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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:
37 km NNE of Amboy, Washington
Period:
17 Jan 2008 06:24:30 - 20 Jan 2008 18:08:51 (3 days 11 hours 44 minutes)
Volcanoes in 100km radius:
St. Helens(0km), West Crater(36km), Indian Heaven(41km), Adams(53km), Rainier(79km), Hood(99km)
Earthquakes:
63
11 swarms found nearby.
2000
5 Nov
2 days 9 hours
45 earthquakes
2004
22 Sep
24 days 15 hours
2267 earthquakes
23 Oct
258 days 6 hours
5484 earthquakes
2005
19 Jul
53 days 4 hours
548 earthquakes
2011
29 Jan
2 days 1 hours
31 earthquakes
14 Feb
3 days 21 hours
85 earthquakes
2013
S20130824.1(17.7km)
23 Aug
2 days 21 hours
56 earthquakes
2018
1 Jan
23 hours
24 earthquakes
3 Jan
2 days 12 hours
81 earthquakes
6 May
7 days 23 hours
91 earthquakes
2019
12 Mar
36 minutes
24 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm VS20080118.1 Near Amboy, Washington: January 2008 Event Analysis

A minor seismic swarm occurred approximately 37 km north-northeast of Amboy in Clark County, Washington, between 17 and 20 January 2008. The sequence began at 06:24 on 17 January and concluded at 18:08 on 20 January, spanning 83 hours and 44 minutes. During this period, 63 earthquakes were recorded, with the majority exhibiting very low magnitudes and shallow focal depths.

Magnitudes ranged from -1.1 to 1.4, and depths clustered between -1 km and 3 km, consistent with superficial crustal activity. The largest event reached magnitude 1.4 on 19 January at a depth of -1 km. Negative magnitudes indicate microseismic events detectable only by sensitive instruments. Activity showed no clear migration pattern, with events distributed throughout the swarm duration rather than clustering in distinct phases.

This swarm represents one of four documented sequences in the region since 1 January 2000. Earlier swarms occurred in 2000 (one event), 2004 (two events), and 2005 (one event). Such episodic low-magnitude swarms are characteristic of the Pacific Northwest’s tectonically active crust.

The Amboy area lies within the southern Washington Cascade Range, influenced by the Cascadia subduction zone where the Juan de Fuca Plate descends beneath the North American Plate. This setting produces both volcanic and tectonic seismicity. Shallow swarms like VS20080118.1 often reflect fluid migration or minor crustal adjustments rather than large-scale fault rupture. No surface rupture or felt shaking was associated with the 2008 sequence.

Regional geology includes Quaternary volcanic deposits and fault systems linked to the broader Cascade volcanic arc. Ongoing monitoring by regional seismic networks continues to track similar microseismic activity, which provides data on stress accumulation along the subduction interface.

References

USGS Earthquake Catalog (historical swarm parameters as provided)
Pacific Northwest Seismic Network regional reports
USGS Geological Survey Professional Papers on Cascade Range tectonics