| Measured displacements of faulted gullies, archaeological dating of an 820 year old Indian stone ring displaced 142 cm in the 1690 earthquake, trenching and radiocarbon dating of 38,820 year old lagoonal sediments displaced 185 cm, and geodetic measurements were used to determine slip rates (5–7 mm/yr), recurrence interval (300–360 years), and the characteristic earthquake displacement (158 cm) for the transtensional North Shore segment, San Andreas fault, Mecca Hills, California. Aligned geomorphic features and vegetation contrasts suggested a newly discovered active fault (Witbaard fault), as did seismic refraction, and ground penetrating radar and magnetometer surveys. Global positioning system measurements (1992–1998) suggest 2–4 mm/yr of aseismic creep along the Witbaard fault, similar to the rate measured on contiguous transpressional San Andreas fault patches. The Witbaard fault may transfer creep by a right step around the main fault trace to retain the locked condition of this transtensional fault segment. |
