Location:

Period:

4 Apr 2010 22:56:40 - 6 Apr 2010 10:21:48 (1 day 11 hours 25 minutes)

Volcanoes in 100km radius:

Salton Buttes(74km)

Earthquakes:

22 swarms found nearby.

2003

S20031113.1(21.8km)

12 Nov

1 day 17 hours

31 earthquakes

2007

S20070117.1(23.7km)

17 Jan

3 days 20 hours

64 earthquakes

2009

S20090410.1(12.6km)

9 Apr

11 hours

24 earthquakes

S20090721.1(21.1km)

20 Jul

1 day 10 hours

32 earthquakes

S20090818.1(10.9km)

17 Aug

1 day 21 hours

39 earthquakes

2010

S20100314.1(21.3km)

13 Mar

2 days 5 hours

39 earthquakes

S20100613.1(26.5km)

12 Jun

9 days 5 hours

239 earthquakes

2013

S20130920.1(19.3km)

19 Sep

1 day 10 hours

31 earthquakes

2015

S20150531.1(20.4km)

31 May

2 days 9 hours

45 earthquakes

2017

S20171207.1(3.4km)

6 Dec

4 days 12 hours

120 earthquakes

2018

S20180314.1(26.2km)

13 Mar

1 day 13 hours

26 earthquakes

2022

S20220510.1(15.5km)

9 May

13 hours

26 earthquakes

S20220714.1(22.6km)

13 Jul

1 day 12 hours

26 earthquakes

S20220825.1(20.6km)

25 Aug

1 day 3 hours

27 earthquakes

S20221008.1(15.4km)

7 Oct

8 hours

28 earthquakes

S20221231.1(25.1km)

31 Dec

2 days 20 hours

86 earthquakes

2023

S20230324.1(5.8km)

23 Mar

2 days 2 hours

50 earthquakes

2024

S20240621.1(24.4km)

20 Jun

3 days 0 hours

41 earthquakes

2025

S20250320.2(29.2km)

19 Mar

6 days 15 hours

81 earthquakes

S20250414.1(21.3km)

13 Apr

10 days 12 hours

381 earthquakes

2026

S20260327.1(11.7km)

26 Mar

2 days 23 hours

51 earthquakes

S20260702.1(28.6km)

1 Jul

1 day 21 hours

31 earthquakes

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Earthquake Swarm S20100405.6 Near Julian, California

Earthquake swarm S20100405.6 occurred 16 km east of Julian, California, in the Peninsular Ranges. The sequence began at 22:56 on 4 April 2010 and concluded at 10:21 on 6 April 2010, spanning 35 hours and 25 minutes. During this interval, 38 earthquakes were recorded.

The swarm exhibited a range of magnitudes from 0.9 to 3.8, with the largest event (magnitude 3.8) occurring at 22:56:40 on 4 April at a depth of 10 km. Subsequent notable events included magnitudes 3.5, 3.2, 3.6, and 3.1, all clustered within the first 24 hours. Depths remained shallow, predominantly between 7 km and 15 km, consistent with upper-crustal faulting in the region.

Temporal distribution showed the highest activity rates immediately after initiation, followed by a gradual decline. On 4 April, 11 events exceeded magnitude 2.0; on 5 April, 12 additional events reached or exceeded this threshold; and on 6 April, only two smaller events were recorded before termination.

Julian lies within the Peninsular Ranges geologic province of southern California, underlain primarily by Mesozoic granitic and metamorphic rocks. The area is influenced by the Elsinore Fault Zone, a northwest-trending right-lateral strike-slip system that accommodates a portion of Pacific–North American plate motion. Seismic swarms in this setting commonly arise from fluid migration or stress triggering along subsidiary faults rather than mainshock-aftershock sequences on major strands.

Historical records indicate six swarms in the immediate region since 1 January 2000. These occurred in 2003 (one swarm), 2007 (one swarm), 2009 (three swarms), and 2010 (this event). Such episodic clustering underscores the area's propensity for distributed, low-to-moderate magnitude seismicity.

The 2010 swarm contributed to ongoing characterization of background seismic rates east of Julian. Depths and magnitudes align with typical values observed along the Elsinore system, where events rarely exceed magnitude 4.0 in recent decades absent larger regional triggers.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
California Geological Survey, Peninsular Ranges Fault Database
SeismoSight internal swarm classification records