M4.5 Earthquake 138 km SSE of Isangel, Vanuatu — August 20, 2021
2021-08-20 22:25:26 UTC (2021-08-20) · approx. 9:25 AM UTC+11 local
Aftershock of the M5.0 mainshock.
On August 20, 2021 at 22:25 UTC, a magnitude 4.5 intermediate depth earthquake struck 138 km SSE of Isangel, Vanuatu, at a depth of 107.6 km and coordinates -20.5911°, 169.9982°.
Physical scale: An earthquake of magnitude 4.5 releases seismic energy equivalent to roughly 85 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 767 m — a useful intuition for the size of the slip patch on the fault.
This earthquake is part of an ongoing aftershock sequence following the magnitude 5.0 mainshock that occurred 21 days ago 110 km SSE of Isangel, Vanuatu. Since the mainshock, the USGS has recorded 0 aftershocks in this area. Aftershock activity is expected to continue for days to weeks as stresses on surrounding faults redistribute.
The epicenter is located in Vanuatu, a region characterized by the New Hebrides subduction zone, where the Australian Plate subducts eastward at approximately 90 mm per year. View all earthquakes in Vanuatu.
Learn more: Magnitude scale · Aftershock sequences
Earthquake Details
169.9982°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.5 earthquake near Isangel, Vanuatu?
The magnitude 4.5 earthquake that struck 138 km SSE of Isangel, Vanuatu on August 20, 2021 at 22:25 UTC had a depth of 107.6 km. For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at -20.5911°, 169.9982°, which is 138 km SSE of Isangel, Vanuatu. View all earthquakes in Vanuatu.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.5 earthquakes can continue for several days and gradually diminish over time.
Is this the same earthquake as the M5.0 one earlier?
No. This magnitude 4.5 earthquake is an aftershock of the larger magnitude 5.0 mainshock that occurred earlier 110 km SSE of Isangel, Vanuatu. Aftershocks are smaller earthquakes triggered by stress changes from the mainshock.
Has Vanuatu had earthquakes this big before?
The largest recorded earthquake in Vanuatu was the M7.9 Vanuatu earthquake of October 7, 2009. Today's magnitude 4.5 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000f95q). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, August 20, 2021). M4.5 Earthquake 138 km SSE of Isangel, Vanuatu — August 20, 2021. Retrieved November 2, 2021 from https://www.earthquaketracker.org/earthquakes/event/us6000f95q/