Structure and Mechanics of the Hayward-Rodgers Creek Fault Step-Over, San Francisco Bay, California

Parsons, Tom; Sliter, Ray W.; Geist, Eric L.; Jachens, Robert C.; Jaffe, Bruce E.; Foxgrover, Amy C.; Hart, Patrick E.; McCarthy, Jill

doi:10.1785/0120020228

Cited by 28 publications

(38 citation statements)

References 42 publications

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“…The basin is defined by velocity anomaly and gravity anomaly lows to be 10 to 20 km long, 5 to 10 km wide, and at least 3 km thick (Figures 3a, 3b, 5b, and 8). The San Pablo Basin has been viewed as a narrow pull‐apart basin between the Hayward and Rodgers Creek Faults [ Smith , 1992; Wright and Smith , 1992], but recently it has been recognized to be a broader basin extending to the east of the Rodgers Creek Fault [ Parsons et al , 2003]. Our model images a strong velocity contrast across the western margin of the basin and a lesser, but still identifiable velocity contrast on its eastern margin.…”

Section: Model Resultsmentioning

confidence: 88%

Three‐dimensional P wave velocity model for the San Francisco Bay region, California

et al. 2007

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[1] A new three-dimensional P wave velocity model for the greater San Francisco Bay region has been derived using the double-difference seismic tomography method, using data from about 5,500 chemical explosions or air gun blasts and approximately 6,000 earthquakes. The model region covers 140 km NE-SW by 240 km NW-SE, extending from 20 km south of Monterey to Santa Rosa and reaching from the Pacific coast to the edge of the Great Valley. Our model provides the first regional view of a number of basement highs that are imaged in the uppermost few kilometers of the model, and images a number of velocity anomaly lows associated with known Mesozoic and Cenozoic basins in the study area. High velocity (V p > 6.5 km/s) features at $15-km depth beneath part of the edge of the Great Valley and along the San Francisco peninsula are interpreted as ophiolite bodies. The relocated earthquakes provide a clear picture of the geometry of the major faults in the region, illuminating fault dips that are generally consistent with previous studies. Ninety-five percent of the earthquakes have depths between 2.3 and 15.2 km, and the corresponding seismic velocities at the hypocenters range from 4.8 km/s (presumably corresponding to Franciscan basement or Mesozoic sedimentary rocks of the Great Valley Sequence) to 6.8 km/s. The top of the seismogenic zone is thus largely controlled by basement depth, but the base of the seismogenic zone is not restricted to seismic velocities of 6.3 km/s in this region, as had been previously proposed.Citation: Thurber, C. H., T. M. Brocher, H. Zhang, and V. E. Langenheim (2007), Three-dimensional P wave velocity model for the San Francisco Bay region, California,

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Section: Model Resultsmentioning

confidence: 88%

Three‐dimensional P wave velocity model for the San Francisco Bay region, California

et al. 2007

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“…In the second set of models, the initial fault geometries follow those inferred from two sets of geophysical observations, including earlier work (Parsons et al, ), and more recent imaging (Watt et al, ). Earlier geophysical data indicate that the Rodgers Creek Fault extends far into the San Pablo Bay (Parsons et al, ), forming an overlapping step over with the Hayward Fault. However, Watt et al () do not find evidence for activity along this fault in the upper 2–5 m and map an underlapping step over within the bay.…”

Section: Methodsmentioning

confidence: 93%

“…The red box indicates study area shown. (b) Fault geometry of step over from previous interpretations in black dashed lines (Parsons et al, ) and more recent interpretations in solid gray lines (Watt et al, ).…”

Section: Introductionmentioning

confidence: 88%

Work Optimization Predicts the Evolution of Extensional Step Overs Within Anisotropic Host Rock: Implications for the San Pablo Bay, CA

2017

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Recent geophysical imaging indicates that the Hayward Fault hard links to the Rodgers Creek Fault at 5 m depth within the San Pablo Bay, CA, suggesting that earthquakes may be able to rupture continuously through the fault network. To investigate fault propagation, interaction, and linkage in segmented fault networks, including those within the San Pablo Bay, we simulate the development of two idealized, underlapping faults within an extensional step over at seismogenic depths using work optimization. We test the sensitivity of fault growth to strength anisotropy, material heterogeneities, and initial fault geometry. The optimal faults propagate toward each other until linking with the other fault at its tip and form a single hard‐linked transverse fault. These faults propagate with relatively high propagation power or rate of efficiency gain. Less efficient faults form wider basins and develop with reduced propagation power. Models with initial fault geometries that more closely match the shallowly imaged Hayward and Rodgers Creek faults suggest that the faults link at seismogenic depths if a mapped segment of the Rodgers Creek that extends into the San Pablo Bay is currently inactive. Predictions of average slip rate, slip per earthquake, and earthquake magnitude from these models closely match paleoseismic estimates. The hard linkage of the Hayward and Rodgers Creek faults imaged in the near‐surface, and predicted by these models, increases local seismic hazard by increasing the upper limit of throughgoing earthquakes to M 7.6.

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“…2) to emerge as the right-lateral Hayward fault in the eastern San Francisco Bay region west of Berkeley (Brown, 1970;Wright and Smith, 1992;Parsons et al, 2003). North of Santa Rosa, the Rodgers Creek fault zone consists of the northern Rodgers Creek fault zone, which locally is referred to as the Healdsburg fault segment of the Rodgers Creek fault zone.…”

Section: Fault Nomenclaturementioning

confidence: 99%

Evolution of the Rodgers Creek-Maacama right-lateral fault system and associated basins east of the northward-migrating Mendocino Triple Junction, northern California

et al. 2012

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The Rodgers Creek-Maacama fault system in the northern California Coast Ranges (United States) takes up substantial rightlateral motion within the wide transform boundary between the Pacifi c and NorthAmerican plates, over a slab window that has opened northward beneath the Coast Ranges. The fault system evolved in several right steps and splays preceded and accompanied by extension, volcanism, and strikeslip basin development. Fault and basin geometries have changed with time, in places with younger basins and faults overprinting older structures. Along-strike and successional changes in fault and basin geometry at the southern end of the fault system probably are adjustments to frequent fault zone re organizations in response to Mendocino Triple Junction migration and northward transit of a major releasing bend in the northern San Andreas fault.The earliest Rodgers Creek fault zone displacement is interpreted to have occurred ca. 7 Ma along extensional basin-forming faults that splayed northwest from a westnorthwest proto-Hayward fault zone, opening a transtensional basin west of Santa Rosa. After ca. 5 Ma, the early transtensional basin was compressed and extensional faults were reactivated as thrusts that uplifted the northeast side of the basin. After ca. 2.78 Ma, the Rodgers Creek fault zone again splayed from the earlier extensional and thrust faults to steeper dipping faults with more northnorthwest orientations. In conjunction with the changes in orientation and slip mode, the Rodgers Creek fault zone dextral slip rate increased from ~2-4 mm/yr 7-3 Ma, to 5-8 mm/yr after 3 Ma.The Maacama fault zone is shown from several data sets to have initiated ca. 3.2 Ma and has slipped right-laterally at ~5-8 mm/yr since its initiation. The initial Maacama fault zone splayed northeastward from the south end of the Rodgers Creek fault zone, accompanied by the opening of several strike-slip basins, some of which were later uplifted and compressed during late-stage fault zone re organi zation. The Santa Rosa pull-apart basin formed ca. 1 Ma, during the reorganization of the right stepover geometry of the Rodgers Creek-Maacama fault system, when the maturely evolved overlapping geometry of the northern Rodgers Creek and Maacama fault zones was overprinted by a less evolved, non-overlapping stepover geometry.The Rodgers Creek-Maacama fault system has contributed at least 44-53 km of right-lateral displacement to the East Bay fault system south of San Pablo Bay since 7 Ma, at a minimum rate of 6.1-7.8 mm/yr.

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Structure and Mechanics of the Hayward-Rodgers Creek Fault Step-Over, San Francisco Bay, California

Cited by 28 publications

References 42 publications

Three‐dimensional P wave velocity model for the San Francisco Bay region, California

Three‐dimensional P wave velocity model for the San Francisco Bay region, California

Work Optimization Predicts the Evolution of Extensional Step Overs Within Anisotropic Host Rock: Implications for the San Pablo Bay, CA

Evolution of the Rodgers Creek-Maacama right-lateral fault system and associated basins east of the northward-migrating Mendocino Triple Junction, northern California

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