SCSNM3.4 – SCSN

09/21/2021, M3.4 near Anza

Zackary Newman — Tue, 21 Sep 2021 23:08:26 +0000

Event

21 Sep 2021 15:41:30 PDT, (33.635, -116.715), depth 13.2km.
10km NNW of Anza, California

Aftershocks

As of 21 Sep 2021, 05:15PM PDT, there have been 61 aftershocks recorded.
The largest was M3.3 (smallest M0.3).
More aftershocks may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock.
There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Possible Foreshocks

There were 25 events during the 3 days prior to the earthquake (within a 10 km radius).
The largest was M1.3 (2021/09/21).

Historical Seismicity

Since our records began in 1932 we’ve had 14 events of M4 or greater within 10km of today’s event.
The largest historic event was M5.6 on 2005/06/12.
The most recent historic event was M4.4 on 15 Aug 2018.

Faults

CFM fault associations: most likely Clark fault; north segment (69%). Alternates: Not associated with a CFM modeled fault (5%), Other CFM faults (26%).*
Nearby faults: San Jacinto fault zone, Anza section (Clark fault) (0.7 km), San Jacinto fault zone, Anza section (Thomas Mountain fault) (2.2 km), San Jacinto fault zone, San Jacinto Valley section (Hot Springs fault) (5.1 km) and San Jacinto fault zone, Anza section (Buck Ridge fault) (7.2 km).**

Additional Information

Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
Visit our special reports page for further information on local notable earthquakes.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed.

*Earthquakes can occur both near or on major known faults, and in places where no clear fault zones are known. Using the statistical method of Evans et al. (in prep. 2019) the location and focal mechanism of this earthquake suggest the above association with modeled faults in the Community Fault Model (CFM) provided by the Southern California Earthquake Center (SCEC) and Harvard University. Note that the CFM fault association may be different from the nearby faults list. Differences may arise due to different fault databases, and because the CFM fault association uses the hypocenter with relation to subsurface 3-dimensional fault orientation models, while the nearby faults list utilizes mapped surface traces as they relate to the epicenter.

CFM Fault: SCEC CFM 5.0 Fault name and closest segment if available; The CFM is maintained by Harvard University, Dept of Earth & Planetary Sciences.

Probability: The probability in percent the earthquake is associated with this fault.

SCSN: Caltech/USGS Southern California Seismic Network

**U.S. Geological Survey and California Geological Survey, 2006, Quaternary fault and fold database for the United States, accessed 2015, from USGS web site: https://earthquake.usgs.gov/hazards/qfaults/

This information is subject to change as more up-to-date data become available.

12/20/2015, M3.4 near Newport Beach

Jennifer Andrews — Tue, 22 Dec 2015 19:20:31 +0000

20 Dec 2015 15:22:32 PST, (33.625, -117.902), depth 9.5km, 3km ENE of Newport Beach, California
Aftershocks: so far (23 Dec 2015) there have been 3 aftershocks recorded, the largest M2.8. More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
Historical seismicity: since our records began in 1932 we’ve had 14 events of M4 or greater within 10km of today’s event, the largest was M6.4 (1933/03/11) and the most recent was M4.8 on 07 Apr 1989.
Nearby faults: Pelican Hill fault (3.0 km), Newport-Inglewood-Rose Canyon fault zone, South Los Angeles basin section (3.1 km), Newport-Inglewood-Rose Canyon fault zone, Dana Point section (3.3 km) and THUMS-Huntington Beach (8.8 km).
Links for: USGS earthquake page, ShakeMap, DYFI.
Visit our special reports page for further information on local notable earthquakes.

11/17/2015, M3.4 near Devore

Zackary Newman — Wed, 18 Nov 2015 14:37:14 +0000

17 Nov 2015 20:41:48 PST, (34.175, -117.435), depth 10.6km, 6km SSW of Devore, California
Aftershocks: so far there have been 4 aftershocks recorded, the largest M1.6. More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
There were 2 events during the 3 days prior to the earthquake (within a 1 km radius), the largest was M2.6 (2015/11/18).
Historical seismicity: since our records began in 1932 we’ve had 12 events of M4 or greater within 10km of today’s event, the largest was M4.6 (1965/04/15) and the most recent was M4.2 on 25 Jul 2015.
Nearby faults: San Jacinto fault zone, San Bernardino section (Lytle Creek fault) (0.7 km), Sierra Madre fault zone, Cucamonga section (Cucamonga fault) (0.7 km), San Jacinto fault zone, San Bernardino section (San Jacinto fault) (2.8 km), San Andreas fault zone, San Bernardino Mountains section (South Branch SAF) (6.9 km) and San Andreas fault zone, San Bernardino Mountains section (9.4 km).
Links for: USGS earthquake page, ShakeMap, DYFI.
Visit our special reports page for further information on local notable earthquakes.