(Newser) – Arkansas residents are dealing with a new rash of minor earthquakes, the AP reports. The quakes—30 since Sunday, with the largest at 3.8 magnitude—have not caused serious damage, but have understandably unnerved the populace. "Now when it happens, people say, 'Well, there's another one,'" says a local fire chief. Geologists say this earthquake swarm has been rattling Arkansas on and off since 2009, though the cause is unclear.

A possible reason is natural-gas mining of the Fayetteville Shale, which underlies the region. Much of this mining is performed by "fracking"—using jets of pressurized water to break open rock deposits. Fracking itself isn't believed to have a connection to the quakes, but "injection wells," the wells in which the water is deposited once it is used, may be the culprit. "We have a disposal well here just outside of the city," said the police chief in Guy. "People are suspecting that to be causing it, even though there isn't any proof of that." (Read more disaster stories.)

