Reservoir water weight blamed for Arkansas earthquake swarm

There have been 10 small earthquakes in the past five days near Harrison, Arkansas. (Photo: Earthquake Track)
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HARRISON, Ark. (AP) -- Earthquakes in northern Arkansas are being linked to the weight of extra water at a flood-swollen reservoir.

Earthquake geologist David Johnston works with the Arkansas Geological Survey. He says the added weight of the water at Bulls Shoals Lake likely triggered 10 earthquakes over five days last week near Harrison, a city about 140 miles north of Little Rock.

Johnston says the reservoir's water level has risen 42 feet because of rainfall since March 1. He says that 6 trillion pounds of added weight can cause a tremendous amount of stress.

Johnston tells the Springfield News-Leader the quakes are small, ranging from 1.5 to 3.6 in magnitude, and aren't expected to end soon.

Johnston says there weren't immediate reports of damage following a 3.6 magnitude quake on June 11. But he says some people reported houses creaking and pictures rattling on walls.

The Arkansas Geological Survey will add more ground-detection devices to better record the earthquakes.