1933 Long Beach earthquake

1933 Long Beach earthquake
W.L.Huber, USGS · Public domain · source
Name	1933 Long Beach earthquake
Timestamp	1933-03-10 17:54:08
Isc-event	906307
Anss-url	official19330310175408_30
Local-date	March 10, 1933
Local-time	5:54:08 p.m. PST
Duration	<10 seconds
Magnitude	6.4 w
Depth	10 km (6.2 mi)
Location	33.63, N, 117.98, W...
Type	Strike-slip
Countries affected	United States
Foreshocks	None
Aftershocks	Many, largest w 5.2
Casualties	115–120 killed, ~500 injured

1933 Long Beach earthquake struck the Greater Los Angeles area on the evening of March 10, 1933, causing widespread devastation. The moderate but shallow temblor centered near the Newport–Inglewood Fault inflicted severe damage to unreinforced masonry buildings, particularly schools. The event proved a pivotal moment for seismic engineering and building code reform in California.

Background

The Southern California region is traversed by a complex network of active faults, including the coastal Newport–Inglewood Fault. Prior to 1933, the area had experienced significant seismic events like the 1857 Fort Tejon earthquake and the 1906 San Francisco earthquake, but rapid urban development in cities like Long Beach and Compton had proceeded with little regard for seismic safety. Building practices at the time heavily utilized unreinforced brick and adobe, materials known to perform poorly during ground shaking. The United States Coast and Geodetic Survey had begun monitoring regional seismicity, but public and governmental awareness of the specific risks remained low.

Damage and casualties

The earthquake caused catastrophic damage across a wide swath of Los Angeles County. The Long Beach City Hall, numerous schools in the Long Beach Unified School District, and commercial buildings in downtown Long Beach were heavily damaged or destroyed. Significant destruction also occurred in Compton, Huntington Park, and Santa Ana. The death toll was officially listed at 115 to 120 people, with approximately 500 more injured. A majority of the fatalities resulted from the collapse of brick parapets and wall facades onto streets and sidewalks. Remarkably, the event occurred after school hours, preventing a far greater tragedy as many school buildings collapsed.

Response and recovery

Immediate response was led by local agencies like the Long Beach Police Department and the American Red Cross, which established emergency shelters. California Governor James Rolph declared a state of emergency and deployed the California National Guard to assist with security and recovery efforts. The California State Legislature acted with unprecedented speed, passing the Field Act within a month. This landmark legislation mandated strict seismic design standards for all new public school construction in California and required the evaluation of existing buildings. Reconstruction of civic infrastructure, such as the Long Beach Civic Center, began under these new guidelines.

Seismological analysis

Modern analysis assigns the earthquake a magnitude of approximately 6.4 . The epicenter was located offshore between Newport Beach and Huntington Beach, with a very shallow hypocenter around 10 kilometers deep along the Newport–Inglewood Fault. The focal mechanism indicated primarily strike-slip motion. The event produced a maximum perceived intensity of VIII (*Severe*) on the Modified Mercalli intensity scale. It generated a vigorous sequence of aftershocks, the largest of which was a magnitude 5.2 event. Studies by institutions like the California Institute of Technology and the United States Geological Survey later used this event to better understand the behavior of the Newport–Inglewood Fault system.

Legacy and preparedness

The lasting legacy of the earthquake was the transformative change it spurred in building safety laws. The Field Act and the subsequent Garrison Act created a model for seismic regulation that influenced codes nationwide. It directly led to the establishment of the Division of the State Architect in California to oversee school construction. The disaster is frequently cited in engineering curricula and by organizations like the Earthquake Engineering Research Institute as a classic case study in preventable structural failure. Annual preparedness events, such as the Great ShakeOut drill, and ongoing research by the Southern California Earthquake Center continue to build upon the lessons learned from this pivotal event. Category:1933 earthquakes Category:History of Long Beach, California Category:Earthquakes in California Category:1933 in California