M7.1 earthquake 11 km NE of Rioja, Peru

Friday, April 5, 1991, 04:19:49 UTC · 5.982°S, 77.094°W

A magnitude 7.1 earthquake struck 11 km NE of Rioja, Peru on Friday, April 5, 1991, 04:19:49 UTC, at a depth of 19.8 km (shallow). It is the strongest earthquake within 300 km since an M7.3 on May 14, 1928.

Magnitude: 7.1; Major · mw
Depth: 20 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VII; Very 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

674 kilotons of TNT

That is about 45 times the Hiroshima bomb. It released about 1,413 times the energy of a magnitude 5.0.

Tectonic setting

158 km

from the nearest mapped plate boundary, between the Sunda and Australian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

20 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 43 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.5 on April 5, 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 126 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 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 1,123 recorded deaths. The most severe:

1946M7.3
Jocaibamba,Cerro Angaschaj,Cerro Sillapata
10 Nov 1946 · 284 km away · intensity XI
800 deathsSevere damage ($5–24M)
1990M6.5
Moyabamba-Riojo
30 May 1990 · 15 km away · intensity VI
200 deaths$1 million damage
1991M6.7
Rioja, Moyobamba, Nueva Cajamarca
5 Apr 1991 · 0 km away · intensity VII
53 deathsSevere damage ($5–24M)
1928M7.3
Chacahpoyas,Huancabamba,Cajamarca,Pinpincos
14 May 1928 · 184 km away · intensity X
29 deathsSevere damage ($5–24M)
1968M6.8
San Martin,Moyobamba,Yantalo,Rioja,Lamas
19 Jun 1968 · 41 km away
15 deathsUnder $1 million damage
1972M6.1
Juanjui
20 Mar 1972 · 97 km away · intensity IX
12 deaths$20 million damage

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

Nearby trackers