"It was a small earthquake, measuring just 3.1 on the Richter scale, but its location in the heart of the Sacramento-San Joaquin Delta has experts buzzing.

The Oct. 15 quake was centered 7 miles northwest of Lathrop, on Union Island. No faults are known to exist in that area, where earthquakes are rare.

The temblor could offer new insights on safety issues in the Delta, where concerns about flood protection and water quality during a major quake have been growing. It is also a reminder that many mysteries lurk below ground – even in California, a nucleus of earthquake research."

Matt Weiser reports for the Sacramento Bee October 27, 2010. [2]