THE EARTH MOVEMENT ON THE FAULT OF APRIL 18, 1906. 63 
it crosses the stage road at the Plantation House, the vertical displacement on the main 
fault measured 6 inches; that on the secondary lines did not exceed an inch. 
At Buttermore’s ranch, about a mile east of Timber Cove, the displacement is dis- 
tributed over three fissures, the principal one running 30 feet west of the dwelling. It 
intersects three fences, all of which show offsets of about 8 feet. The original crooked- 
ness of the fences and the repairs made since the earthquake make the accurate determi- 
nation of the displacement impossible. The fault-trace was followed for some distance 
south and north from the ranch thru the forest, and found to follow the swampy depres- 
sions most of the way with low scarps or ridges to the west. The ranch and its fields 
lie for the most part in a broad swampy saddle. The upthrow in this neighborhood is 
on the west side, not exceeding 15 inches anywhere. 
FORT ROSS. 
Northand south of Fort Ross, the phenomena of displacement are well displayed, both on 
the open-terraced coastal slope and in the timber. The rupture follows for the most part a 
single well-defined line in the path of the old Rift, coinciding in many places with ancient 
scarps and the slopes of low ridges. (See plates 35a and 36p.) The fault-trace is com- 
monly marked by a ridge of heaved sod with diagonal cracks as illustrated in plates 358 
and 36n. New scarps occur as shown in plates 36c, and 38a, B, as well as accentuations of 
old scarps. ‘There are, however, several subparallel cracks. Two of these, having each 
a length of about 150 feet, lie to the west of the main line at a point 1,250 yards northwest 
of Doda’s ranch-house, one 50 and the other 100 feet distant from the main crack and 
disposed en échelon. Within 300 yards to the southeast of this are two short cracks still 
closer to the main one, and springing from it, at about 450 yards northwest of Doda’s 
ranch-house, is a parallel crack 440 feet in length and 60 feet from the main line. In this 
case the scarp appears upon the auxiliary crack, and not upon the main line of rupture. 
Between the short discontinuous crack and the main line is a swampy depression. On 
the southeast side of the ravine, southeast of Doda’s house, the main crack is paralleled 
by two subordinate cracks, one on each side. That on the southwest side is about 250 
feet long and 50 feet from the main line. It has a low scarp facing northeast, but not 
so pronounced as that on the main line of rupture. The crack on the northeast side of the 
main line has a length of about 1,125 feet and converges upon the latter toward the 
northeast. At its northwest end it is 190 feet from the main crack and at its southeast 
end only 50 feet distant. It has a low, discontinuous scarp facing northeast. 
In a distance of 7,250 feet measured along the lineof the fault, there are twelvestretches 
of scarp ranging in length from 125 feet to 1,000 feet, counted both on the main and on the 
auxiliary cracks and aggregating 3,000 feet in length. Of these eight face northeast and 
four southwest. The eight scarps facing northeast aggregate 2,250 feet in length, while 
the four facing southwest aggregate 750 feet. Two of the southwesterly facing scarps, 
however, aggregating 375 feet in length, are on the descent to the ravine southeast of 
Doda’s house, where there is considerable sliding of the ground, and they may possibly 
be accounted for as secondary features due to landslides. ‘The other two scarps facing 
the southwest are unexplained. They are abnormal and are so exceptional that they 
scarcely weaken the general conclusion that the vertical component of the movement on 
the fault was upward on the southwest side. The amount of this vertical movement 
in the vicinity of Fort Ross probably does not exceed 3 feet. In the first hasty examina- 
tion of the ground, it appeared as if the amount of vertical movement might have been 
as much as 4 feet. This impression was due to the fact that in places preéxisting scarps 
were closely followed by the fault-trace, and a sufficiently careful discrimination was not 
made between the proportion of the scarp due to the new displacement, and that due to 
