DashboardNewsSwarmsM 7.0+
VolcanoesSupervolcanoesRegionsGlobal
Favorites
BlogAbout
Privacy PolicyDisclaimer
Follow
Note:This page contains AI-generated content for informational and entertainment purposes only. It may contain inaccuracies. Raw event data is from USGS and EMSC. All statistics, lists, and derived information are generated by this site. Full disclaimerFound an error?
Location:
11 km WSW of Oak Shores, California
Period:
6 Apr 2006 04:46:57 - 17 Apr 2006 15:12:32 (11 days 10 hours 25 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
151
18 swarms found nearby.
2003
S20031222.1(29.4km)
22 Dec
37 days 3 hours
2456 earthquakes
S20031222.2(27.5km)
22 Dec
15 days 17 hours
643 earthquakes
22 Dec
1 day 0 hours
127 earthquakes
S20031224.1(27.6km)
23 Dec
2 days 19 hours
170 earthquakes
31 Dec
2 days 2 hours
67 earthquakes
2004
S20040201.1(25.0km)
31 Jan
9 days 8 hours
199 earthquakes
1 Feb
1 day 12 hours
34 earthquakes
S20040205.1(26.2km)
4 Feb
2 days 23 hours
57 earthquakes
1 Mar
24 days 6 hours
484 earthquakes
S20040303.1(27.2km)
3 Mar
8 days 3 hours
172 earthquakes
16 Mar
7 days 18 hours
281 earthquakes
4 Apr
18 days 8 hours
226 earthquakes
S20040425.1(28.9km)
25 Apr
19 days 16 hours
216 earthquakes
S20040528.1(29.7km)
27 May
2 days 11 hours
49 earthquakes
26 Jul
10 days 1 hours
140 earthquakes
13 Oct
8 days 7 hours
97 earthquakes
2005
1 Oct
10 days 17 hours
151 earthquakes
2009
S20090620.2(13.5km)
20 Jun
4 days 17 hours
84 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Analysis of the April 2006 Earthquake Swarm Near Oak Shores, California

An earthquake swarm designated S20060407.1 occurred in central California, centered 11 km west-southwest of Oak Shores. The sequence began at 04:46 on 6 April 2006 and concluded at 15:12 on 17 April 2006, spanning 274 hours and 25 minutes. During this interval, 151 earthquakes were recorded.

The first 100 events exhibited predominantly low magnitudes, with the majority between 0.6 and 2.9. Depths clustered around 5–8 km, though occasional events reached 23 km. Notable early activity included a magnitude 4.2 event at 01:06 on 7 April at 6 km depth, followed by a magnitude 3.6 shock later that day. Subsequent peaks reached 3.4 on 8 April and 2.9 on 7 April, with most aftershocks remaining under magnitude 2.0. Depths for these initial events averaged near 6 km, consistent with shallow crustal faulting.

This swarm fits within a broader pattern of seismic activity in the region since 2000. Seventeen swarms have been documented, with earlier episodes occurring in 2003 (five swarms), 2004 (eleven swarms), and 2005 (one swarm).

Central California lies within the Pacific–North American plate boundary zone. The area experiences distributed deformation along the San Andreas Fault system and subsidiary structures such as the Rinconada and Hosgri faults. The locale near Oak Shores, in San Luis Obispo County, features Franciscan Complex bedrock and Neogene sedimentary units that record long-term tectonic compression. Historical seismicity includes both mainshock–aftershock sequences and swarm-like clusters, often linked to fluid migration or aseismic slip on minor faults.

The 2006 swarm’s characteristics—high event count, modest maximum magnitudes, and shallow focal depths—align with typical swarm behavior in this tectonically active coastal margin. Such episodes contribute to ongoing strain release without producing damaging ground motion.

References

United States Geological Survey Earthquake Catalog
California Geological Survey Regional Fault Maps
Southern California Earthquake Data Center Swarm Database