


380 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Noises heard at the time of the shock — Continued. 
Locality. Reporter. Observer. Kind, direction, time of noise, ete. 
Modesto....... KE. Hughes... | A. H. Holtman... | Shock preceded by roaring sound. 
O0s emer <2 to ere H. Himtne. cee Rumbling sound. 
Stockton....-.. GOWseres Some persons out | Dull rumbling sound just preceding shock; 
Of doors ene.. some think it emanated from buildings. 
Westley ....... W. G. Carey | Men sleeping on | Heard terrible rumbling 30 s. before shock; 
scow on river.. came out of scow to see what it was, then 
shock came. 
Conejdss. saa H, Picket.se:al)Sames6 occ 2. <2 Awakened by noise like locomotive coming at 
full speed. 
Santa Barbara | J. A. Dodge. | Neighbors....... Rumbling just before shock. 
Lone Pine, Ne- | G. F. Marsh. | Same............ Slight rumbling sound like wind blowing. 
Vadae seme 
Ballarat, Inyo |D. C. Pickett | Same...........-. Awake and up. First indication of earthquake 
Countyzeeeee was low, distant, and increasing roar. 





VISIBLE UNDULATIONS OF THE GROUND. 
The earth-waves generated at the fault past thru the earth’s crust with a velocity of 
probably from 2 to 3 kilometers per second. The undulations of the surface due to the 
passage of such waves would be so swift that they would scarcely be observed visually. 
Yet there is considerable testimony, of a consistent and independent character, that 
much slower undulations were observed. This testimony comes from various parts 
of the region disturbed, and a great deal of it is positive and unequivocal as to what 
seemed to be the fact. The evidence indicates that there is a type of wave in the ground, 
in the region of high intensity, which has not yet been sufficiently recognized, and the 
origin of which is obscure. Some 20 or more observations bearing upon this class of 
phenomena are here summarily recorded : 
Judging from the descriptions given, these waves behaved like undulations in water, 
with an oscillation approximately normal to the surface. They were for the most part 
observed on alluvial tracts, but some of the reports come from districts where there is 
but a thin veneer of alluvium or soil upon the rocks. If it should prove, on the basis 
of more abundant evidence, that these waves are peculiar to alluviated basins, they 
may be explained as reflections from the rocky slopes of such basins. If a bowl of liquid 
be tapt smartly, vibrations are inaugurated in the rigid bowl which have a speed so 
great that the secondary waves generated in the liquid pass out from all parts of the 
walls of the vessel sensibly at the same instant. But the secondary waves thus gener- 
ated in the liquid have so slow a rate of propagation that they are quite apparent to 
the eye, and in the central part of the surface of the liquid, when the waves meet, there 
is a violent commotion. If, instead of a bowl of liquid, we have a rock basin filled with 
water-saturated alluvium, it seems probable that a similar effect would be produced 
in a modified degree; and the visible waves at the surface may have had such an origin. 
But whatever be their origin, it is apparent that they must be a large factor in damaging 
structures situated upon the ground in which they occur, and so raising the apparent 
intensity on any scale based on destructive effects. 
Freshwater, Humboldt County (S. i. Shinn). — My orchard raised up between 2 and 
3 feet like a big breaker coming in. 
Ferndale, Humboldt County (A. W. Blackburn). — Those who claim to have been out 
of doors when the shock came, state that the earth rose and fell like the waves of the sea. 
Fort Bragg, Mendocino County (O. F. Barth). — A man walking along the street was 
thrown down. He is positive the wave traveled southwest. The ground undulations 
were 2 and 3 feet high. 
Point Arena, Mendocino County (W. W. Fairbanks). —'The ground moved in undu- 
lating swells or waves, rising and falling. 
