Academic literature on the topic 'Faults (Geology) Strike-slip faults (Geology) Seismology San Andreas Fault (Calif.)'

Abstract The nature of the connection between the Eastern California shear zone (ECSZ) and the San Andreas fault (SAF) in southern California (western United States) is not well understood. Northwest of San Gorgonio Pass, strands of the ECSZ may be migrating south and west into the convergent zone of the San Bernardino Mountains (SBM) as it is advected to the southeast via the SAF. Using high-resolution topography and field mapping, this study aims to test whether diffuse faults within the SBM represent a nascent connection between the ECSZ and the SAF. Topographic resolution of ≤1 m was achieved using both lidar and unmanned aerial vehicle surveys along two Quaternary strike-slip faults. The Lone Valley fault enters the SBM from the north and may form an along-strike continuation of the Helendale fault. We find that its geomorphic expression is obscured where it crosses Quaternary alluvium, however, suggesting that it may have a low rate of yet-undetermined activity. The Lake Peak fault is located farther south and cuts through the high topography of the San Gorgonio massif and may merge with strands of the SAF system. We find that this fault clearly cuts Quaternary glacial deposits, although the magnitude of offset is difficult to assess. Based on our interpretation of geomorphic features, we propose that the Lake Peak fault has predominantly dextral or oblique-dextral motion, possibly with a slip rate that is comparable to the low rates observed along other strands of the ECSZ (i.e., ≤1 mm/yr). Comparing the geomorphic expressions of these faults is difficult, however, given that the erosive nature of the mountainous landscape in the SBM may obscure evidence of active faulting. Based on these observations, as well as the occurrence of other diffuse faults in the region, we suggest that dextral strain is overprinting the actively convergent zone of the SBM, thereby creating a throughgoing connection between the ECSZ and the SAF west of San Gorgonio Pass.

The correlation of the ca. 23 Ma Pinnacles and Neenach volcanic complexes provides the most robust estimate on the timing and magnitude of Neogene right-lateral displacement on the San Andreas strike-slip fault system (California, United States). Displacement of ∼315 km has been applied rigorously along the plate margin to guide reconstruction of offset paleogeographic features. We present new detrital zircon U-Pb geochronology from the La Honda and western San Joaquin basins to document sediment provenance and reevaluate compositional constraints on a hypothesized key cross-fault tie (i.e., Castle Rock−Recruit Pass submarine fan system). Whereas the Upper Oligocene−Lower Miocene Vaqueros Formation of the La Honda basin was likely recycled from or shared a similar southern Sierra Nevada−western Mojave source with the underlying Eocene stratigraphy, we found that the Temblor Formation of the central Temblor Range (e.g., Recruit Pass submarine fan) was derived directly from Late Cretaceous northern Salinian basement. Furthermore, the Carneros Sandstone of the northern Temblor Range had a central Sierra Nevada batholith source that was likely recycled during early Miocene unroofing of the underlying stratigraphy. Conversely, strata of the southwest San Joaquin basin have provenance characteristics that match more closely with those of the La Honda basin. Our data preclude a contiguous Castle Rock−Recruit Pass submarine fan system across the San Andreas fault. These relationships are resolved by restoring the ca. 105−100 Ma basement of the northernmost Salinian block an additional ∼45 km or greater farther south relative to the Sierra Nevada batholith during late Oligocene−early Miocene time. Inconsistency in displacement along the San Andreas fault with the coeval correlation of the Pinnacles−Neenach volcanic complex is reconciled by postdepositional Miocene−Quaternary off-fault NW-SE structural shortening via major thrusts and/or transrotation of the Tehachapi block, in combination with extension of the northern Salinian block. This additional displacement reduces the need for pre−28 Ma slip on the San Andreas or predecessor faults to resolve Cretaceous through Eocene cross-fault relationships and reconciles an early Miocene discrepancy with Pacific−North America relative plate motion. This study highlights the fact that displacement histories of major strike-slip faults are divergent across changing structural domains, and recognition of slip disparities can constrain the magnitude of deformation.

Thesis (Ph. D.)--Dept. of Geosciences and School of Computing and Engineering. University of Missouri--Kansas City, 2005.
"A dissertation in geosciences and computer networking." Advisor: Tina M. Niemi. Typescript. Vita. Description based on contents viewed Mar. 12, 2007; title from "catalog record" of the print edition. Includes bibliographical references (leaves 331-341). Online version of the print edition.

Damage zones adjacent to or associated with faults are important to the geologic community because of their implications to hazards and their ability to preserve evidence for, and show history of, slip, fluid flow, and deformation associated with large strike-slip faults. We examine two fault zones in southern California where fault zone damage is expressed. We revisit the drilled crystalline core from the Cajon Pass California drill hole, 4 km northeast of the San Andreas fault (SAF), and 1 km north of the Cleghorn fault, to perform a systematic structural analysis of deformation and alteration associated with strike-slip faulting at the site. The core preserved 19 fault zones, 11 of which were not previously identified. The most significant fault is a fully intact steep-dipping fault zone at 3,402 m depth with potassium feldspar and epidote alteration. This fault correlates well with the nearby left-lateral Cleghorn fault. The extent of deformation varies within the core, and is controlled by the size of the fault zones intersected by the core. The extent of deformation varies and is controlled by the size of the faults the core intersected. We also examined the nature of right separation across the Clark fault damage zone along the Santa Rosa segment using a marker assemblage of biotite, hornblende-bearing tonalite - marble - bearing metasedimentary rocks - migmatite located in Coyote Mountain and the southeast Santa Rosa Mountains. Separation measured from this study is 16.8 km + 3.67 km / -6.03 km. Our measurement uses the updated location of the Clark fault in Clark Lake Valley and matches a distinctive lithologic contact across the fault instead of matching the diffuse western boundary of the Eastern Peninsular mylonite zone as previously used. We calculate the errors associated with projecting the contacts across Quaternary cover to the trace of the Clark fault, and consider a range of projections. Additional strain may have been accommodated in folds and small faults within the damage zone of the San Jacinto fault zone. Two large map-scale folds deform the marker assemblage near the San Jacinto fault zone and we tested whether Cretaceous ductile deformation or brittle late Quaternary right slip produced the folds.