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Seismic Creep |
| Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden rupture associated with an earthquake. It is a usually slow deformation of rock resulting from constant stress being applied over a period of time. Sometimes aseismic slip is observed at the ground surface along a ruptured fault that has produced a substantial earthquake. Examples are from the Hollister and Hayward, California, region. Several of the slides are split images of a location, comparing fault movement over the years. |
Calaveras fault crosses street in Hollister | |
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Hollister, California This small, seemingly-insignificant crack indicates the location of the Calaveras fault crossing Locust Street near the intersection with Central Street. The photo looks straight down the fault trace. The fault trace runs along the right middle part of the photo from the near foreground to behind the blue truck. The individual cracks themselves tend to be perpendicular to the curb. They are en echelon cracks. The individual cracks stack together like shingles at the edge of a roof line. The fault cracks at Hollister are remarkably localized. If the deformation was spread over several blocks, it would not be visible without surveying equipment. Photo date: June 18, 1985. Photo credit: Joe Dellinger |
Creep on Locust Street as it looked in 1966 and 1992 | |
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Hollister, California (Left) 164 Locust Street photographed from southeast of the manhole cover in the middle of the street. Note the bend in the curb produced by the Calaveras fault. The photo was taken in December, 1966. Photo credit: Copyright 1995, Dr. Edward Berg, SOEST, University of Hawaii (Right) Same location nearly 26 years later. Note the increase in the offset along the Calaveras fault, producing wave-like curbing. This second photo was taken on August 4, 1992. Photo credit: Joe Dellinger |
Tipped house foundation along fault | |
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Hollister, California Foundation of house at 164 Locust Street. Note that the house has an uneven foundation. Note also the cracks in the sidewalk and street. Photo date: August 4, 1992. Photo credit: Joe Dellinger |
Fault trace crosses intersection | |
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Hollister, California The crack indicates the location of the Calaveras fault where it crosses near the intersection of Central and Locust Streets. It uses the crosswalk, like a good law-abiding fault! Photo date: June 18, 1985. Photo credit: Joe Dellinger |
Effect of 16 years of creep on curb | |
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Hollister, California Curb at north end of crosswalk by Central and Locust Streets, August 4, 1992. Graffiti in the cement of the curb indicates it was poured April 22, 1975, so this photo demonstrates 16 years of creep on the Calaveras fault. The coin is used for scale. Photo credit: Joe Dellinger |
Walkway as it appeared in 1985 and in 1991 | |
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Hollister, California (Left) Walkway to the front of 359 Locust Street, as it appeared in June 1985. The Calaveras fault runs from left to right across the middle of it. (Right) The same walkway as it appeared in February, 1991. According to residents, the walkway was rebuilt in 1989 and the sidewalk along the street was rebuilt in 1987. Reportedly, the walkway bulges up every few years from fault compression, and it has to have sections removed to relieve the bulge. Photo credit (both views): Joe Dellinger |
Two photos depicting same deformed curb in 1966 and 1992 | |
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Hollister, California Northeast corner of 4th and Locust Streets, looking down 4th Street, in December, 1966. The movement along the fault is causing the standing wall to be slightly bent. Note the effect on the sidewalk, more discernible in the right view. Photo credit: Dr. Eduard Berg, SOEST, University of Hawaii, Copyright 1995 |
"Wavy" curb produced by seismic creep | |
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Hollister, California South side of 4th Street, looking east from near Locust Street. Note the "waviness" in the curb. Photo date: June 18, 1985. Photo credit: Joe Dellinger |
Curb on opposite side of street | |
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Hollister, California North side of 4th Street, looking east from near Locust Street. Note the "waviness" in the curb. According to residents, the street develops a dip which has to be fixed every eight to ten years. Photo date: June, 1985. Photo credit: Joe Dellinger |
Bend in curb caused by seismic creep | |
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Hollister, California Southeast corner of 4th Street and Locust Street, looking down 4th Street, during 1966. Note the bend in the curb. Photo credit: Dr. Eduard Berg, SOEST, University of Hawaii, Copyright 1995 |
Bend in sidewalk, Hollister | |
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Hollister, California Bent sidewalk wall on north side of 6th Street, across the street from Dunne Memorial Park. Photo date: June 18, 1985. Photo credit: Joe Dellinger |
Broken curb, Hollister | |
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Hollister, California Broken curb on north side of 6th Street, across from Dunne Memorial Park. Photo date: June 18, 1985. Photo credit: Joe Dellinger |
Offset of street's center line at fault trace | |
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Hollister, California View down 6th Street, across from Dunne Memorial Park. Note the bend in the crack down the middle of the street. This indicates that the fault crosses the street perpendicular to the street's center line. Photo date: August 11, 1990. Photo credit: Joe Dellinger |
Offset of culvert near Almaden Cienega Winery | |
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Almaden Cienega Winery near Hollister, California (Left) Not far away from the town of Hollister is the Almaden Cienega Winery. The winery is located squarely across the San Andreas fault trace, and has been affected by fault creep. Measurements of the alignments of the culvert and floor slabs show a relative offset rate across the San Andreas fault of 1.5 centimeters per year. Small springs abound along this trace. In this photo taken on April 12, 1986, Mr. Dedear is standing astride an open concrete culvert which lies just to the south of the winery. (Right) Another view of the same culvert at Almaden Cienega winery, showing the offset across the fault as it appeared in May, 1990. Photo credit (both views): Joe Dellinger |
Building damage caused by creep in Hayward | |
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Hayward, California The Hayward fault crosses through downtown Hayward leaving evidence of creep. On C Street, evidence of damage due to seismic creep can be seen in the corner of the brick building. Photo credit: Sue Hirschfeld |
En echelon shears crossing street, Hayward | |
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Hayward, California The street shows en echelon shears crossing Foothill Boulevard in San Leandro, just to the north of Hayward. Here the shear zone is quite narrow. Photo credit: Sue Hirschfeld |
Curb offset in 1974 and in 1993 | |
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Hayward, California One of the most dramatic examples of tectonic creep is found in a residential area north of downtown Hayward at the corner of Rose and Prospect Streets. Photographs taken over twenty two years show the offset of the curb by creep. The top photo was taken in 1974. Note the same location in a photo taken in 1993 (bottom photo). Photo credit (both views): Sue Hirschfeld |
Offset of fence in Hayward | |
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Hayward, California A section of 100-year-old fencing at Holy Sepulchre Cemetery in Hayward has been offset by more than three feet of creep. Photo credit: Sue Hirschfeld |
Effect of creep on stadium | |
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Berkeley, California (Left) Fault creep is slowly deforming Berkeley Memorial Stadium, built in 1923 across the Hayward fault. View A provides an overview of the stadium, but creep is not visible in the photo. The crowd is gathered near the location of view B. (Right) Offset of expansion joints and fracturing of the exterior walls of the stadium result from a third of a meter or about 13 inches of fault movement that has deformed the structure. Photo credit (both views): Sue Hirschfeld |
Distorted Fence, Melendy Ranch | |
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Melendy Ranch, California A corral fence was built across the San Andreas fault at Melendy Ranch, California. The fence is distorted by fault creep. Note the change in vegetation on each side of the fault a few feet behind the man leaning against the fence. Photo date: May 19, 1990. Photo credit: Joe Dellinger |