Two "micro-earthquakes" that hit south of Portola Valley in the past five days were too weak to merit updating the United States Geological Survey's (USGS) "probability" prediction for the Peninsula's getting hit by a major quake, a public information officer said Tuesday (Jan. 25).
A 1.7-magntitude earthquake hit the Kaiser Permanente quarry east of Portola Valley on Jan. 20 at 2:24 p.m. A weaker quake followed in a section of the San Andreas fault southeast of Portola Valley in the early hours on Jan. 24.
"They were too small to know" if a larger quake may hit, Public Information Officer Susan Garcia said.
The USGS's 2008 forecast for the Bay Area estimated a 63 percent likelihood that a major earthquake measuring at least 6.7 will shake the region within the next 30 years. For years, USGS scientists have cautioned that such a quake could hit anytime, even within 30 minutes.
The probability is highest for the Hayward-Rodgers Creek Fault system at nearly one in three and lower at the San Andreas Fault, responsible for the 1989 Loma Prieta earthquake, at around one in five.
"There's always the reminder that we do live in earthquake country -- be prepared," Garcia said.