ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 177 
of the fault. A large barn at EK. EK. Fitch’s ranch, thru which the fault past, was practically 
demolished. The animals in the barn fortunately escaped uninjured. 
At Antrim’s ranch, on Alder Creek, a tall shed stands on the line. It threatens to fall, 
but was still up at the time of the visit (May 10, 1906). 
The wagon bridge over Alder Creek (plate 328), which stood astride of the fault, is a com- 
plete wreck. The timbers broke in many places, and the tension rods were twisted and in 
some cases actually ruptured. 
Along the Garcia River, the flumes of the L. E. White Lumber Company were reduced 
to kindling over long distances. Where they crost the river, suspended from steel cables, 
the end supports of the latter failed and let the flume drop down to the river-bed. 
Farther up, between the lumber camp and Hutton’s ranch, extensive landslides occurred, 
chiefly on the east side, wiping out the wagon road which was graded along the mountain 
slopes. Immediately north of Hutton’s ranch, a large landslide plowed into a grain field, 
producing a series of billowy wrinkles in the soft alluvial material. The outermost ridge has 
a steep front about 8 feet high and seems to have been thrust horizontally over the level sur- 
face of the field. The frontage of the slide is fully 400 feet. Hutton’s ranch-houses were all so 
badly damaged as to become uninhabitable; they are practically wrecked, tho still standing. 
Reports from Hot Springs, east of the Garcia, seem to indicate that the buildings there 
suffered but slight damage. The springs themselves had not been affected by the shock. 
From Alder Creek to Irish Gulch, and for a short distance north, rock slides are a common 
feature and cracks in the ground, frequently traversing the stage road, due to the slipping 
and settling of large masses on the steep hillsides, are too numerous to be reported in detail. 
On both sides of Irish Gulch the road was obstructed by slides which had been removed at 
the time of the visit, but which threatened to recur. 
Reviewing his observations as to the intensity between Fort Bragg and Manchester, 
Mr. Matthes concludes as follows: 
The gradual decrease of the intensity as one travels northward from Manchester is to 
be expected, in view of the gradually increasing distances of the several settlements from 
the line of the fault (it being supposed that the latter continues with the bearing measured 
near Alder Creek, N. 28° W.). On this supposition the decrease in intensity should, if 
anything, become more marked from Mendocino on; but such is evidently not the case. 
While the intensity does not materially differ at Caspar, it notably increases toward Fort 
Bragg; so much so, indeed, as to suggest a gradual curving of the fault, roughly parallel 
with that section of the coast. It is to be noted that over the distance between Fort Ross 
and Manchester, some 4 miles, the azimuth of the fault-line decreases steadily from N. 46° W. 
to N.28° W. This gives a total deflection of 18° in 48 miles. Assuming that the curvature 
continues northward at a uniform rate, there will be in the latitude of Fort Bragg, 35 miles 
farther north, a further decrease of the azimuth of nearly 13°. The fault, therefore, may 
bear only N. 15° W. in that neighborhood. Plotted on a map, the line with such a curva- 
ture appears to pass 5 miles west of Fort Bragg. 
Point Arena, Mendocino County. — Population 300. All the brick buildings in the 
place had completely collapsed (see plate 684), and in the opinion of the residents it was 
deemed wisest to replace them by frame structures. All brick chimneys had fallen; plaster 
had cracked and fallen wholesale fashion, especially on the lower floors, and many shop 
windows and smaller panes were broken. A few wooden buildings suffered from the 
collapse of their underpinning. As a result of the shock, fire started in the chemical 
laboratory of the grammar school, and that building, together with the Methodist Church . 
adjoining it, burnt down. 
The Point Arena light-house, 3 fies west of the fault, was thrown out of the vertical, 
and in addition sustained several horizontal cracks thru its masonry. It has been con- 
demned as unsafe and is to be torn down. The keeper’s dwelling suffered little damage, 
one chimney showing cracks, the other appearing intact. The fog signal was not dam- 
aged. On the south side of Point Arena harbor, large masses of rock slid down to the 
beach. Small rock slides took place all along the coast in this neighborhood. A sus- 
pended flume over the Garcia River was wrecked (plate 68n) and large trees were over- 
thrown (plate 69c). 
N 
