Hayward fault slip vector and rate constraints
at Berkeley: Reinterpretation of East Bay Landforms and Tectonic Hazards USGS Award 1434-HQ-97-GR-03080 Patrick L. Williams, University of California - Berkeley, Seismological Lab & Dept of
Geography
(Also see news editorial: The Hayward Fault: Will
it trigger the next quake: What to do if it does
April 10, 1992 By Pat Williams)
Investigations Undertaken
Offset and abandoned channels of Strawberry Creek have been shown to
record the vertical and lateral motions of the northern Hayward fault
at Berkeley. Geological features of the western Berkeley Hills are consistent
with rapid and recent uplift to the west of the fault. Analysis of two
offset channels of Strawberry Creek indicates up-to-the-west uplift
across the Hayward fault at a rate of approximately 0.5 mm/yr. If this
rate is steady, and extends along the 20-kilometer-body of the western
Berkeley Hills, the interpreted 120 m uplift of the Hills occurred during
the past about 250,000 years. With these interpretations, a "characteristic"
northern Hayward fault rupture is implied to be accompanied significant
compressional shortening along the western Berkeley Hills and thus probably
can produce a larger moment-magnitude earthquake than previously estimated.
Rapid uplift of the Hills also has important implications for the geotechnical
stability of significant portions of the East Bay Hills.
Ironically, the UC Berkeley Main Campus is probably the best location
for study of the long-term kinematics of the Hayward fault. The University's
location was chosen, in large part, because of the presence of a reliable
water supply from Strawberry Creek. Motion of the Hayward fault has
displaced the modern, active course of Strawberry Creek by about 300
meters (1000'). Paleochannels are offset 580 meters (1900') and 730
meters (2400'). Strawberry Creek and its paleochannels record both vertical
and lateral components of the strain field across the Hayward fault.
The up-to-the-west deformation that is indicated by fluvial and landform
evidence at Berkeley has important implications for structural geology
of the Hayward fault, and very likely explains the presence of several
thrust-bounded highlands to the west of the fault.
General evidence for the rapid uplift is illustrated in Figure
1, a topographic map along the Hayward fault zone in southeast section
of Berkeley, circa 1923. Note the abrupt increase of slope at the fault-line
to the south of The UC Berkeley football stadium. Obvious stream offsets
occur at Claremont, Hamilton, Strawberry, and Blackberry creeks. Note
that the fault climbs northward from the 400' contour at Strawberry
Creek to the 520' contour north of Blackberry Creek. The fault continues
to climb northward across the western Berkeley Hills ultimately reaching
a height of 800' (Figure 2). Note that the Mining
Circle Channel projects to the fault at about 440'. The Hearst channel
projects to the fault at about 480'. These intercepts are very suggestive
of ongoing uplift across the Hayward at Berkeley.The beheaded Strawberry
channel's origins are supported by the provenance of offset gravels.
Clasts of Claremont Chert are abundant in gravels exposed in excavations
that intersected the paleochannel during expansion of Doe Library in
the central UCB campus. Chert is absent in the hillslope north of Strawberry
Creek, but is abundant in the Strawberry watershed, and so identifies
these as Strawberry Creek deposits. Unpublished notes of George Louderback
also describe chert in three channel deposits of the Lawson Adit (Figure
1), a tunnel bored between the Mining Circle and Hearst paleochannels.
Buwalda (1929) first associated the Adit gravels with fault offset,
documenting that sorting, wear and provenance of the gravels tied them
uniquely to Strawberry Creek, hundreds of feet to the south.
Landforms of the western Berkeley Hills support a hypothesis of uplift
to the west of the fault. The Hayward fault traverses the hills (Figure
2) between Strawberry Creek and Richmond. Dibblee (unpublished mapping
of the Richmond and Oakland East quadrangles) mapped a faultline at
the base of the hills, as illustrated in Figure
2, and labeled as the El Cerrito fault. The Hayward fault climbs
from 400 feet at Strawberry Creek to 800 feet at the crest of the western
Berkeley, a rise of 120 meters. If the about 0.5 mm/yr rate of vertical
motion suggested by the apparent uplift of abandoned Strawberry Creek
channels holds for long period required for uplift of the western Berkeley
Hills across the Hayward fault, the period required to reach their present
configuration is approximately 250,000 years. Lack of a well-developed
fault-line valley along the relatively more stable ridge-top area also
suggests the youthfulness of the present configuration. It is thus proposed
that the western Berkeley Hills block has been upthrust between the
El Cerrito and Hayward faults during Quaternary time.
The earliest detailed landform map in the Hayward fault zone is the
UC Berkeley building and grounds map, compiled in 1897 (Figure
3). This map records the morphology of the abandoned Mining Circle
and Hearst channels of Strawberry Creek at a contour interval of four
feet. The fault climbs approximately 24 meters across this Figure (from
400 to 480'). Once again, the offset channels project to the fault at
about 440 and 480 feet. Note that the near-fault profile of each beheaded
channel is steepened by alluvium, which heightens the apparent channel
intercept with the fault zone. A better estimation of the height of
the intersection can be made by projecting the stream profiles from
a greater distance from the fault (Figure 4).
Note also the area of thickly ponded alluvium behind the Strawberry
Creek shutter ridge. This ponding causes a tendency to underestimate
the depth of the Strawberry Creek Canyon, and consequently underestimate
the total vertical separation between the canyon and the beheaded channels.
A projection to the fault of the bedrock stream profile is thus required
to estimate the Wisconsin-era canyon morphology, and to recover the
maximum vertical separation of the beheaded profiles.
Channel and Bank Profiles are illustrated in Figure
4. The active and beheaded channels of Strawberry Creek are aligned
along the Hayward Fault. Ranges of vertical separation across the fault
are noted graphically. Indicated are at least 10 but no more than 18
m of uplift of the Mining Circle channel. Also indicated are at least
12 but no more than 30 meters of Hearst channel uplift. Flattening of
the active Strawberry Creek profile below the fault, along the length
of the shutter ridge, results from tectonic lengthening of the channel
by fault offset, and consequent alluviation. A "falls" occurred
at the northern end of the shutter ridge. The much greater steepness
of the paleochannels is attributed to control by much lower glacial
base levels. The Strawberry profile is believed to have been greatly
shallowed by agradataion as base-level rose. The much wider morphology
of the modern stream valley that is apparent in Figure 3 is indicative
of alluviation of the glacial era valley.
Reference
Buwalda, John P., 1929, Nature of the Late Movements on the Hayward
Rift, Central California, Bulletin of the Seismological Society of America,
19, 187-199.
Related publications and reports
California Memorial Stadium Commission, California Memorial Stadium
Grading Plan, University of California, Berkeley, California, 1922.
King, M.G., Grounds and Buildings Map, University of California,
Berkeley, Alameda County, California, compiled under the direction of
the College of Civil Engineering, 1897.
Lienkaemper, J.J., Map of recently active traces of the Hayward fault,
Alameda and Contra Costa Counties, California: U.S. Geological Survey
Miscellaneous Field Studies Map MF-2196, 1992.
Williams, P.L., Features and dimensions of the Hayward fault zone
in the Strawberry and Blackberry Creek area, Berkeley California, Lawrence
Berkeley Laboratory Pub. 36852, 1995.
Williams, P.L., Rate determinations for late Quaternary compressional
tectonics across the central California Coast Ranges, EQS Trans AGU,
December 1996.
Topographic May Showing Interpretations
of the Hayward Fault California Memorial Stadium, University of
California Berkeley, California. Geomatrix, Project 5442 Figure 2.
Pre-Development Landform Map, California
Memorial Stadium, University of California Berkeley, California.
Geomatrix, Project 5442 Figure 3.
FIGURE CAPTIONS
Figure 1. Topographic
map in the vicinity of the Hayward fault zone, southeast section of
Berkeley, circa 1923 Note the abrupt increase of slope at the fault-line
and the geometry of streams offset by the Hayward fault. Note that the
fault climbs from the 400 contour at the Creek to the 520 contour north
of Blackberry Canyon. The fault continues to climb northward across
the western Berkeley Hills ultimately reaching a height of 800', see
Figure 2. Contour interval = 20’
.
Figure 2. Topography
of the western Berkeley Hills with Hayward and Dibblee" fault locations.
Map extends from Strawberry Creek to Richmond. The morphology of the
faults traverse over the hills indicates uplift of the western block.
The fault climbs from 400 feet at Strawberry Creek to 800 feet at the
crest of the western Berkeley, a rise of 400 feet (120 meters), Lack
of a well-developed fault-line valley along the relatively more stable
ridge-top area suggests the youthfulness of the present configuration.
If the about 0.5 mm/yr rate suggested by Strawberry Creek stream morphology
holds for long-term uplift across the Hayward fault, the western Berkeley
Hills required approximately 250,000 years to reach their present elevation.
Contour interval = 20'.
Figure 3. Landforms
and culture in the area of the Hayward fault zone. University of California,
Berkeley drawn on a UC Berkeley base map, compiled in 1897. This
map records the morphology of the two abandoned channels of Strawberry
Creek. University of California structures as of AD 1897 are solid.
Selected later University of California structures outlined for reference.
Major fault-related landforrns include: A-A: Strawberry Creek channel
offset; Sr': primary shutter ridge; Sr': remnant shutter ridge MCC:
beheaded Mining Circle Channel; H: beheaded Hearst Avenue Channel. Elevations
of the intersections of ancient and modem channels of Strawberry Creek
with the fault are noted. Contour interval is 4 below 400' and 8' above.
The fault climbs approximately 24 meters across this Figure (from 400’
to 480')
Figure 4. Channel
and Bank Profiles. active and paleochannels of Strawberry Creek, aligned
on the Hayward Fault. Ranges of vertical separation across the fault
are noted graphically. Indicated are at least 10 but no more than 18
m of uplift of the Mining Circle channel. Also indicated are at least
12 but no more than 30 meters of Hearst channel uplift. Flattening of
the active Strawberry Creek profile below the fault, along the length
of the shutter ridge, results from tectonic lengthening of the channel
by fault offset. The drop in the channel at the northern end of the
shutter ridge was called "the falls". The much greater steepness
of the paleochannels is attributed to control by much lower glacial
base level. The Strawberry profile was made gentle by agradatalon as
base-level rose. The wider morphology of the modem channel is indicative
of valley filling.
Non-technical Project Summary
Offset and abandoned channels of Strawberry Creek have been shown to
record the vertical and lateral motions of the northern Hayward fault
at Berkeley. Geological features of the western Berkeley Hills are consistent
with rapid and recent uplift to the west of the fault. Analysis of two
offset channels of Strawberry Creek indicates up-to-the-west uplift
across the Hayward fault at a rate of approximately 0.5 mm/yr. If this
rate is steady, and extends along the 20-kilometer-body of the western
Berkeley Hills, the interpreted 120 m uplift of the Hills occurred during
the past about 250,000 years. With these interpretations, a "characteristic"
northern Hayward fault rupture is implied to be accompanied significant
compressional shortening along the western Berkeley Hills and thus probably
can produce a larger moment-magnitude earthquake than previously estimated.
Rapid uplift of the Hills also has important implications for the geotechnical
stability of significant portions of the East Bay Hills.
Source: http://erp-web.er.usgs.gov/reports/annsum/vo139/nc/g3080.htm
The Hayward Fault: Will it trigger the
next quake: What to do if it does
April 10, 1992 By Pat Williams
Editor's note: LBL geologist Pat Williams examines the probability that
the nearby Hayward Fault will produce a major earthquake, and discusses
how we can prepare for that possibility, both at work and at home.
One day in the future; while many or most of us are still employed at
LBL, there will be a catastrophic earthquake in the Bay Area. Many earthquake
researchers believe that our very close neighbor, the northern Hayward
Fault, is the top candidate to produce the area's next major shock.
Modest preparations at home and at work will make a tremendous difference
in our comfort, safety, and peace of mind in the aftermath of this event.
Long-term earthquake forecasting leans heavily on history for evaluating
earthquake occurrence probabilities. This method relies on three pieces
of information: 1) the fault's long-term rate of slip, 2) the time elapsed
since its last rupture, and 3) the offset expected in a "typical"
fault rupture.
Surprisingly, little of this information can be determined by classical
seismological techniques. Earthquake science now relies heavily on geological
and historical investigation of past fault behavior. Geological fault
studies search for ancient evidence of slip rate, the size of past offsets,
and the times of past ruptures.
Investigators scan old newspapers to learn the extent and size of historical
ruptures. Studies of the Hayward Fault have provided the following clues:
its average slip rate is about 9 mm/yr (0.35 in/yr); the latest rupture
of its southern segment (Fremont to San Leandro) occurred in 1868; and
rupture of the northern section (San Leandro to Pinole) probably occurred
in 1936. Earthquake forecasters estimate an average earthquake recurrence
interval of 167 years. Other concepts, particularly the idea that strain
of the earth's crust in the Bay Area has slowly "recharged"
after being greatly relaxed by the 1906 San Francisco earthquake, suggest
that new Hayward Fault earthquakes are likely during the period of the
next few years to decades.
LBL's Exploratory Research and Development Fund enabled a direct study
of the Hayward Fault's earthquake history. Current results of that study
indicate that the fault's past ruptures occurred, on average, every
150-250 years. This appears to support the 167- year average recurrence
estimated by earthquake forecasters.
Following a large earthquake, the greatest concern we will probably
have, after our personal safety, will be the safety and whereabouts
of our families. Due to heavy damage to the transportation infrastructure
at the Lab and in the Bay Area, it is likely that most of us will have
to leave the site under our own power in order to reunite with our families.
This will be more difficult for those of us who live very far from the
Lab.
Lab roads will probably be closed by landslides and ground rupture along
faults. The accompanying figure shows that ground rupture on the Hayward
Fault is likely to close both Centennial Drive and Cyclotron Road for
some period of time. Roads closed by fault breaks may be made passable
by the Lab's own crews within a few hours. Roads closed by landslides
are generally more difficult to repair, and are likely to remain impassable
for days to weeks. Even after Lab roads are made passable, use will
generally be restricted to emergency vehicles only. Lab earthquake procedures
(located on the inside-back cover of the LBL telephone directory) instruct
us "not" to leave the Laboratory by car.
After a major seismic event in the Bay Area, bridges and rail systems
are likely to remain closed for a few hours to a few weeks while they
are inspected, and if necessary, repaired. Those of us who used bridges
and rail transit to commute to work may be stranded away from home for
a day or more, and when we do go home, we are likely to cover most of
the distance on foot.
Reasonable preparations for a long walk home include keeping sturdy
shoes, a jacket, a hat, and a backpack, containing some high-energy
nonperishable food, a water bottle, and a flashlight, at your work place
and/or in your car. Additionally, it is essential that we "write down"
a family earthquake plan and in it include as participants teachers,
friends, neighbors, and relatives who can help us in reuniting our families
and whom we can help during the crisis.
In the plan:
- 1) make a school/daycare evacuation plan;
- 2) choose a primary
and an alternate family meeting site;
- 3) identify some person(s) outside
the area to coordinate family messages (long distance lines will be
the first to be reestablished;
- 4) include someone in the plan would
could care for your children if the family is separated during an earthquake.
Store adequate food, water, batteries and other supplies to last three
or more days after the earthquake. Be sure that both the structural
and non-structural elements of your residence are earthquake safe. The
telephone white pages contain an excellent summary of earthquake emergency
information. By preparing for future Bay Area earthquakes, we acknowledge
the potency of the active faults of this region, we contribute to our
own peace of mind, and we set the stage for a more rapid post-earthquake
recovery of LBL and the community.
Source: http://www.lbl .gov/Science-Articles/Archive/hayward-fault.html