SCSNM4.4 – SCSN

08/12/2024, M4.4 near Highland Park

Zackary Newman — Mon, 12 Aug 2024 19:38:35 +0000

Event

12 Aug 2024 12:20:24 PDT, (34.085, -118.185), depth 12.1km.
4km SSE of Highland Park, California

Aftershocks

As of 12 Aug 2024, 12:33PM PDT, there has been 1 aftershock recorded, M2.5.
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 M1.7 (2024/08/12).

Historical Seismicity

Since our records began in 1932 we’ve had 15 events of M4 or greater within 10km of today’s event.
The largest historic event was M5.9 on 1987/10/01.
The most recent historic event was M4.5 on 19 Sep 2020.

Faults

CFM fault associations: most likely Lower Elysian Park fault (45%). Alternates: Other CFM faults (55%).*
Nearby faults: Raymond fault (3.9 km), Eagle Rock fault (5.2 km), Verdugo fault (7.9 km), Hollywood fault (8.3 km), East Montebello fault (9.2 km), Sierra Madre fault zone, Sierra Madre B section (Sierra Madre fault) (12.8 km), Sierra Madre fault zone, Sierra Madre C section (Sierra Madre fault) (13.1 km), Sierra Madre fault zone, Sierra Madre B section (13.9 km), San Gabriel fault zone, Big Tujunga section (South Branch-Vasquez Creek) (14.1 km) and Sierra Madre fault zone, Sierra Madre B section (Gould Canyon thrust) (15.0 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.

*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.

01/15/2024, M4.4 near San Clemente Is

Zackary Newman — Mon, 15 Jan 2024 14:54:32 +0000

Event

15 Jan 2024 02:44:10 PST, (32.463, -118.288), depth 5.9km.
40km S of San Clemente Is.

Aftershocks

As of 05 Feb 2024, 11:53AM PST, 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 5 events of M4 or greater within 10km of today’s event.
The largest historic event was M5.0 on 2005/10/16.
The most recent historic event was M4.3 on 19 Oct 2005.

Faults

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.

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

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

09/30/2020, M4.9 Westmorland Swarm

Jennifer Andrews — Thu, 01 Oct 2020 00:18:14 +0000

Significant Events

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.

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

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

09/28/2018, M4.4 near Delta, Baja California

Zackary Newman — Mon, 01 Oct 2018 15:08:41 +0000

28 Sep 2018 19:17:46 PDT, (32.348, -115.183), depth 28.7km, 1km SE of Delta, B.C., Mexico
Aftershocks: so far there have been no aftershocks recorded. Some 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 118 events of M4 or greater within 10km of today’s event, the largest was M7.2 (2010/04/04) and the most recent was M4.0 on 08 Apr 2015.
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.

08/28/2018, M4.4 near La Verne

Jennifer Andrews — Wed, 29 Aug 2018 02:43:55 +0000

28 Aug 2018 19:33:28 PDT, (34.137, -117.775), depth 5.5km, 4km N of La Verne, California
Aftershocks: so far (29 Aug 2018, 08:05AM PDT) there have been 37 aftershocks recorded, the largest M3.4 (smallest M0.5). 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 9 events of M4 or greater within 10km of today’s event, the largest was M5.5 (1990/02/28) and the most recent was M4.5 on 17 Apr 1990.
Nearby faults: Sierra Madre fault zone, Sierra Madre E section (Sierra Madre fault) (0.6 km), San Antonio fault (2.5 km), Sierra Madre fault zone, Sierra Madre D section (Sierra Madre fault) (6.5 km), San Jose fault (6.8 km), Sierra Madre fault zone, Sierra Madre D section (Upper Duarte fault) (8.0 km), Stoddard Canyon fault (8.9 km), San Gabriel fault zone, San Gabriel River section (San Gabriel fault) (10.1 km), Sierra Madre fault zone, Cucamonga section (Cucamonga fault) (10.5 km), San Gabriel fault zone, San Gabriel River section (Weber fault) (11.2 km) and Sierra Madre fault zone, Clamshell-Sawpit section (Clamshell-Sawpit Canyon flt) (12.6 km).
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.

08/14/2018, M4.4 near Aguanga

Jennifer Andrews — Wed, 15 Aug 2018 01:42:19 +0000

14 Aug 2018 18:24:26 PDT, (33.477, -116.803), depth 1.9km, 7km NE of Aguanga, California
Aftershocks: so far (16 Aug 2018, 10:48AM PDT) there have been 435 aftershocks recorded, the largest M2.9 (smallest M0.0). 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 95 events during the 3 days prior to the earthquake (within a 10 km radius), the largest was M2.3 (2018/08/12). This area has been experiencing swarm activity for over 2 years (referred to as Cahuilla swarm), seeing elevated seismicity rates since early 2016. This region has hosted earthquake swarms since the 1980s, each lasting for weeks or a few months. The swarm starting early 2016 is the most prolific swarm recorded, with several thousand events observed so far.

2018 seismicity in the region of the Cahuilla swarm as of 15 August 2018. Circles plot individual earthquakes at all magnitudes in the SCSN catalogue, with size indicating magnitude. Events with magnitude 3.0 or greater are shown as red stars. The red line plots the cumulative number of events with magnitude 1.49 or greater.

Seismicity in the Cahuilla swarm from 1 day before the M4.4 event to approximately 40 hours after. Top plot shows the cumulative event number and the number of events per 20 minutes, both showing the aftershock event rate decay. Bottom plot shows event magnitudes against time.

Historical seismicity: since our records began in 1932 we’ve had 13 events of M4 or greater within 10km of today’s event, the largest was M5.6 (2005/06/12) and the most recent was M4.1 on 17 Nov 2008.
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.The closest station to the earthquake shown in the view is CI.HMT2 near Anza-Borrego at approximately 30km from the epicenter.

12/29/2015, M4.4 near Devore

Jennifer Andrews — Wed, 30 Dec 2015 03:45:47 +0000

29 Dec 2015 17:48:57 PST, (34.192, -117.413), depth 7.0km, 4km SSW of Devore, California
Aftershocks: so far (06 Jan 2016, 07:44PM PST) there have been 112 aftershocks recorded, the largest M3.8. 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.
There was 1 event during the 3 days prior to the earthquake (within a 1 km radius), with magnitude M1.4 (2015/12/29).
The figure shows the cumulative event rate as well as magnitude against time for the sequence.

Historical seismicity: since our records began in 1932 we’ve had 10 events of M4 or greater within 10km of today’s event, the largest was M4.6 (1965/04/15) and the most recent was M4.4 on 15 Jan 2014.
The figure shows the historic seismicity as grey stars and the recent sequence as circles, coloured by the time of occurrence (blue early, red late) and sized by magnitude. The main M4.4 event is shown as a black star. Red lines indicate the fault traces and the town of Devore is marked by a green triangle.

The event occurred in a geologically complex area, at the junction of a number of major fault strands (the San Andreas, San Jacinto and Cucamonga). The focal mechanism is more consistent with motions on the San Andreas and San Jacinto.
Nearby faults: San Jacinto fault zone (0.4 km), Sierra Madre fault zone, Cucamonga section (Cucamonga fault) (2.8 km), San Andreas fault zone, San Bernardino Mountains section (Tokay Hill fault) (3.8 km), Waterman Canyon fault zone (Waterman Canyon fault) (5.1 km), Red Hill-Etiwanda Avenue fault (Etiwanda Avenue fault) (9.6 km), Cleghorn fault zone, southern Cleghorn section (Cleghorn fault) (10.3 km), San Gabriel fault zone, San Gabriel River section (San Gabriel fault) (13.2 km).
Preliminary relocations for events in the sequence are shown in the figure below, indicating one larger and two small adjacent clusters. All three are associated with adjacent segments of the San Jacinto fault. (Prepared by Egill Hauksson.)

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