Location:

Period:

28 May 2021 11:59:10 - 29 May 2021 04:30:59 (16 hours 31 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

28 swarms found nearby.

2003

S20031003.1(10.5km)

3 Oct

1 day 20 hours

34 earthquakes

S20031009.1(27.1km)

8 Oct

2 days 19 hours

40 earthquakes

S20031123.1(14.2km)

22 Nov

2 days 23 hours

36 earthquakes

2004

S20040603.1(26.7km)

2 Jun

8 days 0 hours

197 earthquakes

2005

S20050521.1(17.5km)

21 May

1 day 10 hours

39 earthquakes

S20050918.1(23.0km)

17 Sep

2 days 13 hours

34 earthquakes

S20051207.2(13.6km)

7 Dec

2 days 20 hours

40 earthquakes

2007

S20070509.1(16.0km)

8 May

2 days 16 hours

36 earthquakes

2008

S20081121.2(26.5km)

21 Nov

1 day 17 hours

26 earthquakes

2012

S20120408.2(24.9km)

8 Apr

2 days 17 hours

45 earthquakes

S20120623.1(21.6km)

22 Jun

1 day 13 hours

37 earthquakes

S20120627.1(23.7km)

26 Jun

3 days 22 hours

58 earthquakes

2013

S20130605.1(27.0km)

5 Jun

2 days 0 hours

56 earthquakes

S20130617.1(27.4km)

16 Jun

6 days 16 hours

72 earthquakes

2014

S20140404.2(16.4km)

3 Apr

1 day 13 hours

40 earthquakes

S20140623.1(24.8km)

22 Jun

1 day 19 hours

28 earthquakes

2015

S20150408.1(26.3km)

8 Apr

2 days 9 hours

57 earthquakes

2016

S20160319.2(25.5km)

18 Mar

20 hours

29 earthquakes

2017

S20170729.1(23.5km)

29 Jul

14 hours

26 earthquakes

S20171226.1(29.8km)

26 Dec

22 hours

33 earthquakes

2018

S20180726.1(13.2km)

26 Jul

1 day 8 hours

40 earthquakes

S20181205.1(29.4km)

4 Dec

1 day 21 hours

39 earthquakes

S20181220.1(25.6km)

20 Dec

2 days 19 hours

45 earthquakes

2019

S20190911.1(20.5km)

11 Sep

18 hours

26 earthquakes

2020

S20200321.1(25.7km)

21 Mar

14 days 4 hours

402 earthquakes

2021

S20210426.1(0.4km)

25 Apr

3 days 1 hours

45 earthquakes

2023

S20230918.1(12.0km)

18 Sep

15 hours

41 earthquakes

2024

S20240721.2(1.2km)

20 Jul

1 day 13 hours

51 earthquakes

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Seismic Swarm Analysis: Dollar Point, California, May 2021

A seismic swarm designated S20210528.2 occurred 8 km southeast of Dollar Point, California, on the north shore of Lake Tahoe. The sequence began at 11:59 on 28 May 2021 and concluded at 04:30 on 29 May 2021, spanning 16 hours and 31 minutes. During this interval, 33 earthquakes were recorded, with magnitudes ranging from 0.9 to 4.1 and focal depths between 3 km and 9 km.

The largest event reached magnitude 4.1 at 15:25:21 on 28 May at a depth of 7 km. Subsequent activity included multiple events above magnitude 2.0 clustered within the first several hours, followed by a gradual decline in both frequency and magnitude. Depths remained consistently shallow, indicating activity within the upper crust. The swarm exhibited typical characteristics of clustered microseismicity, with no single mainshock dominating the sequence.

Lake Tahoe lies within the northern Sierra Nevada, where tectonic deformation is driven by northwest-directed extension associated with the Walker Lane belt and the broader Basin and Range province. Active normal faults, including strands of the Tahoe-Sierra Frontal Fault Zone and the North Tahoe Fault, accommodate this strain. Historical seismicity in the region reflects this setting, with recurrent earthquake swarms linked to fluid migration or stress transfer along these structures.

Since 1 January 2000, 26 swarms have been documented in the area. Yearly counts include three swarms each in 2003, 2005, 2012, and 2018; two each in 2013, 2014, and 2017; and single swarms in 2004, 2007, 2008, 2015, 2016, 2019, 2020, and 2021. This pattern indicates persistent low-level seismic productivity consistent with the regional fault network.

The May 2021 swarm aligns with established geological understanding of shallow crustal faulting near Lake Tahoe. No surface rupture or significant damage was associated with events of this scale, though felt reports are common for magnitudes above 3.0 in the populated shoreline communities.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
California Geological Survey, Regional Fault Maps
Nevada Seismological Laboratory, Lake Tahoe Seismic Monitoring Reports