132 THE SAN FRANCISCO EARTHQUAKE AND FIRE. 
It was a rupture and slip along this fault, plainly evident for 
nearly 200 miles, that shook so violently the thousands of square 
miles of the earth's surface in central California. The first snap and 
movement of the crust were registered at the observatory of the 
State University as proceeding from south-southeast to north-north- 
west, or about parallel to the fault. This movement was there re- 
corded as over 3 inches horizontally, and was accomplished, as esti- 
mated by the California earthquake investigation commission, in one 
second of time. The vertical movement at the same place and time 
was believed to be about 1 inch. Professor Omori, the distinguished 
Japanese seismologist, also estimated the vibration in San Francisco 
to be 3 inches in one second. 
Instantly following this first snap were rebounds, reactions, and 
terranean reverberations from all parts of the greatly disturbed area 
on either side of the fault trace, which made the record on the seis- 
mograph resemble a tangled spider's web. It was this part of the 
earthquake — the temblors — that created and continued the racking 
vibrations, the twistings, and the wrenchings that brought down 
chimneys, Avails, and towers. 
Members of the California earthquake investigation commission 
advanced the belief that the first break, slip, and shock in the crust 
began at the northwest extremity of the fault trace, and that from 
this point the rupture and shearing extended progressively toward 
the southeast. This view seems to be borne out by later investi- 
gations, and certainly the greatest disturbances on the line of the 
fault were at and near its northern extremity. The earthquake was 
felt to a greater or less degree over a vast extent of territory, stretch- 
ing from Coos Bay, in Oregon, to Los Angeles, in southern Califor- 
nia, and from western Nevada over the greater part of middle Cali- 
fornia, and even out to sea. Although not noticeable to the senses, it 
was recorded on seismographs in Washington, D. C. ; Tokyo, Jappn; 
and Potsdam, Germany. 
A STUDY OF THE EFFECT OF NATURAL FEATURES ON THE 
INTENSITY OF DESTRUCTION. 
DISTANCE FROM THE FAULT LINE. 
The actual area of destruction was about 400 miles long (from 
north to south) and 50 miles wide on either side of the fault trace. 
The destruction wrought by the earthquake in its severe effects was 
proportional in a way to the nearness of the locality to the fault trace, 
but varied greatly according to the character of the rock and soil 
formation throughout the disturbed area. 
Directly on the fault trace the disturbance and destruction were 
at a maximum. Many buildings and other structures were wrenched, 
