Землетрясение в Южной Калифорнии и его последствия.

Earthquake in southern California

The main shock occurred near the northwestern border of Puente Hills north of the Whittier Narrows at a depth of First motion polarities, along with modeling of teleseismic P and S waves, established that the thrust fault responsible for the shock strikes east west with a dip of 25° dip to the north. The shock was located adjacent to the west northwest striking Whittier fault, which is primarily a strike slip fault, but also has a minor thrust component. Although most of the Los Angeles metropolitan area saw shaking in line with Mercalli Intensity values of VI (Strong) or VII (Very strong), Whittier experienced effects consistent with MMI values of VIII (Severe). The old commercial district saw the worst damage, as these were the oldest buildings, and were also heavily damaged in the 1929 Whittier earthquake, a shock may have been a result of movement on the Norwalk Fault. While total casualties amounted to eight, the destruction of homes was significant. Throughout Los Angeles, Orange, and Ventura counties, 123 homes and 1,347 apartments were destroyed, and an additional 513 homes and 2,040 apartments were damaged. An inspection of a highway bridge on Interstate 605 revealed that there were fractures on the support columns, which resulted in temporary closure, and minor damage affected 28 other bridges. Other typical failures included more than 1,000 gas leaks, with many resulting in fire, ceramic elements on high voltage substation equipment breaking and phone systems becoming overwhelmed.

Caltech scientists recorded the events on a cluster of twelve strong motion sensors that were placed throughout the region with a total of 87 channels of recorded data. Nine of these instruments were located on the Caltech campus, two were at the nine story Jet Propulsion Laboratory building 180 (ten miles northwest of the campus) and the final device was placed on a hillside 5 km to the west. Investigation of the accelerograms from these units revealed the strongest shaking lasted 4–5 seconds. The vertical accelerations were considered relatively high and early analysis (pre digitalization) indicated that the mainshock was complex, with a double train of P waves arriving with a 1.4–1.8 second interval. The National Strong Motion Instrumentation Network (NSMIN) (a cooperative effort including the United States Geological Survey and other organizations) also monitored a set of 52 strong motion stations in the Los Angeles area. Most of the stations successfully captured the event, and the closest unit to the mainshock, a rock site at Garvey Reservoir, recorded a peak horizontal acceleration of 0.47 g. A twelve story steel frame building in Alhambra was outfitted with accelerographs in the basement, at mid level, and the top of the structure. The top floor instruments recorded a peak acceleration of 0.18 g during the 1971 San Fernando earthquake and instruments on the sixth floor recorded a peak acceleration of 0.47 g at the time of the Whittier mainshock. A ten story reinforced concrete building in Whittier (7215 Bright Ave.) saw a peak horizontal reading of 0.63 g in the basement.

A magnitude 5.2 event occurred three days later on October 4, causing additional damage in Alhambra, Pico Rivera, Los Angeles, and Whittier. The shock's effects were assessed at VII (Very strong) on the Mercalli Intensity Scale with damaged chimneys, broken windows, and the collapse of two bell towers at the San Gabriel Civic Auditorium. This event was also responsible for several injuries and one additional death. On February 11 of the following year, another small aftershock again damaged chimneys, broke windows, cracked drywall, and some homes' foundations in Pico Rivera, Pasadena, and Whittier.

The 1929 Whittier earthquake occurred on July 8 with a local magnitude of 4.7 and maximum perceived intensity of VII (Very strong) on the Mercalli Intensity scale. The shock occurred at a depth of and was most intense to the southwest of the city, where a school and two homes were heavily damaged and other homes sustained chimney collapses. In Santa Fe Springs, oil towers were damaged and some short cracks appeared in the ground. This earthquake was felt from Mount Wilson to Santa Ana, and from Hermosa Beach to Riverside. Numerous aftershocks occurred in the first several hours and persisted through early 1931.

In order to gather funds to help the rebuilding effort, the city of Whittier approved the establishment of a 521 acre earthquake recovery redevelopment area. Through this initiative, property tax revenue is directed to the city rather than to the county and schools, the originally designated recipients. The arrangement will remain in effect until the year 2037. A nonprofit organization called the Whittier Conservancy was formed shortly after the Whittier Narrows earthquake. The group aids in the preservation of the city's historical style of construction. During the earthquake, several notable buildings were destroyed, including the Harvey Apartments. They were built with bricks that appeared to have been made by hand during the 19th century; the mud used to make them came from the San Gabriel River. The Conservancy felt that these bricks were worth saving, not only for their historical value but also for their aesthetics. Some effort was made to save and use the bricks for rebuilding the historic apartment on the corner of Greenleaf Avenue and Hadley Street. They spent $15,000 to prevent the usable bricks from being taken during the final demolition of the building. The bricks were then cleaned, then stored until they could be used in the rebuilding of the apartment. The Whittier Conservancy also collaborated in the rezoning of the Hadley neighborhood and was able to help control the rate of new multiple family dwelling construction.

Spalding Gray related his experience of the earthquake in his film Monster in a Box.