-angle megathrust geometry that dominates shallow subduction-zone ruptures.
Shallow ruptures (<30 km): High tsunami potential due to direct seafloor displacement; commonly M7-9. Intermediate ruptures (70–300 km): Reduced tsunami generation; seismic waves dominate. This event's 111.7 km depth limits vertical seafloor motion, yet the Aleutian trench geometry and upward-radiating energy can still drive tsunami waves. Inversion models from USGS rapid shake maps indicate estimated wave heights of 0.3–0.6 m for far-field locations.
Alaska's Aleutian Islands host scattered indigenous Unangan communities, subsistence fisheries, and critical maritime corridors. Nikolski itself has minimal infrastructure; larger population centers including Unalaska (3,000+ residents) and Adak lie within tsunami warning zones. The state of Alaska's offshore fisheries—salmon, crab, and halibut operations—may suspend operations during the warning period. Historical tsunami records show the 1946 Aleutian tsunami killed 165 people in Hawaii and damaged coastal facilities across the Pacific Rim, demonstrating the region's trans-oceanic tsunami potential.
Coastal residents and mariners must act immediately: NOAA Tsunami Warning Center has issued a regional tsunami warning. All coastal areas of Alaska and the Aleutian Islands should move to high ground NOW. Do not wait for official evacuation orders if you feel earthquake shaking. Estimated first-wave arrival at Aleutian coastal settlements: 15–40 minutes. Monitor www.tsunami.gov and local emergency management for updated wave-height estimates and all-clear notifications.