Basin Structure beneath the Santa Rosa Plain, Northern California: Implications for Damage Caused by the 1969 Santa Rosa and 1906 San Francisco Earthquakes

McPhee, D. K.; Langenheim, Victoria E.; Hartzell, Stephen H.; McLaughlin, Robert J.; Aagaard, Brad T.; Jachens, Robert C.; McCabe, Craig A.

doi:10.1785/0120060269

Cited by 25 publications

(32 citation statements)

References 25 publications

(17 reference statements)

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“…They have been active in the Quaternary, but have relatively minor down-to-the-east displacements of less than a few meters, and are discontinuous at the surface. These faults are also weakly expressed in the subsurface based on gravity data, compared to the major subsurface basement escarpment bounding the east side of the Santa Rosa Plain McPhee et al, 2007). Based on this structural relief we interpret normal fault displacement to have been focused along the east side of the plain and to refl ect earliest slip on the Rodgers Creek fault zone.…”

Section: Evolution Of the Rodgers Creek-maacama Fault Systemmentioning

confidence: 83%

“…900-1400-m-high west-facing basement escarpment that is evident in gravity data (Langen heim et al, 2008(Langen heim et al, , 2010McPhee et al, 2007). This west-facing basement surface is inferred to be a west-side-down zone of normal faults bounding the Santa Rosa Plain, as shown in Figure 5 (section C-C′).…”

Section: Evolution Of the Rodgers Creek-maacama Fault Systemmentioning

confidence: 84%

“…The timing of faulting and basin formation is determined from the sedimentologic and structural relations of interbedded sedimentary and volcanic units. Confi gurations of structural basins that we interpret to have formed during evolution of the Rodgers Creek-Maacama fault system are constrained from recent gravity and aeromagnetic investigations McPhee et al, 2007). The amounts of offset and slip rates for the principal faults of the Rodgers Creek-Maacama fault system are determined from best estimates of the limits of distribution of the displaced volcanic and sedimentary sequences, including Mesozoic bedrock units.…”

Section: Geologic Setting Of the Rodgers Creek-maacama Fault Systemmentioning

confidence: 99%

“…The part of the Rodgers Creek fault zone extending south of Santa Rosa is here referred to as the southern Rodgers Creek fault zone. (Allen, 2003), but chemistry and stratigraphic relations now indicate unit is older than Roblar and younger than rhyodacitic rocks of Zamaroni Quarry ( A le x a n d e r D r y D r y C r e e k on May 9, 2012 geosphere.gsapubs.org Downloaded from Collectively, the southern and northern Rodgers Creek fault zones step right, and also go through a complexly evolved releasing bend in transferring slip to the Maacama fault zone northeast of Santa Rosa (Wong and Bott, 1995;McLaughlin et al, 2005McLaughlin et al, , 2006McLaughlin et al, , 2008McPhee et al, 2007;Langenheim et al, 2008). Multiple strands and segments composing the separate northern Rodgers Creek and Maacama fault zones form a right step in which the two fault zones are subparallel and overlap along strike for ~40 km between Santa Rosa and Geyserville.…”

Section: Fault Nomenclaturementioning

confidence: 99%

“…The Santa Rosa pull-apart basin McPhee et al, 2007) is a structure that defi nes the most recent stage of Rodgers Creek-Maacama fault system reorganization. This pull-apart structure is a young, ~3-km-wide extensional depression between the Rod gers Creek and Maacama faults in the Santa Rosa area, fi lled with a thin cover of undeformed Quaternary sediments (Figs.…”

Section: Santa Rosa Pull-apart Basinmentioning

confidence: 99%

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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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Section: Evolution Of the Rodgers Creek-maacama Fault Systemmentioning

confidence: 83%

Section: Evolution Of the Rodgers Creek-maacama Fault Systemmentioning

confidence: 84%

Section: Geologic Setting Of the Rodgers Creek-maacama Fault Systemmentioning

confidence: 99%

Section: Fault Nomenclaturementioning

confidence: 99%

Section: Santa Rosa Pull-apart Basinmentioning

confidence: 99%

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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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Testing the inference of creep on the northern Rodgers Creek fault, California, using ascending and descending persistent scatterer InSAR data

Jin

Funning

2017

JGR Solid Earth

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We revisit the question of whether the Rodgers Creek fault in northern California is creeping, a question with implications for seismic hazard. Using imagery acquired by Envisat between 2003 and 2010, we process two persistent scatterer interferometric synthetic aperture radar (InSAR) data sets, one from an ascending track and the other from a descending track, covering the northernmost segment of the Rodgers Creek fault between the cities of Santa Rosa and Healdsburg. The two different viewing geometries provided by the two different tracks allow us to distinguish vertical velocities, which may reflect nontectonic deformation processes, from fault‐parallel velocities, which can be used to identify creep. By measuring offsets in InSAR line‐of‐sight velocity from 12 fault‐perpendicular profiles through both data sets, we identify seven locations where we have a high degree of confidence that creep is occurring (estimated creep rate is more than two standard deviations above zero). The preferred creep rates at these locations are in the range 1.9–6.7 mm/yr, consistent within uncertainty with alignment array measurements. Creep is probable (P≥0.70) at another three locations, defining a creeping zone ∼20 km long in total, extending northwest from Santa Rosa. We also estimate the map patterns of fault‐parallel and vertical velocities in the region covered by both data sets; these suggest that the Rodgers Creek fault immediately southeast of Santa Rosa remains locked.

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Geophysical Investigation and 3D Modeling of Bedrock Morphology in an Urban Sediment-Filled Basin: The Case of Bolzano (Northern Italy)

Giulia,

Corrado,

Giovanni

et al. 2024

Pure Appl. Geophys.

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Bedrock mapping is essential for understanding seismic amplification, particularly in sediment-filled valleys or basins. However, this can be hard in urban environments. We conducted a geophysical investigation of the sediment-filled Bolzano basin in Northern Italy, where three valleys converge. This study uses low-impact, single-station geophysical methods suitable for urban areas to address the challenges of mapping in such environments. A dataset of 574 microtremor and gravity measurements, along with three seismic reflection lines, allows for the inference of the basin’s deep bedrock morphology, even without direct stratigraphic data. The dataset facilitates a detailed analysis of the spatial patterns of resonance frequencies and amplitudes, revealing 1D and 2D characteristics of the resonances. Notably, 2D resonances predominate along the Adige valley, i.e., the deepest part of the basin with depths up to 900 m. These 2D resonances, which cannot be interpreted through simple 1D frequency-depth relationships, are better understood by integrating gravity data to develop a depth model. The study identifies resonance frequencies ranging from 0.27 to over 3 Hz in Bolzano, affecting different building types during earthquakes. Maximum resonance amplitudes occur at lower frequencies, specifically at 2D resonance sites, therefore primarily impacting high structures. The 2D resonances are directional, with the most significant amplification occurring longitudinally along the valley axes. The resulting 3D bedrock model aids in seismic site response modeling, hydrogeological studies, and geothermal exploration and provides insights into the geological history of the basin, highlighting the role of the Adige Valley as a major drainage pathway.

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Basin Structure beneath the Santa Rosa Plain, Northern California: Implications for Damage Caused by the 1969 Santa Rosa and 1906 San Francisco Earthquakes

Cited by 25 publications

References 25 publications

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

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

Testing the inference of creep on the northern Rodgers Creek fault, California, using ascending and descending persistent scatterer InSAR data

Geophysical Investigation and 3D Modeling of Bedrock Morphology in an Urban Sediment-Filled Basin: The Case of Bolzano (Northern Italy)

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