Paleoseismic Evidence for the 21 April 1918 Mw 6.9 Surface Rupture of the Northern Clark Strand of the Central San Jacinto Fault, California

In this study, we present the results of a new paleoseismic investigation in the South Fork Wilderness similar to 7 km southeast of Blackburn Canyon, similar to 5 km northwest of Hog Lake near Anza, California, that demonstrate that the northern Clark fault has ruptured twice in the past 300 yrs. These new results corroborate previously made interpretations that were based solely on surficial geomorphology-that the northern Clark fault (with a recurrence interval of similar to 100 yrs) ruptured in both the November 1800 and April 1918 earthquakes and has a more frequent recurrence interval than the central and southern Clark fault.