Research ArticleSeismology

Missing link between the Hayward and Rodgers Creek faults

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Science Advances  19 Oct 2016:
Vol. 2, no. 10, e1601441
DOI: 10.1126/sciadv.1601441

Figures

  • Fig. 1 Map of the Hayward-Rodgers Creek fault zone in the San Francisco Bay Area.

    Extent of the Hayward-Rodgers Creek fault zone shown in red (1, 2). Black lines show other major faults (23, 44). White box shows study area. Cities are marked with letters: AR, Alum Rock; H, Healdsburg; L, Livermore; O, Oakland; SF, San Francisco; SR, Santa Rosa.

  • Fig. 2 Marine magnetic map of San Pablo Bay.

    Warm colors show magnetic highs, and cool colors show magnetic or dipole lows. Plus signs show locations of the offshore Hayward fault along chirp seismic profiles. Thick red lines show Late Pleistocene and younger traces of Hayward and Rodgers Creek faults (23). Black lines are older Quaternary faults (23). Thick gray lines show locations of seismic profiles in Fig. 3. Capital letters E, F, G, H, and J are discussed in the text. Black circles show exploratory well locations (5). Base map, 2010 (1 m) National Oceanic and Atmospheric Administration Lidar. Inset: New Hayward fault strand (yellow) connecting directly to the Rodgers Creek fault. Gray lines show locations of chirp seismic track lines. Small black circles show relocated earthquakes (22).

  • Fig. 3 Chirp seismic profiles along the offshore Hayward fault.

    (A) to (D) are discussed in the text. Note vertical exaggeration of ~195:1. NW, northwest; SE, southeast.

  • Fig. 4 Isostatic gravity map of San Pablo Bay.

    Map shows isostatic gravity anomalies in San Pablo Bay (4547). Thick dashed white line shows the location of the horizontal gravity gradient maxima relative to the location of the Hayward fault (black plus signs). Orange star shows the location of a steep tomographic gradient along a seismic velocity profile (dotted black line) (6).

  • Fig. 5 Seismic profiles illustrating subtle on- and off-fault deformation along the offshore Hayward fault in San Pablo Bay.

    (A to C) Seismic profiles and extended views of corresponding profiles A and C in Fig. 3. Note the presence of an elongate depression (blue arrows) along the Hayward fault in the northern portion of the bay. Black arrows mark the inferred location of the Rodgers Creek fault (RCF). Dashed black line shows location of Hayward fault. Thin black lines indicate older or subsidiary fault structures. Yellow dashed line shows the upper limit of subsurface gas layer. Note vertical exaggeration of ~330:1. Inset: Map of Hayward-Rodgers Creek fault (H-RCF, red line) showing location of seismic profiles A to C (thick black lines). Blue line shows axis of depression along Hayward fault. Gray dashed lines show the previously inferred (4, 6) locations of the Hayward and Rodgers Creek faults in San Pablo Bay. Yellow circles show relocated earthquakes (22). SW, southwest; NE, northeast.

  • Fig. 6 Kinematic finite element models of the Hayward-Rodgers Creek fault in San Pablo Bay.

    (A) Model showing the predicted magnitude of horizontal shear stress after 5 ky of slip [9 mm/year (25)] along a disconnected Hayward-Rodgers Creek fault (red line). The model fault is relieving stress continually, except at fault endpoints. (B) Throughgoing fault model showing predicted vertical deformation after 100 ky of slip. Gray lines indicate locations of seismic profiles shown in Fig. 5. See Materials and Methods for detailed description of model methods and parameters.

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