Constraints from Precariously Balanced Rocks on Preferred Rupture Directions for Large Earthquakes on the Southern San Andreas Fault

Kim B. Olsen, & James N. Brune

Published April 2008, SCEC Contribution #1143

We have compared near-fault ground motions from TeraShake simulations of Mw7.7 earthquake scenarios on the southern San Andreas Fault with precariously balanced rock locations. The TeraShake scenarios with different directions of rupture generate radically different ground motions to the northwest of the Los Angeles Basin, primarily because of directivity effects, and thus provide constraints on the ground motion and rupture direction for the latest (1690) large event on that section of the San Andreas Fault. Due to the large directional near-field ground motions predicted by the simulations, we expect the precariously balanced rocks to be located primarily in the backward rupture direction or near the epicenter. Preliminary results favor persistent nucleation at or slightly northwest of the San Gorgonia Pass fault zone for large earthquakes on the southern San Andreas Fault.

Citation
Olsen, K. B., & Brune, J. N. (2008). Constraints from Precariously Balanced Rocks on Preferred Rupture Directions for Large Earthquakes on the Southern San Andreas Fault. Journal of Seismology, 12(2), 235-241. doi: 10.1007/s10950-007-9078-7.