62 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
its floor and end panels bent and the tension rods in the last two panels were buckled 
and twisted. 
The upthrow on the fault east of Stewart’s Point is on the west side; but farther up 
stream, where the fault runs along the steep west side of the valley below Casey’s ranch, 
the upthrow is apparently on the east side. The foot trail from Casey’s ranch to the 
river follows a marked longitudinal depression in the steep slope for 100 feet, and it is 
along the abrupt west side of the small ridge flanking the hollow (see fig. 14) that the 
fault-trace is located. The upthrow measures fully 2 feet, while the height of the 
ridge above the hollow varies from a few feet to more than 10 feet. The depression 
pitches to the north and is drained by a tiny brook. The fault-trace happens to coincide 
with the latter at a point where the trail crosses the watercourse over a rough wooden 
bridge. The horizontal movement along the fault practically destroyed the bridge. No 
measure of the displacement could be obtained here, but the indications are such as to 
warrant the belief that it did not amount to 15 feet, and that probably some of the 
horizontal shear had been distributed over minor lines of displacement higher up the 
slope, and marked by landslides. These landslides above the depression in which the 


Casey’s ranch 
Trail Brook 


South Fork 
Gualala River 
FAULT 


Fig. 14.— Profile of southwest side of South Fork of Gualala River, showing relation of fault to 
geomorphic features. 
fault-trace lies are an important factor in the interpretation of the phenomena. It is 
easily possible that the scarp looking southwesterly over the depression referred to does 
not represent the real movement on the fault plane, but is a landslide effect. In any 
event, the proximity of the landslide weakens very much any judgment that might be 
formed, implying a reversal of the vertical movement which normally prevails along 
the line of the fault. 
From Casey’s ranch southeast, detailed observations were found to be impracticable 
owing to the dense tangle of brush and fallen timber. The ridge between the upper 
stretch of the river and the coast is crost by the fault-trace thru a swampy saddle above 
Plantation House, and the fault-trace traverses the swamp. Plantation House stands 
practically on the line of disturbance, about midway in a zone 270 feet wide traversed 
by six roughly parallel lines of rupture. The general bearing of the principal line was 
found to be N. 388° W. Southward the main fault passes thru a series of swampy hollows 
along an abandoned road, now impassable because of the cracks thru it. The line was 
traced south for 2 miles, its general appearance being found to remain the same thruout. 
There is a marked upthrow along its west side, not exceeding a foot at any place. Where 
