Restraining segments and reactivation of the Santa Monica–Dume–Malibu Coast fault system, offshore Los Angeles, California

Abstract

[1] A regional west striking system of surface and blind faults transects northern metropolitan Los Angeles, separating the Santa Monica Mountains from two deep sedimentary basins. The surface faults include the Santa Monica, Dume, and Malibu Coast faults. The three-dimensional (3-D) geometries of these faults and deformed dated strata were examined in order to determine how oblique shortening is accommodated, how structural relief grows along a mountain front, and how block translation is related to block rotation. Industry seismic reflection, well, and outcrop data were used to construct digital structure-contour maps of several of these faults and three stratigraphic horizons that intersect them. These maps, swath bathymetry, digital elevation models, and seismicity were incorporated into a 3-D digital database. Modeling included new approaches to determining strike-slip displacement by separate analyses of shortening and structural relief in a restraining double bend. Stratigraphic thicknesses indicate Miocene extension across the Santa Monica and Dume faults, which have been reactivated as a single or linked moderately dipping arcuate fault that accommodates one coherent block motion via left-lateral and left-reverse displacement. Modeling indicates 5 km (+8/À1 km) of left-lateral displacement on part of the Santa Monica-Dume fault and $11°of clockwise rotation of the Santa Monica Mountains during the last $4 ± 1 m.y. Modern displacement rates modeled from GPS data are similar to our modeled post-$4 Ma rates of westward escape and clockwise rotation of the Santa Monica Mountains.

Coarse-grained sediment delivery and distribution in the Holocene Santa Monica Basin, California: Implications for evaluating source-to-sink flux at millennial time scales

“…Rates determined from a longer-term record along a left-lateral fault that marks the northern boundary of Santa Monica Basin and structural front of the Western Transverse Ranges have been estimated to be ~1.25 m/k.y. (Sorlien et al, 2006). Movement along this fault likely had a direct effect on timing of large failure-induced turbidity currents.…”

“…Since ca. 5 Ma, the northwest-southeast-trending normal faults in the northern Borderland and Western Transverse Ranges have been reactivated as reverse faults, oblique thrusts, and strikeslip faults as a result of regional transpression (Crouch and Suppe, 1993;Vedder, 1987;Sorlien et al, 2006). Active west-striking faults, including Dume, Santa Monica, and Malibu Coast faults, separate the high-relief onshore Western Transverse Ranges from the offshore basins of the northern Borderland (Sorlien et al, 2006).…”

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

“…To better estimate fault displacement, we take advantage of the fact that a nonvertical strike-slip fault with bends along strike will exhibit varying components of dip slip along strike. Based on our experience, moderately dipping faults like the San Mateo-Carlsbad fault are most suitable for kinematic analysis because most deformation including structural relief growth is limited to the fault and its hanging wall (e.g., Sorlien et al, 2006). If the 3D geometry of a suitable fault is known, and the structural relief due to faulting and local folding of a dated horizon is also known, then it is a relatively simple trigonometric problem to figure out the fault displacement, including its slip direction.…”

“…Regional shortening initiated about the beginning of Pliocene time from offshore south-central California through the Santa Barbara Channel, Santa Monica Bay, and northern Los Angeles basin (Clark et al, 1991;Sorlien et al, 1999Sorlien et al, , 2006Seeber and Sorlien, 2000;Willingham et al, 2013;Wright, 1991;Schneider et al, 1996). However, contractional folding did not start on the offshore the San Pedro shelf and escarpment until about the beginning of Quaternary time (Sorlien et al, 2013).…”

Geohazard Challenges of the Woodside OceanWay LNG Development, Offshore Southern California

“…Subduction processes dominated throughout the Cretaceous and and early Tertiary, during which time the oceanic Farallon Plate collided with and was subducted beneath the continental crust of North America (Crouch and Suppe, 1993). Reorientation of the plate margin approximately 4 to 5 Ma resulted in transpressional structures and tectonic inversion of NW-SE trending normal and detachment faults as reverse oblique faults and strike-slip faults (Atwater and Stock, 1998;Lonsdale, 1991;Sorlien et al, 2006). Large-scale detachment faulting and block rotation of the WTR occurred during this period (Nicholson et al, 1994).…”