We don’t hear much of earthquakes rocking the United States east of the Rocky Mountains even though some serious ones have occurred. Considered a relatively stable portion of the continent, it can go years without an earthquake that can be felt. However, the eastern U.S. does experience infrequent small earthquakes. This region is far removed from plate boundaries where this activity is more likely to occur. Today (October 19, 2007) a 2.5 magnitude earthquake occurred near Litton Common, MA.
Earthquake prediction research is focusing on these smaller earthquakes as the “nucleation” for much larger ones. USGS seismologist predict that an earthquake of 6.2 to 6.7, similiar to the magnitude of the Loma Prieta, will strike the San Francisco Bay area in the next 30 years. The San Andreas Fault Observatory At Depth is tapping into the San Andreas Fault to uncover the processes that result in small earthquakes. For more details see KQED’s Quest video podcast “Earthquakes: Breaking New Ground” at iTunes.
Image: Aerial view of collapsed sections of the Cypress viaduct of Interstate Highway 880. [H.G. Wilshire, U.S. Geological Survey] (Source)