Annual Meeting - SCEC.org

SCEC Research Accomplishments | Report
Two new regions with geomorphic offsets were studied in 2011. Salisbury et al. (in review) compared field and lidar-based
measurements of hundreds of offsets along the Clark fault, and found that the geomorphic record of slip events favors fairly
regular offsets with maximum displacement near Anza of 3-4 m, and possible evidence for surface rupture associated with the
historical (1918) earthquake, which they relocate to the Clark strand of the San Jacinto fault (Figure 76). New trenching to the
northwest of Hog Lake may support this interpretation. On the San Andreas fault, Williams completed terrestrial lidar scans
of a dozen offset gullies along the Mission Creek section. These offsets are also fairly regularly spaced, lending additional
support for repetition of similar-sized earthquakes along the southernmost San Andreas fault and preference for rupture on
the Mission Creek fault over the San Gorgonio section in most events based on the recurrence data from nearby Thousand
Palms (Fumal et al., 2002).
Synthesis and Proposal Activities
This year the SoSAFE community developed and submitted an NSF Tectonics proposal geared to exploring the spatiotemporal
behavior of the San Andreas and San Jacinto fault systems. A team of PIs from nine institutions worked
collaboratively to identify key gaps in existing coverage of the SAF/SJF system, such as spatial gaps where lower (M7) events
could be overlooked and temporal gaps produced by insufficient dating or stratigraphic context in past projects, with the goal
of developing a full rupture history for the system. Modeling efforts were also included to explore the stress changes over
several earthquake cycles as constrained by paleoseismic data. This proposal received high marks from the external reviews.
Although declined for funding, the actualization of this proposal served to invigorate the SoSAFE community, aided in
identification of new ways to integrate paleoseismic data with other geophysical approaches, and fostered new collaborations
between researchers.
References
Blisniuk, K., Rockwell, T., Owen, L., Oskin, M., Lippincott, C., Caffee, M., and Dorch, J., (2010): Late Quaternary slip-rate
gradient defined using high-resolution topography and 10Be dating of offset landforms on the southern San Jacinto fault,
California, Journal of Geophysical Research – Solid Earth, Vol. 115, B08401, doi:10.1029/2009JB006346
Janecke, S., Dorsey, R., Forand, D., Steely, A., Kirby, S., Lutz, A., Housen, B., Belgarde, B., Langenheim, V., Rittenour, T. (2010)
High Geologic Slip Rates since Early Pleistocene Initiation of the San Jacinto and San Felipe Fault ZOnes in the San
Andreas Fault System: Southern California, USA, Geological Society of America Special Paper 475.
Zielke, O., Arrowsmith, J., Grant-Ludwig, L., and Akciz, S. (2010) Slip in the 1857 and earlier large earthquakes along the
Carrizo Plain, San Andreas fault, Science, v. 327, p. 1119-1121.
Grant-Ludwig, L., Akciz, S., Noriega, G., Zielke, O., and Arrowsmith, J. (2010) Climate-modulated channel incision and
rupture history of the San Andreas fault in the Carrizo Plain, Science, v. 327, p. 1117-1119.
Akciz, S., Grant-Ludwig, L., Arrowsmith, J., and Zielke, O. (2010) Century-long average time intervals between earthquake
ruptures of the San Andreas fault in the Carrizo Plain, California, Geology, v. 38, p. 787-790.
Working Group on California Earthquake Probabilities
The Working Group on California Earthquake Probabilities (http://www.WGCEP.org) is actively building the 3rd Uniform
California Earthquake Rupture Forecast (UCERF3). The main innovations for this model will be: 1) the relaxation of fault
segmentation assumptions and the inclusion of multi-fault ruptures; and 2) the addition of spatiotemporal clustering
(earthquake triggering and aftershocks), which will form the basis of an operational earthquake forecast. Our plan for both
these enhancements was bolstered tragically by the 2011 Tōhoku, Japan and Christchurch, New Zealand earthquakes.
The main accomplishment over the last year was the development of our Proposed UCERF3 Plan, which also includes
prototype model components (http://www.wgcep.org/sites/wgcep.org/files/UCERF3_Project_Plan_v52.pdf).
This was reviewed by the general scientific community at a marathon series of workshops in June, 2011, and a formal review
was conducted by our Scientific Review Panel [1] on June 13th and 14th, 2011. The Final UCERF3 Plan is due at the end of
September, 2011, and the final model is due June 30, 2012. The many details of this project can be found in the preliminary
plan referenced above.
2011 SCEC Annual Meeting | 91