Ophiolitic basement to the Great Valley forearc basin, California, from seismic and gravity data: Implications for crustal growth at the North American continental margin

Godfrey, Nicola J.; Beaudoin, B. C.; Klemperer, S. L.

doi:10.1130/0016-7606(1997)109<1536:obttgv>2.3.co;2

Cited by 141 publications

(122 citation statements)

References 51 publications

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“…Densities are 2.5-2.6 g/cm 3 and 2.6-2.7 g/cm 3 for the upper and lower formations, respectively (Constenius et al, 2000). The Nicolas forearc belt is composed of 7-8 km thick volcano-sedimentary strata, similar to the Great Valley sequence (California) with densities of 2.5-2.6 g/cm 3 (Godfrey et al, 1997;Godfrey and Klemperer, 1998). This sedimentary complex is most likely underlain by Franciscan rocks to the west, and Catalina blueschists to the east (Bohannon and Geist, 1998).…”

Section: The Patton Accretionary and Nicolas Forearc Beltsmentioning

confidence: 99%

Two lithospheric profiles across southern California derived from gravity and seismic data

Romanyuk¹,

Mooney²,

Detweiler³

2007

Journal of Geodynamics

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Section: The Patton Accretionary and Nicolas Forearc Beltsmentioning

confidence: 99%

Two lithospheric profiles across southern California derived from gravity and seismic data

Romanyuk¹,

Mooney²,

Detweiler³

2007

Journal of Geodynamics

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“…If the 'Moho' in these earlier studies is actually the Moho in the stalled fossil slab, then the material just above it that has intermediate wave speeds (6 to 7 km/s) and was previously interpreted as 'lower crust', could be reinterpreted as a thin, partially serpentinized ultramafic mantle. A broad magnetic anomaly in northern California has been modeled and interpreted as defining an 'ophiolitic' magnetic basement underlying the Franciscan crust that extends at least as far west as the Hayward fault (Jachens et al 1995;Godfrey et al 1997;Ponce et al 2003a,b) (Figure 7). Brocher and others (1999) reinterpreted previously identified Moho reflections in northern California as reflections on fossil slab material ( Figure 5).…”

Section: Implications For the Safs General Relevancementioning

confidence: 99%

A large mantle water source for the northern San Andreas fault system: a ghost of subduction past

2014

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Recent research indicates that the shallow mantle of the Cascadia subduction margin under near-coastal Pacific Northwest, USA is cold and partially serpentinized, storing large quantities of water in this wedge-shaped region. Such a wedge probably formed to the south in California during an earlier period of subduction. We show by numerical modeling that after subduction ceased with the creation of the San Andreas Fault System (SAFS), the mantle wedge warmed, slowly releasing its water over a period of more than 25 Ma by serpentine dehydration into the crust above. This deep, long-term water source could facilitate fault slip in San Andreas System at low shear stresses by raising pore pressures in a broad region above the wedge. Moreover, the location and breadth of the water release from this model gives insights into the position and breadth of the SAFS. Such a mantle source of water also likely plays a role in the occurrence of non-volcanic tremor (NVT) that has been reported along the SAFS in central California. This process of water release from mantle depths could also mobilize mantle serpentinite from the wedge above the dehydration front, permitting upward emplacement of serpentinite bodies by faulting or by diapiric ascent. Specimens of serpentinite collected from tectonically emplaced serpentinite blocks along the SAFS show mineralogical and structural evidence of high fluid pressures during ascent from depth. Serpentinite dehydration may also lead to tectonic mobility along other plate boundaries that succeed subduction, such as other continental transforms, collision zones, or along present-day subduction zones where spreading centers are subducting.

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“…Godfrey et al (1997) have studied the complex structure and tectonic history of this region and indicated that the Great Valley basement is oceanic crust underlain by oceanic mantle, which is vertically stacked above continental crust and mantle.…”

Section: Discussionmentioning

confidence: 99%

Interstation phase speed and amplitude measurements of surface waves with nonlinear waveform fitting: application to USArray

Hamada

Yoshizawa

2015

Geophys. J. Int.

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S U M M A R YA new method of fully nonlinear waveform fitting to measure interstation phase speeds and amplitude ratios is developed and applied to USArray. The Neighbourhood Algorithm is used as a global optimizer, which efficiently searches for model parameters that fit two observed waveforms on a common great-circle path by modulating the phase and amplitude terms of the fundamental-mode surface waves. We introduce the reliability parameter that represents how well the waveforms at two stations can be fitted in a time-frequency domain, which is used as a data selection criterion. The method is applied to observed waveforms of USArray for seismic events in the period from 2007 to 2010 with moment magnitude greater than 6.0. We collect a large number of phase speed data (about 75 000 for Rayleigh and 20 000 for Love) and amplitude ratio data (about 15 000 for Rayleigh waves) in a period range from 30 to 130 s. The majority of the interstation distances of measured dispersion data is less than 1000 km, which is much shorter than the typical average path-length of the conventional single-station measurements for source-receiver pairs. The phase speed models for Rayleigh and Love waves show good correlations on large scales with the recent tomographic maps derived from different approaches for phase speed mapping; for example, significant slow anomalies in volcanic regions in the western Unites States and fast anomalies in the cratonic region. Local-scale phase speed anomalies corresponding to the major tectonic features in the western United States, such as Snake River Plains, Basin and Range, Colorado Plateau and Rio Grande Rift have also been identified clearly in the phase speed models. The shortpath information derived from our interstation measurements helps to increase the achievable horizontal resolution. We have also performed joint inversions for phase speed maps using the measured phase and amplitude ratio data of vertical component Rayleigh waves. These maps exhibit better recovery of phase speed perturbations, particularly where the strong lateral velocity gradient exists in which the effects of elastic focussing can be significant; that is, the Yellowstone hotspot, Snake River Plains, and Rio Grande Rift. The enhanced resolution of the phase speed models derived from the interstation phase and amplitude measurements will be of use for the better seismological constraint on the lithospheric structure, in combination with dense broad-band seismic arrays.

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Ophiolitic basement to the Great Valley forearc basin, California, from seismic and gravity data: Implications for crustal growth at the North American continental margin

Cited by 141 publications

References 51 publications

Two lithospheric profiles across southern California derived from gravity and seismic data

Two lithospheric profiles across southern California derived from gravity and seismic data

A large mantle water source for the northern San Andreas fault system: a ghost of subduction past

Interstation phase speed and amplitude measurements of surface waves with nonlinear waveform fitting: application to USArray

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