M5.6 earthquake 66 km WSW of Banda Aceh, Indonesia

Saturday, May 21, 2005, 23:01:16 UTC · 5.281°N, 94.797°E

A magnitude 5.6 earthquake struck 66 km WSW of Banda Aceh, Indonesia on Saturday, May 21, 2005, 23:01:16 UTC, at a depth of 55.6 km (shallow). USGS received 7 “Did You Feel It?” reports, with a maximum reported intensity of VI (strong). It is the strongest earthquake within 300 km since an M6.1 on May 18, 2005.

Magnitude: 5.6; Moderate · mwb
Depth: 56 km; Shallow
Felt reports: 7; Max intensity VI
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 75 km aftershock search area

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

85 km

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

Depth: shallow

56 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
Banda Aceh, Aceh, Indonesia	VI · Strong	6	85 km
Meulaboh, Aceh, Indonesia	IV · Light	1	201 km

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 lists 14 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.5 on May 31, 2005. 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 510 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 21 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 230,110 recorded deaths. The most severe:

2004M9.1
Sumatra: Aceh: Off West Coast
26 Dec 2004 · 257 km away
227,899 deaths$10 billion damagetsunami
1907M8.2
Nw Sumatra: Gunungsitoli, Barus
4 Jan 1907 · 300 km away
2,188 deathsSevere damage ($5–24M)tsunami
1967M6.1
N Sumatera,Malay Peninsula
12 Apr 1967 · 278 km away
14 deathsSevere damage ($5–24M)tsunami
1936M7.3
Banda Aceh,Lhok Sukon,Lhoksemawe
23 Aug 1936 · 92 km away · intensity VIII
9 deathsModerate damage ($1–5M)tsunami
1964M7.0
Banda Aceh
2 Apr 1964 · 121 km away · intensity VII
Severe damage ($5–24M)tsunami
1837M7.3
Banda Atjeh
29 Sep 1837 · 135 km away
Moderate damage ($1–5M)tsunami

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

Nearby trackers