M6.9 earthquake 68 km WSW of Sabang, Indonesia

Monday, April 4, 1983, 02:51:34 UTC · 5.723°N, 94.722°E

A magnitude 6.9 earthquake struck 68 km WSW of Sabang, Indonesia on Monday, April 4, 1983, 02:51:34 UTC, at a depth of 78.5 km (intermediate). It is the strongest earthquake within 300 km since an M6.9 on April 2, 1964.

Magnitude: 6.9; Strong · mw
Depth: 79 km; Intermediate
Felt reports: 0; Did You Feel It?
Est. shaking: VII; Very strong (ShakeMap)
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

338 kilotons of TNT

That is about 22 times the Hiroshima bomb. It released about 708 times the energy of a magnitude 5.0.

Tectonic setting

59 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: intermediate

79 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 PAGER estimate is available for this event.

After the main event

Aftershocks within 100 km

USGS lists 5 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.9 on April 4, 1983. 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 114 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 18 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 23 recorded deaths. The most severe:

1967M6.1
N Sumatera,Malay Peninsula
12 Apr 1967 · 286 km away
14 deathsSevere damage ($5–24M)tsunami
1936M7.3
Banda Aceh,Lhok Sukon,Lhoksemawe
23 Aug 1936 · 42 km away · intensity VIII
9 deathsModerate damage ($1–5M)tsunami
1964M7.0
Banda Aceh
2 Apr 1964 · 110 km away · intensity VII
Severe damage ($5–24M)tsunami
1837M7.3
Banda Atjeh
29 Sep 1837 · 144 km away
Moderate damage ($1–5M)tsunami
1983M6.6
Sumatera: Banda Aceh
4 Apr 1983 · 0 km away · intensity VII
$1 million damage
1982M6.3
Little Nicobar Island
20 Jan 1982 · 158 km away · intensity VIII
Moderate damage ($1–5M)

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

Nearby trackers