Seismic Creep
Seismic Creep
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Seismic Creep General Information
Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden rupture associated with an earthquake. It is an usually slow deformation of rock resulting from constant stress being applied over a period of time.
Active faults exhibit a variety of deformational phenomena; the most obvious is earthquake slip. In addition, faults may continue to move after an earthquake occurs (afterslip), move slowly over time in the absence of earthquake activity (fault creep), or move slowly as pressure builds before an earthquake (pre-seismic slip). Fault creep may be constant over time, or the motion may alternate between periods of slow and relatively rapid movement. Usually, such episodes of fault slip are aseismic—that is, they are not accompanied by local earthquakes. The characteristics of the fault itself and the total mechanical system that produces the fault movement are the major factors determining the type of creep. As more information is acquired about the fault itself and about the stresses upon it, interpretations are made about movement along that fault, including creep.
Fault creep (horizontal fault slippage) has been identified on a number of faults around the world including the north Anatolian fault at Ismetpasa in Turkey, along the Jordan Valley rift in Israel, and the Hayward, San Andreas, and Calaveras faults in California.
Sometimes aseismic slip is observed at the ground surface along a ruptured fault that has produced a substantial earthquake. For example, along the San Andreas fault near Parkfield, California, offsets of road pavement increased by a few centimeters in the days following the June 27, 1966, earthquake. Such continued adjustment of the crustal rock after the initial major offset may be caused partly by the minor slips that produce aftershocks. They may also result from the yielding of the weaker surface rocks and gouge in the fault zone as they accommodate to the adjusted tectonic forces in the region.
Seismic creep, when it occurs in developed areas, may result in structural damage. Creep has damaged the huge concrete- lined water tunnel from the Sierra Nevada that brings water to cities on the east of San Francisco Bay. It has damaged Berkeley Memorial Stadium at the University of California and the Almaden Cienega Winery near Hollister.
The tunnel and the stadium straddle the active Hayward fault which is undergoing right-lateral slip at the rate of 2 to 5 millimeters a year. When the tunnel was drained in 1966, cracks several centimeters across were discovered. These encircled the concrete lining where the tunnel and fault zone intersect. A concrete drainage culvert under the stadium shows considerable cracking where it crosses the Hayward fault trace; instruments that were placed across the cracks in 1966 show that the right-lateral slip continues to occur.
Obviously, faults should be avoided when considering locations for man-made structures. When utility lines, roads, and railroads must be laid across active faults, they should have jointed or flexible sections within the fault zone.
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Calaveras fault crosses street in Hollister Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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 were spread over several blocks,
it would not be visible without surveying equipment. [Photo date: June
18, 1985. Photo credit: Joe Dellinger.]
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Creep on Locust Street as it looked in 1966 and 1992 Hollister,
California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. A. 164 Locust Street photographed from southeast of the manhole cover in the middle of the street, using a 50 mm lens. 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.] B. Same location nearly 26 years later, photographed using a 50 mm lens.
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.]
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Tipped house foundation along fault Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.]
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Fault trace crosses intersection Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.]
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Effect of 16 years of creep on curb Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.] File:eq-creep-05 |
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Walkway as it appeared in 1985 and in 1991 Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. A. 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, offsetting it in steps. B. 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.]
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Two photos depicting same deformed curb in 1966 and 1992 Hollister,
California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. Two Views of a slightly-bent curb 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 center
crack on the sidewalk in the second photo. [Photo credit: Copyright 1995,
Dr. Eduard Berg, SOEST, University of Hawaii.]
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"Wavy" curb produced by seismic creep Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.]
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Curb on opposite side of street Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.]
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Bend in curb caused by seismic creep Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. Southeast corner of 4th Street and Locust Street, looking down 4th Street, during 1966. Note the bend in the curb. A second photo taken in 1992 by Joe Dellinger showed little change at this location. [Photo credit: Copyright 1995, Dr. Eduard Berg, SOEST, University of Hawaii.] File:eq-creep-10 |
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Bend in sidewalk, Hollister Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.]
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Broken curb, Hollister Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. Broken curb on north side of 6th Street, across from Dunne Memorial
Park. [Photo date: June 18, 1985. Photo credit: Joe Dellinger.]
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Offset of street's center line at fault trace Hollister, California
In the town of Hollister, the Calaveras fault (a subsidiary of the famous San Andreas fault) is slowly slipping, producing noticeable offsets and damage to curbs, sidewalks, fences, and even houses. A map on the following page provides location information for the next thirteen slides. The black arrows indicate the fault’s motion. The coast of California is moving north laterally, in a splinter-like fashion. The Pacific plate is dragging the western edge of the North American continent, causing northward movement as far east as the Wasatch fault in central Utah. 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.] File:eq-creep-13 |
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Offset of culvert near Almaden Cienega Winery Almaden Cienega
Winery near Hollister, California
A. 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, Lee Dedear is standing astride an open concrete culvert which lies just to the south of the winery. B. 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.] File:eq-creep-14 |
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Building damage caused by creep in Hayward Hayward, California
The Hayward fault crosses through downtown Hayward leaving evidence of creep. (See maps, next page.) On C Street, evidence of damage due to seismic creep can be seen in the corner of the brick building. [Photo credit: Sue Hirschfeld.] File:eq-creep-15 |
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En echelon shears crossing street, Hayward 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.] File:eq-creep-16 |
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Curb offset in 1974 and in 1993 Hayward, California
A & B. 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 photograph taken in 1993 (bottom photo). [Photo credit (both views): Sue Hirschfeld.] File:eq-creep-17 |
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Offset of fence in Hayward Hayward, California
A section of hundred-year-old fencing at Holy Sepulchre Cemetery in Hayward has been offset by more than three feet of creep. [Photo credit: Sue Hirschfeld.] File:eq-creep-18 |
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Effect of creep on stadium Berkeley, California
A. 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. B. 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.]
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Distorted Fence, Melendy Ranch 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. The photograph was taken on May 19, 1990. [Photo credit: Joe Dellinger.] File:eq-creep-20 |