A swarm of earthquakes has been affecting central Arkansas for several days; the strongest so far was this morning, estimated at magnitude 4.1. That, like several other events in the swarm, was large enough to be felt across the state.
The US Geological Survey says in a press release that Arkansas has a history of swarms. "Scientists do not know why swarms start, why they stop, or how long to expect them to last. The possibility of a larger earthquake cannot be discounted, but none of the other swarms have caused any reason to expect a future earthquake large enough to cause significant damage in central Arkansas."
These little shakers are not deadly, but the region was devastated 200 years ago by very large earthquakes, and a regionwide earthquake drill involving ten states will be taking place on 28 April. Consider them a consciousness-raising device from your local lithosphere.
More:
USGS page for the 4.1 event
Live quake map of Arkansas
April ShakeOut drill
About earthquakes
Earthquake resources for the eastern U.S.A.
Geology of Arkansas
US Geological Survey image
Comments
Back in the summer of 1982 there was a swarm of about 90 earthquakes in that same area of central Arkansas, north of Little Rock. Four had magnitudes between 4.0 and 4.5. They recorded about 40,000 earthquakes in that area between 1982 and 1985, then it went quiet again, until lately.