Using high-resolution multibeam bathymetry to identify seafloor surface rupture along the Palos Verdes fault complex in offshore southern California

Abstract

INTRODUCTION Geologic Setting The Palos Verdes Peninsula (Figs. 1 and 2) is dominated by the Palos Verdes Hills, the topographic expression of a doubly plunging anticlinorium that is currently active (Ward and Valensise, 1994). Uplift and anticlinal growth of the peninsula have been linked in part with activity of the northwest-trending, southwest-dipping Palos Verdes fault (Fig. 1; Woodring et al., 1946; Yerkes et al., 1965; Ward and Valensise, 1994). However, a study by Clarke et al. (1998) in the inner Los Angeles Harbor suggests that only about 20%-30% of this uplift during late Pleistocene and Holocene time (Ponti and Lajoie, 1992) can be attributed directly to the vertical component of Palos Verdes fault displacement. This finding implies that another, as yet unlocated, fault (or faults) is a major contributor to the balance of late Quaternary uplift determined for the Palos Verdes Hills. The Palos Verdes fault is divisible into southern, central, and northern segments (Fig. 1; Ward and Valensise, 1994). The northern segment underlies Santa Monica Bay. The central segment, about 20 km long, is located onshore adjacent to the Palos Verdes Hills. The southern segment extends offshore beneath San Pedro Bay, and this segment may bifurcate below the shelf edge into two fault strands that trend southeastward to Lasuen

The Palos Verdes Fault offshore Southern California: Late Pleistocene to present tectonic geomorphology, seascape evolution, and slip rate estimate based on AUV and ROV surveys

“…The PVF dips to the east along the western edge of Lasuen Knoll and exhibits up‐to‐the‐northeast displacement [ Fisher et al , ]. Previous studies identified seafloor scarps along these sections and proposed the fault has been active recently [ Marlow et al , ]. However, prior to the present study, constraints on the horizontal slip rate and paleoseismic history of the PVF seaward of the shelf edge did not exist due to the paucity of high‐resolution marine geophysical data and high‐precision geological sampling.…”

“…The San Pedro Shelf edge is sinuous in plan view, weaving around the head of San Gabriel Canyon and smaller indentations to the west San Gabriel Canyon associated with gullies (Figures a and b). Below the shelf edge, San Gabriel Canyon is relatively straight and follows the trend of the PVF to the northwestern edge of Lasuen Knoll, where it splits into two channels on the seafloor; the eastern channel is bounded by Lasuen Knoll, whereas the western channel meanders along the basin floor [ Fisher et al , ; Marlow et al , ; Normark et al , ].…”

“…The map frame is rotated to align with the trend of the PVF (~N25°W). Active faults are solid red lines; faults and/or folds that are potentially active are dashed [ Fisher et al , , , and references therein; Marlow et al , ; this study]. (b) Enlarged section over the shelf edge and the west fork of the San Gabriel Canyon.…”

“…Fisher et al [, ] noted evidence for transtension and normal faulting along the continental slope section of the fault. Strata along the shelf edge and upper slope are tilted toward San Gabriel Canyon, and the western edge of the canyon appears to follow the trend of the PVF from the shelf edge down to a water depth of ~600 m (Figures and ) [ Fisher et al , ; Marlow et al , ; Normark et al , ].…”

Erosion of the submarine flanks of the Canary Islands

“…We note that many submarine landscapes imaged with multibeam sonar also show less apparent denudation offshore compared to their adjacent subaerial mountain scapes. For example, multibeam data from offshore Los Angeles show that submarine slopes around the Palos Verdes Peninsula (a late Pleistocene anticline associated with the strike‐slip faults) are incised, though less degraded than the subaerial headland itself [ Marlow et al , 2000].…”