308 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
partly thrown down at the northwest corner. Wooden houses suffered no damage except 
the cracking of plaster. No window panes were broken. 
Two bridges near Pleasanton were inspected, one north of the town over Arroyo Valley 
and the other over Arroyo de la Laguna, 1.5 miles west of the town. These bridges rest 
on conerete abutments, and examination showed that in both cases the concrete had 
sheared horizontally by the longitudinal oscillations of the superstructure. The cracks 
were about even with the lower side of the stringers. In the case of the first bridge 
mentioned, these cracks extended to the wing wall at the south end. A vertical crack was 
also found near the west corner of the south abutment, running thru the entire height of 
the structure. A similar crack was also found at the east corner of the north abutment. 
The disposition of these vertical cracks seems to indicate torsional movements of the 
bridge, with right-handed rotation. The concrete was of poor quality, being traversed 
by streaks of coarse gravel alternating with others of finer texture. 
Thru the courtesy of F. H. Tibbets and Harold Woods, surveyors for the Pleasanton 
Hop Company, access was obtained to their records on well borings made in the neigh- 
borhood of Pleasanton. Most of these borings did not reach bedrock, but 2 of them did: 
one near the graveyard south of Pleasanton, which strikes disintegrated shales at a depth 
of 275 feet; the other 0.75 mile northeast of Pleasanton, just south of the railroad track, 
which strikes similar material at a depth of 180 feet. 
Livermore (F. E. Matthes).— Many chimneys were cracked and about 50 per cent 
thrown down. Several tall brick chimneys in various parts of the town were left intact. 
Those on brick piers between Livermore and Pleasanton were undamaged. A block of 
old, weak-looking buildings northeast of the depot suffered no more than a few cracks. 
Glassware in saloons and bars was thrown to the floor in quantities, in various directions. 
A heavy water-tank at the depot fell, owing to weakness of supports. The direction of 
the fall is north, but this is not necessarily indicative of the direction of the shock, as the 
wooden support probably gave way piecemeal. Concrete bridges about town were unhurt. 
The town is on alluvium. 
An interesting feature appears 0.25 mile north of Meyn’s ranch, west of the road leading 
north from Livermore, about 2 miles northof that place. It is on the summit of a smoothly 
rounded hill, sloping gently down to an even, peaty meadow traversed by the arroyo of 
Cayetana Creek. The hill is really one of a number of spurs of the higher land south of 
the meadow. Its soil is peaty, with many sun cracks due to recent drying. Deep cattle 
tracks show that it must be quite soft in wet weather, much like the adjoining meadow. 
The summit of the hill in question was found crowned by a series of concentric deforma- 
tions, rising stepwise above one another. A number of nearly concentric cracks were 
found extending northward into a sort of panhandle, along each of which an upward 
movement of the soil had apparently taken place. The uplift along the 2 principal cracks 
was found to be 19 and 16 inches, respectively. Along the minor cracks the vertical 
displacement amounted to an inch or two only. The surface of each step or bench was 
found to slope inward, and in some places the edge even appeared to have curled inward. 
The material must have been wet and more or less plastic at the time of the disturbance, 
but has since dried and hardened, as peaty soil will in dry weather. While the phenom- 
enon is described by many as a “mud flow” or “mud spring,” there are no indications 
whatever of a “flow,” strictly speaking. The inward slope of the raised benches sug- 
gests the dropping back of the central portions after their upheaval; the scarps remain- 
ing, probably, owing to the friction between the opposite walls of the fissures, which 
prevented the complete return of the adjoining edges to their former level. ‘The concen- 
tric arrangement of the cracks seems to indicate a centralized upward thrust, and the 
small diameter of the entire deformation shows that the effect of the thrust rapidly 
decreased away from the center. While there is no rock visible, it is quite possible 
