Everyone in California is well aware of a potential for a devastating earthquake in populated cities or rural communities within our state. How we view that real possibility and provide some predictive aspects as to where one may strike can be best found in our geologic prehistory of these major faults. The San Andreas remains our biggest worry and the major fault, spanning the state’s length, having immense capability to destroy and injure. It would seem knowing this fault’s prehistoric faulting cycles of movement, magnitude and intervals between major events can help give us some reasonable predictive time frame of when we might expect another “Big One”.
Probability of Major Earthquake next 50 yrs. Click for More
Patterns of large earthquakes on the southern San Andreas Fault from paleoseismic data
Abstract of Talk
Large earthquakes are infrequent along a single fault, and therefore historic, well-characterized earthquakes exert a strong influence on fault behavior models. This is true of the 1857 Fort Tejon earthquake (estimated M7.7–7.9) on the southern San Andreas Fault (SSAF), but an outstanding question is whether the 330 km long rupture was typical. New paleoseismic data for six to seven ground-rupturing earthquakes from the Frazier Mountain site on the Big Bend and recent work from the Elizabeth Lake trench site on the Mojave section of the SSAF restrict the pattern of possible ruptures on the 1857 stretch of the fault. Specifically, in conjunction with existing sites, we show that over the last ~650 years, at least 75%of the surface ruptures are shorter than the 1857 earthquake, with estimated rupture lengths of 100 to <300 km. These results suggest that the 1857 rupture was unusual, perhaps leading to the long open interval, and that a return to pre-1857 behavior would increase the rate of M7.3–M7.7 earthquakes
The Presenter - Dr. Kate Scharer
Dr. Kate Scharer studies active tectonics, with a primary emphasis on the prehistoric occurrence and effects of large earthquakes. Much of her work is on the San Andreas Fault system, where she has developed long series of paleoearthquake records in order to explore variations in the timing and size of these events. As part of this research area, she studies tectonic geomorphology and works to improve our ability to radiocarbon date Holocene sediments. Dr. Scharer also researches tectonic processes at longer timescales, investigating the slip rates on active faults and the development and growth of folds and thrust belts.
Dr. Scharer holds a Ph.D. from the University of Oregon and a B.S. in Geological Sciences from the University of Washington. She was a professor at Appalachian State University in North Carolina, but most of her fieldwork has been on the geology of southern California.
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Updated Jan. 17th, 2015 Feb. Program, PSAAPG and upcomming