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Long Beach Earthquake: 70th Anniversary
Seventy years ago, at 5:54 p.m. on March 10, 1933, southern California experienced its deadliest seismic disaster in recorded history when a magnitude (MW) 6.4 earthquake struck the Long Beach area. The Long Beach earthquake occurred along the Newport-Inglewood fault zone centered just off the coast of Newport Beach, with a hypocentral depth of 10 kilometers. Seismic records suggest a maximum slip along the fault of about 1 meter, with a total rupture length of roughly 15 kilometers. The actual earthquake rupture lasted only 5 seconds, though ground shaking (as is typical) lasted at least twice as long. The maximum recorded ground acceleration was 0.22g, or 22% the force of gravity (though the nearest recording site for this data was 27 kilometers from the epicenter). Despite these rather modest seismological numbers, the earthquake killed over 120 people and caused property losses estimated at $50 million (1933) dollars.
More than two-thirds of the 120 deaths occurred when people ran outside and were struck by falling bricks, cornices, parapets, and building ornaments. Among the buildings severely damaged or destroyed in the earthquake were many schools in and around Long Beach. Had the quake occurred a few hours earlier, while children were still in these schools, the deaths might have numbered in the thousands. The poor performance of school buildings in withstanding the shaking led to the passage, just one month later, of the Field Act (named for California Assembly Member Charles Field). This new state law mandated improved building codes for new public school construction, and direct state review of public school design.
The cities of Compton, Long Beach and Huntington Park suffered the most in the earthquake. Thousands of chimneys toppled, porches collapsed and walls fell. Unreinforced masonry (brick-and-mortar) construction fared the worst, while wood-frame and concrete buildings generally survived intact. Long Beach experienced 127 breaks in water distribution mains. Seal Beach was without water for several days.
Six million gallons of water poured out of the Los Angeles Water Department's Western Avenue tank. Nineteen fires were reported in Long Beach during the night of the earthquake, seven due to broken gas lines. Liquefaction occurred along much of the sparsely-populated coast between Newport Beach and Long Beach. That same area experienced aftershocks for many months after March 10.
Fortunately, part of the Pacific Fleet had just returned to their home base in Long Beach Harbor after a six-month cruise, and the U.S. Navy sent ashore emergency supplies and about 2,000 sailors and Marines. The Army also sent men and supplies from Fort McArthur in San Pedro. The presence of soldiers on their streets led many Long Beach residents to think the city was under martial law (it wasn't; the troops took orders from the City Manager's Office). The National Guard set up food kitchens, and by 6:00 a.m. the next morning, people were served breakfast in every park in the city. Water was also trucked in for those in areas where water mains had broken.
The Long Beach earthquake was the first significant earthquake and aftershock sequence to be recorded and analyzed in detail by the Seismological Laboratory at the California Institute of Technology in Pasadena. (The catalog of the Southern California Seismic Network, available here, goes back only to 1932.) Relatively speaking, however, seismologists do not consider the 1933 event along the Newport-Inglewood fault zone to have been a very large earthquake. Much of what occurred in 1933 would not happen today due to improved construction practices. Most of these practices owe their existence to disasters like the Long Beach earthquake, which, though tragic, have provided building designers with invaluable information on the performance of different building materials and designs when subjected to shaking. This information, when put into practice, can help avert tragedy when the next earthquake inevitably strikes.
All photos above are from "Earthquake '33: A Photographic History," copyright 1981, The Historical Society of Long Beach, and may not be taken from this site and re-used elsewhere, excepting fair use and proper citation. For more information, contact The Historical Society of Long Beach, P.O. Box 1869, Long Beach, CA 90801.
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