The August 23 (2011) Virginia Earthquake: Virginia Tech Global Seismological Lab

The August 23 (2011) Virginia Earthquake

A moderate earthquake occurred in central Virginia on August 23 at 1:51 pm local time. USGS located the epicenter at about 61 km northwest from Richmond and 135 km southwest from Washington DC. The earthquake depth is about 6 km, it is not directly associated with any surface fault, the focal mechanism shows a reverse faulting (due to compression) on a northeast-striking plane. One of the possible origins of the compressional force comes from the spreading of the mid-Atlantic ridge.

We calculated maximum displacement (strongest shaking) in regions close to earthquake epicenter using spectral element wave propagation simulation (Komatitsch \& Tromp 1999). Harvard moment tensor and PDE locations are used in the simulation of wave propagation in a mantle model FFSW1 (Zhou et al 2006) and global crustal model (Bassin et al 2000).

Central Virginia Seismic Zone

Large earthquakes in eastern North America share characteristics with those of central North America. Most of them occur at sites of ancient rift valleys lack of significant recent faults. The most recent rift system developed about 200 million years ago as Pangaea was torn apart. Some rift arms succeeded, combining to create today's Atlantic Ocean basin. Other rift arms failed and left behind as weakened zones within continents.

Central Virginia Seismic Zone (USGS)

About Earthquake

"Earthquakes dot not kill, buildings do." Before an earthquake, check inside and outside of your home, visualize what might fall during strong shaking, and anchor those objects. The most severe shaking often last under a couple of minutes.

The amount of shaking depends on the size of the earthquake, distance from hypocenter, usually (not always, see the butterfly pattern on top of the page) there is more damage in regions closer to an earthquake. It also depends on the type of rock or sediment making up ground surface. Structures built on hard rocks usually experience less shaking. Low frequency surface waves can be amplified by tall buildings far away from epicenter. Modern 1 , 2 story wood frame houses usually perform well in earthquakes.