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Cape Mendocino, California Earthquakes, April 25 & 26, 1992 |
| On April 25, 1992 at 11:06 am local time (April 25 at 18:06 GMT), a magnitude 7.1 earthquake occurred in the Cape Mendocino area. Two additional earthquakes, magnitudes 6.6 and 6.7 occurred the next morning (April 26 at 00:41 and 04:18 am local time). The first earthquake was located six miles north of Petrolia, California, in a sparsely populated part of southwestern Humboldt County. Five small communities were located within a 50-mile radius of these events: Honeydew, Petrolia, Rio Dell, Scotia, and Ferndale. This slide set illustrates the effects and damage of a moderately large earthquake and moderate aftershocks on this sparsely settled area. |
Garage slid down hill due to earth shaking | |
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This garage slid downhill due to shaking in Rio Dell, California (population 2,900). The garage extended out over the north bank of the Eel River. The garage was supported by a framework of wooden stilts. The stilts collapsed and the garage fell backwards from street level. Other buildings in the neighborhood had similar damage, but the damage was not as severe or as impressive. A total of twelve homes in Rio Dell were destroyed, and 57 were severely damaged. On Main Street, fifteen out of twenty of the older one- and two-story buildings incurred damage such as broken glass, fallen bricks, and cracked plaster. Buildings shifted as much as two feet from their pre-earthquake positions. The earthquake broke water mains and sewer pipes, and interrupted telephone, gas and electricity services. The total earthquake damage in Rio Dell was estimated at $8 million. Photo credit: Lindie Brewer, U.S. Geological Survey |
View of mall at Scotia that was destroyed by earthquake-caused fire | |
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View of a shopping mall at Scotia, California (population 1,000). The mall was destroyed by a fire on April 26. It is believed that the fire resulted from an electrical short caused by the earthquake. Before the fire, the mall consisted of five one- to two-story, wood-frame, commercial buildings including a lumber yard, pharmacy, coffee shop, grocery store, and variety store. While local firefighters were attempting to save the mall, the second major shock occurred, snapping the town's water main. Firefighters drew water from a nearby log pond in order to continue fighting the fire. Telephone, gas and electricity services were interrupted. Total damage in Scotia was estimated at between $10 and $15 million. Photo credit: Lindie Brewer, U.S. Geological Survey |
Second view of Scotia mall | |
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A second view of the shopping mall in Scotia. Photo credit: Lindie Brewer. U.S. Geological Survey |
Support pillar on Scotia's Lumber Museum | |
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A redwood support pillar shifted during the earthquake. This is the Lumber Museum, located on Scotia's Main Street, just across the street from the burned-out mall. Windows in the museum cracked or were broken. Photo credit: Lindie Brewer, U.S. Geological Survey |
Damage to 70-year old house and chimney in Honeydew | |
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Earthquake damage to a house and chimney in Honeydew, California. This wood-frame, stucco-veneer house (built in 1922) was severely cracked when the chimney pulled away from the house. The east-west sway of the structure caused the separation between the chimney and the house. The house was vacant at the time. The damage was typical of houses in the area. However, a single-story, wood-frame building housing the post office and general store showed no signs of movement on its foundation. Photo credit: Lindie Brewer, U.S. Geological Survey |
Remains of Petrolia's business district after earthquake and fire | |
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The remains of the business district in Petrolia, California. Downtown Petrolia (population 100)
consisted of a post office, a 100-year-old general store, a gas station,
and a volunteer fire station. The post office, gas station, and the
general store burned to the ground in an earthquake-related fire. The
first large shock jammed the door of the fire station. Several
firefighters had to raise the door before the fire equipment could be
removed. The fire station was later condemned. One- and two-story, wood-frame houses and commercial buildings were the most common type of construction in Petrolia. A total of five homes were destroyed, 28 sustained major damage, and 25 required minor repairs. Total damage in Petrolia was estimated at $1 million. As in other towns in Humboldt County, services including water, sewer, telephone, gas and electricity were interrupted. Photo credit: Lindie Brewer, U.S. Geological Survey |
Chimney damage in Petrolia | |
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This brick chimney, typical of many others in Petrolia, toppled due to the severe shaking. Chimneys (even those with steel rods) were broken, or cracked. The fireplace inside this house was also shattered. Photo credit: Lindie Brewer, U.S. Geological Survey |
Earthquake bounced this front-end loader one foot into the air | |
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This large front-end loader, located in a residential neighborhood of Petrolia about three blocks east of the burned business district, reportedly bounced one foot into the air. On this same street, new homes of good construction were not damaged by the earthquake. Nearby, an older, wood-frame home was severely damaged when it moved off its foundation. Photo credit: Lindie Brewer, U.S. Geological Survey |
Petrolia residence shifted on foundation | |
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This Petrolia residence shifted on its foundation, causing the house to separate from the porch. Wooden skirting on the ground shows the direction of movement of the house. Photo credit: Lindie Brewer, U.S. Geological Survey |
Residence south of Petrolia that shifted off foundation | |
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This residence south of Petrolia shifted because the house was not anchored to the foundation. The structure, which was declared a total loss by insurance standards, shifted toward the northwest. A primitive post and pier foundation was common in the Petrolia area. This view shows separation of the porch from the rest of the structure. The house damage was more severe where additions were attached to the original structure. Photo credit: Lindie Brewer, U.S. Geological Survey |
Second view of damage to residence south of Petrolia | |
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The photo shows a three-foot displacement between the house and the porch (located in the upper left corner of the slide). It also shows the wooden skirting that covers the post and pier foundation and gives a close-up of the foundation. Photo credit: Lindie Brewer, U.S. Geological Survey |
Third view of damage to residence south of Petrolia | |
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Kitchen in the same house, after the earthquake. Appliances moved several inches away from the wall. Items were shaken off the shelves in the pantry, a room just off the kitchen. In other rooms, the damage was extremely variable. For example, a glass china cabinet in the living room was not damaged nor was its contents. Some windows were cracked, others were not. Some pictures fell from walls, other shifted out of place. Homes in the area moved as much as two to three feet off their foundations. Photo credit: Lindie Brewer, U.S. Geological Survey |
Removal of landslide on Mattole Road | |
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Heavy equipment operators remove a landslide on Mattole Road, near Petrolia. Many small landslides were observed along Mattole Road between Ferndale and Petrolia. Photo credit: Lindie Brewer, U.S. Geological Survey |
Landslide on Mattole Road | |
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A distant view of the same slide. Landslides were widespread and blocked or impeded traffic on the few roads available in the area. Two large landslides occurred east of Petrolia and Honeydew. These created large dust clouds and generated noise that was heard all over the valley. The slides that flowed across the roadways into neighboring ravines broke off trees and brushes. The slides hampered rescue and relief efforts. Photo credit: Lindie Brewer, U.S. Geological Survey |
Cracks on Mattole Road | |
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This view shows the cracks in Mattole Road going north toward Ferndale. In this area, severe cracking reduced traffic to one lane (one way). The road cracks were due to soil compaction and downhill slumping of the adjacent road shoulders. Photo credit: Lindie Brewer, U.S. Geological Survey |
Ferndale's Valley Grocery lost brick facade smashing two cars | |
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Ferndale, California (population 1,450). The brick facade from the Valley Grocery collapsed and smashed two cars. During the 1906 San Francisco earthquake, the facade of the same grocery fell, killing two cows! The grocery was the only all-masonry building on Main Street. Thirty-six homes in Ferndale were damaged. Foundations collapsed under at least a dozen homes; there was sporadic fracturing of water lines. Forty businesses (80% of the total) were damaged in the four-block business district. Utilities were also interrupted. Losses in Ferndale were estimated at $10.4 million. Photo credit: Lindie Brewer, U.S. Geological Survey |
Victorian wood-frame home slide on foundation in Ferndale | |
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This red-colored Victorian wood-frame home in Ferndale was damaged severely. The horizontal shift of the house is seen by the relative position of the house and the steps (still standing). The wooden skirting (on its side) indicates the original height of the house above ground level and its horizontal shift. The main floors of older Victorian homes were typically elevated on post and pier foundations, as much as 3 to 4 feet above the ground. Since these homes were not tied to the foundation, they were particularly vulnerable to earthquake shaking. Photo credit: Lindie Brewer, U.S. Geological Survey |
Chimney damage to Victorian home in Ferndale | |
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This yellow Victorian house in Ferndale shifted, causing the brick chimney to break into two parts. The bottom of the chimney shifted toward the east. The gray stripe along the side of the house shows the original position of the top half of the chimney. Photo credit: Lindie Brewer, U.S. Geological Survey |
Sandblow in Mattole showing liquefaction | |
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Surface effects, Mattole River. Stratigraphy of a sandblow on a Mattole River estuary showing three liquefaction episodes, caused by each of the three large earthquakes in the Cape Mendocino sequence. Photo credit: T. Dunklin, Humboldt State University, U.S. Geological Survey |
Uplift of coastline near Mussel Rocks caused death of organisms | |
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Surface effects, coastline near Mussle Rocks. Sudden coastal uplift caused the death of many marine organisms. The tidal pool became stagnant. Photo Credit: T. Dunklin, Humboldt State University, U.S. Geological Survey |