• 13 Feb 2024 23:53:13 PST, (33.128, -115.623), depth 9.8km.
• 10km N of Westmorland, California

Aftershocks

• As of 14 Feb 2024, 09:56AM PST, there have been 23 aftershocks recorded.
• The largest was M2.6 (smallest M1.1).
• 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 3 events during the 3 days prior to the earthquake (within a 10 km radius).
• The largest was M2.5 (2024/02/14).

Historical Seismicity

• Since our records began in 1932 we’ve had 109 events of M4 or greater within 10km of today’s event.
• The largest historic event was M6.2 on 1987/11/24.
• The most recent historic event was M4.1 on 02 Aug 2023.

Faults

• CFM fault associations: most likely Westmorland fault; main segment (67%). Alternates: Not associated with a CFM modeled fault (7%), Other CFM faults (26%).*
• Nearby faults: San Jacinto fault zone, Superstition Hills section (Lone Tree fault) (13.8 km) and San Jacinto fault zone, Superstition Hills section (Superstition Hills flt) (14.7 km).**

Additional Information

• Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
• Visit our special reports page for further information on local notable earthquakes.
• Visit scedc.caltech.edu to access any data recorded by the SCSN.

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

• 23 Oct 2021 23:49:12 PDT, (32.968, -115.877), depth 11.2km.
• 25km WSW of Westmorland, California

Aftershocks

• As of 24 Oct 2021, 09:05AM PDT, there have been no aftershocks recorded.
• 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.

Historical Seismicity

• Since our records began in 1932 we’ve had 62 events of M4 or greater within 10km of today’s event.
• The largest historic event was M6.6 on 1987/11/24.
• The most recent historic event was M4.5 on 10 May 2020.

Faults

• CFM fault associations: most likely Superstition Mountain fault (44%). Alternates: Not associated with a CFM modeled fault (6%), Other CFM faults (50%).*
• Nearby faults: San Jacinto fault zone, Superstition Mountain section (fault) (0.4 km), San Jacinto fault zone, Superstition Hills section (Elmore Ranch fault) (6.2 km), San Jacinto fault zone, Superstition Hills section (Superstition Hills flt) (6.2 km), San Jacinto fault zone, Superstition Hills section (6.9 km), San Jacinto fault zone, Superstition Hills section (East Elmore Ranch fault) (7.6 km), San Jacinto fault zone, Superstition Hills section (Lone Tree fault) (8.5 km), unnamed faults north of Coyote Wash (9.0 km), San Jacinto fault zone, Borrego Mountain section (Coyote Creek fault) (9.1 km), San Jacinto fault zone, Superstition Hills section (West Elmore Ranch fault) (12.5 km) and San Jacinto fault zone, Superstition Hills section (Kane Spring fault) (13.6 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.

• 23 Aug 2021 07:57:23 PDT, (33.138, -115.642), depth 7.2km.
• 12km N of Westmorland, California

Aftershocks

• As of 23 Aug 2021, 08:39AM PDT, there have been 5 aftershocks recorded.
• The largest was M1.7 (smallest M1.2).
• 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 1 events during the 3 days prior to the earthquake (within a 10 km radius).
• The largest was M1.4 (2021/08/21).

Historical Seismicity

• Since our records began in 1932 we’ve had 106 events of M4 or greater within 10km of today’s event.
• The largest historic event was M6.2 on 1987/11/24.
• The most recent historic event was M4.1 on 12 Jun 2021.

Faults

• CFM fault associations: most likely Westmorland fault; main segment (46%). Alternates: Not associated with a CFM modeled fault (18%), Other CFM faults (36%).*
• Nearby faults: San Jacinto fault zone, Superstition Hills section (Lone Tree fault) (12.8 km) and San Jacinto fault zone, Superstition Hills section (Superstition Hills flt) (13.6 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.

• Largest event: M4.9, 30 Sep 2020 17:31:27 PDT, (33.057, -115.590), depth 11.5km. 4km NE of Westmorland, California
• As of 01 Oct 2020, 05:54AM PDT, the following events have been recorded in the swarm:
• M≥4: 6
• M≥3: 54
• M≥2: 270
• Other M4 events recorded:
• Ml 4.0 Oct 1, 2020 03:37:04UTC 33.052, -115.575 ci37456405
• Mw 4.5 Oct 1, 2020 03:36:34UTC 33.068, -115.597 ci39643328
• Mw 4.1 Oct 1, 2020 01:10:25UTC 33.049, -115.592 ci39641880
• Mw 4.1 Oct 1, 2020 00:58:13UTC 33.065, -115.593 ci39641768
• Mw 4.2 Oct 1, 2020 00:41:18UTC 33.073, -115.601 ci39641616

Swarm Numbers

• There were 96 events during the 3 days prior to the M4.9 (within a 10 km radius). As of 01 Oct 2020, 01:37PM PDT, there have been 632 events recorded after the M4.9.
• The SCSN has so far recorded over 700 events in the swarm, the smallest M1.1. Many of the smaller events are still being analyzed and will be gradually added to the catalogue.
• More activity is expected in the next few days. 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 112 events of M4 or greater within 10km of today’s event.
• The largest historic event was M6.2 on 1987/11/24.
• The most recent historic event was M4.3 on 30 Sep 2020.
• Similar swarms in this area have been recorded in 1981 and 2012 with similar/same sense of motion and maximum magnitudes within the M5 range. For more informtation about the 2012 swarm visit M5.5 Brawley Swarm.

Faults

• CFM fault associations: most likely Westmorland fault; splay segment (94%). Alternates: Not associated with a CFM modeled fault (4%), Other CFM faults (2%).*
• Nearby faults: Imperial fault (13.8 km).**

Additional Information

• Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
• Visit our special reports page for further information on local notable earthquakes.
• Visit our SoCal swarms page for general information on local swarm monitoring.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. Note that a M2.7 event is visible for the first 36 seconds before the M4.9 is detected. More videos of the swarm will be available soon.