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

3. Mystic Lake Site

6. Mystic Lake site seen in 1940 Air Photo

7. NESWsoutheast wall

8. 3 more shallow trenches in 2010- saw same relationships. Trench 6 Trench 7

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

10. 1738- 1853 1521-1616 1349- 1445 1076- 1258 807- 961 579- 845 Years AD 1670-1828

11. Mystic Lake events normalized probability density functions 1.5 1829 1574 1428 1189 888 711 1670-1828 Recurrence Interval= 159 to 210 years

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

13. Comparison with SAF record

14. Comparison with Wrightwood record

15. 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

16. 400m long trench

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