M4.7 earthquake 176 km SSE of Sumbawa Besar, Indonesia

Tuesday, September 20, 1977, 21:55:42 UTC · 10.035°S, 117.823°E

A magnitude 4.7 earthquake struck 176 km SSE of Sumbawa Besar, Indonesia on Tuesday, September 20, 1977, 21:55:42 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.1 on September 16, 1977.

Magnitude: 4.7; Light · 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 earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

169 tons of TNT

That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.

Tectonic setting

146 km

from the nearest mapped plate boundary, between the Sunda and Australian 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 50 km

USGS lists 15 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.6 on October 9, 1977. 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 154 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 6 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 189 recorded deaths. The most severe:

1977M8.3
Sunda Islands
19 Aug 1977 · 139 km away
189 deaths$1 million damagetsunami
1836M7.5
Flores Sea
28 Nov 1836 · 216 km away
Limited damage (under $1M)tsunami
1954M6.8
Sumabawa: Bima,Raba
2 Nov 1954 · 261 km away · intensity VIII
Limited damage (under $1M)
1837
Sumbawa Island: Bima
28 Nov 1837 · 186 km away · intensity IX
Limited damage (under $1M)
1836
Flores Sea
5 Mar 1836 · 216 km away
tsunami
1856
Lombok Island
25 Jul 1856 · 263 km away
tsunami

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

Nearby trackers