Small, Very Shallow Quake Hits Stanislaus County

Overview

• The U.S. Geological Survey recorded a magnitude about 3.1–3.2 earthquake at roughly 9:18 p.m. on Wednesday that was unusually shallow in depth.
• USGS location data put the epicenter northwest of San Luis Reservoir near the Stanislaus–Merced–Santa Clara county border and about 14–21 miles southwest of nearby towns.
• The reported depth was effectively at the surface, with one automated reading showing negative 0.4 miles, a value that reflects measurement uncertainty for very shallow events.
• Only a single felt report was logged and there were no other quakes above magnitude 3.0 within 100 miles in the prior seven days, and local officials reported no damage.
• Fault attribution is pending even though the epicenter lies about 1.3 miles southwest of the Ortigalita fault zone, and experts say the short-term probability of a larger quake is very low.