SLIP ALONG THE HAYWARD FAULT, CALIFORNIA, ESTIMATED FROM SPACE-BASED SYNTHETIC-APERTURE RADAR INTERFEROMETRY

For 3-5 years following the 1989 M 7.1 Loma Prieta earthquake, creep a long the southern Hayward fault, California, slowed or ceased. Slip ap parently resumed pre-earthquake rates by 1994 except for a locked simi lar to 3-km-long segment at the southern fault tip, which had consiste ntly slipped at similar to 9 mm/yr before 1989, We use repeated interf erometric synthetic aperture radar (IntSAR) measurements to map active deformation along the Hayward fault while slip rates recovered betwee n 1992 and 1995. If pure strike slip is assumed, then the slip rates e stimated from IntSAR range changes between 1992 and 1995 are generally consistent with creepmeter and alignment-array measurements along muc h of the fault and confirm the temporary locking of the southernmost f ault segment. However, along similar to 6 km of the Fremont segment, I ntSAR slip estimates appear to be at least twice those measured in the field. Transient vertical slip (northeast side up) of 23 mm/yr near t he southern tip of the creep patch could explain this observation. Fir st-order boundary-element models of a vertical frictionless fault in a n elastic half-space predict some, but not all, of the inferred vertic al slip.