Late Miocene–Quaternary fault evolution and interaction in the southern California Inner Continental Borderland

Abstract

Changing conditions along plate boundaries are thought to result in the reactivation of preexisting structures. The offshore southern California Borderland has undergone dramatic adjustments as conditions changed from subduction tectonics to transform tectonics, including major Miocene oblique extension, followed by transpressional fault reactivation. However, consensus is still lacking about stratigraphic age models, fault geometry, and slip history for the near-offshore area between southern Los Angeles and San Diego (California, USA). We interpret an extensive data set of seismic reflection, bathymetric, and stratigraphic data from that area to determine the three-dimensional geometry and kinematic evolution of the faults and folds and document how preexisting structures have changed their activity and type of slip through time. The resulting structural representation reveals a moderately landward-dipping San Mateo-Carlsbad fault that converges downward with the steeper, right-lateral Newport-Inglewood fault, forming a fault wedge affected by Quaternary contractional folding. This fault wedge deformed in transtension during late Miocene through Pliocene time. Subsequently, the San Mateo-Carlsbad fault underwent 0.6-1.0 km displacement, spatially varying between reverse right lateral and transtensional right lateral. In contrast, shallow parts of the previously identified gently dipping Oceanside detachment and the faults above it appear to have been inactive since the early Pliocene. These observations, together with new and revised geometric representations of additional steeper faults, and the evidence for a pervasive strike-slip component on these nearshore faults, suggest a need to revise the earthquake hazard estimates for the coastal region.

Morphology, structure, and kinematics of the San Clemente and Catalina faults based on high-resolution marine geophysical data, southern California Inner Continental Borderland (USA)

“…14) geophysical data. The ICB basins may have started to open in the late Miocene-early Pliocene based on general consensus that ICB kinematic history includes a period of Miocene-Pliocene extension or transtension (Crowell, 1974;Legg, 1991b;Crouch and Suppe, 1993;Bohannon and Geist, 1998;ten Brink et al, 2000;Legg and Kamerling, 2003;Sorlien et al, 2015;DeMets and Merkouriev, 2016), and that uplift of Santa Catalina Island began by earliest Pliocene (Castillo et al, 2018). The steep island topography we observe today (i.e., San Clemente Island, San Clemente Ridge, Santa Catalina Island, and…”

“…It is well understood that pre-existing crustal fabrics can influence strike-slip fault propagation or fault reactivation (e.g., Christie-Blick and Biddle, 1985;Scholz, 2002;Cunningham and Mann, 2007). Numerous studies have documented reactivation of pre-existing fault structures, including in our study area offshore of southern California (e.g., Crouch and Suppe, 1993;Fisher et al, 2009;Sorlien et al, 2015), and others have analyzed the effects of crustal structures on strike-slip fault geometry (e.g., Johnson and Watt, 2012;Johnson et al, 2018). Christie-Blick and Biddle (1985) differentiated between "essential" and "incidental" pre-existing structures, i.e., structures that significantly influence strike-slip fault geometry and propagation and those that are inherited and do not affect strike-slip deformation, respectively.…”

“…Stratigraphic control in the ICB basins comes from Ocean Drilling Program (ODP) sites in the Santa Monica Basin (ODP Leg 167, Site 1015; e.g., Normark and McGann, 2004;Normark et al, 2004b;Romans et al, 2009) and in the San Nicolas Basin (ODP Leg 167, Site 1013; e.g., Shipboard Scientific Party, 1997;Janik et al, 2004;De Hoogh, 2012). Stratigraphic age constraints also come from industry wells in some nearshore areas (e.g., Sorlien et al, 2015) and from shallow sediment cores and grab samples (Nardin et al, 1979;Barron, 1986;Vedder et al, 1986;Vedder, 1990;Normark et al, 2004b). Acoustic basement throughout the ICB (which we refer to herein as simply "basement") consists of the Catalina Schist, as well as intrusive granitic and volcanic rocks in some areas (e.g., Crouch and Suppe, 1993;Bohannon and Geist, 1998).…”

Neogene Development of the Terror Rift, Western Ross Sea, Antarctica

“…Some global strike‐slip fault zones have vertical components that do not increase consistently downwards into older sedimentary rocks. These strike‐slip faults can even vary within a short distance from normal to reverse separation with switching of the side that is downthrown, such as for the Palos Verdes fault near Los Angeles (Brankman & Shaw, 2009; C. C. Sorlien et al., 2013), and the Newport‐Inglewood fault also near Los Angeles (C. C. Sorlien et al., 2015). In contrast, we interpret that even the subvertical fault strands have the same sense of vertical stratigraphic separation along their full lengths, and this vertical separation increases with depth and thus ages at any one location on a fault strand.…”

Scales of Stress Heterogeneity Near Active Faults in the Santa Barbara Channel, Southern California

“…However, there is a significant boundary near platform Holly at which each of these faults exhibit significant changes in orientation. Beneath the platform, the two deepest faults of this system, the Pitas Point and North Channel faults, show around a 25° clockwise change in strike, which is accomplished by a geometric segment boundary in the North Channel fault, and a continuous double bend in strike of the Pitas Point fault (Sorlien et al, ; Sorlien & Nicholson, ) (Figure ). At this same location, there is also a significant segment boundary and change in strike of the steeply dipping Red Mountain fault, which is divided into two segments that overlap just west of the platform (Figure a).…”