224 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
No. 2. Maximum acceleration is 900 mm. per sec. per sec. Walls in Japanese houses 
cracked; old wooden houses thrown slightly out of the vertical; tombstones and stone 
lanterns of bad construction overturned; in a few cases changes are produced in hot 
springs and mineral waters; ordinary factory chimneys not damaged. 
No. 3. Maximum aeceleration is 1,200 mm. per sec. per sec. About one fabtoty 
chimney in every four is damaged; brick houses of bad construction are partially or 
totally destroyed; a few old wooden dwellings and warehouses totally destroyed; wooden 
bridges slightly damaged; some tombstones and stone lanterns overturned; shoji 
(Japanese Panceonean sliding doors) broken; roof tiles of wooden houses disturbed 
some rock fragments thrown down from mountain sides. 
No. 4. Maximum acceleration is 2,000 mm. per sec. per sec. All factory chimneys 
are broken; most of the ordinary brick buildings partially or totally destroyed; some 
wooden houses totally destroyed; wooden sliding doors and shoji mostly thrown out of 
their grooves; cracks 2 or 3 inches in width, in soft or low ground; embankments slightly 
damaged here and there; wooden bridges partially destroyed; and ordinary stone lan- 
terns overthrown. 
No. 5. Maximum acceleration is 2,500 mm. per sec. per sec. All ordinary brick 
houses very severely damaged; about 3 per cent of the wooden houses totally de- 
stroyed; a few tera, or Buddhist temples, are thrown down; embankments severely 
damaged; railway lines slightly curved or contorted; ordinary tombstones overturned ; 
ishigaki, or masonry walls, damaged here and there; cracks 1 to 2 feet in width pro- 
duced along river banks; water in rivers and ditches thrown over the banks; wells 
mostly affected with changes in their waters; landslips produced. 
No. 6. Maximum acceleration is 4,000 mm. per sec. per sec. Most of the tera, or 
Buddhist temples, are thrown down; 50 to 80 per cent of the wooden houses totally de- 
stroyed; embankments shattered almost to pieces; roads made thru paddy fields so much 
cracked and deprest as to stop the passage of wagons and horses; railway lines very much 
contorted; wooden bridges partially or totally destroyed; tombstones of stable construc- 
tion overturned; cracks a few feet in width formed in the ground, accompanied sometimes 
by the ejection of water or sand; earthenware buried in the ground mostly broken; low 
grounds, such as paddy fields, very greatly convulsed both horizontally and vertically, 
sometimes causing trees and vegetables to die; numerous landslips produced. 
No. 7. Maximum acceleration is much above 4,000 mm. per sec. persec. All build- 
ings except a very few wooden houses are totally destroyed; some houses, gates, etc., pro- 
jected 1 to 3 feet; remarkable landslips produced, accompanied by faults and shears of 
the ground. 
In the foregoing scale, in addition to these definitions by destructive effects, it will be 
noticed that a range of values for the acceleration is assigned to each scale number. These 
acceleration values have been tested experimentally by Professor Omori, and found 
accurate within narrow limits. Consequently it is called an absolute scale. It is the best 
intensity scale yet proposed. Since, however, it is defined in terms of damage produced 
upon Japanese structures, it would require constant critical interpretation in use in an 
American city. For this reason, it is believed to be not so well adapted to the purposes 
of this investigation as the scale proposed below. This is especially true since the values 
of the acceleration necessary to produce the destructive effects encountered here have not 
been determined by experiment. A use of the absolute scale would, therefore, pretend 
to an accuracy not attained with any certainty. The following scale will be referred to 
as the San Francisco scale: 
Grade A. Very violent. —Comprizes the rending and shearing of rock masses, earth, 
turf, and all structures along the line of faulting; the fall of rock from mountain sides; 
numerous landslips of great magnitude; consistent, deep, and extended fissuring in natural 
earth; some structures totally destroyed. 
