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Location:
8km SW of Anza, CA
Period:
2 Jul 2020 22:10:01 - 6 Jul 2020 14:39:09 (3 days 16 hours 29 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
70
74 swarms found nearby.
2001
S20011031.1(27.9km)
31 Oct
10 days 17 hours
471 earthquakes
2002
S20021024.3(21.3km)
23 Oct
2 days 17 hours
38 earthquakes
2003
S20030306.1(15.8km)
5 Mar
1 day 2 hours
35 earthquakes
2005
S20050612.1(18.9km)
12 Jun
26 days 19 hours
904 earthquakes
S20050820.1(24.2km)
19 Aug
3 days 23 hours
96 earthquakes
2009
S20090726.1(15.1km)
25 Jul
1 day 19 hours
29 earthquakes
2010
S20100209.1(24.7km)
8 Feb
3 days 22 hours
44 earthquakes
S20100708.1(26.2km)
7 Jul
35 days 19 hours
1709 earthquakes
S20101203.2(23.0km)
2 Dec
10 days 0 hours
68 earthquakes
2011
S20110202.2(16.3km)
1 Feb
1 day 18 hours
43 earthquakes
S20110319.1(29.2km)
18 Mar
1 day 23 hours
34 earthquakes
S20110416.1(20.6km)
15 Apr
7 days 6 hours
90 earthquakes
S20110727.1(20.9km)
26 Jul
4 days 1 hours
42 earthquakes
2012
S20120521.3(29.5km)
20 May
4 days 2 hours
45 earthquakes
S20120630.1(25.8km)
29 Jun
2 days 0 hours
31 earthquakes
2013
S20130311.1(29.9km)
10 Mar
72 days 2 hours
2118 earthquakes
S20130922.1(23.1km)
21 Sep
8 days 10 hours
91 earthquakes
S20131231.1(28.9km)
30 Dec
8 days 18 hours
91 earthquakes
2014
S20140127.1(17.1km)
26 Jan
2 days 4 hours
38 earthquakes
18 Apr
8 days 7 hours
191 earthquakes
S20140510.1(18.6km)
9 May
2 days 9 hours
44 earthquakes
S20140808.1(28.6km)
7 Aug
1 day 13 hours
28 earthquakes
2015
S20150211.2(14.4km)
10 Feb
12 days 21 hours
168 earthquakes
S20150401.1(25.4km)
31 Mar
38 days 7 hours
543 earthquakes
2016
S20160610.1(26.7km)
9 Jun
33 days 4 hours
1773 earthquakes
S20160614.1(17.0km)
14 Jun
7 days 5 hours
80 earthquakes
S20160720.2(25.3km)
19 Jul
6 days 5 hours
68 earthquakes
21 Dec
1 day 21 hours
34 earthquakes
S20161230.1(22.2km)
29 Dec
4 days 7 hours
48 earthquakes
2017
2 May
5 days 5 hours
91 earthquakes
9 May
15 days 6 hours
129 earthquakes
S20170609.1(18.6km)
8 Jun
3 days 22 hours
61 earthquakes
26 Jul
14 days 9 hours
192 earthquakes
6 Sep
14 days 21 hours
245 earthquakes
S20170926.1(17.9km)
25 Sep
124 days 21 hours
2217 earthquakes
2018
S20180203.1(15.3km)
2 Feb
28 days 21 hours
426 earthquakes
4 Mar
19 days 17 hours
203 earthquakes
2 Apr
10 days 14 hours
197 earthquakes
19 Apr
69 days 21 hours
1109 earthquakes
S20180527.1(20.0km)
26 May
4 days 20 hours
54 earthquakes
29 Jun
41 days 14 hours
582 earthquakes
11 Aug
209 days 15 hours
6032 earthquakes
2019
27 Mar
5 days 20 hours
79 earthquakes
25 Apr
1 day 22 hours
37 earthquakes
S20190905.1(15.1km)
4 Sep
4 days 3 hours
56 earthquakes
2020
8 Jan
11 days 9 hours
159 earthquakes
21 Jan
3 days 12 hours
57 earthquakes
1 Feb
8 days 17 hours
147 earthquakes
S20200301.1(20.3km)
29 Feb
6 days 16 hours
67 earthquakes
S20200404.1(28.9km)
4 Apr
40 days 3 hours
2928 earthquakes
25 May
7 days 18 hours
100 earthquakes
6 Jun
9 days 19 hours
109 earthquakes
7 Jul
26 days 8 hours
287 earthquakes
S20200926.2(16.3km)
25 Sep
3 days 10 hours
42 earthquakes
S20201219.1(19.0km)
18 Dec
5 days 0 hours
66 earthquakes
2021
S20210328.1(10.8km)
27 Mar
2 days 21 hours
33 earthquakes
S20210427.1(12.4km)
26 Apr
5 days 5 hours
80 earthquakes
8 Jun
5 days 16 hours
126 earthquakes
S20210921.1(13.3km)
20 Sep
8 days 7 hours
216 earthquakes
S20211223.1(18.6km)
22 Dec
1 day 1 hours
46 earthquakes
S20211231.1(18.4km)
30 Dec
4 days 1 hours
63 earthquakes
2022
S20220109.1(18.4km)
8 Jan
18 hours
37 earthquakes
S20220113.1(29.5km)
13 Jan
4 days 5 hours
157 earthquakes
S20220419.1(19.0km)
18 Apr
8 days 1 hours
76 earthquakes
S20220519.2(25.2km)
18 May
1 day 8 hours
29 earthquakes
S20220702.1(14.6km)
1 Jul
3 days 23 hours
49 earthquakes
S20220922.1(27.9km)
22 Sep
1 day 18 hours
31 earthquakes
S20220930.2(26.5km)
29 Sep
4 days 5 hours
69 earthquakes
S20221026.1(14.5km)
25 Oct
1 day 10 hours
35 earthquakes
2023
20 Feb
1 day 17 hours
25 earthquakes
S20230326.1(17.2km)
25 Mar
2 days 6 hours
38 earthquakes
2024
S20240829.1(12.2km)
28 Aug
2 days 1 hours
31 earthquakes
2025
16 May
4 days 7 hours
45 earthquakes
S20251128.1(17.6km)
28 Nov
7 days 2 hours
82 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20200703.1 Near Anza, California

The Anza region in Riverside County, southern California, lies within the San Jacinto Fault Zone, a major component of the Pacific-North American plate boundary. This right-lateral strike-slip fault system accommodates a significant portion of regional plate motion and is characterized by frequent small to moderate earthquakes. The area includes the Anza Seismic Gap, a locked segment of the fault that has not produced a major rupture in historical times and remains a focus of geophysical monitoring due to its potential for larger events.

Earthquake swarms are common in this tectonically active setting, often linked to fluid migration or stress transfer along fault segments. Historical records since 2000 document 52 swarms in the broader region, with annual counts rising notably after 2016. The provided statistics list the following yearly totals: 2001 (1), 2002 (1), 2003 (1), 2005 (2), 2009 (1), 2010 (3), 2011 (4), 2012 (2), 2013 (3), 2014 (4), 2015 (2), 2016 (5), 2017 (6), 2018 (7), 2019 (3), and 2020 (7).

Swarm S20200703.1 began at 22:10 UTC on 2 July 2020 and concluded at 14:39 UTC on 6 July 2020, centered 8 km southwest of Anza. Over 88 hours and 29 minutes, 70 earthquakes were recorded. Event magnitudes ranged from 0.0 to 1.9, with the majority below 1.0. Focal depths varied between 2 km and 17 km, clustering predominantly between 3 km and 8 km. The sequence showed peak activity on 3 July, including the largest event of magnitude 1.9 at 21:41 UTC at 3 km depth. Later events on 4–6 July were generally smaller and more scattered in depth.

Analysis of timing and parameters reveals a typical swarm pattern: an initial low-magnitude onset followed by clustered bursts over several days without a dominant mainshock. Depths indicate activity within the seismogenic zone of the San Jacinto Fault, consistent with shallow crustal deformation in the region.

References

USGS Earthquake Catalog
Southern California Earthquake Data Center
California Geological Survey Fault Activity Map