This EC is part of a larger series of ECs all focusing on features of the Hayward Fault [this series is currently under construction, but individual ECs are being released sequentially to allow the largest number of cachers an opportunity for a FTF]. There is a final cache in the series (TBD) that can only be logged once you visited all the others in the series. Also, if you're interested in logging the final it is recommended you check out final in advance since observations you've made at this cache and other caches in the series will be helpful/required to log the final. Each of the ECs in the series contains slightly different information regarding the fault, with some overlap. Please see the Geotour for more information on this series (To be established).
This EC is located in the public right-of-way near Contra Costa Community College. Caution, look at street signs as some parking is only permitted for students with Parking Passes.
The Hayward Fault is a splay off a the Calaveras Fault in the vicinity of San Jose, and the Calaveras Fault originates off the San Andreas Fault at a bend in the vicinity of Hollister (Figure of faults in the Bay Area http://i41.servimg.com/u/f41/16/31/61/01/haywar10.jpg ). The Hayward Fault starts in the vicinity of east of San Jose and extends at the foot of the East Bay Hills until disappears under San Pablo Bay at Point Pinole. The Hayward Fault is what is referred to as a right lateral strike-slip fault; this means that if standing on one side of the fault facing the other side of the fault, the opposite moves laterally (horizontally) to the right of the side your standing on.
At this cache you'll primarily be observing the effects of fault creep and one way the fault results in a particular geomorphic (earth surface shape) feature.
GZ: At GZ you'll be a concrete traffic barricade. There is a nice little bricked patio with a very large planter box in the middle. Look north down the line of bricks. You will notice that the joints between the bricks go straight, then curve and go straight again (see offset with sense of motion at attached link http://b.static.trunity.net/files/119601_119700/119650/620px-Creep.jpg ). The bricks were all straight when laid down, but have moved as the Hayward Fault has creeped. Measure the offset between the two straight parts of the brick joints. As a side not, if you look at the now abandon buildings to the east, this is the now abandoned El Portal school. The fault skirts right at the edge (mostly) of buildings.
Question #1: At GZ measure the offset in the brick joints. Assume an average movement along the fault of 4 or 5 millimeters per year, how many years has it been since the bricks were lain based on the offset of the two sets of parallel lines on opposite sides of the fault? THE PLAZA HAS BEEN RECONSTRUCTED AND THIS FEATURE CAN NO LONGER BE OBSERVED. YOU CAN NO LONGER ANSWER THIS QUESTION, SO JUST GO TO THE OTHERS BELOW. IF YOU INTERESTED, YOU CAN SEE HOW IT USE TO LOOK AT THIS WEB LINK: http://b.static.trunity.net/files/119601_119700/119650/620px-Creep.jpg
Way Point #1. This will is by a geomorphic (earth surface form) feature that is oriented parallel to the fault. During movement, the fault crushes the rock and sediments, weaken the native materials facilitating the formation of this geomorphic feature.
Question #2: What is the geomorphic feature at Way Point #1? How might this process facilitate the formation of the geomorphic feature you see here? Why do you think this feature formed parallel to the Hayward Fault?
Way Point #2. This is located at a public bus stop. The roadway in this area is concrete not asphalt. Look at the joints in the roadway, when this was constructed the designers to into consideration the orientation of the Hayward Fault and creep along the fault to minimize the potential of cracking of the pavement surface.
Question #3: The concrete slabs were constructed with joints that are not perpendicular to the curb. What is the angle formed by the joints in the concrete roadway and the curb? How might the orientation of this individual slabs reduce cracking?
Go ahead and log your find. However, to avoid deletion of your log, as required by Groundspeak, please email the answers to CO.
If you'd like to do a more extensive tour of the Hayward Fault, please see a wonderful Hayward Fault field trip guide at:
http://pubs.usgs.gov/of/2008/1135/of2008-1135.pdf