SOUTHERN CALIFORNIA EARTHQUAKE SPEEDS ACTION ON NEW BUILDING CODE|
From the Fireman's Fund Record, April 1933.
At dusk on the evening of March 10, Los Angeles County and surrounding communities over an area of approximately 25 miles by 35 miles, were severely shaken by an earthquake which proved to be the first of a series of shocks of diminishing intensity.
The intensity of heavy shaking in the major tremor was relatively short, the duration varying from 7 to 12 seconds, depending on location. The epicenter is thought to have been some two miles offshore westward of Newport Beach. v The cities of Long Beach and Compton sustained serious and extensive damage, while the south end of Los Angeles and a dozen other neighboring cities also sustained some damage.
The property damage has been placed at about $40,000,000. One hundred and thirteen lives were lost and about 2000 people were treated for injuries.
While the earthquake's toll in the value of property destroyed is considerable, it is really very small compared with the total value of buildings in the affected area, and the loss to underwriters, including the companies of the Fireman's Fund Group, is very nominal.
Prompt action in shutting off gas and electric service, together with the fact that water pressure could be maintained in all the affected cities, held the potential fire hazard to the minimum and thus Southern California was spared the fate that overtook San Francisco following the 1906 earthquake.
It will be remembered that the collapse of San Francisco's water system made it impossible to cope with the spread of the fire that ultimately accounted for the major part of the enormous property loss.
It is interesting to note that in an address before the National Board of Fire Underwriters in New York in May, 1926, Dr. Bailey Willis, of Stanford University and president of the Seismological Society of America, said: "Figuring on the time since the last earthquake, and according to past records, I regard as probable that in Southern California there will be a severe shock which is more likely to come in three years than in ten and more likely to come in five years than in three."
In defining an earthquake on the same occasion, Dr. Willis said:
"It is an elastic snap of the earth's crust, just such a snap as you can give to a steel rod as you bend it to one side and let it go suddenly. Rocks under pressure in the earth's crust are as elastic as steel. They are pressed out of shape.
"They yield like the steel rod by bending, and as the pressure acts very slowly, they bend for many years before they snap. But when they do snap, all the energy that has been stored up in their elastic masses is instantly released and the crust is set to vibrating for many miles around the break or earthquake focus."
Since earthquakes cannot he prevented, it is necessary to safeguard lives and investments by the erection of buildings that will withstand earthquake shock.
In the first place, Dr. Willis and other scientists and engineers stress the importance of solid foundations. Time and again experience with earthquakes has proved that the greatest damage is sustained by structures placed on alluvial or "made" ground, or where part of a structure rests on rock and part of it on "made" ground.
"On what material does a building stand? On a rock, or on a bowl of jelly?" is the way Dr. Willis puts it.
On the other hand, it is obvious that no matter how good the foundation may be, careful precautions are necessary in the design of the building. Adequate bracings against lateral pressure or thrusts are imperative throughout the structure.
Poor material and poor workmanship have in the past borne the brunt of the blame for earthquake damage to buildings, but it is becoming increasingly clear that unsuitable design, complicated by poor material and poor workmanship, is responsible for structural inability to withstand earthquake shock.
Dr. Harry O. Wood, of the Carnegie Institute's Central Seismological Laboratories in Southern California, said:
"The practical lesson of the recent tremor, as of all others, is to build well and choose or prepare strong foundations. Design for strength of construction, conscientiously using good materials. Only very rare shocks of the most exceptional power can seriously injure excellent construction."
These theories have been proved, even in Japan, where the most devastating earthquakes occur.
The views of these scientists were clearly proved in the Southern California disaster and we find the Los Angeles Times asking:
"Why did so many costly, comparatively new school buildings in the major quake area collapse, while all other modern structures stood?"
The majority of the schools of the joisted masonry type of construction in Long Beach and Compton suffered severely and in many instances the buildings had to be condemned. In structures that were not of this type of construction, damage was slight, although parapets and heavy ornaments, which were not suitably anchored, fell in almost every instance.
It has been proved that buildings can be erected to withstand earthquakes at an additional cost that is not excessive, and although the earthquake hazard in California has long been recognized, the fact remains that building codes throughout the state have not been designed accordingly.
The California State Chamber of Commerce, however, will shortly submit for adoption by the various municipalities a state-wide building code that represents the matured judgment and experience of seismologists, engineers, architects and contractors. The work along this line was initiated almost seven years ago.
Following the Santa Barbara earthquake in June, 1925, a wide-spread demand for earthquake insurance developed in California. In fact, the demand was so wide-spread that underwriters were incapable of supplying the coverage and, in consequence, rates climbed to levels that were almost prohibitive.
For a time it looked as if the insistence on earthquake insurance by banks and other financial institutions, taken together with the high rates, might paralyze building throughout the state.
This situation led to the appointment, by the California State Chamber of Commerce, of a state-wide committee with representatives from San Francisco and Los Angeles.
As a result of the investigations made by this committee, the banks and financial institutions were persuaded to take a more rational view of the situation, and as the demand for earthquake insurance diminished, the insurance rates naturally followed.
Coincident with this movement, the State Chamber of Commerce initiated work on the state-wide building code, the idea being to require the erection of earthquake-resistant structures, just as fire-resistant structures have been built for years.
The recent earthquake has naturally brought to the front the necessity for the adoption of such a code, and it is understood that the code will be ready for presentation to the State Chamber of Commerce early in July.
[Fireman's Fund Archives: 4-1-3-4-44; 0409.]
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