M 3.8 - 42 km S of Unalaska, United States
(42 km S of)Seismic Telemetry Specifications
3.8MB
Minor Seismic Class
81.0km
Upper Mantle
53.496° N, 166.497° W
GPS Coordinates
8 tons
TNT Equivalent Power
US
USGS Real-time Feed
Epicenter Location & Tectonic Fault Map
Is This Earthquake Dangerous?
A magnitude 3.8 event is classified as a minor earthquake. Often felt by people indoors, especially on upper floors. Hanging objects may swing slightly; structural damage is extremely rare.
Estimated Shaking Radius
~25–50 km
Potential Damage Zone
None
Focal Depth Effect
Moderate Damping
What Does Magnitude 3.8 Mean?
Earthquake strength is measured on a logarithmic scale. Compare this event with the full seismic scale:
Logarithmic Energy Multiplier
Because seismic scales are logarithmic, each whole integer increase represents:
10× Ground Motion Amplitude
The seismograph wave amplitude jumps by tenfold for every 1.0 magnitude step.
~31.6× Radiated Kinetic Energy
Total energy release increases exponentially (101.5 ≈ 31.62 times per magnitude unit).
Why Did This Earthquake Happen?
The western North American margin is shaped by the Pacific Ring of Fire, including the 800-mile San Andreas transform fault system and the Cascadia Subduction Zone. Lateral strike-slip motion between the Pacific and North American plates drives continuous crustal deformation across the region.
Originating at a depth of 81.0 km (Upper Mantle / Wadati-Benioff Zone (70–300 km)), this rupture occurred originated within the descending oceanic plate inside the upper mantle. shaking radiates over a wider geographic area with attenuated high frequencies.
Earthquake Safety Action Plan
- •Drop, Cover, and Hold On: Take cover beneath a sturdy table or desk.
- •Stay indoors away from exterior glass windows and heavy unanchored fixtures.
- •If outdoors, move into an open area away from power lines and building facades.
- •Inspect utilities for damaged gas lines, water leaks, or electrical hazards.
- •Expect Aftershocks: Secondary tremors frequently strike after moderate and strong events.
- •Avoid damaged structures and listen to official emergency broadcasts.
- •Maintain a 72-hour emergency go-bag with water, non-perishable food, and first aid.
- •Anchor heavy furniture, water heaters, and appliances to structural wall studs.
- •Establish a family emergency communication protocol and meeting point.
Did You Feel This Earthquake?
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