Late Quaternary slip rate gradient defined using high‐resolution topography and ¹⁰Be dating of offset landforms on the southern San Jacinto Fault zone, California

Abstract

Recent studies suggest the San Jacinto fault zone may be the dominant structure accommodating PA‐NA relative plate motion. However, because the late Quaternary slip history of the southern San Andreas fault system is insufficiently understood, it is difficult to evaluate the partitioning of deformation across the plate boundary and its evolution. Landforms displaced by the Clark fault of the southern San Jacinto fault zone were mapped using high‐resolution airborne laser‐swath topography and selected offset landforms were dated using cosmogenic 10Be. Beheaded channels at Rockhouse Canyon, displaced by 500 ± 70 m and 220 ± 70 m, have been dated to 47 ± 8 ka and 28 ± 9 ka, respectively. Farther south, near the southern Santa Rosa Mountains, an alluvial deposit displaced by 51 ± 9 m has been dated to 35 ± 7 ka. From these sites, the slip rate of the Clark fault is determined to diminish southward from 8.9 ± 2.0 to 1.5 ± 0.4 mm/yr. This implies a slip‐rate decrease along the Clark fault from Anza southeastward to its surface termination near the Salton Trough, where slip is transferred to the Coyote Creek fault, and additional deformation is compensated by folding and thrusting in the basin. These data suggest that since ∼30 to 50 ka, the slip rate along the southern San Jacinto fault zone has been lower than, or equivalent to, the rate along the southernmost San Andreas fault. Accordingly, either the slip rate of the San Jacinto fault has substantially decreased since fault initiation, or fault slip began earlier than previously suggested.

The kinematics of central-southern Turkey and northwest Syria revisited

“…As already noted (see above; section 4), the Karataş and Yumurtalık faults may conversely have Holocene slip rates of zero even though there is evidence of significant Pleistocene left-lateral slip on them. Such effects have been documented on other strike-slip fault zones elsewhere (e.g., Blisniuk et al, 2010;Ferry et al, 2011) and seem to arise because of complexities in the manner in which interseismic elastic strain becomes converted into permanent deformation. In effect, a fault may slip slowly during a span of time then later accelerate to 'catch up' with the expected long-timescale slip rate, this effect being possibly influenced by changes in crustal rheology during the course of the faulting (e.g., Cowie et al, 2007).…”

The role of waterfalls and knickzones in controlling the style and pace of landscape adjustment in the western San Gabriel Mountains, California

“…We hypothesize that this activity is related to the initiation of the rightlateral San Jacinto fault zone, which likely occurred ca. 1 Ma (Lutz et al, 2006;Kirby et al, 2007) to 1.8 Ma (Blisniuk et al, 2010). Morton and speculated that the onset of activity on the San Jacinto fault zone led to accelerated reverse slip along the Cucamonga fault zone in the eastern San Gabriel Mountains, but the implications for the western San Gabriel Mountains are unclear.…”

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

“…B. Lake records for Sonoran, southern California and Chihuahuan deserts (Kirby et al, 2006;Lozano-García et al, 2002;Roy et al, 2012;2014;Metcalfe et al, 2002) C. Alluvial chronology data for the westernmost Mojave and NW Sonoran deserts, organized according to latitude (on the left); cosmogenic depth profiles marked with squares (e.g., Blisniuk et al, 2010Blisniuk et al, , 2012; individual boulder ages marked with circles (Frankel et al, 2007;Matmon et al, 2005;Spelz et al, 2008;van der Woerd et al, 2006;Kent, 2011). D. Magnetic stratigraphy in core MD02-2508 offshore Baja California (Fig.…”