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New paleoseismic data from the northern San Jacinto Fault Zone, southern California

New paleoseismic data from the northern San Jacinto Fault Zone, southern California. Nate Onderdonk (CSULB) Tom Rockwell (SDSU) Sally McGill (CSUSB) Gayatri Marliyani (SDSU). Funded by SCEC. Site Location- northern San Jacinto fault zone. San Andreas Fault.

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New paleoseismic data from the northern San Jacinto Fault Zone, southern California

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  1. New paleoseismic data from the northern San Jacinto Fault Zone, southern California Nate Onderdonk (CSULB) Tom Rockwell (SDSU) Sally McGill (CSUSB) Gayatri Marliyani (SDSU) Funded by SCEC

  2. Site Location- northern San Jacinto fault zone San Andreas Fault • topography along the fault zone (google earth?) San Jacinto Fault 2 Image from http://www.atmos.ucla.edu/~alexhall/res.html

  3. Mystic Lake Site

  4. Mystic Lake site seen in 1940 Air Photo

  5. NE southeast wall SW

  6. Trench 6 • 3 more shallow trenches in 2010- saw same relationships. Trench 7

  7. Depositional model 1. Event on SW fault strand causes subsidence 2. Sag fills with clay, silt, sand 3. Soil layer develops 4. Repeat NE southeast wall SW

  8. 1738- 1853 1670-1828 1521-1616 1349- 1445 1076- 1258 807- 961 579- 845 Years AD

  9. Mystic Lake events normalized probability density functions 1829 1670-1828 1574 1428 Recurrence Interval= 159 to 210 years 1189 888 711 1 .5

  10. Comparing Mystic Lake events to Hog Lake record ? ?

  11. Comparison with SAF record

  12. Comparison with Wrightwood record

  13. Conclusions Mystic Lake is a great source of paleoseismic info for the SJF and has potential for a long record Shallow trenches show evidence for 7 events in past 1700 years (avg. RI = 185 years) Non-Conclusions Some events may correlate with Hog Lake events? and maybe Wrightwood as well? if so: San Jacinto step-over is not a segment boundary, and neither is juncture with SAF

  14. 400m long trench

  15. Correlated stratigraphy across the entire sag SW fault zone is locus of activity

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