4.0

M4.0 Earthquake 125 km N of Saipan, Northern Mariana IslandsDecember 6, 2021

2021-12-06 18:55:32 UTC (2021-12-06) · approx. 4:55 AM UTC+10 local

MagnitudeM4.0(mb)
Time18:55 UTC4:55 AM UTC+10
Depth531.9 kmdeep-focus
Coordinates16.346°, 145.859°
Felt byNo felt reports
Status✓ Reviewed by USGS

On December 6, 2021 at 18:55 UTC, a magnitude 4.0 deep-focus earthquake struck 125 km N of Saipan, Northern Mariana Islands, at a depth of 531.9 km and coordinates 16.3458°, 145.8592°.

Physical scale: An earthquake of magnitude 4.0 releases seismic energy equivalent to roughly 15 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 347 m — a useful intuition for the size of the slip patch on the fault.

Map showing earthquake epicenter at 16.35°, 145.86°

Earthquake Details

Magnitude
4.0 mb
Depth
531.9 km
deep-focus
Location
16.3458°N
145.8592°E

Technical Information

Event ID
us6000gb69
Event Type
earthquake
Status
✓ Reviewed
Significance
246
Azimuthal Gap
89.0°
Min Station Distance
2.902°
RMS Residual
0.60 sec
Last Updated
2022-02-12 23:07:29 UTC

Common Questions

How strong was the magnitude 4.0 earthquake near Saipan, Northern Mariana Islands?

The magnitude 4.0 earthquake that struck 125 km N of Saipan, Northern Mariana Islands on December 6, 2021 at 18:55 UTC had a depth of 531.9 km. For context, this was a light earthquake commonly felt near the epicenter.

Were there aftershocks?

Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.0 earthquakes can continue for several days and gradually diminish over time.

Understanding This Data

Magnitude 4.0 earthquakes are often felt but rarely cause damage.

Learn more about magnitude →

Authoritative source: USGS event page (event ID: us6000gb69). All scientific values on this page are sourced verbatim from the USGS feed.

Cite this page: EarthquakeTracker.org. (2021, December 6, 2021). M4.0 Earthquake 125 km N of Saipan, Northern Mariana IslandsDecember 6, 2021. Retrieved February 12, 2022 from https://www.earthquaketracker.org/earthquakes/event/us6000gb69/