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Landers and Big Bear, California Earthquakes, June 28, 1992 |
| Southern California residents were rudely awakened Sunday morning June 28, 1992 at 04:57 am (June 28 at 11:57 GMT), by an earthquake of magnitude 7.6 (Ms) followed by a smaller 6.7 (Ms) magnitude earthquake about three hours later (June 28 at 15:05 GMT). The largest shock occurred approximately 6 miles southwest of Landers, California and 110 miles east of Los Angeles. The second earthquake was entered approximately 8 miles southeast of Big Bear City in the San Bernardino Mountains near Barton Flats. A distance of 17 miles and 7,000 feet in elevation separate the two earthquake locations. In addition to depicting the differences in terrain of the two locations, examples of structural damage, liquefaction, surface faulting, and earthquake-generated landslides are illustrated. |
Four to six foot fault scarp, Landers earthquake | |
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This figure shows the four to six foot fault scarp of the Landers earthquake. The ground rupture, initiated on the Johnson Valley Fault west of Landers, traveled northward along a series of northwest trending faults and terminated in the Rodman Mountains south of Barstow. Measurements indicate a movement along the fault line a maximum of 18 feet horizontally and six feet vertically. The width of the rupture zone appeared to range from eleven feet at the narrowest point to 140 feet across at the widest point. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Liquefaction adjacent to Santa Ana River near Big Bear epicenter | |
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This figure shows a soil failure adjacent to the Santa Ana River near the epicenter of the Big Bear earthquake. Light colored tan sand lies on top of the gray soil on the cracked road bed. These secondary cracks produced by earth shaking were found near the entrance to the South Fork campground, on slopes and in the stream embankments. There were no reports of a primary ground rupture in connection with the Big Bear earthquake. Such soil failures (liquefaction) as depicted here occur when ground water near the surface is forced between the grains of sand during an earthquake. The sandy soil behaves like a very thick liquid. The eruption of liquefied sediment is facilitated by fissures in the ground. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Ground cracking near Aberdeen | |
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This figure shows the ground cracking near Aberdeen on State Highway 247. A portion of this highway, the main north - south traffic artery through Johnson Valley, Landers, Flamingo Heights, and Yucca Valley was closed to through traffic. The surface faulting reportedly interrupted the ten mile section of State Highway 247. Road cracks, some described as 30 feet long, a foot deep, and measuring 1 to 2 feet wide, made travel impossible in some sections of the roadway. Motorists were reported stranded in the more severely buckled sections. The Lander's postmaster reported that the intensity of the shaking in the Landers earthquake appeared to be strongest near this highway. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Buckled water tank lifted off base by Landers earthquake | |
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At the intersection of Reche Road and Lander Lane, 210,000 gallon, 24-foot high, bolted-steel water tank was lifted off a gravel base six to ten inches and set back almost in place, denting the tank's bottom ("elephant's foot buckle"). Metal bolts that held the tank sides together were sheared off near the bottom of the tank. The tank was about two-thirds full at the time of the earthquake. After the earthquake, the tank was resting on the gravel base about 12-inches lower (due to buckle) and shifted about an inch to the west. The well at the tank site continued to flow and residents stood in line to fill containers with water from a hose connected to a faucet near the damaged tank. The tank, operated by the San Bernardino County, was located about two miles east of the fault rupture. Damage to water storage tanks was common. Some tanks ruptured contributing to the loss of water in the area. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Exterior of house 20 yards from fault scarp | |
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The Hudson residence was located north of Landers and south of Johnson Valley near the intersection of Linn and Dusty Mile Roads. The hilltop house was located about 20 yards from the fault scarp that exhibited a 4-foot vertical offset. The north-south oriented residence, a single-story, wood-frame construction, was set on a concrete slab foundation. The house, anchored to the foundation with bolts, was heaved off the foundation to the west about five feet. Some anchor bolts remained vertical while others were bent (flattened) over to the west. A deep crack in the concrete slab sliced through the living room area in a general east-to-west direction. The crack appeared to be five or more inches in width in some places. The intense shaking distorted the wood-frame, (the interior and exterior walls were out of vertical plumb) destroyed the reinforced chimney, and shattered the inside fireplace. Furniture was often overturned and/or broken, plumbing fixtures were dislodged from the floor and walls. This image shows the exterior of the house and the collapsed chimney. The damage that was done to this well-built house was a deciding factor in giving a maximum rating of IX on the Modified Mercalli Intensity Scale (MMI, Wood and Neumann, 1931) to this earthquake. Photo Credit: Lindie Brewer, U.S. Geological Survey |
View of same house (No. 5) showing movement on foundation | |
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The Hudson residence was located north of Landers and south of Johnson Valley near the intersection of Linn and Dusty Mile Roads. The hilltop house was located about 20 yards from the fault scarp that exhibited a 4-foot vertical offset. The north-south oriented residence, a single-story, wood-frame construction, was set on a concrete slab foundation. The house, anchored to the foundation with bolts, was heaved off the foundation to the west about five feet. Some anchor bolts remained vertical while others were bent (flattened) over to the west. A deep crack in the concrete slab sliced through the living room area in a general east-to-west direction. The crack appeared to be five or more inches in width in some places. The intense shaking distorted the wood- frame, (the interior and exterior walls were out of vertical plumb) destroyed the reinforced chimney, and shattered the inside fireplace. Furniture was often overturned and/or broken, plumbing fixtures were dislodged from the floor and walls. This view shows four to five feet of horizontal movement of the structure from the foundation. The damage that was done to this well-built house was a deciding factor in giving a maximum rating of IX on the Modified Mercalli Intensity Scale (MMI, Wood and Neumann, 1931) to this earthquake. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Details of collapse of house (No. 5) | |
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The Hudson residence was located north of Landers and south of Johnson Valley near the intersection of Linn and Dusty Mile Roads. The hilltop house was located about 20 yards from the fault scarp that exhibited a 4-foot vertical offset. The north-south oriented residence, a single-story, wood-frame construction, was set on a concrete slab foundation. The house, anchored to the foundation with bolts, was heaved off the foundation to the west about five feet. Some anchor bolts remained vertical while others were bent (flattened) over to the west. A deep crack in the concrete slab sliced through the living room area in a general east-to-west direction. The crack appeared to be five or more inches in width in some places. The intense shaking distorted the wood-frame, (the interior and exterior walls were out of vertical plumb) destroyed the reinforced chimney, and shattered the inside fireplace. Furniture was often overturned and/or broken, plumbing fixtures were dislodged from the floor and walls. This view shows details of the collapse. The damage that was done to this well-built house was a deciding factor in giving a maximum rating of IX on the Modified Mercalli Intensity Scale (MMI, Wood and Neumann, 1931) to this earthquake. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Close-up of damaged house (No. 5) | |
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The Hudson residence was located north of Landers and south of Johnson Valley near the intersection of Lnn and Dusty Mile Roads. The hilltop house was located about 20 yards from the fault scarp that exhibited a 4-foot vertical offset. The north-south oriented residence, a single-story, wood-frame construction, was set on a concrete slab foundation. The house, anchored to the foundation with bolts, was heaved off the foundation to the west about five feet. Some anchor bolts remained vertical while others were bent (flattened) over to the west. A deep crack in the concrete slab sliced through the living room area in a general east-to-west direction. The crack appeared to be five or more inches in width in some places. The intense shaking distorted the wood- frame, (the interior and exterior walls were out of vertical plumb) destroyed the reinforced chimney, and shattered the inside fireplace. Furniture was often overturned and/or broken, plumbing fixtures were dislodged from the floor and walls. This view shows details of the collapse. The damage that was done to this well-built house was a deciding factor in giving a maximum rating of IX on the Modified Mercalli Intensity Scale (MMI, Wood and Neumann, 1931) to this earthquake. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Large crack in cement floor (same house as in No. 5) | |
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The Hudson residence was located north of Landers and south of Johnson Valley near the intersection of Linn and Dusty Mile Roads. The hilltop house was located about 20 yards from the fault scarp that exhibited a 4-foot vertical offset. The north-south oriented residence, a single-story, wood-frame construction, was set on a concrete slab foundation. The house, anchored to the foundation with bolts, was heaved off the foundation to the west about five feet. Some anchor bolts remained vertical while others were bent (flattened) over to the west. A deep crack in the concrete slab sliced through the living room area in a general east-to-west direction. The crack appeared to be five or more inches in width in some places. The intense shaking distorted the wood- frame, (the interior and exterior walls were out of vertical plumb) destroyed the reinforced chimney, and shattered the inside fireplace. Furniture was often overturned and/or broken, plumbing fixtures were dislodged from the floor and walls. This view shows a large crack in the floor that passed through the house. The damage that was done to this well-built house was a deciding factor in giving a maximum rating of IX on the Modified Mercalli Intensity Scale (MMI, Wood and Neumann, 1931) to this earthquake. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Damage to bowling alley near Landers epicenter | |
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Yucca Bowl (bowling alley) shown here was located on the eastern edge of the Yucca Valley business istrict. The Yucca Bowl was housed in a north-south oriented, steel-frame, masonry building. The east wall of the reinforced masonry building pulled away from the building and fell on the adjacent vacant lot. Portions of the roof also collapsed and the interior of the building was exposed. The west wall of the structure had reportedly been strengthened to withstand the prevailing strong westerly winds. The failure of the east wall has been attributed to inadequate roof-to-wall connections. The west wall was only lightly cracked by the earthquake. A K-Mart department store, located about 1/2 mile west of the Yucca Bowl, was the other heavily damaged building. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Detail of damage to bowling alley | |
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A second view of Yucca Bowl (bowling alley) located on the eastern edge of the Yucca Valley business district. The Yucca Bowl was housed in a north-south oriented, steel-frame, masonry building. The east wall of the reinforced masonry building pulled away from the building and fell on the adjacent vacant lot. Portions of the roof also collapsed and the interior of the building was exposed. The west wall of the structure had reportedly been strengthened to withstand the prevailing strong westerly winds. The failure of the east wall has been attributed to inadequate roof-to-wall connections. The west wall was only lightly cracked by the earthquake. A K-Mart department store, located about 1/2 mile west of the Yucca Bowl, was the other heavily damaged building. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Damage to Monument Market near Landers epicenter | |
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A view of Monument Market located on the eastern edge of Joshua Tree on Highway 62. The building, probably constructed in the late 1960's, was a single story concrete masonry unit structure with a wood-frame roof. The front of the building included glass panels extending the full length of the building. During the earthquakes, the west wall pulled away from the rest of the building and leaned against the adjacent retaining wall. Figure 13 shows a close-up view of the damage. The Market had been closed following an earlier earthquake in April of 1992. Photo Credit: Lindie Brewer, U.S.Geological Survey |
Detail of damage to Monument Market | |
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A view of Monument Market located on the eastern edge of Joshua Tree on Highway 62. The building, probably constructed in the late 1960's, was a single story concrete masonry unit structure with a wood-frame roof. The front of the building included glass panels extending the full length of the building. During the earthquakes, the west wall pulled away from the rest of the building and leaned against the adjacent retaining wall. Figure 13 shows a close-up view of the damage. The Market had been closed following an earlier earthquake in April of 1992. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Landslides along Highway 18 in the San Bernardino Mountains | |
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This figure shows a view of the landslides along Highway 18 that connects Redlands to Big Bear in the San Bernadino Mountains. The strong shaking also caused landslides to occur along Highway 38. The steep slopes are white in color because of the white decomposed granite soil. Big boulders were embedded in the soil covered slopes. The dust clouds created by the landslides were similar to smoke clouds from forest fires. People thought that forest fires were occurring. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Repair of earthquake-damaged road | |
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This figure shows a close-up of road repair. Seismic damage to the transportation systems consisted of broken and offset pavement at surface expressions of faulting. Some sections of the asphalt roadway were so badly cracked that road crews graded the sandy shoulders to allow emergency and local residents to bypass the severely damaged sections. Some dirt or gravel roads in the vicinity of Landers were impassable. In some instances, where the rupture zones crossed the roads, large fissures made travel difficult even for four-wheeled vehicles. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Path of huge boulder dislodged by Big Bear earthquake | |
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Several huge boulders reportedly bounded down Yucaipa Ridge above Forest Falls. One large boulder crashed down the hillside, mowing down tall cedars in its path. The boulder, the size of a small garage and measuring 16 ft by 16 ft by 14 ft, came to rest about 20 yards behind the Clarke residence on Prospect Drive in the western edge of Forest Falls. The boulder was estimated to have descended 1,000 feet vertically and covered a horizontal distance of 1,000 feet. It was said to be airborne most of the way as it hit the ground only three times on the way down. This view shows the ridge where the boulder was located prior to its fall. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Dislodged boulder destroyed forest in its path | |
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Several huge boulders reportedly bounded down Yucaipa Ridge above Forest Falls. One large boulder crashed down the hillside, mowing down tall cedars in its path. The boulder, the size of a small garage and measuring 16 ft by 16 ft by 14 ft, came to rest about 20 yards behind the Clarke residence on Prospect Drive in the western edge of Forest Falls. The boulder was estimated to have descended 1,000 feet vertically and covered a horizontal distance of 1,000 feet. It was said to be airborne most of the way as it hit the ground only three times on the way down. This view shows a portion of the boulder's path through the forest. Photo Credit: Lindie Brewer, U.S. Geological Survey |
One of the large dislodged boulders rests against a tree | |
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Several huge boulders reportedly bounded down Yucaipa Ridge above Forest Falls. One large boulder crashed down the hillside, mowing down tall cedars in its path. The boulder, the size of a small garage and measuring 16 ft by 16 ft by 14 ft, came to rest about 20 yards behind the Clarke residence on Prospect Drive in the western edge of Forest Falls. The boulder was estimated to have descended 1,000 feet vertically and covered a horizontal distance of 1,000 feet. It was said to be airborne most of the way as it hit the ground only three times on the way down. This view shows the boulder itself. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Collapse of a chimney on home at Big Bear City | |
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This figure shows the collapse of a chimney on a structure at Big Bear City. Approximately 40 percent of the structures in the area had some damage. Approximately 2,600 chimneys were destroyed in the Big Bear area and roughly 20 residences detached from their foundations. Photo Credit: Lindie Brewer, U.S. Geological Survey |
Roof damage to restaurant in Big Bear City | |
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Part of Divinos' Steak House in Big Bear City located at the intersection of Knight and Big Bear Road collapsed. It was a unreinforced masonry structure. Such structures performed very poorly during this earthquake and several that partially collapsed have been demolished. Photo Credit: Lindie Brewer, U.S. Geological Survey |