Investigation of nearfield postseismic slip following the M sub(w) 7.3 Landers earthquake sequence of 28 June 1992, California

Repeated precise surveys of six nearfield trilateration arrays reveal that minor horizontal displacements occurred across the several fault ruptures in the five months following the Landers earthquake sequence. The displacements range from 0 plus or minus 2 mm on the Camp Rock and Emerson faults, to 3 plus or minus 2 mm on the Landers fault, to 9plusmn; 2 mm on the Johnson Valley fault, to 40 plus or minus 5 mm on the Eureka Peak fault, consistent in magnitude and duration with GPS and creepmeter measurements by other investigators. The relative lack of afterslip at all sites except across the Eureka Peak fault is probably due to the lack of a thick alluvial cover. Concomitant precise resurveys of level lines across the San Andreas fault in Coachella Valley and of a trilateration array at Durmid Hill, south easternmost San Andreas fault, failed to reveal vertical or horizontal displacements greater than the allowable uncertainty (