• 31 May 2024 10:26:53 PDT, (34.463, -119.193), depth 17.6km.
• 5km ENE of Ojai, California

Aftershocks

• As of 31 May 2024, 11:41AM PDT, there has been 1 aftershock recorded, M0.9.
• 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 7 events of M4 or greater within 10km of today’s event.
• The largest historic event was M5.1 on 2023/08/20.
• The most recent historic event was M4.0 on 03 Nov 2023.

Faults

• CFM fault associations: most likely Santa Ynez fault; 60dip segment (38%). Alternates: Not associated with a CFM modeled fault (18%), Other CFM faults (44%).*
• Nearby faults: San Cayetano fault (1.3 km), Mission Ridge fault system, Santa Ana section (Santa Ana fault) (1.5 km), Lion Canyon fault (3.7 km), Sisar fault zone (Big Canyon fault) (4.8 km), Sisar fault zone (Sisar fault) (4.8 km), Faults near Oakview and Meiners Oaks (La Vista fault) (5.0 km), faults near Oakview and Meiners Oaks (Villanova fault) (6.4 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.

• 03 Nov 2023 13:12:18 PDT, (34.420, -119.165), depth 10.4km.
• 8km ESE of Ojai, California
• This event is a late aftershock of the M5.1 Ojai event in August 2023

Aftershocks

• As of 03 Nov 2023, 01:56PM PDT, there has been 1 aftershock recorded, M1.9.
• 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 M1.2 (2023/11/02).

Historical Seismicity

• Since our records began in 1932 we’ve had 6 events of M4 or greater within 10km of today’s event.
• The largest historic event was M5.1 on 2023/08/20.
• The most recent historic event was M5.1 on 20 Aug 2023.

Faults

• Nearby faults: Sisar fault zone (Big Canyon fault) (0.5 km), Sisar fault zone (Sisar fault) (0.5 km), Lion Canyon fault (1.2 km), Mission Ridge fault system, Santa Ana section (Santa Ana fault) (2.3 km), San Cayetano fault (2.6 km), Faults near Oakview and Meiners Oaks (La Vista fault) (6.9 km), faults near Oakview and Meiners Oaks (Villanova fault) (7.9 km), faults near Oakview and Meiners Oaks (Devils Gulch fault) (8.7 km), Oak Ridge fault (9.0 km), faults near Oakview and Meiners Oaks (Oak View fault) (9.7 km), Sisar fault (9.7 km), faults of Orcutt and Timber Canyons (Orcutt fault) (10.8 km), Santa Ynez fault zone, eastern section (12.2 km), Red Mountain fault zone (Red Mountain fault) (12.8 km), Mission Ridge fault system, Arroyo Parida section (Arroyo Parida fault) (13.3 km), Mission Ridge fault system, Arroyo Parida section (13.4 km) and faults of Orcutt and Timber Canyons (Culbertson fault) (13.5 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.

• 15 Oct 2023 12:50:16 PDT, (34.563, -119.137), depth 7.0km.
• 16km NE of Ojai, California

Aftershocks

• As of 15 Oct 2023, 01:43PM PDT, there have been 2 aftershocks recorded.
• The largest was M3.5 (smallest M1.3).
• 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.

Historical Seismicity

• Since our records began in 1932 we’ve had 7 events of M4 or greater within 10km of today’s event.
• The largest historic event was M5.1 on 2023/08/20.
• The most recent historic event was M5.1 on 20 Aug 2023.

Faults

• CFM fault associations: most likely Southern San Cayetano; Ventura segment (60%). Alternates: Not associated with a CFM modeled fault (19%), Other CFM faults (21%).*
• Nearby faults: Pine Mountain fault (1.7 km), Santa Ynez fault zone, eastern section (3.7 km), San Cayetano fault (11.9 km), Mission Ridge fault system, Santa Ana section (Santa Ana fault) (12.9 km), Lion Canyon fault (14.8 km), Sisar fault zone (Big Canyon fault) (14.8 km) and Sisar fault zone (Sisar fault) (14.8 km).**

Additional Information

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

• 20 Aug 2023 14:41:00 PDT, (34.408, -119.188), depth 4.8km.
• 7km SE of Ojai, California

Aftershocks

• As of 23 Aug 2023, 07:39AM PDT, there have been 172 aftershocks recorded with the following totals by magnitude for this sequence:
• 6>M≥5: 1
• 5>M≥4: 0
• 4>M≥3: 12
• 3>M≥2: 55
• The largest aftershock was M3.9 (smallest M1.0).
• More aftershocks may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock.

This magnitude stick plot shows the episodic time evolution of the sequence. Note that the M3.9 on 2023/08/22 had its own aftershock sequence.

• There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.

Possible Foreshocks

• There were 19 events during the 3 days prior to the earthquake (within a 10 km radius).
• The largest was M2.6 (2023/08/20).

This b-value plot shows a b-value of 0.68, which is unusually small. On average the b-value for southern California is approx. 1.0. This small b-value suggests that these earthquakes are occurring in an environment with above average tectonic stress, which is driving the large number of M3+ aftershocks.

Seismic observations provided by Egill Hauksson, Caltech. With consultation by Hiroo Kanamori, Caltech.

These interpretations may change, SCSN data are still preliminary, and the locations/ magnitudes may change as event analysis continues.

1. The sequence started 2023/08/19 at 18:27 with 19 recorded foreshocks (M 1.3 – 2.5) on a north-northeast trend located in the southern corner of the aftershock distribution.
2. The mainshock occurred on 2023/8/20 at 21:41, 26 hours after the sequence started, at a depth of 5.5 km. The moment tensor (see map plot) shows mixed strike-slip and thrust faulting on the northeast striking nodal plane, which is most likely the fault plane. However, the moment tensor has a 70% non-double component suggesting a non-planar fault. This is confirmed with longer-period w-phase solutions. Hypocenter alignments within the depth distribution of the aftershocks also suggest the presence of additional fault planes with different orientation. These details of the faulting will be worked out in future studies.
3. As of 2023/8/21 20:00 a total of 120 aftershocks have been recorded, with two largest events of M3.9. The whole sequence occurred mostly in the depth range from 4.0 to 6.5 km depth.


The map and cross section show a steep west dip in the south, and shallower northwest dip to the north of the mainshock hypocenter. Events within the yellow square in the map are projected onto the A-B cross section.

4. Associating this sequence to a fault is not easy although numerous active faults are mapped in the region. For instance, the sequence crosses the Lion Canyon Fault at an oblique angle, and does not seem to trigger aftershocks along it. There are some short northeast striking faults in the wider area but these tend to be discontinuous and unnamed.

3D Graphical observations and Community Fault Model (CFM) images provided by Craig Nicholson, UCSB.

Viewing the analyzed hypocenters from the sequence in 3D and comparing them to the 3D faults in the CFM, the sequence is primarily between the Sisar and Arroyo Parida S-dipping faults.

View of M5.1 Ojai sequence events and surrounding CFM faults along strike (to the west) of the Arroyo Parida Fault.

View of M5.1 Ojai sequence events and surrounding CFM faults rotated to view downdip in the plane(s) of slip of the aftershock sequence.

However, rotating the frame of reference to look downdip in the plane(s) of slip that seem to be defined by the aftershocks, it looks like, as with earlier observations, that the primary rupture is on a fairly steeply dipping secondary cross fault that dips west and south in the footwall of the Sisar fault system, with a possible nearly orthogonal secondary slip along the APF (dashed lines).

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 M4.3 on 1954/11/17.
• The most recent historic event was M4.1 on 12 Mar 2016.

Additional Information

• Links for: USGS earthquake page, ShakeMap, DYFI
• 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.