104 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
due to settling of loosely accumulated or unsupported earth. For this reason no credence 
is given to the idea that an uplift or downthrow occurred along this part of the fault. 
This statement is based entirely on the evidence collected on the ground shortly after 
the earthquake and has nothing to do with the direction or amount of earlier displace- 
ment along this same fault-line. In some places an upward thrust seems to have taken 
place, as in the case of raising 7 pipes. This may, however, have been caused by wave- 
like movement in the ground near the surface or simply by the local heaving up of the 
ground as the result of compression. 
CRYSTAL SPRINGS LAKE TO CONGRESS SPRINGS. 
For our knowledge of the character and extent of the earth’s movement on the fault 
for that portion of its course lying within the limits of the Santa Cruz quadrangle of the 
U. S. Geological Survey, or between Crystal Springs Lake and the vicinity of Congress 
Springs, we are indebted to observations made by Messrs. H. P. Gage, F. Lane, 8. Taber, 
and B. Bryan, under the direction of Professor J.C. Branner. The notes of these gentle- 
men are preceded by a summary statement, and are arranged as far as possible in 
sequence from northwest to southeast in the following section: 
Summary statement (J. C. Branner). — The fault-trace that follows the San Andreas 
Valley continues southeastward in a nearly straight line. Beyond Crystal Springs Lake, 
it passes thru the village of Woodside, the Portola Valley, crosses Black Mountain a mile 
southwest of the triangulation station, follows down the general course of Stevens Creek 
a distance of 5 miles, and thence, following the same general direction along the eastern 
slope of Castle Rock Ridge, passes off the eastern side of the Santa Cruz quadrangle 
near latitude 37° 10’. West of Stanford University it follows along the northeastern 
base of the mountains that lie between the Pacific Ocean and the Bay of San Francisco, 
but as it passes toward the southeast, it cuts into the range and leaves Black Mountain 
and Monte Bello Ridge on the northeast side, while south of Saratoga it keeps well within 
the mountains. A singular feature of the fault, as it appears at the surface, is that in- 
stead of following the bottoms of the valleys, it often skirts along the base of one of the 
enclosing ridges, as shown in the accompanying sections. (Fig. 41.) This is not an in- 
variable rule, however. 
It will be seen from the map,'No. 22, of the isoseismal lines on the Santa Cruz quadrangle 
that there are several other faults within the area of the quadrangle, but evidences of 
movement at the time of the earthquake have been found only on this San Andreas 
fault-line, with the possible exception of slight movements along part of the Black 
Mountain fault. Cracks in the ground occur here and there almost all over the area 
covered by the sheet, but the cracks away from the San Andreas fault are due to incipient 
landslides or to the settling of loose or wet ground, and are not otherwise related to the 
more profound faults. 
The movement that took place along the fault in this portion of its course at the time 
of the earthquake was almost entirely a horizontal one. At several places evidences 
were seen of vertical displacement, but further examination showed in many instances 
that the appearances were deceptive or due to local causes. For example, where the 
fault crosses the top of Black Mountain there was apparently an upthrust on the north- 
east side of the fault. But it was found later that a great wedge-shaped piece nearly 
half a mile across had settled on the southwest side of the fault, producing this appearance. 
The direction of the horizontal displacement is uniformly a relative southeastward 
movement of the land on the northeast side of the fault. The amount of displacement 
varies in this area from near zero to 8.5 feet. This variation appears to be due to the 
character and condition of the ground. Usually ground that was wet and incoherent at 
