M7.2 earthquake in The 1992 Petrolia, California Earthquake

Saturday, April 25, 1992, 18:06:05 UTC · 40.335°N, 124.229°W

A magnitude 7.2 earthquake struck in The 1992 Petrolia, California Earthquake on Saturday, April 25, 1992, 18:06:05 UTC, at a depth of 9.9 km (shallow). USGS received 118 “Did You Feel It?” reports, with a maximum reported intensity of IX (violent). It is the strongest earthquake within 300 km since an M7.2 on November 8, 1980.

Magnitude: 7.2; Major · mw
Depth: 10 km; Shallow
Felt reports: 118; Max intensity IX
Est. shaking: VIII; Severe (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

951 kilotons of TNT

That is about 63 times the Hiroshima bomb. It released about 1,995 times the energy of a magnitude 5.0.

Tectonic setting

16 km

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

Depth: shallow

10 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
95521<br>0.230	VII · Very strong	14	60 km
95540<br>0.236	VII · Very strong	13	31 km
95503<br>0.255	VII · Very strong	10	44 km
95501<br>0.262	VIII · Severe	9	52 km
95536<br>0.269	VIII · Severe	8	17 km
95542<br>0.293	VII · Very strong	5	40 km
95554<br>0.293	VI · Strong	5	32 km
95519<br>0.302	VII · Very strong	4	70 km
95565<br>0.320	IX · Violent	2	23 km
95562<br>0.320	IX · Violent	2	20 km
95528<br>0.320	IX · Violent	2	33 km
95560<br>0.320	VIII · Severe	2	37 km

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 597 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.6 on April 26, 1992. 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 153 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 20 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 3 recorded deaths. The most severe:

1969M4.8
Santa Rosa
2 Oct 1969 · 246 km away · intensity VIII
1 death$8 million damage
1954M6.6
Humboldt County
21 Dec 1954 · 63 km away
1 death$2 million damage
1932M6.5
Eureka
6 Jun 1932 · 44 km away · intensity VIII
1 deathModerate damage ($1–5M)
1992M7.1
Humboldt County: Ferndale, Petrolia
25 Apr 1992 · 8 km away · intensity VIII
$75 million damagetsunami
1980M7.2
North Coast
8 Nov 1980 · 87 km away · intensity VII
$2 million damage
1898M6.5
Sonoma County
31 Mar 1898 · 285 km away · intensity VIII
Moderate damage ($1–5M)tsunami

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

Nearby trackers