102 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
southeast, it crosses a small point projecting into the lake from the northeast side. 
Half a mile beyond it passes thru the dam between Upper and Lower Crystal Springs ~ 
Lakes. This dam is now simply a causeway across the lake, the water on both sides 
standing at the same level. The dam was rendered superfluous except as a causeway 
by the construction of the great concrete dam at the outlet of the present Lower 
Crystal Springs Lake. The latter was uninjured by the earthquake, a careful exami- 
nation having failed to reveal even a crack in the splendid structure. 
Where the fault intersects the causeway dam between Upper and Lower Crystal 
Springs Lakes, the dam was dislocated and offset about 8 feet. (Fig. 40.) This dis- 
placement was well marked in the roadway across the dam and in the fences which 
parallel it. The fences on both sides of the road were broken and the boards were 
buckled and shoved over each other; the telephone wires crossing the lake sagged con- 
, siderably, showing that the movement brought 
the poles closer together. The facts indi- 
cate, as previously stated, that, in addition to 
the offset of the dam along the line of the 
fault, there was a notable compression in the 
direction normal to it. Beyond this dam the 
trace of the fault is partly beneath the lake 
and partly skirts its southwest shore (for the ° 
water level of April, 1906), and finally leaves 
the lake on that side about 0.25 mile from its 
southeast end. 
Exposures of the fault-plane (R. Anderson). 
— In addition to the evidence given by fences 
and pipes, there is the displacement of land 
surfaces and actual exposures of the fault face 
at the surface. Examination of mounds, em- 
bankments, and shore lines crost by the rup- 
ture usually revealed a displacement of the 
surface, and an interruption of the old topo- 
graphic outlines. In the case of mounds cut 
pice ff i suthwestwardly from ths by the fracture, the displacement makes itself 
eee Wy Total net shortening of pipe 58," | apparent in vertical scarps in consequence of 
fl the curved surfaces being faulted past each 
other. At the northwest face of a_ hillock, 
near where the furrow emerges from Crystal 
Springs Lake, the northeast side of the mound 
—the side away from the lake—has retreated 
relatively, leaving a portion of its lower slope in juxtaposition with the higher slope of 
the other side. A horizontal line across the exposed face would give the distance moved, 
provided no subsidence had taken place, which does not seem to have been the case. 
The distance could be only approximately measured, but it is at least 8 or 10 feet. A 
crack 2 to 3 feet wide and several feet deep separates the two walls locally. Looking at 
the other side of the same mound an irregular face several feet in height is exposed on 
the northeast side of the fault, the natural result of a longitudinal slipping. The fault- 
ing of raised surfaces after this fashion was discovered in various other instances. 
Large hills were crost only two or three times in this stretch of the fault. They were 
not so affected. 
The banks of stream channels sometimes preserved evidence of the movement even 
more completely than did mounds. Almost every gully crost by the fracture suffered 
Scale in feet 
Di, 20s 2 SO 
1 50 

Fic. 39.—Intersection of fault and Locks 
Creek pipe. After H. Schussler. 
