M7.2 earthquake in South Sandwich Islands region

Saturday, May 28, 2016, 09:46:59 UTC · 56.241°S, 26.935°W

A magnitude 7.2 earthquake struck in South Sandwich Islands region on Saturday, May 28, 2016, 09:46:59 UTC, at a depth of 78.0 km (intermediate). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M7.2 on December 27, 1991.

Tsunami flagUSGS sets this flag for large events in oceanic regions so tsunami warning centers review them. It does not by itself mean a tsunami occurred. Check tsunami.gov and local authorities for official messages.

Magnitude: 7.2; Major · mww
Depth: 78 km; Intermediate
Felt reports: 0; Max intensity I
Est. shaking: VI; Strong (ShakeMap)
PAGER alert: Green; Impact estimate
Tsunami: Flag; Check tsunami.gov

Outlined circle: this earthquakeDashed circle: 200 km aftershock search area

In context

How big was it, and why here?

Energy released

951 kilotons of TNT

That is about 63 times the Hiroshima bomb. It released about 1,995 times the energy of a magnitude 5.0.

Tectonic setting

85 km

from the nearest mapped plate boundary, between the Sandwich and South American plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: intermediate

78 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

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 populated area was estimated to feel noticeable shaking.

After the main event

Aftershocks within 200 km

USGS lists 39 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.2 on June 22, 2016. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 1,144 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 3 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1929M8.1
South Sandwich Islands
27 Jun 1929 · 179 km away
1961M7.7
South Sandwich Islands
5 Sep 1961 · 196 km away
1961M7.7
South Sandwich Islands
8 Sep 1961 · 22 km away

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers