Paleoseismic investigations along faults is the only way to document their past rupture history. Such data from the Bidart Fan site along the Carrizo section of the San Andreas Fault indicate six surface rupturing earthquakes (>M6?) occurred along this section of the fault since 1300 A.D. These data helped formulate several new testable hypothesis regarding the rupture behavior of the San Andreas Fault. There is still a lot more work to be done in order to expand this record to 1000-2000 yrs. and determine the magnitudes of these events.

One such project at the Van Matre Ranch site just got completed. Two others recently got published:

Grant Ludwig, L., Akçiz, S. O., Arrowsmith, J R., and Salisbury, J. B. (2019). Reproducibility of San Andreas fault slip rate measurements at Wallace Creek in the Carrizo Plain, CA . Earth and Space Science, 6, 156-165.

Salisbury, J. B., Arrowsmith, J. R., Brown, N., Rockwell, T., Akçiz, S. O., & Ludwig, L. G. (2018). The Age and Origin of Small Offsets at Van Matre Ranch along the San Andreas Fault in the Carrizo Plain, California. Bulletin of the Seismological Society of America, Vol.108, 639-653.

You must have all heard us talk about the "Big overdue earthquake" on the San Andreas Fault, but a much slower (1 mm/yr) and quieter (recurrence intervals 2000-5000 yrs) fault system that extends for over 200 km from the Channel Islands to Pasadena also poses a great risk to Los Angeles. This left-laterally slipping fault system consisting of seven short (15-90 km) but closely spaced (separated by less than 2 km) faults is capable of causing a large earthquake of Mw 7.5 that ruptures right through downtown Los Angeles. Despite this potentially catastrophic hazard, there is no information on whether each of the faults rupture individually or together during an earthquake. Documentation of slip distribution along the Santa Cruz Island Fault is a first attempt in inferring the past history of this fault system.

Eastern Peninsular Ranges Mylonite Zone is an ideal analog for the deep crustal shear zone associated with the Coachella Valley segment of the SAF system. The purpose of our current investigation is to directly observe and sample this analog shear zone to place geologic constraints on the rheology of deep-crustal shear zones for direct incorporation into the SCEC Community Rheology Model. But there is so much more to be done: What was the lifetime of this shear zone? What is the spatial distribution of strain in this crustal-scale ductile shear zone? What was its exhumation history? This shear zone is holding a lot of clues into the geological evolution of the area past and present.

Earth science students are expected to develop knowledge about geological features and processes by visualizing 2-D drawings and photos. These exercises are not very intuitive to many at first because they were never given an opportunity or a reason to develop 3-D visualization skills before starting in college. 3-D printing offers a unique opportunity to create new types of geologic block models that can transform the way students improve their spatial thinking skills. The first goal of these models is for students to see what these structures look like in 3-D. We anticipate the students to get engaged more with the topic during the class times and learn more efficiently by rotating these blocks with their hands and recording what they see in their minds, in a process much similar to their daily experiences. They may even print out a copy themselves at home if they want to study more at their own time. The second goal of these models is to improve their penetrative thinking skills. All models contain at least one detachable drill core which should help them with this skill development. Assessment of the efficacy of these models as tools for fostering spatial visualization abilities is currently ongoing.

Joseph Gutierrez will be presenting a poster at the GSA Annual Meeting in Phoenix. Don't forget to stop by and find out all about it