Crustal structure and tectonics from the Los Angeles basin to the Mojave Desert, southern California

Fuis, Gary S.; Ryberg, Trond; Godfrey, Nicola J.; Okaya, D. A.; Murphy, Janice M.

doi:10.1130/0091-7613(2001)029<0015:csatft>2.0.co;2

Cited by 104 publications

(135 citation statements)

References 18 publications

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“…Interestingly, both model curves are consistent with Pelona Schist at all depths Ͼ1 km, as measured on the LARSE I transect, but are not generally consistent with other rock types. We note in contrast that Fuis et al (2001b) concluded from similar comparisons of lab and model curves on the LARSE I transect that Pelona Schist is not present in the Mojave Desert, although it underlies most of the central Transverse Ranges. Rock samples from the LARSE II transect must be collected and measured in the laboratory before any firmer interpretations of rock type are possible.…”

Section: Our Inversion Models and Laboratory Velocity Measurements Ofcontrasting

confidence: 67%

“…Inverse and forward modeling of first arrivals (Lutter et al, 1999;Fuis et al, 2001b) provided an image of velocity structure that, when combined with oil-test well data (Brocher et al, 1998) and laboratory rock-velocity measurements (McCaffree Pellerin and Christensen, 1998), constrained interpretation of basin depth (Los Angeles and San Gabriel Valley basins), the geometry of the Sierra Madre Fault at depth, and the subsurface lateral extent of the Pelona Schist. Ryberg and Fuis (1998) and Fuis et al (2001b) have identified a gently north-dipping bright reflective layer in the middle crust of the San Gabriel Mountains that they interpret as a fracture zone containing fluids. This reflective zone is interpreted to be part of a decollement connecting the San Andreas Fault (SAF) with re-verse faults to the south, including the Sierra Madre Fault and the causative fault for the 1987 M 5.9 Whittier Narrows earthquake.…”

Section: Introductionmentioning

confidence: 99%

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Upper Crustal Structure from the Santa Monica Mountains to the Sierra Nevada, Southern California: Tomographic Results from the Los Angeles Regional Seismic Experiment, Phase II (LARSE II)

Lutter¹,

Fuis²,

Ryberg³

et al. 2004

Bulletin of the Seismological Society of America

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Section: Our Inversion Models and Laboratory Velocity Measurements Ofcontrasting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Upper Crustal Structure from the Santa Monica Mountains to the Sierra Nevada, Southern California: Tomographic Results from the Los Angeles Regional Seismic Experiment, Phase II (LARSE II)

Lutter¹,

Fuis²,

Ryberg³

et al. 2004

Bulletin of the Seismological Society of America

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“…The Whittier fault is projected to its point of intersection with the thrust fault beneath the Coyote Hills at approximately 8 km depth. This value is similar to the 10 km depth of intersection obtained for the intersection between the Whittier fault and the Puente Hills thrust based on deep seismic profile, LARSE 1 [Fuis et al, 2001] suggesting that the Puente Hills thrust and the thrust beneath the Coyote Hills are part of the same thrust system. in alluvium.…”

Section: Transfer Of Strike Slip From the Elsinore Fault To The Puentsupporting

confidence: 69%

Dislocation modeling of blind thrusts in the eastern Los Angeles basin, California

2003

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The East and West Coyote Hills in the eastern Los Angeles Basin are the surface expression of uplift accompanying blind reverse faulting. Folded Quaternary strata indicate that the hills are growing and that the faults underlying them are active. Detailed subsurface mapping in the East Coyote Oil Field shows that a previously mapped, reverse separation fault is predominantly an inactive, left‐lateral, strike‐slip fault that is not responsible for the uplift of the East Coyote Hills. The fault responsible for folding and uplift of the Coyote Hills does not cut wells in either the East or West Coyote Oil Fields. To characterize the geometry of the blind fault responsible for folding, we employ dislocation modeling. The dip and upper fault tip depths obtained from modeling suggest that the thrust fault beneath the Coyote Hills may be an extension of the Puente Hills blind thrust fault that continues westward beneath the Santa Fe Springs Oil Field. Modeling results suggest that the segment of the thrust fault responsible for folding the Coyote Hills would have accumulated 1500 m of reverse displacement over the last 1.2 Myr, yielding an average slip rate of 1.3 ± 0.5 mm/yr. The Santa Fe Springs segment of the fault has a slip rate of 1.5 ± 0.4 mm/yr for the last 1.2 Myr. The estimated moment magnitude for a reverse displacement earthquake on the Puente Hills blind thrust ranges from 6.6 to 7.2, depending on the length of the rupture. The estimated average recurrence interval for these earthquakes is 1700–3200 years.

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“…The basin fill materials are typically composed of interbedded poorly consolidated clay, silt, sand, and gravel [Galloway et al, 1998]. A number of studies in the region suggest that the fault is vertical [e.g., Fuis et al, 2001]; however, available evidence does not exclude the possibility that along some of its length, the fault dips steeply ($75°) to the southwest beneath the San Gabriel Mountains [e.g., Griscom and Jachens, 1990]. This segment of the San Andreas fault is locked, and last ruptured in the 1857 M 7.8 Fort Tejon earthquake [Ellsworth, 1990].…”

Section: Geologic Setting and Backgroundmentioning

confidence: 99%

Topographically driven groundwater flow and the San Andreas heat flow paradox revisited

2003

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[1] Evidence for a weak San Andreas Fault includes (1) borehole heat flow measurements that show no evidence for a frictionally generated heat flow anomaly and (2) the inferred orientation of s 1 nearly perpendicular to the fault trace. Interpretations of the stress orientation data remain controversial, at least in close proximity to the fault, leading some researchers to hypothesize that the San Andreas Fault is, in fact, strong and that its thermal signature may be removed or redistributed by topographically driven groundwater flow in areas of rugged topography, such as typify the San Andreas Fault system. To evaluate this scenario, we use a steady state, two-dimensional model of coupled heat and fluid flow within cross sections oriented perpendicular to the fault and to the primary regional topography. Our results show that existing heat flow data near Parkfield, California, do not readily discriminate between the expected thermal signature of a strong fault and that of a weak fault. In contrast, for a wide range of groundwater flow scenarios in the Mojave Desert, models that include frictional heat generation along a strong fault are inconsistent with existing heat flow data, suggesting that the San Andreas Fault at this location is indeed weak. In both areas, comparison of modeling results and heat flow data suggest that advective redistribution of heat is minimal. The robust results for the Mojave region demonstrate that topographically driven groundwater flow, at least in two dimensions, is inadequate to obscure the frictionally generated heat flow anomaly from a strong fault. However, our results do not preclude the possibility of transient advective heat transport associated with earthquakes.

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Crustal structure and tectonics from the Los Angeles basin to the Mojave Desert, southern California

Cited by 104 publications

References 18 publications

Upper Crustal Structure from the Santa Monica Mountains to the Sierra Nevada, Southern California: Tomographic Results from the Los Angeles Regional Seismic Experiment, Phase II (LARSE II)

Upper Crustal Structure from the Santa Monica Mountains to the Sierra Nevada, Southern California: Tomographic Results from the Los Angeles Regional Seismic Experiment, Phase II (LARSE II)

Dislocation modeling of blind thrusts in the eastern Los Angeles basin, California

Topographically driven groundwater flow and the San Andreas heat flow paradox revisited

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