M7.6 earthquake 7 km N of Pantla, Mexico

Saturday, September 21, 1985, 01:37:13 UTC · 17.802°N, 101.647°W

A magnitude 7.6 earthquake struck 7 km N of Pantla, Mexico on Saturday, September 21, 1985, 01:37:13 UTC, at a depth of 30.8 km (shallow). It is the strongest earthquake within 300 km since an M8.0 on September 19, 1985.

Magnitude: 7.6; Major · mw
Depth: 31 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

3.8 megatons of TNT

That is about 252 times the Hiroshima bomb. It released about 7,943 times the energy of a magnitude 5.0.

Tectonic setting

82 km

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

Depth: shallow

31 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 20 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M5.7 on September 25, 1985. 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 132 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 55 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 13,972 recorded deaths. The most severe:

1985M8.1
Michoacan: Mexico City
19 Sep 1985 · 103 km away · intensity IX
9,500 deaths$4.0 billion damagetsunami
1806M7.5
Jalisco,Oaxaca,Michoacan
25 Mar 1806 · 258 km away · intensity VIII
2,000 deathsExtreme damage ($25M+)
1818M8.2
Morelos-Guerrero,Mexico City,Guadalajara
31 May 1818 · 282 km away · intensity X
2,000 deathsSevere damage ($5–24M)tsunami
1912M6.7
Central, Acambay, Tixmadeje
19 Nov 1912 · 270 km away
202 deathsSevere damage ($5–24M)
1941M7.6
Michoacan, Colima, Jalisco
15 Apr 1941 · 172 km away · intensity VII
84 deaths$2 million damagetsunami
1964M7.3
Guerrero
6 Jul 1964 · 116 km away
78 deathsSevere damage ($5–24M)

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

Nearby trackers