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Location:
7km NW of Banning, CA
Period:
5 Mar 2020 03:39:15 - 5 Mar 2020 14:28:33 (10 hours 49 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
27
10 swarms found nearby.
2003
S20030628.1(29.0km)
27 Jun
23 hours
25 earthquakes
2005
S20050616.1(12.4km)
16 Jun
1 day 19 hours
67 earthquakes
S20051018.1(14.6km)
18 Oct
2 days 4 hours
46 earthquakes
2010
S20100214.1(18.6km)
13 Feb
12 days 3 hours
213 earthquakes
2014
S20140703.1(24.0km)
3 Jul
10 days 3 hours
258 earthquakes
2017
S20170910.1(23.8km)
9 Sep
3 days 12 hours
53 earthquakes
2018
S20180508.1(16.7km)
8 May
4 days 11 hours
113 earthquakes
2020
S20200523.1(24.0km)
22 May
2 days 15 hours
44 earthquakes
2023
S20230305.1(22.9km)
5 Mar
1 day 2 hours
25 earthquakes
2025
S20251017.1(27.7km)
16 Oct
2 days 2 hours
31 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20200305.1: Analysis of Activity Northwest of Banning, California

On 5 March 2020, a seismic swarm designated S20200305.1 was recorded approximately 7 km northwest of Banning, California. The sequence began at 03:39 and concluded at 14:28 the same day, encompassing 27 earthquakes over a duration of 10 hours and 49 minutes. This event cluster occurred within the tectonically active San Gorgonio Pass region, part of the broader San Andreas Fault system in Southern California.

The swarm exhibited low-magnitude events, with magnitudes ranging from 0.5 to 1.9. Depths were predominantly shallow, concentrated between 2 km and 7 km, though one outlier reached 13 km. The sequence featured a notable peak in activity around 09:12 to 09:37, including the largest event of magnitude 1.9 at 2 km depth. Subsequent events maintained similar shallow characteristics, reflecting typical swarm behavior driven by fluid migration or stress redistribution along local fault structures rather than a single mainshock-aftershock pattern.

Regional Geological Context

Banning lies within the San Gorgonio Pass, a structurally complex zone where the San Andreas Fault undergoes a right step-over. This geometry involves multiple interacting fault strands, including the Banning Fault and the San Gorgonio Pass Fault Zone. The pass accommodates oblique slip and experiences elevated seismic hazard due to its role as a restraining bend. Historical fault mapping indicates Quaternary activity on these structures, consistent with ongoing Pacific-North American plate boundary deformation.

Seismic swarms in this setting are not uncommon, often linked to the distributed fault network and potential hydrothermal influences at depth. The 2020 swarm aligns with patterns observed in prior clusters, underscoring the region's persistent low-level seismicity.

Historical Swarm Activity

Records since 1 January 2000 document seven prior swarms in the immediate area. These occurred in 2003 (one swarm), 2005 (two swarms), 2010 (one swarm), 2014 (one swarm), 2017 (one swarm), and 2018 (one swarm). Such episodic clusters highlight the intermittent nature of seismic release along the local fault system without progression to larger events.

The S20200305.1 swarm contributes to ongoing monitoring efforts that inform hazard assessments for the densely populated Inland Empire region. Continued observation of similar sequences aids in refining models of fault interaction within the San Andreas system.

References

  • United States Geological Survey Earthquake Catalog (USGS)
  • California Geological Survey Fault Activity Map
  • Southern California Earthquake Data Center (SCEDC)