THE EARTH MOVEMENT ON THE FAULT OF APRIL 18, 1906. 79 
of 1907, and it was then overspread by a fresh deposit brought by Papermill Creek. The 
ridges varied somewhat in height, the amplitude from crest to trough ranging from 1 to 
3 feet and possibly more. Their general trend was parallel to the fault-trace, but there 
were notable exceptions, and over small tracts the direction was even at right angles to it. 
In some cases, where the minor ridges were parallel, there were larger ridges traversing 
them obliquely. Fig. 25 reproduces a sketch map of the local- 
ity showing the greatest complexity. So far as the broad undu- 
lations of the tide lands were seen in conjunction with the 
ridging, the greater ridges were on the swells and not in the 
hollows. 
Without going deeply into the question of interpretation, it 
would seem that in the production of this.ridging the tidal mud 
must have behaved as a quasi-liquid, being thrown into waves by 
the agitation to which it was subjected. When the agitation = 
IG. 25.— Arrangement of 
ceased it became once more a quasi-solid, and preserved the form ridges on tidal flat near 
it had at the moment of change. Ternees, ib. 
There was also a horizontal shifting of ail over a considerable area. Residents 
familiar with depths of water in the vicinity of Inverness stated that the earthquake 
caused a decided shoaling along the coast, but that the relation of water levels to firm 
ground was unchanged. It was also stated that a channel which had existed parallel 
to the west shore of the bay, and to which piers had been run, was obliterated by the 
earthquake. The shoaling might have been caused either by an uplift of the bottom 
or by a shifting of the mud of which it is composed toward the shore. That the second 
of these explanations is correct seems to be shown by the following facts. 








“Firm ground | oor 
Fia. 26.—Sketch of Inverness piers. Full lines show 
positions of piers after earthquake; broken lines show 
positions before earthquake. Dotted line shows shore- 
ward limit of the shifting of bottom. 
Fia. 27.— Diagrams with exaggeration of vertical scale, 
to illustrate deformation of Inverness piers by shifting 
of mud toward the shore. Bailey’s pier above; Mar- 
tinelli’s below. 



At various places along the shore, from Inverness to a point 1.5 miles southward, the 
tidal mud seemed to be crowded against the firmer ground at the shore, being pushed up 
in a ridge, as shown in the accompanying photograph. (Plate 558.) Two piers at 
Inverness, light wooden structures, resting on piles and extending out several hundred 
feet from the shore, were telescoped. (Figs. 26 and 27.) In the case of Martinelli’s pier 
the telescoping was shown by the inclination given to piles at the landward and bayward 
ends, from which it appears that the ground in which the piles were set was crowded 
together, so that the foundation of the pier was shortened, while the superstructure 
resisted shortening. The resistance was temporary only, for before the agitation ceased 
the pier was broken in two; and the inclination of the piles is supposed to have been 
given during the early stages of the tremor. Coincident with the movement of the 
