M4.8 earthquake 83 km N of Gorontalo, Indonesia

Thursday, June 20, 1991, 08:06:18 UTC · 1.288°N, 123.005°E

A magnitude 4.8 earthquake struck 83 km N of Gorontalo, Indonesia on Thursday, June 20, 1991, 08:06:18 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.6 on June 20, 1991.

Magnitude: 4.8; 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

239 tons of TNT

That is about 1/63 of the Hiroshima bomb. A magnitude 5.0 releases about 2 times more energy.

Tectonic setting

59 km

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

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 8 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.4 on June 21, 1991. 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 556 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 123 recorded deaths. The most severe:

1845M7.0
N Sulawesi: Menado, Tikala, Tomohon
8 Feb 1845 · 206 km away · intensity IX
118 deathsModerate damage ($1–5M)tsunami
1990M7.6
Minahassa Peninsula: Bolaang-Gorontalo
18 Apr 1990 · 20 km away
3 deathsSevere damage ($5–24M)
1983M6.1
Central Sulawesi
25 Oct 1983 · 239 km away · intensity VII
2 deathsModerate damage ($1–5M)
1991M7.5
Minahassa: Gorontalo, Mamado
20 Jun 1991 · 26 km away · intensity VI
Severe damage ($5–24M)
1939M8.0
Centrtal Sulawesi: Kalo,Luwuk,Sula I
21 Dec 1939 · 143 km away
Moderate damage ($1–5M)tsunami
1983M6.0
Celebes: Minahassa: Tolitoli
16 Oct 1983 · 218 km away
Moderate damage ($1–5M)

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

Nearby trackers