HFS #1: Who used up all the Agua Caliente? EarthCache
Hidden : 11/17/2013
Difficulty:
1.5 out of 5
Terrain:
1 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:


This EC is first (from south to north) 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 in the vicinity of Agua Caliente Park in Fremont.  After logging this cache to have your log not deleted provide the CO with the answers to the two questions below.
 
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 (visit link) ).  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. 
 
In and around Agua Caliente Park in Fremont is the southernmost location where prominent features of the Hayward Fault can be observed.  The two most prominent include a sag pond and buckling of asphalt where the fault creeps (1).  This park was in the middle of a Mexican Land grant named Rancho Agua Caliente.  In the 1850s the southern portion of the land grant was sold to the attorney Abram Harris, and a town and resort of Harrisburg and a winery were develop in the area.  The resort centered around the natural springs located in the vicinity of this park.  The earthquake on the Hayward Fault in 1868 destroyed the winery (2) caused the springs to dry up.   With springs dried up associated resort failed.

GZ:  You are standing near the location of the former springs and above sag ponds formed by the fault and formerly filled by the springs.  Sag features like the ponds below are a direct result of grinding and movement on the fault causing deflation in the ground surface.  Springs can cease to flow following an earthquake.  Often springs occur where a impermeable geological layer of sediment or fault gouge (3) forces the natural flow of groundwater to the ground surface much like a dam forces the water level in a stream to a high elevation (Here at Aqua Caliente it was fault gouge that created the springs).  When an earthquake occurs it can fracture these impermeable layers and rather than force the groundwater to the surface the groundwater is allowed to flow to lower geological layers.  This happened to the Agua Caliente springs following the 1868 earthquake.  I am personally familiar with a similar occurrence following the 1989 Loma Prieta earthquake.  The Christian Conference Center Mount Hermon receives its water from springs in the sand deposits around Mount Hermon and Scotts Valley.  The 1989 quake fractured a clay layer in the sands allowing the groundwater to seep to a deeper layer, and the springs dried up.  In this case the clay layers resealed and the springs reappeared several years later.  Here at Agua Caliente the springs never did reappear.

Question#1:  Approximately how many feet is GZ above the floor of the sag pond?

Way Point #1.  You should be standing on the sidewalk on Ivy Way near the intersection of Gardenia Way.  Looking to the southeast across the street towards the opposite curb you'll see the bucketed asphalt.  This asphalt is continually damaged by the 4 to 5 millimeters (4) per year of creep on the Hayward Fault.

Question #2:  From the north curb provide compass bearing of the fault based on your best estimate of damage to the pavement.

(1) Creep = slow continuous movement along a fault verse the abrupt movement that occurs during an earthquake.

(2) Some of the ruins of the winery are located at N37  31.973 -  W121  57.157 behind the fence of some BART owned property on the southeast corner of Osgood and Washington (parking on Bruce St).  These ruins can be viewed from across the fence and a wall with about a 2.5 foot offset can be observed.  Since it is on private property these ruins are not part of the geocache.

(3) Fault gouge = During the movement of a fault the native rock can be ground to a fine grained "powder" unrecognizable from the parent rock, this material is fault gouge.

Additional Hints (No hints available.)



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