Reviewed by USGSIndonesia42y ago
M7.4 earthquake 91 km SW of Gorontalo, Indonesia
Monday, August 6, 1984, 12:01:52 UTC · 0.086°S, 122.517°E
A magnitude 7.4 earthquake struck 91 km SW of Gorontalo, Indonesia on Monday, August 6, 1984, 12:01:52 UTC, at a depth of 242.3 km (intermediate). It is the strongest earthquake within 300 km since an M7.4 on November 8, 1941.
- Magnitude
- 7.4
- Major · mw
- Depth
- 242 km
- Intermediate
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- V
- Moderate (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
1.9 megatons of TNT
That is about 126 times the Hiroshima bomb. It released about 3,981 times the energy of a magnitude 5.0.
Tectonic setting
171 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
242 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 200 km
USGS lists 4 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.5 on August 15, 1984. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 350 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 · 32 km E of this epicenter
- 7.8160 km W of Gorontalo, IndonesiaJanuary 22, 1905 · 126 km NW of this epicenter
- 7.7120 km NE of Palu, IndonesiaMay 19, 1938 · 220 km W of this epicenter
- 7.433 km NW of Gorontalo, IndonesiaNovember 8, 1941 · 97 km N of this epicenter
- 7.1156 km NW of Gorontalo, IndonesiaJanuary 11, 1913 · 175 km N of this epicenter
- 6.8161 km S of Luwuk, IndonesiaNovember 19, 1913 · 256 km S of this epicenter
- 6.8109 km WSW of Luwuk, IndonesiaMarch 17, 1909 · 146 km SW of this epicenter
- 6.747 km WNW of Luwuk, IndonesiaJune 30, 1964 · 75 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 14 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 69 recorded deaths. The most severe:
- 1927M6.2
Sulawesi: Donggala
1 Dec 1927 · 215 km away · intensity VII
50 deathsSevere damage ($5–24M)tsunami
- 1938M7.7
Sulawesi Island
19 May 1938 · 220 km away · intensity IX
17 deathsSevere damage ($5–24M)tsunami
- 1983M6.1
Central Sulawesi
25 Oct 1983 · 229 km away · intensity VII
2 deathsModerate damage ($1–5M)
- 1939M8.0
Centrtal Sulawesi: Kalo,Luwuk,Sula I
21 Dec 1939 · 55 km away
Moderate damage ($1–5M)tsunami
- 1983M6.0
Celebes: Minahassa: Tolitoli
16 Oct 1983 · 208 km away
Moderate damage ($1–5M)
- 1907
Sulawesi: Lemo, Colo, Anja, Olu Congko
30 Jul 1907 · 272 km away · intensity VIII
Moderate damage ($1–5M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.