M4.9 Earthquake 146 km NE of Colonia, Micronesia — September 28, 2021
2021-09-28 16:26:55 UTC (2021-09-28) · approx. 1:26 AM UTC+9 local
Felt by 1 person across nearby locations.
On September 28, 2021 at 16:26 UTC, a magnitude 4.9 shallow crustal earthquake struck 146 km NE of Colonia, Micronesia, at a depth of 10.0 km and coordinates 10.4909°, 139.0299°.
Physical scale: An earthquake of magnitude 4.9 releases seismic energy equivalent to roughly 338 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.4 km — a useful intuition for the size of the slip patch on the fault.
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 1 citizen response to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
139.0299°E
Technical Information
Common Questions
How strong was the magnitude 4.9 earthquake near Colonia, Micronesia?
The magnitude 4.9 earthquake that struck 146 km NE of Colonia, Micronesia on September 28, 2021 at 16:26 UTC had a depth of 10.0 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 10.4909°, 139.0299°, which is 146 km NE of Colonia, Micronesia.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.9 earthquakes can continue for several days and gradually diminish over time.
Actions
Authoritative source: USGS event page (event ID: us7000ff8l). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, September 28, 2021). M4.9 Earthquake 146 km NE of Colonia, Micronesia — September 28, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us7000ff8l/