Hayward Fault Gallery
Part 2, Southern Segment: Hayward to Fremont
The city of Hayward is full of the same types of features shown in part 1. In fact, the old City Hall sits directly on the fault and is now uninhabitable. Farther south, the fault becomes much more visible as the trees and development lessen. The image of a shutter ridge in the Image Gallery comes from this region. See more photos along the fault in downtown Hayward in this photo gallery.
A strip of several small springs on this dry hillside marks the fault trace. It is very common for faults of all kinds to disrupt the flow of groundwater. In this case the fault is a barrier that forces the local groundwater to the surface. In October at the height of the dry season, the green spot is a narrow bench, knee-deep in thick grass and reeds, in the midst of a bone-dry slope. (All photos (c) 2001 Andrew Alden, licensed to About.com.)
The fault trace runs midway down this strip of vacant land between new apartments on the downhill side and new homes above. California's pioneering Alquist-Priolo Act has done much to prevent inappropriate developments in fault zones. Homebuyers must be fully informed when purchasing property in officially mapped fault zones. Here, the city planners have kept the fault trace bare.
At the Shinn station in northern Fremont, the train tracks are all bent to varying degrees by fault creep. This old rail fence has warped much more than the tracks. Presumably the tracks are repaired often, but there has never been a need to fix the fence.
View north across the fault trace next to the Fremont BART station. Here, one strand of the Hayward fault ends while another one begins, offset about a hundred meters to the right. In the short distance where the strands overlap, the balance of forces allows the land between the strands to sink. The result is called a sag basin, and it may be occupied by a sag pond. This natural sag pond occupies the basin between one strand on the opposite bank and another directly underfoot, at the edge of the parking lot. The far strand ends here while the near strand continues to the south. The map below should make this clearer; notice that the old air photo doesn't show the new houses across the pond. (Image courtesy U.S. Geological Survey)
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