Last updated 26 August 2011

Overview

On Tuesday, August 23, 2011, at 17:51:04 UTC, a magnitude 5.8 earthquake struck roughly 6 km (3.7 miles) below the surface of the Earth, 8 km (5 miles) southwest of Mineral, Virginia.

The earthquake occurred within the Central Virginia Seismic Zone, which has produced many small and moderate earthquakes throughout recorded human history in the area, including a magnitude 4.8 in 1875 and a 4.5 event in 2003.

View more info at USGS.

UNAVCO Response Support

UNAVCO stands ready to support responses to this event. Current actions include:

• Recent satellite SAR (ENVISAT) data acquisitions have been confirmed and future acquisitions (ENVISAT and TerraSAR-X) have been requested covering the region near the epicenter. WInSAR users will have access to ENVISAT data. Detailed information will be posted in the forums.
• Campaign GPS systems are field-ready and on standby for deployment if requested.
• Plans for possible PBO permanent GPS sites are in development.
• It has been determined that there is no surface expression of the fault rupture visible around the epicenter. Structural damage is reported mostly for brick buildings, but no rupture. Based on this information, there are no current plans to collect TLS data near the epicenter.

In response to this event, community members are welcome to request support from UNAVCO. Please visit the Community Event Response Coordination page.

Relevant Event Data

• See surrounding GPS stations in the Data Archive Interface
• SAR Data
• 1 Hz UNAVCO PBO GPS data for BLA1, ACSO, and P779 for days 232 - 238; see the forum post for direct links to these data directories
• 1 Hz GPS data available at NGS and Leica SmartNet
• UNAVCO Community members Seth Stein and Frank lead a discussion about the tectonic setting
• Detailed information will be posted in the forums.

Event Coordination

Community members, please post relevant information about this event at our forum.

UNAVCO Event Response Coordinator: David Phillips, phillipsunavco.org

Tectonic Setting: East Coast Tremors

Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast. A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 100 km (60 mi) from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 500 km (300 mi) from where it occurred, and sometimes causes damage as far away as 40 km (25 mi). (USGS)

U.S. Geological Survey seismologist Susan Hough notes that, "The waves are able to reverberate and travel pretty happily out for miles."
Quoted from Forbes. Please see full article here.

Links and Resources

• USGS Event Site
• USGS News Release
• Earthquakes in Virginia and Vicinity 1774 − 2004
• IRIS Event Plot Suite
• USArray Ground Motion Visualization
• IRIS Teachable Moment
• East Coast shaken by 5.9-magnitude earthquake Tuesday; from Ocean City Today
• Hurriquake! Mudslami! Volnado! from Slate

Visualizations

Figure 1 - Map of Envisat ASAR scenes ordered by UNAVCO. The pair of frames in the southeast are centered over the epicenter, and the northwestern footprint shows the location of the one pre-event scene available, acquired by European Space Agency July 6 and now available in the WInSAR archive. Scenes will be acquired September-December to look for post-seismic changes. These scenes are synthetic aperture radar, and can be used to derive precise topographic maps and detect changes in topography. Images to come from Synthetic Aperture Radar (SAR), a powerful remote sensing system, enabling observations of the Earth’s surface day or night, in all weather conditions from airborne platforms and from space. [View full scale image].

Figure 2 - This USGS Community Internet Intensity Map or 'Felt Map' map shows the earthquake epicenter with color plots depicting the average shake/damage intensity per ZIP code felt by the people who experienced the Virginia earthquake and reported their experience to the USGS. (USGS).