Lb. Grant et al., PALEOSEISMICITY OF THE NORTH BRANCH OF THE NEWPORT-INGLEWOOD FAULT ZONE IN HUNTINGTON-BEACH, CALIFORNIA, FROM CONE PENETROMETER TEST DATA, Bulletin of the Seismological Society of America, 87(2), 1997, pp. 277-293
Application of cone penetrometer testing (CPT) is a promising method f
or studying subsurface fault zones in stratified, unconsolidated sedim
ent where trenching is not feasible. Analysis of data from 72 CPTs, sp
aced 7.5 to 30.0 m apart, and 9 borings indicates that the North Branc
h fault, the active strand of the Newport-Inglewood fault zone (NIFZ)
in Huntington Beach, has generated at least three and most likely five
recognizable surface ruptures in the past 11.7 +/- 0.7 ka. Additional
smaller earthquakes similar to the M-w 6.4 1933. Long Beach earthquak
e may also have occurred but would not be recognizable with this metho
d. The minimum right-lateral Holocene slip rate of the NIFZ in the stu
dy area is estimated to be 0.34 to 0.55 mm/yr. The actual slip rate ma
y be significantly higher.