Geometries of deep crustal faults: Evidence from the COCORP Mojave survey

Cheadle, M. J.; Czuchra, B. L.; Ando, Clifford; Byrne, Tim; Brown, L. D.; Oliver, Jack; Kaufman, S.

doi:10.1029/gd014p0305

Cited by 13 publications

(15 citation statements)

References 12 publications

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“…These reflections are coincident with regional low-angle fault structures interpreted by Cheadle et al (1985Cheadle et al ( , 1986 from the same data set. These reflections are coincident with regional low-angle fault structures interpreted by Cheadle et al (1985Cheadle et al ( , 1986 from the same data set.…”

Section: Discussionsupporting

confidence: 60%

“…This shot-gather stack is not shown, but all of the reflections identified by Cheadle et al (1985Cheadle et al ( , 1986) on COCORP's midpoint stacks could be identified. This shot-gather stack is not shown, but all of the reflections identified by Cheadle et al (1985Cheadle et al ( , 1986) on COCORP's midpoint stacks could be identified.…”

Section: Western Mojavementioning

confidence: 95%

“…From the extensive COCORP data set in the western Mojave Desert, Cheadle et al (1985Cheadle et al ( , 1986 identified several shallowly dipping, regional reflections. They interpreted these reflections as arising from horizontal shear zones, with several models available for their ages and sense of motion.…”

Section: Western Mojavementioning

confidence: 99%

“…The extensive COCORP survey across the western Mojave imaged several deep crustal reflectors over a wide area (Cheadle et al, 1986). With the exception of one reflection which they believe can be traced to surface exposures, the geologic interpretation of middle and deep crustal reflections by Cheadle et al (1985Cheadle et al ( , 1986 was guided by reflector geometry. They consider the major reflectors to be low-angle fault structures.…”

Section: Introductionmentioning

confidence: 99%

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Physical properties of deep crustal reflectors in southern California from multioffset amplitude analysis

Louie

1990

GEOPHYSICS

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Analysis of reflection waveforms before stack can constrain the physical properties of reflectors in the deep crust. To simplify this analysis, recorded amplitudes are assumed to be reflections from weak elastic heterogeneities. With these assumptions, trends in reflection amplitudes with offset may indicate whether the signs of a reflector's density and rigidity contrast agree with or oppose the sign of its Lame's parameter contrast. The slope of the trend indicates the degree of Poisson's ratio contrast. No attempt is made to invert for the individual modulus or density contrasts. By examining only gross amplitude-versus-offset (AVO) trends, deep reflections constrain some crustal properties.

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Section: Discussionsupporting

confidence: 60%

Section: Western Mojavementioning

confidence: 95%

Section: Western Mojavementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Physical properties of deep crustal reflectors in southern California from multioffset amplitude analysis

Louie

1990

GEOPHYSICS

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“…Common midpoint (CMP) stacked sections of the COCORP survey data revealed several subhorizontal reflectors in the middle and deep crust, extending across most of the western Mojave. Cheadle et al [1985] made three alternative interpretations of these structures on the basis of their overall southwest dip and ramp-and-flat geometry. All the interpretations propose that the reflectors originated as regional thrust or decollement surfaces between the late Paleozoic and the Miocene.…”

mentioning

confidence: 99%

Subsurface imaging of the Garlock Fault, Cantil Valley, California

Louie¹,

Qin²

1991

J. Geophys. Res.

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Imaging of the Garlock fault from seismic reflection data tests tectonic models for the Mojave Desert region of southern California. Models developed from geologic and geodetic evidence of fault movement rates disagree on whether the Garlock fault should dip north or south. Such models are further at odds with focal mechanism and dislocation analyses consistent with a vertical strike‐slip fault. Our analysis demonstrates a nonvertical, southward dip for the Garlock fault. Consortium for Continental Reflection Profiling Mojave line 5 collected seismic reflection data across the Garlock in Cantil Valley, where the 3‐km‐deep Cantil pull‐apart basin has developed between the southwest and east branches of the fault. We analyze the reflection data for evidence of the fault's structure to 5 km depths. Garlock fault plane reflections on unprocessed shot gathers merge with the first arrival as the source progresses to the surface trace of the east branch, explicitly tracing the Garlock fault as a seismic reflector from depth to the mapped contemporary fault trace. The apparent velocity of these reflections gives a 37°±10° south dip for the east branch of the fault. A prestack Kirchhoff sum migration images the east branch reflector with a 45° south dip. Our migration process fully accounts for the bending of seismic rays through the strong lateral velocity variations in Cantil basin. The south dip of the Garlock's east branch together with basement steps that decrease to the south suggest that Cantil basin developed from a 0.4–1 mm/yr component of extension normal to the fault. Development of the basin by detachment provides a mechanism to widen it as left‐lateral motion lengthens it, allowing the pull‐apart to maintain the globally constant length‐to‐width ratio of 3. Detachment by the Garlock at Cantil Valley similarly requires 0.4–1 mm/yr of dextral strike slip on a northwest striking fault such as the Helendale that cuts the Mojave between the Garlock and Pinto Mountain faults. Such motion is consistent with regional tectonic models.

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Geometry of the Garlock fault zone based on seismic relection data

Serpa¹,

Dokka²

1992

J. Geophys. Res.

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Detailed examination of shot gathers from line 3 of the Consortium for Continental Reflection Profiling Mojave experiment indicates a low‐velocity, high‐amplitude seismic event that may originate from a south dipping portion of the Garlock fault zone. Part of this event was previously interpreted as a subhorizontal surface located in the midcrust. Our analysis indicates, however, that the distance to this event varies consistently with the distance of the shot and receivers from the fault zone and that the velocities are too low for seismic waves traveling through predominantly crystalline rocks. These characteristics are more consistent with the presence of a subvertical reflector located near the Garlock fault zone than with the previously inferred subhorizontal reflector beneath the seismic line.

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Geometries of deep crustal faults: Evidence from the COCORP Mojave survey

Cited by 13 publications

References 12 publications

Physical properties of deep crustal reflectors in southern California from multioffset amplitude analysis

Physical properties of deep crustal reflectors in southern California from multioffset amplitude analysis

Subsurface imaging of the Garlock Fault, Cantil Valley, California

Geometry of the Garlock fault zone based on seismic relection data

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