The first earthquake attributed to the Whittier Fault and felt strongly in the Whittier area was an earthquake July 8, 1929 at 8:45am with an estimated magnitude of 4.7. It was believed to be located (felt strongest) in the area of East Whittier, which had ($50,000-$350,000) damage. It was also felt very strongly in the Los Nietos/Santa Fe Springs area where (4) people were injured.
It is very likely that this earthquake was located on the Norwalk fault or even on the recently discovered (1999) Puente Hills fault system that runs from the Coyote Hills in North Orange County towards Brea to the east to Downtown Los Angeles towards the West (thru the Los Nietos/Santa Fe Springs area), with distinct segments underneath LA city, Santa Fe Springs, & Coyote Hills. Several seconds of shaking were reported being felt in Los Angeles and its suburbs for a 50 mile radius around the epicenter.
The next strong quake in the Whittier area was on the evening of June 15, 1967 centered East of Whittier. It had a magnitude of 4.1 and was felt as a rolling quake throughout much of the LA basin and parts of Orange County, knocking objects from shelves and causing minor damage. It may have been centered in the Puente Hills, possibly North of La Habra.
The next large earthquake on the Whittier Fault occured on Jan. 1, 1976 at 9:20 am with a magnitude of 4.2. It was centered in the Puente Hills of Los Angeles County and caused damage in the Whittier area.
Then on Oct. 1, 1987, during the Centennial (100 year) Anniversary Celebration Year of the founding of Whittier, the Whittier Narrows Earthquake struck at 7:42 am with a 5.9M quake located in the Whittier Narrows region that lasted about 20 seconds and was centered near the intersection of Rosemead Blvd. and San Gabriel Blvd. Much of the damage occurred in the older Uptown Whittier area, but there was major damage throughout the Los Angeles Basin, especially in the cities of Pasadena, Alhambra, and San Gabriel.
It killed 8 people, injured several hundred, damaged over 10,000 buildings, and caused in excess of $350 million in property losses, mostly in the areas east and northeast of Los Angeles-mainly at Whittier. It was felt as far away as Las Vegas, NV. It destroyed 123 single-family homes in Los Angeles, Orange, and Ventura counties, as well as 1347 apartment units.
Major damage was sustained to 513 single-family homes and to 2,040 apartment units. Property damage at Cal State LA was estimated at over $20 million. About 1400 gas leaks occurred and many fires were ignited.
The most severe damage to transportation systems was the Interstate 605/Interstate 5 interchange, a major nine-span bridge that was built in 1964. The five supporting columns sustained severe shear fractures and the overpass was closed temporarily for a day. Minor damage also occurred on 23 other bridges in the area.
Business structures in the old Whittier commercial district were the most severely damaged by the main earthquake. In the 24-square-block shopping area known as Whittier Village, 12 commercial buildings had to be razed, and another 20 buildings were declared unsafe.
Most of the damage to buildings in the Uptown Whittier area was due to the fact that many of them were made of unreinforced brick and masonry. About 100 chimneys in the area were knocked down as well. Much of the rest of the damage followed the Whittier Fault trend to the northwest, especially from the Turnbull Canyon area to the area north of the inter-section of Norwalk Blvd, Workman Mill Road, and Beverly Blvd.
Damage and dysfunction of lifelines included the often observed failure of ceramic elements on high-voltage substation equipment, damage to large liquid-storage tanks, and saturation of the telephone system with inappropriate calls. About 1,400 gas leaks occurred on customer property, and many fires were ignited.
This earthquake sequence ruptured a small and previously unidentified, gently north-dipping,west-striking thrust fault beneath the uplifted Puente Hills and Elysian Park-Montebello Hills.
Although many ground cracks formed along the base of the Puente Hills between Turnbull Canyon and Norwalk Boulevard, ground breakage in that area was limited to slope failures, including extensional cracks, minor landslides, and rockfalls. Ground-surface cracks also were observed at Worsham Creek oil field and Whittier Narrows golf course.
Data obtained from monitoring the main shock and aftershocks defined a thrust fault that dips 30°N. Such a fault projects to the ground surface at Norwalk, far south of the trace of the Whittier fault. This is near the northwestern terminus of the trace of the inferred Norwalk fault, considered as the source of the M 4.7 Whittier earthquake that occurred in 1929.
Surface and inferred subsurface geologic relationships indicate that the Whittier Narrows earthquakes did not occur on a previously known fault. A study of the seismicity of the northern Los Angeles Basin determined that concentrated seismic activity occurs near the junction of the Hollywood-Raymond fault and the projected trace of the Whittier fault.
Of the 82 incorporated cities in Los Angeles County, the cities receiving the most damage were Whittier, Monterey Park, Montebello, El Monte, South El Monte, Santa Fe Springs, Norwalk, Alhambra, Pasadena, San Gabriel, Arcadia, Monrovia, Rosemead, and Pico Rivera. Several unincorporated areas in east Los Angeles also received damage. Cities in northern Orange County, including La Habra, also were damaged.
Most seriously damaged were older, unreinforced structures — some constructed prior to 1900 — located as far away from the immediate epicentral area as Pasadena to the north and central Los Angeles to the west. Historical buildings badly damaged included the San Gabriel Mission. Many parked automobiles were damaged by falling walls and bricks.
Houses were partially shaken from their foundations in Whittier and chimneys were damaged at least as far away as Arcadia. One of the eight deaths directly caused by the October 1 earthquake involved shifting earth that trapped a Southern California Edison employee in a construction excavation for an electrical power-line transmission standard in the San Gabriel Mountains. A second death was caused when a large slab of concrete from a parking structure fell onto a student at California State University, Los Angeles.
Initial strong motion data of the earthquakes released by the DMG indicated that ground shaking was intense at localities in the western San Gabriel Valley and eastern San Fernando Valley. Damage was severe along the trace of the northwestern portion of the Whittier fault in the northern “uptown” section of Whittier, and along Whittier Boulevard, two miles to the south. The apparent south-trending pattern of the most severe damage in Whittier is similar to the pattern of intensity that took place there during the M 4.7 Whittier earthquake of 1929.
The main shock was followed by about 500 locatable aftershocks, an unusually small number for an earthquake of this magnitude. The largest aftershock, a 5.3M quake, occurred on October 4, 1987 @ 3:59 am and was located about 3km northwest of the epicenter of the October 1st earthquake. It killed one person, injured several, and caused additional property damage in Alhambra, Los Angeles, Pico Rivera, and Whittier.
Several chimneys twisted, fell, or broke at the roofline; stone fences cracked and toppled; windows broke; and large cracks formed in sidewalks and highways. The press reported that one of the two bell towers collapsed on the San Gabriel Civic Auditorium. Also felt in Orange, Riverside, San Bernardino, and San Diego Counties.