After these preliminary words to sketch some of the previous history involved, we now turn to what is sometimes thought of as the “villain of the piece” in San Francisco’s past the well-advertised San Andreas Fault.
A fault is defined as a fracture in the earth’s crust. The one called the “San Andreas” is the ”master” fault of an intricate network of such faults that cut through the coastal region of California. This fault is a high fracture about 600 miles long and extending almost vertically into the earth to a depth of at least twenty miles. It forms a continuous break from Northern California southward to Cajon Pass in San Bernardino County.
What is of more immediate pertinence is that the San Andreas Fault lies entirely outside the limits of the city and county of San Francisco. Hence, it is but legend to say that the city is built above such a fault-it is more correct to say that San Francisco is adjacent to this fault, but, obviously, it is sufficiently close to it to respond dramatically to any of its movements or convolutions.
Seismologists always stress the fact that no one can predict, with absolute accuracy, when earthquakes will occur. Hence, there was no special reason to think that the Wednesday in Easter Week, April 13, 1906, was going to be a decisive day in the history of San Francisco. Yet this was to be a day of destiny in its history for, on that morning, the seismograph located at the University of California in Berkeley recorded a major seismic disturbance which lasted for forty eight seconds from 5:12:06 A.M. to 5:12:54 A.M.
The main shock (then were no warnings or previous shocks) was felt in the city at 5:16 A.M. when, among others, the clock of the Ferry Building stopped.
The local disturbance was part of a more general one, which extended up and down the San Andreas Fault centering around the town of Olema in western Marin County. One hundred-twenty separate shocks were recorded on April 18, through a long and frightening day, with further complications coming from a burning city.
However, it should be pointed out immediately, that the earthquake damage amounted, in the end, to only about 20 percent of the total damage to the stricken city and that it is considerably more than merely local patriotism to claim that it was fire that destroyed the Vitals of San Francisco rather than earthquake.
Loss of life from earthquakes is usually quite high; when Tokyo was so afflicted in 1923, about 100,000 were killed in a frightful holocaust.
The most accurate figures concerning the total loss of life in San Francisco (this includes those who died as a result of the fires) estimate that approximately 667 were casualties of either fire and earthquake, with about 352 listed simply as missing. The comparatively light loss of life is partially explained by the fact that, just as in 1868, most of the inhabitants of the city were at home in their wooden frame dwellings (by 1906, about 90 percent of the homes in the city were of wooden construction) and these stood up well, despite creakings and groanings, when the quake came.
While bricks and stone facades and the like are liable to shake and fall, frame buildings have the capacity to “ride out” an earthquake without too much damage except to the composure of their inhabitants. It seems that many of the deaths in San Francisco happened in the flimsy waterfront hotels built upon filled ground, which collapsed around their unfortunate occupants. Of more importance is the fact that the massive shock, which came at approximately 5:15 A.M., triggered a set of events that involved San Francisco in three days and nights of terror and destruction.
The chain reaction went somewhat as follows: the great shake or quake immediately caused a breakage of major water mains, one of 30 and another of 40 inches, both coming from Spring Valley Lakes through Baden, near Holy Cross cemetery, in San Mateo County. With these major breaks, one of the principal sources of water was destroyed.
Obviously, this was to be of key importance in the tragic hours that now lay ahead of San Francisco. Before turning to a consideration of those hours, mention should be made of an optical report made later on which summed up the damage that came to the city from the earthquake:
The physical effects of the earthquake in and upon the city of San Francisco were
1. The displacement of the earth’s surface in the Region of “tilled” or “made” ground over water or former swampy area
2. The demolition of a few buildings that were already verging on collapse and the injury to other buildings by the fracturing of brick or stone walls and the movement of frame building: upon their foundations
3. The rupture of underground pipes in the neighborhood of the earth‘s displacement. This was the most serious in the case of the water pipes, which were used to carry the city’s water supply from the reservoir twenty miles away. One of these pipe lines was laid along the “fault line“ for a distance of six miles and was practically totally destroyed. Other pipelines crossed marshy and tilled ground and were broken at such points
4. The causing of numerous fires, due to broken gas connections, crossing of electric wires, the breaking of chimneys, overturning of stoves, the liberation of chemicals (principally in drug stores) and like effects.
It it is recorded that fifty-two fires occurred, most of which were extinguished while incipient.
It has already been indicated that San Franciscans are sensitive on the point of how most of the damage was done to the city in 1906. However, facts amply support the position that, had it not been for the fires that followed the quaking of the earth, San Francisco would have recovered rather quickly from any and all earthquake damage.
It is also a fact that fire, which consumed so much of the city, gave it the distinction, if such it may be called, of being the scene of the greatest conflagration in the recorded history of cities, even exceeding the famous Chicago fire of 1871.
As will be seen, approximately 411 square miles, comprising 514 city blocks, were burned in the 1906 conflagration. This furnishes the sober retention that the heart of the city was burned away in the three days and nights of fire that followed the early morning quake of April 18, 1906.
- San Francisco 1906: Earthquake and Fire – Part 1
- San Francisco 1906: Earthquake and Fire – Part 3
- San Francisco 1906: Earthquake and Fire – Part 4