ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 239 
50 per cent of the chimneys were left standing, and no serious structural damage was 
noted. No comment seems needed to establish clearly the fact that the change in the 
character of the ground, this being the only variable factor, is in some way the cause of 
the change in the degree of intensity. 
On Ninth Street, east of Dore Street, between Bryant and Brannan Streets, the block 
pavement was badly damaged by fissuring, slumping, and the formation of surface 
waves. Frame dwellings were thrown from their underpinning, and a few collapsed. 
Plate 914 shows a wave trough near Bryant Street, with the resulting disturbance of the 
pavement. The dwellings immediately in the trough have dropt from their founda- 
tion posts. In plate 918, looking along Ninth Street from near Brannan Street, is shown 
the depression and fissuring of the street and its slumping or flow westward toward the 
former channel of a short branch of Mission Creek, which occupied the present location 
of Dore Street. Streets, curbing, car tracks, etc., are deflected from 6 to 8 feet from 
their former positions. The frame dwellings were not destroyed, but a careful examina- 
tion of the picture will show that most of them are badly injured. Many were left in 
a dangerous condition by the shock. 
On Tenth Street, between Bryant and Brannan Streets, less violence was noted and 
the slumping of flow eastward (toward the channel of the little branch of Mission Creek) 
is scarcely noticeable. 
Again, along the creek bed frcm Folsom Street, between Seventeenth and Eighteenth 
Streets, to the vicinity of Valencia Street at Eighteenth, great destruction was con- 
spicuously prevalent. Less than a third of the frame dwellings in this tract retained 
their vertical positions, and a few collapsed completely. Others remained standing 
only by leaning against each other. The south side of Howard Street, between Seven- 
teenth and Eighteenth Streets, which escaped the fire, furnishes a good illustration of 
the damage produced here. (See plate 93a.) As in other places, the streets were de- 
prest, fissured, and thrown into waves. (Plate 90c.) Car rails were arched and _ bent 
laterally in a violent fashion. (Plate 92x.) 
Sewers and water-mains were broken. At Eighteenth and Valencia Streets there 
was a serious break in the water-pipe. Here, on both sides of the street, the ground 
sank about 6 feet, causing the roadway to arch in a very noticeable way. (Plate 93x.) 
Ten-inch car rails were bowed up into arches from 24 to 30 inches in height. The Va- 
lencia Street Hotel collapsed so that occupants of the fourth story could step out into 
the street. Casualties in this district can never be known accurately, owing to the 
immediate onset of the fire, and the complete devastation it produced. 
On land made by filling in, ‘The Willows,” a marshy tract formerly extending up the 
Eighteenth Street Valley from Mission Lagoon, near the corner of Nineteenth and Guer- 
rero Streets, there was observed a considerable slumping or flow movement of the surface. 
The photograph (plate 944) shows the Youth’s Directory, a charitable institution for 
boys, where the street and building were moved northward and slightly eastward, toward 
the former channel and downstream, fully 6 feet. 
Enough evidence has been cited to demonstrate that high intensity prevailed thru- 
out this district. Here, as in the other tract of made land which occupies the site of 
the old tidal marsh, the materials used for filling were shaken together, and caused a 
general depression of the surface over the whole district, accompanied by slumping or 
flow movements. The surface was deformed into waves, with accompanying fissures 
and sharp compressional arches. Here too, as in the tract previously described, the 
materials used for filling constitute a relatively thin rigid layer deposited upon the 
marshy fringes or in the shallow waters of the creek. 
The creek (see map No. 17) formerly extended for about 2 blocks eastward from Ninth 
and Brannan Streets before it reached the old shore line of Mission Bay. This portion 
