EPOD 20th - Hollister Offset
September 09, 2020
We’re celebrating 20 years of Earth Science Picture of the Day during the month of September! Today’s photo features a popular EPOD from the past. Thanks to all of our followers (on the blog, Facebook, Instagram and Twitter) for supporting us. Thanks also to all of you who’ve submitted your photos. We’re most appreciative. This EPOD was originally published September 28, 2006.
Provided and copyright by: David Lynch
Summary author: David Lynch
The boundary between the North American Plate and the Pacific Plate is a complex region of intertwining faults that follow the granddaddy of them all, the San Andreas Fault. One of the major splinters is the Calaveras Fault. It runs through Hollister, California and is most evident in the vicinity of Dunne Park. Unlike the San Andreas Fault, which is usually locked for many years until it shifts and causes an earthquake, the Calaveras Fault is creeping steadily along at about half an inch per year. As a result, roads and houses built on the fault are slowly being sheared and shifted and must be patched frequently. When it is not feasible to repair them, the damage accumulates year by year.
In the vicinity of Dunne Park, the fault is obvious as offset curbs and sidewalks for many blocks north and south of the Park. A low scarp roughly two feet high runs through the barbecue area on the east side of the park. In this photograph, the built-up motion is revealed as a prominent 2 ft (.65 m) side step in the sidewalk where the fault crosses from right to left. This means that the last time they paved the sidewalk was about 50 years ago. Offsets in the curbs are much smaller, the result of more recent paving and straightening of the road. How would you like to be a real estate agent in Hollister? Photo taken in May of 2004.
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