VOLCANO MADNESS: [Geology2] Historic Earthquakes Long Beach, California

Tuesday, March 10, 2015

[Geology2] Historic Earthquakes Long Beach, California

1933 March 11 01:54 UTC (local time: March 10 17:54 PST)
Magnitude 6.4
Intensity VIII

Although only moderate in terms of magnitude, this earthquake caused serious damage to weak masonry structures on land fill from Los Angeles south to Laguna Beach. Property damage was estimated at $40 million, and 115 people were killed.

Severe property damage occurred at Compton, Long Beach, and other towns in the area. Most of the spectacular damage was due to land fill, or deep water-soaked alluvium or sand, and to badly designed buildings. Minor disturbances of ground water, secondary cracks in the ground, and slight earth slumps occurred, but surface faulting was not observed. Along the shore between Long Beach and Newport Beach, the settling or lateral movement of road fills across marshy land caused much damage to the concrete highway surfaces and to approaches to highway bridges.

At Compton, almost every building in a three-block radius on unconsolidated material and land fill was destroyed. At Long Beach, buildings collapsed, houses were pushed from foundations, walls were knocked down, and tanks and chimneys fell through roofs. Damage to school buildings, which were among the structures most commonly and severely damaged by this earthquake, led to the State Legislature passing the Field Act, which now regulates building-construction practices in California.

This destructive earthquake was associated with the Newport-Inglewood fault. The earthquake was felt almost everywhere in the 10 southern counties of California and at some points farther to the northwest and north in the Coast Range, the San Joaquin Valley, the Sierra Nevada, and the Owens Valley. It also was reported in northern Baja California. A sharp foreshock occurred near Huntington Beach on March 9, and many aftershocks occurred through March 16. For several years, minor aftershocks continued to occur, most often centering near the two ends of the disturbed segment of the Newport-Inglewood fault.

Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.

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