A 3.8-magnitude earthquake jolted some Lake County communities near The Geysers Tuesday night, according to U.S. Geological Survey reports.
The quake — larger than the many tiny temblors that occur in the area regularly - struck at 9:43 p.m.
It was centered about two miles east-southeast of The Geysers and 13 miles northeast of Healdsburg.
It was a shallow quake, just over one mile deep.
The thermal steam fields straddle Lake and northeastern Sonoma counties. Seven people in the Healdsburg area and two in the Lower Lake area reported feeling a weak quake and 18 people from the Middletown area told the USGS the earthquake felt light.
None of the responders to the agency's website reported any damage.
The USGS initially gave the temblor a 3.6-magnitude, then upgraded it to 4.1 then dropped it to 3.8, according to the agency website.
Dozens of tiny quakes occur in the area each month, attributed to the injection of wastewater and removal of steam to run power plants.
Most are in the 1.5-magnitude range.