5.5

M5.5 Earthquake in the Macquarie Island region — August 8, 2021

2021-08-08 22:19:11 UTC (2021-08-08) · approx. 9:19 AM UTC+11 local

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MagnitudeM5.5(mww)
Time22:19 UTC≈ 9:19 AM UTC+11
Depth10.0 kmshallow crustal
Coordinates-59.786°, 159.546°
Felt byNo felt reports
Status✓ Reviewed by USGS· green PAGER
green Alert— no significant casualties or damage expected

On August 8, 2021 at 22:19 UTC, a magnitude 5.5 shallow crustal earthquake struck in the Macquarie Island region, at a depth of 10.0 km and coordinates -59.7858°, 159.5461°. The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected.

Physical scale: An earthquake of magnitude 5.5 releases seismic energy equivalent to roughly 3 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 3.8 km — a useful intuition for the size of the slip patch on the fault.

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Map showing earthquake epicenter at -59.79°, 159.55°

ShakeMap — predicted shaking intensity

Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.

USGS ShakeMap intensity contours for the M5.5 earthquake near Macquarie Island region

Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS

Earthquake Details

Magnitude
5.5 mww
Depth
10.0 km
shallow crustal
Location
-59.7858°N
159.5461°E
Intensity (MMI)
0.0
weak

Technical Information

Event ID
us6000f3ga
Event Type
earthquake
Status
✓ Reviewed
Significance
465
Azimuthal Gap
54.0°
Min Station Distance
14.291°
RMS Residual
0.78 sec
Last Updated
2025-12-22 22:13:21 UTC

Common Questions

How strong was the magnitude 5.5 earthquake in the Macquarie Island region?

The magnitude 5.5 earthquake that struck in the Macquarie Island region on August 8, 2021 at 22:19 UTC had a depth of 10.0 km. For context, this was a moderate earthquake that could be widely felt.

Where did the earthquake occur?

The earthquake epicenter was located at -59.7858°, 159.5461°, which is in the Macquarie Island region.

Were there aftershocks?

Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.5 earthquakes can continue for days to weeks and gradually diminish over time.

Actions

View on USGSDid You Feel It?

Authoritative source: USGS event page (event ID: us6000f3ga). All scientific values on this page are sourced verbatim from the USGS feed.

Cite this page: EarthquakeTracker.org. (2021, August 8, 2021). M5.5 Earthquake in the Macquarie Island region — August 8, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us6000f3ga/