The August 23, 2011 earthquake

M5.8near Mineral, Virginia

A magnitude 5.8 earthquake 3.7 miles deep, centred in Louisa County. The strongest in Virginia’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900. 11 aftershocks of magnitude 2.5 or more followed within 30 days.

Watch the sequence unfold

Magnitude 5.8 · August 23, 2011

How the ground moved

Every recorded earthquake in the sequence, in order, through the month after.

About this replay

Local time (EDT)—Historical replay — logged times

Main shock—

Aftershocks—of 11 in 30 days

Largest so far—

Sequence milestones

EarthquakesSized by magnitude; each flares as it strikes, then fades

Main shockMagnitude 5.8 at 3.7 miles deep

Shaking frontsThe faster and slower seismic waves, drawn at typical speeds of 6 and 3.5 km per second, not measured ones

Sequence areaEarthquakes within 20 miles are counted, the length of fault a magnitude 5.8 typically breaks

Source: U.S. Geological Survey ComCat catalogue, every event it holds within 20 miles of the epicentre from seven days before to 30 days after. Times as logged, shown in local time (EDT); the clock runs faster as the sequence slows. Towns are today’s Census places.

The earthquake

Magnitude: 5.8; moment magnitude (mw)
Depth: 3.7 mi; 6.0 km below the surface
Local time: Tuesday, August 23, 2011; 13:51 EDT; 17:51 UTC
Epicentre: 37.91°N, 77.94°W; In Louisa County
In Virginia’s record: 1st; strongest of 91 since 1900
Within 50 miles: 37; counties; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event se609212 (“11 km SSW of Mineral, Virginia”). 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.

Aftershocks in 30 days

4.5

Largest aftershock, Aug 25, 2011

On the first day

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, nearest 30 of 37

Louisa CountyVA · inside
Goochland CountyVA · 6.3 mi
Fluvanna CountyVA · 6.9 mi
Spotsylvania CountyVA · 13.0 mi
Orange CountyVA · 14.4 mi
Hanover CountyVA · 14.5 mi
Powhatan CountyVA · 15.1 mi
Cumberland CountyVA · 16.2 mi
Caroline CountyVA · 16.7 mi
Albemarle CountyVA · 20.3 mi
Henrico CountyVA · 21.8 mi
Buckingham CountyVA · 22.4 mi
Madison CountyVA · 27.0 mi
Culpeper CountyVA · 28.3 mi
Chesterfield CountyVA · 28.4 mi
Amelia CountyVA · 28.7 mi
Charlottesville cityVA · 29.6 mi
Greene CountyVA · 30.2 mi
Richmond cityVA · 31.1 mi
King William CountyVA · 33.2 mi
Stafford CountyVA · 34.4 mi
Fredericksburg cityVA · 34.5 mi
Fauquier CountyVA · 36.5 mi
Nelson CountyVA · 40.5 mi
King George CountyVA · 40.7 mi
Prince Edward CountyVA · 40.8 mi
King and Queen CountyVA · 40.9 mi
Essex CountyVA · 43.3 mi
Rappahannock CountyVA · 44.2 mi
Rockingham CountyVA · 44.6 mi

Cities, largest first

RichmondVA · 36.3 mi
CharlottesvilleVA · 31.2 mi
FredericksburgVA · 36.4 mi
CulpeperVA · 38.9 mi

Earthquakes around the epicentre

18 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.

No earlier earthquake of magnitude 5 or more within 50 miles in the catalogue since 1900.

USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.