M7.3 earthquake 201 km ENE of Neiafu, Tonga

Tuesday, October 6, 1987, 04:19:06 UTC · 17.940°S, 172.225°W

A magnitude 7.3 earthquake struck 201 km ENE of Neiafu, Tonga on Tuesday, October 6, 1987, 04:19:06 UTC, at a depth of 16.0 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on April 2, 1977.

Magnitude: 7.3; Major · mw
Depth: 16 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: IV; Light (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

1.3 megatons of TNT

That is about 89 times the Hiroshima bomb. It released about 2,818 times the energy of a magnitude 5.0.

Tectonic setting

32 km

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

Depth: shallow

16 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 200 km

USGS lists 11 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.2 on November 3, 1987. 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 505 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 10 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 · 284 km away
2 deathsModerate damage ($1–5M)tsunami
1919M8.1
Tonga Islands
30 Apr 1919 · 55 km away
Limited damage (under $1M)tsunami
1865M8.0
Tonga Islands
18 Nov 1865 · 219 km away
Limited damage (under $1M)tsunami
1977M7.6
Apia
2 Apr 1977 · 139 km away · intensity VI
Limited damage (under $1M)tsunami
1902M7.8
Tonga Islands
9 Feb 1902 · 295 km away
1975M7.8
Samoa Islands
26 Dec 1975 · 188 km away · intensity V
tsunami

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

Nearby trackers