Reviewed by USGSIndonesia35y ago
M4.7 earthquake 60 km NNE of Luwuk, Indonesia
Saturday, July 20, 1991, 11:45:34 UTC · 0.430°S, 122.937°E
A magnitude 4.7 earthquake struck 60 km NNE of Luwuk, Indonesia on Saturday, July 20, 1991, 11:45:34 UTC, at a depth of 117.1 km (intermediate). It is the strongest earthquake within 300 km since an M4.9 on July 15, 1991.
- Magnitude
- 4.7
- Light · mb
- Depth
- 117 km
- Intermediate
- 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
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
153 km
from the nearest mapped plate boundary, between the Molucca Sea and Sunda plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: intermediate
117 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 50 km
USGS has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 522 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.11939 Sulawesi EarthquakeDecember 21, 1939 · 49 km N of this epicenter
- 7.8160 km W of Gorontalo, IndonesiaJanuary 22, 1905 · 186 km NW of this epicenter
- 7.875 km NNW of Gorontalo, IndonesiaApril 18, 1990 · 180 km N of this epicenter
- 7.7120 km NE of Palu, IndonesiaMay 19, 1938 · 270 km W of this epicenter
- 7.579 km NNW of Gorontalo, IndonesiaJune 20, 1991 · 182 km N of this epicenter
- 7.433 km NW of Gorontalo, IndonesiaNovember 8, 1941 · 130 km N of this epicenter
- 7.491 km SW of Gorontalo, IndonesiaAugust 6, 1984 · 60 km NW of this epicenter
- 7.1156 km NW of Gorontalo, IndonesiaJanuary 11, 1913 · 230 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 17 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 72 recorded deaths. The most severe:
- 1927M6.2
Sulawesi: Donggala
1 Dec 1927 · 248 km away · intensity VII
50 deathsSevere damage ($5–24M)tsunami
- 1938M7.7
Sulawesi Island
19 May 1938 · 270 km away · intensity IX
17 deathsSevere damage ($5–24M)tsunami
- 1990M7.6
Minahassa Peninsula: Bolaang-Gorontalo
18 Apr 1990 · 180 km away
3 deathsSevere damage ($5–24M)
- 1983M6.1
Central Sulawesi
25 Oct 1983 · 289 km away · intensity VII
2 deathsModerate damage ($1–5M)
- 1991M7.5
Minahassa: Gorontalo, Mamado
20 Jun 1991 · 182 km away · intensity VI
Severe damage ($5–24M)
- 1939M8.0
Centrtal Sulawesi: Kalo,Luwuk,Sula I
21 Dec 1939 · 48 km away
Moderate damage ($1–5M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.