Paleoseismicity of the North Branch of the Newport-Inglewood Fault Zone from Cone Penetrometer Test Data

Lisa B. Grant Ludwig, John Waggoner, C. von Stein, & Thomas K. Rockwell

Published April 1997, SCEC Contribution #290

Application of cone penetromerer testing (CPT) is a promising method for studying subsurface fault zones in stratified, unconsolidated sediment where trenching is not feasible. Analysis of data from 72 CPTs. spaced 7.5 to 30.0 m apart, and 9 borings indicates that the North Branch 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 Mw 6.4 1933 Long Beach earthquake may also have occurred but would not be recognizable with this method. The minimum rightlateral Holocene slip rate of the NIFZ in the study area is estimated to be 0.34 to 0.55 mm/yr. The actual slip rate may be significantly higher.

Citation
Grant Ludwig, L. B., Waggoner, J., von Stein, C., & Rockwell, T. K. (1997). Paleoseismicity of the North Branch of the Newport-Inglewood Fault Zone from Cone Penetrometer Test Data. Bulletin of the Seismological Society of America, 87(no 2), 277-293.