M5.6 earthquake western Indian-Antarctic Ridge

Monday, April 11, 1977, 02:15:18 UTC · 52.287°S, 114.590°E

A magnitude 5.6 earthquake struck western Indian-Antarctic Ridge on Monday, April 11, 1977, 02:15:18 UTC, at a depth of 33.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.

Magnitude: 5.6; Moderate · mb
Depth: 33 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquake

In context

How big was it, and why here?

Energy released

4 kilotons of TNT

That is about 1/4 of the Hiroshima bomb. It released about 8 times the energy of a magnitude 5.0.

Tectonic setting

213 km

from the nearest mapped plate boundary, between the Australian and Antarctic plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

33 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 75 km

USGS has not published any M2.5+ earthquake within 75 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 2 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

Nearby trackers