The August 22, 2011 earthquake
M5.3near Valdez, Colorado
A magnitude 5.3 earthquake 2.5 miles deep, centred in Las Animas County. The 3rd strongest in Colorado’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900. 24 aftershocks of magnitude 2.5 or more followed within 30 days.
Watch the sequence unfoldMagnitude 5.3 · August 22, 2011
How the ground moved
Every recorded earthquake in the sequence, in order, from the foreshocks to a month after.
The earthquake
- Magnitude
- 5.3
- moment magnitude (mwr)
- Depth
- 2.5 mi
- 4.0 km below the surface
- Local time
- Monday, August 22, 2011
- 23:46 MDT; 05:46 UTC on Aug 23, 2011
- In Colorado’s record
- 3rd
- strongest of 543 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event usp000j6wm (“6 km S of Valdez, Colorado”). 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.
24
Aftershocks in 30 days
4.0
Largest aftershock, Aug 23, 2011
10
On the first day
3
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
- Las Animas CountyCO · inside
- Huerfano CountyCO · 23.9 mi
- Costilla CountyCO · 25.5 mi
- Taos CountyNM · 29.0 mi
- Colfax CountyNM · 29.0 mi
- Union CountyNM · 38.5 mi
Earthquakes around the epicentre
193 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.