Microplate capture, rotation of the western Transverse Ranges, and initiation of the San Andreas transform as a low-angle fault system

Nicholson, Craig; Sorlien, Christopher C.; Atwater, Tanya; Crowell, John C.; Luyendyk, Bruce P.

doi:10.1130/0091-7613(1994)022<0491:mcrotw>2.3.co;2

Cited by 313 publications

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“…Geological evidence (e.g. Wilson et al 2005), in agreement with thermo-mechanical and kinematic modelling (Nicholson et al 1994), show that the main strand of the brittle fault system jumped inland in several discrete steps to its current position, the San Andreas fault. These jumps were associated with inland diffusion of the ductile roots of the deformation system, probably triggered by lower crustal and upper mantle temperature diffusion, or controlled by integrated lithospheric strength variations (Popov 2009).…”

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confidence: 75%

“…In central California, total displacement of the Pacific plate relative to fixed North America is estimated to about 820 ± 50 km (Nicholson et al 1994), and has been distributed over various fault strands (Dickinson et al 2005) since subduction of Farallon oceanic plate ceased and the SAF system was initiated 20 Ma ago.…”

Section: Geological Settingmentioning

confidence: 99%

“…Geodynamic and thermo-mechanical models of ceased Farallon subduction include microplate capture, slab breakoff and the formation of a slab windows beneath the overriding North American plate (Nicholson et al 1994;Wilson et al 2005, e.g.). In settings where the ridge is near the trench (Fig.…”

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Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Becken

Ritter

2011

Surv Geophys

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Fluids residing in interconnected porosity networks have a significant weakening effect on rheology of rocks and can strongly influence deformation along fault zones. The magnetotelluric (MT) technqiue is sensitive to interconnected fluid networks, and can image these zones on crustal and upper mantle scales. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, fault creep is supported. In response to fluid flux from deeper levels in combination with meteoric and crustal metamorphic fluid supply, and in response to fault creep, high-conductivity zones develop as fault zone conductors in the brittle portion of crust. In turn, the absence of crustal fluid pathays may be characteristic for mechanically locked segments. MT models suggest that those fluids are trapped at depth and kept at high pressures. It is speculated that fluids may infiltrate neighbouring rocks and induce non-volcanic tremor. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, strain provides a means to develop and maintain permeability structure, and thus electrical conductivity, within the damage zone. Accordingly, these conductivity models played an important role in pin-pointing the SAFOD drilling location near Parkfield. *abstractClick here to download abstract: abstract.txt Surv. Geophys. manuscript No.In this paper, we consider MT studies at the SAF near Hollister and Carrizo The SAF has also been a target for telluric (Madden et al. 1993;Park et al. 2007) and magnetotelluric monitoring (e.g. Kappler et al. 2010). These installations attempted to monitor long-term electric (and magnetic) field variations of internal origin due to resistivity variations assiciated with earthquakes, large scale fluid flow or other causes. To date, it was not possible to identify significant field variations which can be attributed to tectonic processes. In this paper, we don't discuss details of this issue. 7The main objective of this paper is to review the MT results from the SAF in combination with other geophysical, geological and geochemical data and models in order to address fluid-related processes and their potential implications on the geodynamic setting, active tectonic processes and the mechanical ...

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confidence: 75%

Section: Geological Settingmentioning

confidence: 99%

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Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Becken

Ritter

2011

Surv Geophys

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“…This stress reversal was once generally attributed to the end of subduction at the Pacific margin, but we now know that formation of the Pacific/North America transform margin (Figure 1d) was a gradual process beginning at 28 Ma [Nicholson et al, 1994]. Therefore it happened too late to be the principal cause of this stress change.…”

Section: Oligocene Extension In the Basin And Rangementioning

confidence: 99%

Stress direction history of the western United States and Mexico since 85 Ma

Bird

2002

Tectonics

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[1] A data set of 369 paleostress direction indicators (sets of dikes, veins, or fault slip vectors) is collected from previous compilations and the geologic literature. Like contemporary data, these stress directions show great variability, even over short distances. Therefore statistical methods are helpful in deciding which apparent variations in space or in time are significant. First, the interpolation technique of Bird and Li [1996] is used to interpolate stress directions to a grid of evenly spaced points in each of seventeen 5-m.y. time steps since 85 Ma. Then, a t test is used to search for stress direction changes between pairs of time windows whose sense can be determined with some minimum confidence. Available data cannot resolve local stress provinces, and only the broadest changes affecting country-sized regions are reasonably certain. During 85 -50 Ma, the most compressive horizontal stress azimuthŝ 1H was fairly constant at $68°(United States) to 75°(Mexico). During 50 -35 Ma, both counterclockwise stress changes (in the Pacific Northwest) and clockwise stress changes (from Nevada to New Mexico) are seen, but only locally and with about 50% confidence. A major stress azimuth change by $90°occurred at 33 ± 2 Ma in Mexico and at 30 ± 2 Ma in the western United States. This was probably an interchange between s 1 andŝ 3 caused by a decrease in horizontal compression and/or an increase in vertical compression. The most likely cause was the rollback of horizontally subducting Farallon slab from under the southwestern United States and northwest Mexico, which was rapid during 35 -25 Ma. After this transition, a clockwise rotation of principal stress axes by 36°-48°occurred more gradually since 22 Ma, affecting the region between latitudes 28°N and 41°N. This occurred as the lengthening Pacific/North America transform boundary gradually added dextral shear on northwest striking planes to the previous stress field of SW-NE extension.

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“…Because of its kinematic applicability, the slab window scenario was used as an idealized model to explain some observations in the California Coast Ranges (CR) like the migrating volcanism [Dickinson and Snyder, 1979] and the high heat flow [Lachenbruch and Sass, 1980;Zandt and Furlong, 1982]. Later, Bohannon and Parsons [1995] argued that the slab window model is nonunique and is unable to explain some major observations, particularly, the existence of fossil ridges offshore of California [e.g., Nicholson et al, 1994], and they proposed ''the stalled Figure 1. Heat flow map of the California and northern Baja California transform margins (modified from Blackwell and Richards [2004]).…”

Section: Introductionmentioning

confidence: 99%

Transient thermal regimes in the Sierra Nevada and Baja California extinct outer arcs following the cessation of Farallon subduction

Erkan

Blackwell

2009

J. Geophys. Res.

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[1] We examine the thermal relaxation of the Sierra Nevada and Baja California extinct outer arc blocks following the progressive cessation of Farallon subduction under western North America beginning at $30 Ma. Being parts of the same outer arc until the inland jump of the San Andreas transform fault at $5 Ma, these two regions show many similarities in their geology, geomorphology, rigid body behavior, and their relatively low seismicity. In the thermal model, we combine results of different geophysical and geophysical studies to constrain the thermal state and geometry of the outer arcs before the cessation of subduction and then model the postsubduction temperature responses in these regions using the results of the tectonic reconstructions. A well-constrained regional thermal model of these blocks using the results of many earlier studies in these regions confirms that the present low heat flow values in these regions are the remnants of the very cold outer arc thermal regime of the subduction zone even as long as 30 Ma after cessation of subduction. Thus the entire Pacific boundary of the North American plate is still in a transient thermal state. The calculated low lithospheric temperatures in the Sierra Nevada and Peninsular blocks correlate very well with their rigid body behavior obtained from geodetic studies, and seismogenic layer thicknesses obtained from seismological studies. This is in contrast with the fact that both regions are surrounded by intense deformation associated with the western North America intraplate and extraplate motions. These low-temperature islands play important roles in the present interaction of the North American and Pacific plates and contribute to the broad deformation of the transform boundary. The thermal relaxation of the extinct outer arcs includes both vertical heating from the underlying asthenosphere and the lateral heating from the extinct back arc (Basin and Range), which has remained as a high heat flow region after the cessation of the subduction. We suggest that the significant lateral heat transfer from the Basin and Range in the Sierra Nevada (and from the Gulf of California spreading center in the Peninsular block since $5 Ma) may be the main driving mechanism of the postsubduction volcanism/magmatism along the extinct volcanic arc and the recent tilted uplift of the Sierra Nevada block. The low lithospheric temperatures in Sierra Nevada region may also explain the observation of the high seismic velocities in the mantle beneath the southern Sierra Nevada where the downwelling of the mantle lithosphere proposed.

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Microplate capture, rotation of the western Transverse Ranges, and initiation of the San Andreas transform as a low-angle fault system

Cited by 313 publications

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Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Stress direction history of the western United States and Mexico since 85 Ma

Transient thermal regimes in the Sierra Nevada and Baja California extinct outer arcs following the cessation of Farallon subduction

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