Recurrence Intervals Frequency – Average time between past seismic events – aka “recurrence interval” Recurrence Interval = Average slip per major rupture / Slip Rate Quote: The next large earthquake on the southern San Andreas Fault could affect 10 million people or more. “It could (The Big One) be tomorrow or it could be 10 years or more from now” -Yuri Fialko, September 2005

Prediction vs. Forecasting Recurrence Intervals – Past occurrence of random events. Prediction – Determining the hazard of seismic activity of given areas is important to predict future occurrences. Forecasting - Future likelihood of random events. – Using probability of seismic activity occurring in a given area during a given time – Assessing both the slip rate of the fault and the risk the fault presents

Recurrence Intervals Segments Northern Segment – Average slip rate (1.3 – 1.5 inches per year) – Meaningful average recurrence interval 200 with an uncertainty of 50 years – 1906 San Francisco Earthquake 7.8M Central Segment – Aseismic creep – slips continuously without causing earthquakes – 1857 Fort Tegon Earthquake 7.9M Few exceptions i.e. Parkfield Southern Segment (Mojave Segment) – Average slip rate (1.3 – 1.5 inches per year) – Meaningful average recurrence interval 200 with an uncertainty of 50 years – No major earthquake in over 250 years *( M) YIKES! Fun Fact: Probable Magnitudes on the SAF are M W (Hang on!) Creeping at Hollister, CA

References Furnal, Thomas E., Silvio K. Pezzopane, Ray J. Weldon, II, and David P. Schwartz. "A 100-Year Average Recurrence Interval for the San Andreas Fault at Wrightwood, California." Science 259 (1993): n. pag. Science. Web. "Information and Resources about the San Andreas Fault." Information and Resources about the San Andreas Fault. Ed. David K. Lynch. N.p., Web. 17 June Nester, Irene K. "San Andreas Transform Fault Zone." San Andreas Transform Fault Zone. Emporia State University, 25 Apr Web. 13 June Richardson, Eliza. "Different Methods for Determining Recurrence Interval." Welcome to the Dutton E-Education Institute!Pennsylvania State University, n.d. Web. 14 June