Preliminary report on the environmental geology of selected areas of the Southern California continental borderland

Greene, H. Gary; Clarke, Samuel H.; Field, Michael E.; Linker, F.I.; Wagner, H.C.

doi:10.3133/ofr75596

Cited by 15 publications

(15 citation statements)

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“…The offshore parts of the fault are a little better understood from shallow refraction studies [Nardin and Henyey, 1978]. Several offshore geophysical investigations provide evidence for substantial right-lateral offset in the form of abrupt changes both in the configuration of the basement surface and in the lithology and thickness of middle Miocene, upper Miocene, and Pliocene sedimentary rock units [Dames and Moore, 1973;Greene et al, 1975;Darrow and Fischer, 1983;Clarke et al, 1983Clarke et al, , 1985. Gravity [McCulloh, 1960] and reflection data [Nardin and Henyey, 1978;Stephenson et al, 1992] suggest that the fault has a left-stepping, restraining bend geometry with significant changes in strike at the segment intersections.…”

Section: Marine Terraces the Marine Terraces Of The Palos Verdesmentioning

confidence: 99%

The Palos Verdes terraces, California: Bathtub rings from a buried reverse fault

Ward¹,

Valensise²

1994

J. Geophys. Res.

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Uplift of the Palos Verdes peninsula has long been associated with a northwest trending, southwest dipping, reverse fault. Unfortunately, the Palos Verdes Hills fault has no obvious surface displacement and little background seismicity to substantiate its dimension, orientation, or earthquake potential. In this paper we investigate the tectonic style and slip rate of the Palos Verdes Hills fault and the uplift history of the Palos Verdes Hills by analyzing the geometry of 13 marine terraces that encircle the peninsula in a bathtub ring configuration. Elevations of 211 terrace remnants constrain a fault model with 3.0 to 3.7 mm yr−1 of oblique, dextral/reverse slip on a fault dipping 67° at 6 to 12 km depth beneath the peninsula. If the rate was constant through time, fault inception would have occurred 2.4–3.0 Ma. We propose that the largest credible earthquakes on the fault have magnitude ≈6¾ and could revisit every 2000 years.

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Section: Marine Terraces the Marine Terraces Of The Palos Verdesmentioning

confidence: 99%

The Palos Verdes terraces, California: Bathtub rings from a buried reverse fault

Ward¹,

Valensise²

1994

J. Geophys. Res.

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“…If so, however, the Avalon Knoll fault must be west of the Holocene Cabrillo fault (Fig. 1), which is well located from seismic-reflection data from the Palos Verdes shelf and which does not appear to be cut by other faults (Greene et al, 1975;Clarke et al, 1985;Vedder et al, 1986).…”

Section: Palos Verdes and Avalon Knoll Faultsmentioning

confidence: 91%

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

Marlow

Gardner

Normark

2000

Geol

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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

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“…The exposed bedrock is composed of consolidated sedimentary and volcanic rock of probable Tertiary age. 22 A generalized geoacoustic model from the neighboring Tanner Bank indicates a variable sediment overburden of 0 to 6 m with bedrock compressional and shear wave speeds of 2500 and 900 m/s, respectively. 23 Because of the proximity and similar geologic origin of the two banks, these parameters should be approximately representative of the Cortes Bank as well.…”

Section: A the Cortes Bankmentioning

confidence: 99%

Estimating the compressional and shear wave speeds of a shallow water seabed from the vertical coherence of ambient noise in the water column

Carbone

Deane

Buckingham

1998

The Journal of the Acoustical Society of America

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Due to the multiple bottom reflections encountered in shallow water environments, the spatial structure of the ambient noise field depends strongly on the geoacoustic properties of the seabed, which are invariant over time scales associated with most measurements. The vertical directionality and coherence are relatively stable features of the noise that are determined primarily by the seabed, rather than temporal variations in the surface source distribution. In this paper, estimates of the compressional and shear wave speeds are determined from ambient noise measurements over shear supporting seabeds. Using a model of wind-generated noise over an elastic seabed, it is shown that the noise is sensitive to the compressional and shear wave speeds in the upper few meters of seabed. An inversion procedure is developed based on a matched field of the complex, broadband coherence from a single hydrophone pair. Using ambient noise data from two shear supporting sites, compressional and shear wave estimates are obtained that are in good agreement with independent surveys. For one site where the bedrock is exposed, a half-space model of the seabed yields reasonable estimates of the seabed parameters. For the other site, the presence of a thin sedimentary layer results in a low estimate from the half-space model. However, when the layer is included in the model, the estimates of the underlying bedrock are in good agreement with a seismic survey.

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Preliminary report on the environmental geology of selected areas of the Southern California continental borderland

Cited by 15 publications

References 0 publications

The Palos Verdes terraces, California: Bathtub rings from a buried reverse fault

The Palos Verdes terraces, California: Bathtub rings from a buried reverse fault

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

Estimating the compressional and shear wave speeds of a shallow water seabed from the vertical coherence of ambient noise in the water column

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