M7.7 earthquake 171 km NNW of Sola, Vanuatu

Monday, April 21, 1997, 12:02:26 UTC · 12.584°S, 166.676°E

A magnitude 7.7 earthquake struck 171 km NNW of Sola, Vanuatu on Monday, April 21, 1997, 12:02:26 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M7.9 on July 17, 1980.

Magnitude: 7.7; Major · mwc
Depth: 33 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VI; Strong (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

5.4 megatons of TNT

That is about 355 times the Hiroshima bomb. It released about 11,220 times the energy of a magnitude 5.0.

Tectonic setting

87 km

from the nearest mapped plate boundary, between the Pacific and Australian 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 200 km

USGS lists 148 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.2 on April 21, 1997. 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 1,093 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 22 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1973M7.5
Espiritu Santo, Luganille
28 Dec 1973 · 209 km away · intensity VII
Moderate damage ($1–5M)
1910M7.2
Espiritu Santo
10 Nov 1910 · 159 km away
Moderate damage ($1–5M)tsunami
1973M7.2
Luganville, Lamap
29 Dec 1973 · 283 km away · intensity VIII
Moderate damage ($1–5M)
1997M7.7
Santa Cruz Islands; Vanuatu
21 Apr 1997 · 0 km away
Limited damage (under $1M)tsunami
1980M7.5
Santa Cruz Islands: Banks
8 Jul 1980 · 37 km away
Limited damage (under $1M)tsunami
1980M6.1
Vanuatu Islands
12 May 1980 · 248 km away · intensity VI
Limited damage (under $1M)tsunami

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

Nearby trackers