Reviewed by USGSTonga42y ago
M6.0 earthquake 18 km WNW of Hihifo, Tonga
Friday, October 19, 1984, 14:37:50 UTC · 15.888°S, 173.950°W
A magnitude 6.0 earthquake struck 18 km WNW of Hihifo, Tonga on Friday, October 19, 1984, 14:37:50 UTC, at a depth of 121.1 km (intermediate). It is the strongest earthquake within 300 km since an M7.2 on October 15, 1984.
- Magnitude
- 6.0
- Strong · mw
- Depth
- 121 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 earthquakeDashed circle: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
15 kilotons of TNT
That is about the energy of the Hiroshima bomb. It released about 32 times the energy of a magnitude 5.0.
Tectonic setting
69 km
from the nearest mapped plate boundary, between the Tonga and Niuafo'ou plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: intermediate
121 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 4 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M4.6 on October 31, 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 617 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.0The 1917 Samoa-Tonga EarthquakeJune 26, 1917 · 123 km NE of this epicenter
- 7.8146 km ESE of Hihifo, TongaDecember 26, 1975 · 164 km E of this epicenter
- 7.7133 km NE of Hihifo, TongaSeptember 1, 1981 · 139 km NE of this epicenter
- 7.6199 km ESE of Hihifo, TongaApril 2, 1977 · 217 km SE of this epicenter
- 7.219 km ENE of Hihifo, TongaOctober 15, 1984 · 33 km E of this epicenter
- 7.1112 km NNE of Hihifo, TongaApril 14, 1957 · 114 km NE of this epicenter
- 7.0146 km NW of Neiafu, TongaMay 22, 1972 · 239 km SW of this epicenter
- 7.0206 km SE of Hihifo, TongaJune 17, 1978 · 225 km SE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2 recorded deaths. The most severe:
- 1917M8.3
Samoa Islands
26 Jun 1917 · 110 km away
2 deathsModerate damage ($1–5M)tsunami
- 1981M7.7
Apia; American Samoa: Pago Pago
1 Sep 1981 · 139 km away · intensity VI
Limited damage (under $1M)tsunami
- 1977M7.6
Apia
2 Apr 1977 · 217 km away · intensity VI
Limited damage (under $1M)tsunami
- 1975M7.8
Samoa Islands
26 Dec 1975 · 164 km away · intensity V
tsunami
- 1957M7.5
Samoa Islands
14 Apr 1957 · 110 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.