Kern County Earthquake – California – July 21, 1952

The largest Californian earthquake since 1906 struck Kern County in 1952. The epicenter was located about twenty-three miles south of Bakersfield.

An earthquake of magnitude 7.3 shook an area in Kern County, twenty-three miles south of Bakersfield, on July 21, 1952. It was the largest in the conterminous United States since the San Francisco event of 1906 and the largest in southern California since Fort Tejon in 1857 and Owens Valley in 1872. It claimed twelve lives and caused property damage worth $60 million.

Near the epicenter, on the Southern Pacific Railroad, the earthquake cracked reinforced concrete tunnels with walls that were eighteen inches thick and shortened the distance between portals of two tunnels by ten feet, bending the rails in the process into S-shaped curves. At Owens Lake, more than one hundred miles from the epicenter, a pipeline was broken and salt beds were shifted by the quake.

The earthquake occurred on the White Wolf Fault near the intersection of the Garlock and San Andreas faults. The area shaken was impressively large. It was felt in Reno, Nevada, and in Las Vegas it required the assistance of a construction crew to realign steel structures. Shaking was experienced in San Francisco in the upper floors of high rise buildings and, in Los Angeles, there were power outages. Many surface ruptures occurred along the slopes of Bear Mountain and, in the surrounding valley areas where the alluvium was poorly consolidated, there were numerous cracked and re-contoured surface breaks.

To the southwest of Arvin, in the San Joaquin Valley, the concrete foundation of one house was split, causing partial collapse of the structure. To the east of the epicenter there were numerous evidences of the event: a surface rupture four feet wide and two feet deep, fill areas along Highway 466 lowered by as much as one foot in one location and raised by two feet vertically while moved sideways by eighteen inches in another location, and a large part of the same highway cracked and wrinkled.

Property damage was heavy in Tehachapi. Both brick and adobe buildings were damaged with the adobe structures suffering the most. Nine of the twelve casualties occurred here. Only a few wood-frame homes were destroyed, far fewer than was experienced in earlier earthquakes in similar locations. Bakersfield experienced relatively moderate damage. A few walls were knocked down and there were cracks in many brick buildings. High rise steel and concrete buildings had their ground floors damaged and Kern General Hospital was heavily damaged. The main shock was felt over most of California as well as in Phoenix.

The California Institute of Technology at Pasadena recorded six aftershocks on July 21 and later of magnitude 4 and slightly higher, some of which sufficiently affected buildings in Kern County that they had to be taken down. Reports of long period wave effects from the earthquake were widespread. Water splashed from swimming pools in Los Angeles, water damage to tall buildings there was nonstructural but extensive, and water that splashed from pressure tanks on tops of buildings in San Francisco did minor damage. At least one building was damaged in San Diego.

This earthquake on the White Wolf Fault in Kern County was a major surprise to geologists and seismologists. It had never been previously considered as an earthquake risk and, when it did rupture, its size seemed disproportionate to its length. White Wolf is only thirty-four miles in length, much too short in the mind of geologists to produce a major earthquake. By comparison the San Andreas Fault is about 250 miles in length. The amount of displacement at the surface was also small in relation to the amount of energy released.

The conclusions that geologists and seismologists arrived at all related to the underground characteristics of the fault. It may be that much of the fault is buried so that there is no surface trace. If it were a deep rupture on a nonvertical fault, that could explain the quake’s large size. A shorter but deeper rupture on a fault with a significant dip would release as much energy as a lengthier, shallow rupture on a vertical fault, since it is the rupture area, not merely the length, that determines the energy released in an earthquake.

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