Location:

Period:

22 Jul 2020 07:10:37 - 27 Jul 2020 08:51:23 (5 days 1 hour 40 minutes)

Volcanoes in 100km radius:

Dana(99km)

Earthquakes:

126

7 swarms found nearby.

2007

PS20071002.1(72.2km)

2 Oct

2 hours

5 earthquakes

2011

S20110505.2(21.9km)

5 May

3 days 7 hours

50 earthquakes

2020

PS20200722.1(114.2km)

22 Jul

15 hours

6 earthquakes

S20200722.1(21.1km)

22 Jul

13 days 17 hours

332 earthquakes

PS20201019.2(86.6km)

19 Oct

1 day 4 hours

12 earthquakes

2023

S20230716.3(28.8km)

16 Jul

6 days 3 hours

65 earthquakes

2025

S20250716.4(28.9km)

16 Jul

14 days 21 hours

502 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20200722.2: Analysis of Activity South of Sand Point, Alaska

Seismic swarm S20200722.2 occurred 62 km south of Sand Point, Alaska, within the tectonically active Aleutian subduction zone. This region lies along the convergent boundary where the Pacific Plate subducts beneath the North American Plate at rates of approximately 6–7 cm per year, generating frequent earthquakes and volcanic activity across the Alaska Peninsula and Aleutian Islands. The swarm initiated at 07:10 on 22 July 2020 and concluded at 08:51 on 27 July 2020, spanning 121 hours and 40 minutes with a total of 126 recorded events. Analysis of the first 100 events reveals a typical swarm pattern characterized by a rapid onset followed by a gradual decline in frequency. Magnitudes ranged from 1.2 to 5.0, with the majority falling between 1.5 and 2.5. Depths clustered predominantly between 13 and 28 km, though several larger events reached 41–45 km. Key events included a magnitude 4.9 earthquake at 42 km depth on 22 July at 11:02, a magnitude 4.7 at 41 km on 23 July at 19:56, and two magnitude 5.0 events at 43 km and 45 km depth on 24 July at 03:07 and 13:24, respectively. These deeper shocks likely reflected slip along the subduction interface, while shallower activity indicated crustal adjustments. The swarm's temporal distribution showed peak activity in the first 24 hours, with events occurring at intervals of minutes to hours, transitioning to more sporadic occurrences by 24–27 July. Depths remained consistent within the upper to mid-crustal range, consistent with stress release in the overriding plate and along the megathrust. Geologically, Sand Point sits near the Shumagin Islands segment of the subduction zone, an area known for both megathrust earthquakes and swarm-like sequences driven by fluid migration or aseismic slip. Historical records since 2000 indicate only four such swarms in the vicinity: single events in 2007 and 2011, plus two in 2020. This low frequency underscores the episodic nature of swarm activity amid the region's overall high seismicity. The 2020 swarms, including S20200722.2, align with ongoing monitoring of the Alaska Peninsula's seismic hazards. No surface rupture or significant aftershock migration beyond the swarm cluster was noted. Such sequences provide valuable data for refining models of subduction zone behavior and improving regional earthquake forecasting.

References

Alaska Earthquake Center, University of Alaska Fairbanks (updated seismic catalogs through 2023)
USGS Earthquake Hazards Program, Aleutian Subduction Zone reports
SeismoSight internal swarm classification database