Slip in the 1857 and Earlier Large Earthquakes Along the Carrizo Plain, San Andreas Fault

Slip, Tripped, and Faulted Earthquake risk assessment can be improved if we were able to quantify the recurrence and magnitude of slip events. Until recently though, a lack of sophisticated seismometers has forced us to rely on anecdotal evidence from those who survived major earthquakes or to look for clues in the landscape. Zielke et al. (p. 1119 , published online 21 January; see the Perspective by Scharer ) analyzed high-resolution images of the San Andreas Fault in southern California. The data showed that major surface ruptures, such as the 1857 Fort Tejon earthquake, resulted from slips of only about 5 meters; much less than previously thought. In a study that lends support to this discovery, Grant Ludwig et al. (p. 1117 , published online 21 January; see the Perspective by Scharer ) suggest from analysis of the geomorphic features of this region that several smaller earthquakes have occurred during recent centuries rather than infrequent but larger movements. The Perspective by Scharer (p. 1089 ) discusses how paleoseismological studies like these may be valuable for feeding data into earthquake prediction.