o44 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
of VIII, extended up the valley as far as Chualar; and the limit of intensity, VI, was 
reached only at King City, 45 miles above Salinas; VI in the vicinity of San Ardo, 65 
miles; and V at Pass Robles, 99 miles above the same point. The isoseismals drawn 
thru these points are almost parallel to the river, the intensity to the east and west 
diminishing rapidly. The town of Salinas is about 13 miles distant from San Juan, 
in a direction normal to the fault-trace. On the northern end of the Gavilan Range, 
which intervenes between the two valleys, the apparent intensity dropt to V and then 
rose rapidly to [X in the Salinas Valley. The limitation of the high apparent intensity to 
the valley-floor, the practically symmetrical parallelism of the isoseismals to the median 
line of the valley, and the diminution of the intensity with the thinning of the alluvium 
and the constriction of the valley upstream, all indicate dependence of the character of 
the shock upon the constitution of the underlying formations, and suggest no other 
factor. 
Still farther south in San Luis Obispo and Santa Barbara Counties, far beyond the 
isoseismal IV, an apparent intensity of IV is indicated by the effects observed in the 
valley-lands at San Luis Obispo, Edna, Arroyo Grande, Pismo, Santa Maria, Casmalia, 
and Lompoc. In the flat alluviated valley-bottom in which the town of Hollister is 
situated, about 8 miles east of the southern end of the fault at San Juan, the apparent 
intensity rose to IX, but diminished very rapidly on the hill lands immediately to the 
east of the valley to VI, which appears to have been the normal intensity for the moun- 
tainous tract between Hollister and the San Joaquin Valley. 
Farther southeast there was a similar but less marked rise in the apparent intensity 
at Lonoak, Priest Valley, and Hernandez, all of these being on alluviated bottoms. 
In the alluviated valleys to the east of the Berkeley Hills, the apparent intensity was 
abnormally high and the area occupied by these valleys constitutes an isolated area in 
which the intensity ranges from VII to VIII in the midst of a belt in which the range 
is from VI to VII. At Pleasanton the intensity was somewhat higher than at Sunol, 
altho the latter is nearer the fault of April 18, 1906, and is situated, moreover, on the 
line of an old fault which traverses the west side of Livermore Valley and extends up 
Calaveras Valley into the Mount Hamilton Range. At Livermore, in the more open 
part of the valley, where the alluvium is deeper, tho 8.5 miles farther from the seat 
of disturbance, the intensity was about the same as at Sunol. At Martinez, on an 
alluviated embayment of Suisun Bay, the damage due to the shock was much greater 
than in neighboring towns situated on rock, even when the latter were nearer the fault. 
Beyond Martinez to the eastward there is a very marked bulge to the east of Suisun 
Bay, in the isoseismal VII, which can be attributed only to the low and marshy character 
of the ground. The apparent intensity at Antioch was a degree higher in the seale than 
that at Mount Hamilton, altho it is double the distance from the fault of April 18; and 
altho there are several old faults in the vicinity of Mount Hamilton and none are known 
near Antioch. 
The influence of the valley-lands upon the apparent intensity is well shown on a large 
scale in the disposition of the isoseismal curves about the Sacramento Valley. In the 
mountains to the west of the Sacramento Valley the apparent intensity ranges in gen- 
eral from VI to V; but on the floor of the valley eastward to beyond the Sacramento 
River, it is very uniformly about VI or VI+. 
The most interesting case of high apparent intensity in a valley-bottom remote from 
the San Andreas fault is that of the San Joaquin Valley. This case merits especial 
consideration, since of all the valleys here considered it is the one which is most sug- 
gestive of the occurrence of a local earthquake, distant from, tho connected with, 
the main movement on the San Andreas fault. While the suggestion is strong, however, 
the eyidence is not conclusive of the occurrence in this region of a quasi-independent 
