3.8

M3.8 Earthquake 260 km WSW of Adak, Alaska — December 7, 2020

2020-12-07 20:38:23 UTC (2020-12-07) · approx. 8:38 AM UTC+12 local

MagnitudeM3.8(mb)
Time20:38 UTC≈ 8:38 AM UTC+12
Depth5.4 kmshallow crustal
Coordinates51.238°, 179.746°
Felt byNo felt reports
Status✓ Reviewed by USGS

On December 7, 2020 at 20:38 UTC, a magnitude 3.8 shallow crustal earthquake struck 260 km WSW of Adak, Alaska, at a depth of 5.4 km and coordinates 51.2383°, 179.7456°.

Physical scale: An earthquake of magnitude 3.8 releases seismic energy equivalent to roughly 7.6 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 252 m — a useful intuition for the size of the slip patch on the fault.

Map showing earthquake epicenter at 51.24°, 179.75°

Earthquake Details

Magnitude
3.8 mb
Depth
5.4 km
shallow crustal
Location
51.2383°N
179.7456°E

Technical Information

Event ID
us7000crd7
Event Type
earthquake
Status
✓ Reviewed
Significance
222
Azimuthal Gap
222.0°
Min Station Distance
0.956°
RMS Residual
0.72 sec
Last Updated
2021-02-12 22:41:44 UTC

Common Questions

How strong was the magnitude 3.8 earthquake near Adak, Alaska?

The magnitude 3.8 earthquake that struck 260 km WSW of Adak, Alaska on December 7, 2020 at 20:38 UTC had a depth of 5.4 km. For context, this was a minor earthquake typically detected only by instruments.

Were there aftershocks?

Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.8 earthquakes can continue for several days and gradually diminish over time.

Understanding This Data

Magnitude 3.8 earthquakes are typically only recorded by instruments.

Learn more about magnitude →

Authoritative source: USGS event page (event ID: us7000crd7). All scientific values on this page are sourced verbatim from the USGS feed.

Cite this page: EarthquakeTracker.org. (2020, December 7, 2020). M3.8 Earthquake 260 km WSW of Adak, Alaska — December 7, 2020. Retrieved February 12, 2021 from https://www.earthquaketracker.org/earthquakes/event/us7000crd7/