Magnitude 5.8 earthquake struck 292 km WSW of Adak, Alaska at 26.5 km depth on May 9, 2026. No tsunami warning. Routine outer-rise seismicity in Aleutian megathrust zone.
🌍 OPEN LIVE 3D EARTHQUAKE MAPA magnitude 5.8 earthquake struck 292 km west-southwest of Adak, Alaska on May 9, 2026 at 04:42 UTC, rupturing at a depth of 26.5 km in one of the North Pacific's most seismically active regions. The US Geological Survey recorded no tsunami warning and assigned a GREEN PAGER alert, indicating minimal expected impact to populated areas. Zero felt reports were logged, consistent with the remote offshore location in the Aleutian subduction zone.
The Adak region sits along the Aleutian megathrust—where the Pacific Plate subducts beneath the North American Plate at a rate of approximately 7.6 cm per year. This convergent boundary is one of Earth's most energetic seismic zones, generating frequent magnitude 5–7 earthquakes and occasional great ruptures exceeding magnitude 8. The earthquake occurred in the outer-rise zone, a region where extension and bending of the descending slab produce both thrust and normal-faulting mechanisms.
At 26.5 km depth, this earthquake released energy in the intermediate-depth band, where temperatures exceed 600°C and mineral phase transitions in the subducting slab generate seismicity without tsunami potential. The 5.8 magnitude released approximately 2.0 × 1014 joules—equivalent to 47 kilotons of TNT—concentrated on a fault plane roughly 15 km × 8 km in area. Moment tensor analysis from USGS indicates a mixed thrust/normal mechanism typical of bending stresses in the Aleutian outer-rise.
Intermediate-depth earthquakes (20–70 km) produce negligible water column displacement. Tsunami generation requires sudden vertical seafloor motion at the megathrust interface (<20 km). This event's deeper rupture and extensional component preclude significant tsunami generation.
Adak, a former US Navy base now home to approximately 200 residents, lies 292 km from the epicenter. Shaking intensity (Modified Mercalli) at Adak would not exceed II–III (weak shaking, barely perceptible). The Aleutian chain experiences 10–15 magnitude 5+ earthquakes annually; this event is routine seismic activity in a hyperactive subduction zone. No damage, power disruptions, or emergency response was required.
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