The February 28, 2001 earthquake
M6.8Nisqually, Washington
A magnitude 6.8 earthquake 32.2 miles deep, centred in Pierce County. The strongest in Washington’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900. 2 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 6.8
- duration magnitude (md)
- Depth
- 32.2 mi
- 51.8 km below the surface
- Local time
- Wednesday, February 28, 2001
- 10:54 PST; 18:54 UTC
- In Washington’s record
- 1st
- strongest of 5,002 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event uw10530748 (“The 2001 Nisqually, Washington Earthquake”). The USGS event page carries the ShakeMap, felt reports and the official summary.
Aftershocks
Earthquakes of magnitude 2.5 or more within 20 miles of the epicentre in the 30 days after.
2
Aftershocks in 30 days
3.4
Largest aftershock, Mar 1, 2001
2
On the first day
0
In the 7 days before
- The search radius is the surface rupture length expected for an earthquake of this magnitude (Wells and Coppersmith, 1994), at least 20 and at most 600 miles, so a great earthquake's sequence is counted along its whole fault.
Counties and cities within 50 miles
Distance from the epicentre to each county boundary (zero when inside) and to each city centre.
Counties
- Pierce CountyWA · inside
- Thurston CountyWA · 3.1 mi
- Mason CountyWA · 6.3 mi
- King CountyWA · 16.0 mi
- Kitsap CountyWA · 17.9 mi
- Grays Harbor CountyWA · 22.8 mi
- Lewis CountyWA · 32.0 mi
- Jefferson CountyWA · 33.8 mi
- Pacific CountyWA · 39.1 mi
- Snohomish CountyWA · 46.1 mi
Earthquakes around the epicentre
180 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first
- April 29, 1965M6.7
- April 13, 1949M6.7
- November 12, 1939M6.1
- February 14, 1946M5.8
- July 2, 1999M5.8
- March 16, 1904M5.3
- October 27, 1940M5.1
- January 28, 1995M5.0
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.