The Long Beach Earthquake of 1933

Susan Fatemi and Charles James
National Information Service for Earthquake Engineering

The Long Beach earthquake, estimated magnitude 6.25 Ms, occurred at 5:55 p.m., March 10, 1933. Engineered buildings and reinforced concrete buildings sustained little or no structural damage in the earthquake. Brick buildings with unreinforced masonry walls, including many of the school buildings in Long Beach and surrounding areas, failed catastrophically.  If the earthquake had struck a few hours earlier, when school was in session, the loss of life would have been appalling. As it was, 120 people died in the quake largely from collapsed houses and small buildings or falling debris, including 5 children who died in failed gymnasia.

The school buildings damaged or destroyed were of an "irregular shape," built of brick and not designed to resist any lateral stress. As well, part of the failure of the brick buildings was due to shoddy workmanship and inferior mortar. Several of the failed school buildings were designed with elaborate entrance towers that collapsed in a hail of bricks and architectural ornamentation. Reinforced concrete school buildings survived the quake with no structural damage. (Below: Franklin Junior High School before and after the 1933 earthquake. Photo: Historical Society of Long Beach)

As a direct result of the structural failures of unreinforced masonry schools, earthquake-resistant design and construction were mandated for public schools: K-12 and community colleges. This was due largely to the efforts of California Assembly Member, Charles Field and the law, known as the Field Act was passed on April 10, 1933. It and its subsequent revisions authorized the Division of Architecture of the California State Department of Works to review and approve all public school plans and specifications and to furnish general supervision of the construction work. No Field Act school has ever failed in an earthquake.

The Uniform Building Code (UBC) of 1927 had addressed the first comprehensive earthquake code requirements for buildings in general in California. The 1935 version of the UBC, following the Long Beach earthquake and the legislative efforts to prevent school buildings from structural collapse provided a formula for calculating lateral earthquake forces which new buildings had to resist:

F = CW where:

F equals the horizontal force in pounds

W equals total dead load (i.e. gravity load or weight of the building) plus 1/2 the total vertical designed live load.

C is the coefficient derived from tables: it depends on seismic zone, height of building (i.e. number of stories), soil type, and other variables. It is expressed as a percentage and has varied with succeeding codes. Initially it was .08 for Zone 3, which included the Los Angeles-Long Beach area.

Long Beach was also the first earthquake for which acceleration records were obtained from the recently developed strong-motion accelerograph but the accelerations exceeded the range of the first instrument.

For further reading on the Long Beach Earthquake:

Andrus, F.M. "Earthquake design requirements of the Uniform Building Code." In Proceedings of the Symposium on Earthquake Blast Effects on Structures. Berkeley, 1952. pp. 314-316.

Binder, R.W. "Engineering aspects of the 1933 Long Beach earthquake". In Proceedings of the Symposium on Earthquake Blast Effects on Structures. Berkeley, 1952. pp.186-211.

Bolin, Harry W. "The Field Act of the State of California." In Proceedings of the Symposium on Earthquake Blast Effects on Structures. Berkeley, 1952. pp. 309-313.

Davis, Raymond E. Effect of Southern California earthquake upon buildings of unit masonry construction. Berkeley, 1933.

Historical Society of Long Beach. Earthquake '33. Long Beach, 1981.

Kromer, Clarence H. Structural problems in connection with the design of earthquake-resistive school buildings. BSSA 24:4 (1934) pp. 404-418.

National Board of Fire Underwriters, Committee on Fire Prevention and Engineering Standards. Report on the Southern California Earthquake of March 10, 1933. New York, 1933.

U.S. Coast and Geodedetic Survey. Abstract of reports received regarding the earthquake which occurred in Southern California on March 10, 1933. San Francisco, 1933.

Wood, Harry O. Preliminary report on the Long Beach earthquake. BSSA 23:2 (1933) pp.44-56.