California earthquakes

M4.0 earthquake 6km NW of Pinnacles, CA

A magnitude 4.0 earthquake struck 6km NW of Pinnacles, CA on Tue, Aug 31, 2021, 9:09 AM PDT (16:09 UTC), 9 km (5 mi) below the surface.

A larger quake followed: M4.7 18km NW of San Simeon, CA. This one was a foreshock.

Soledad forecast More in California

Map

Where this earthquake was located, with the others nearby. Select one for its page.

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The earthquake

Magnitude: 4.0 (Mw, moment), light
Magnitude from: Northern California Seismic System
Local time: Tue, Aug 31, 2021, 9:09 AM PDT
UTC: 2021-08-31 16:09:56 UTC
Depth: 8.5 km (5.3 mi), shallow
Epicenter: 36.578° N, 121.183° W
Region: California
Felt reports: 265
Strongest shaking: V, moderate shaking
PAGER alert: Green
Tsunami flag: Yes: a large quake in an oceanic region
Status: Reviewed by a seismologist

Magnitude estimates

Different scales measure different things and differ by a few tenths. The USGS marks one as preferred, and it is the one this page uses.

Mag.	Scale	Computed by	Notes
4.05	Mw, moment	Northern California Seismic System	Preferred · Final · 4 stations
4.1	Mwr, regional moment	USGS National Earthquake Information Center	Reviewed · 4 stations
4.2	ML, local (Richter)	NOAA National Tsunami Warning Center	Reviewed · 19 stations
4.3	Mw, moment	EW	Preliminary · ±0.2 · 22 stations

Tsunami

The USGS flags a quake this large in an oceanic region. The flag does not mean a tsunami happened; the tsunami warning centers decide that, and their messages are below when they issued any.

Current tsunami warnings: tsunami.gov. Warnings in force in the US also appear on our alerts pages.

Shaking

The USGS ShakeMap: shaking estimated from seismic stations and the quake’s size, on the Modified Mercalli intensity scale.

Strongest estimated: V, moderate shaking
Peak ground acceleration: 7.1% of gravity
Peak ground velocity: 1.0 cm/s
Map: Automatic

USGS ShakeMap: estimated shaking intensity around the epicenter — Estimated shaking intensity. Map: USGS ShakeMap.

Did you feel it?

265 people reported to the USGS what they felt; the strongest reported shaking was IV, light shaking.

Estimated impact

The USGS PAGER system estimates deaths and economic losses from the shaking and the population and buildings exposed to it.

Alert level: Green: little or no damage or loss of life expected

Deaths: estimated chance of each range
Range	Chance
Under 1	65%
1 to 10	30%
10 to 100	4%
100 to 1,000	Under 1%
1,000 to 10,000	Under 1%
10,000 to 100,000	Under 1%
100,000 to 10,000,000	Under 1%

Economic losses: estimated chance of each range
Range, million USD	Chance
Under 1	65%
1 to 10	30%
10 to 100	4%
100 to 1,000	Under 1%
1,000 to 10,000	Under 1%
10,000 to 100,000	Under 1%
100,000 to 10,000,000	Under 1%

Fault motion and ground failure

How the rock slipped, from the moment tensor, and the USGS estimate of landslides and liquefaction.

Moment magnitude: 4.0 Mw

How well it is located

Reviewed by a seismologist.

Location uncertainty: About 0.1 km horizontally, 0.3 km in depth
Depth from: From location
Station coverage gap: 64°
Stations used: 76

Nearest places

Distance and direction from each place to the epicenter, with its forecast.

Nearby

Within 100 km, magnitude 1.5 and up: 119 in the 60 days after this one and 69 in the 30 days before it.

After

The first 60 of 119.

Before

Earthquakes today California earthquakes Live radar here

Sources

From the USGS Earthquake Hazards Program and its partner networks, event nc73618401 (also filed as ew1630426200, at00qypowk, us7000f69g). Read Sun, Oct 4, 2026, 5:14 PM UTC.