70 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Measurements of throw. — At all points where horizontal throw was observed, the 
ground at the southwest, as compared to ground at the northeast, moved northwestward. 
On Pepper Island in Bolinas Lagoon a horizontal displacement was shown by jogs in the 
directions of the south coast, of the limit of vegetation at the north, and of a well-defined 
change of flora dependent on the relation of land levels to tide. These various features 
are too indefinite to give value to measurement of offset, but the general indication is 
that the amount of throw is somewhat larger on the island than at the nearest points of 
measurement on the mainland. 
A mile northwest of the head of Bolinas Lagoon the fault-trace intersects a row of 
eucalyptus trees which had been set to mark a property line, the boundary between lands 
of 8.8. Southworth and 8. McCurdy. The row is now both dislocated and curved, and 
as there is reason to believe it was originally alined with care, its present condition shows 
the distortion of the ground at the time of the earthquake. ‘The fault-trace, as shown by 
the accompanying map (fig. 18), is here offset en échelon, and the row of trees is not only 
crost by one section of the trace but approached by the other. At the point of crossing 
the dislocation is 10 feet. On the northwest side of the fault are six trees, all in line. 
On the southwest side are a dozen or more trees of which all but three are in line. If the 
line of either straight division be projected across the fault (broken lines in map) it 
passes 13.5 feet to the left of the line of the other division. The three trees nearest the 

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Fia, 18.—Dislocated row of % Fic. 19.—Dislocated fence on farm of S. S. South- 
eucalyptus trees. j worth, near Woodville. 
fault on the southwest side follow a gently curving line. The indication is that about 
three-fourths of the whole displacement. occurred on the main plane of the fracture, and 
the remainder was diffused thru the ground adjoining on the southwest. A closely related 
condition exists at the southern limit of the same field, where the fault-trace intersects 
afence at right angles. The offset is 7 feet 8 inches, and this is accompanied by a change 
of direction. (Fig. 19.) Unfortunately the fence is too short to indicate in full the 
changes of the ground, but the suggestion is that in addition to the visible offset, there is 
a diffused shear affecting the ground southwest of the fault so that the entire displace- 
ment is greater than the amount shown by the offset. Assuming the fence to have been 
originally straight, the total displacement here was more than 12 feet. 
On Mr. E. R. Strain’s place, west of Woodville, measurements are afforded by the dis- 
turbance of two fences. The more southerly (fig. 20) is crost by two visible branches of 
the fault, and there is probably more or less diffused shear in the intervening ground. 
The fence, said by Mr. Strain to have been originally straight, has now two straight por- 
tions, AB and CD, and the distance from AB to E, on the line of CD produced, is 15 
feet. The second fence, standing a little farther.north, is intersected by one visible fault- 
trace, the continuation of the trace which crosses the first fence near B. On this 
line the fence is broken and offset 8.5 feet. The remnant of fence to the southwest 
is straight, but swerves in approaching the fault-trace, as indicated in fig. 21 and in 
plate 494. The total displacement of the straight portions of the fence is about 11 feet. 
