Spatial and temporal analysis of geologic slip rates, Cucamonga Fault, California, USA: Implications for along-strike applications and multi-fault rupture
To constrain fault processes and hazard, fault slip rates may be extrapolated over different fault lengths or time intervals. Here, we investigate slip rates for the Cucamonga Fault (CF). The CF is located at the junction of the Transverse Range fault system with the San Andreas and San Jacinto Faults, and it is hypothesized to connect with these faults, promoting the propagation of large, multi-fault earthquakes. Previous work has shown that CF displacements on late Quaternary alluvial fan surfaces are highly variable along strike. We present two new 10Be surface exposure ages from depth profiles on the alluvial fans. Slip rates are consistent with a rate of 1.4 ± 0.3 m/kyr over time intervals of ∼20, ∼30, and ∼40 kyr. If the CF participates in multi-fault ruptures, then these earthquakes occur either rarely or with sufficient regularity to maintain apparently steady rates over multiple intervals. We also explore along-strike fault displacement variability using a calibrated morphological model. The model successfully reproduces scarp profiles and indicates that fault displacement variability can be explained in part by scarp age but not uplift rate. We infer that both erosion by ephemeral gullying and distributed deformation contribute to fault displacement variability, although both are difficult to detect confidently without excavations across the scarp. These investigations show that better characterization of cumulative-slip variability along strike may improve accuracy and precision of slip rates. Slip rates that do not consider epistemic uncertainties may not be suitable for extrapolation over longer fault sections.
Citation Information
| Publication Year | 2023 |
|---|---|
| Title | Spatial and temporal analysis of geologic slip rates, Cucamonga Fault, California, USA: Implications for along-strike applications and multi-fault rupture |
| DOI | 10.1029/2022JB024942 |
| Authors | Devin McPhillips, Katherine Scharer |
| Publication Type | Article |
| Publication Subtype | Journal Article |
| Series Title | Journal of Geophysical Research: Soild Earth |
| Index ID | 70242885 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | Earthquake Science Center |
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This report summarizes the age-dating results from two alluvial fan surfaces (map units Qyf2 and Qyf3) that are broken by strands of the Cucamonga Fault, in southern California, at Day Canyon and Etiwanda Canyon. Within this report are detailed the methodology used to collect samples of rock and sediment, determine concentrations of cosmogenic beryllium-10 in purified quartz isolated from the samp - Connect