THE EARTH MOVEMENT ON THE FAULT OF APRIL 18, 1906, 71 
The four localities last mentioned are included in the space of 0.5 mile. Their several 
indications of the total displacement, in the order of position from south to north, are 
12+, 138.5, 15, and 11 feet. The range of these determinations is 4 feet and their approxi- 
mate mean 13 feet. At each locality the indicated displacement consists partly of definite 
faulting along one or two planes of fracture, and partly of diffused shear, distributed thru 
a belt of rock, or at least a belt of soil. At each locality the indicated shear is all in one 
direction. At each locality the measurement depends for its authority on the assumption 
that the disturbed fence or row of trees was originally straight. 
Kight miles farther north, at Mr. W. D. Skinner’s place, near Olema, the entire fault is 
apparently concentrated in a single narrow zone, and the several measurements made 
are in close accord. The fence 
south of his barn (fig. 22) was / j / 
offset 15.5 feet. The barn, be- / ( 
neath which the fault-trace past, 55 / ( 
remained attached to the foun- Shy la on NL ae ee ee 
dation on the southwest side, but zZ— i fi 
was broken from it on the north- i / 
west side and dragged 16 feet. ts a 
A path in the garden, originally 
opposite steps leading to the y, 
porch, was offset 15 feet. (Plate aa 
38p.) A row of raspberry } 
bushes in the garden was offset a 
14.5 feet. The mean of these 
four measurements is 15.25 feet, / 
and their range is 1.5 feet. 
The road running southwest Figs. 20 and 21.—Dislocated fences on farm of E. R. Strain, near | 
Woodville. 
from Point Reyes Station and 
crossing the valley at the head of Papermill Creek delta was offset 20 feet. (Fig. 23 
and plate 47s.) As the fault-trace at this point was between 50 and 60 feet wide, and 
as the embankment of the road for that distance was broken into several pieces, it was 
not possible to make certain that the dissevered remnants of the road had originally 
been in exact alinement. It is probable, however, that the road was approximately 
straight before the earthquake, and that the exceptionally great offset at this point is to - 
be explained as the result of a horizontal shifting of the surface materials. The embank- 
ment of the road rested on marshy ground so soft that a portion of the embankment sank 
into it, and material of this character was in other localities demonstrably shifted. 
A number of other measurements of displacement were made, but these, for various 
reasons, do not seem worthy of record, altho some of them were noted in an earlier report. 
Several were connected with the dislocation of trails, but in every such instance the trail 
made only a small angle with the strike of the fault and part of it was broken up along 
with the fractured turf. The endeavor to find more favorable angles of intersection drew 
attention to the fact that because the dominant trend of hills and valleys in the Rift is 
northwest-southeast, the lines of easy travel, minor as well as main, are largely parallel to 
the fault-trace. Other measurements were connected with the offset of fences, and, altho 
definite in themselves, have little value because there is reason to believe they represent 
only a part of the local displacement. The part represented by them is in every case less 
than 10 feet. It is noteworthy in this connection that most farm fences which were 
intersected by the fault-trace either terminated within a few yards of it or changed direc- 
tion at about that place. Like the trails, they were adjusted to topographic peculiarities 
created by earlier faulting along the same line. 
