Description
The objective of this assignment is for you to demonstrate an ability to communicate details about the Hayward Fault.
While you are absolutely allowed to write a standard academic report
Content : Among other things that you can explore are : how the fault moves and its tectonic context, how we can see evidence of the fault on the surface, the size of earthquakes it is capable of producing, some potential consequences of such an event, how the fault interacts with or influences structures on campus, …
The field trip stops provide ample opportunity to discuss those and explain that the stops are manifestations or consequences of the fault being nearby.
If submitting a standard report : The limit is 800 words. (The max limit is 850, anything beyond that won’t be taken into account.)
Grading: You will be graded dominantly on factual accuracy, not the quality of your art. We are looking for knowledge and critical comprehension.
Unformatted Attachment Preview
Horst Rademacher
The Hayward Fault
at the Campus of the
University of California, Berkeley
A Guide to a Brief Walking Tour
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Content
1.
1.1
1.2
Introduction
Hearst Memorial Mining Building
Memorial Gallery
Seismic Base Isolation
3
5
6
6
1.3
2.
3.
4.
5.
5.1
The Moat
Lawson Adit
Founders’ Rock
Seismic borehole station CMSB
The California Memorial Stadium
Stairway on North Side of Stadium
7
8
9
10
11
15
5.2
5.3
5.4
5.5
5.6
6.
7.
Exterior Wall – North Side of Stadium
North Tunnel
Section KK
Concourse Level
Prospect Court Parking Lot
Hamilton Creek
Dwight Way
Illustration Sources and References
15
16
17
18
19
20
21
22
Acknowledgements
Like everything else in Earth science this guide is the result of a cooperative effort. Numerous people in
UC Berkeley’s Department of Earth and Planetary Science have contributed bits and pieces of their
knowledge about the Hayward Fault. Tim Teague prepared the thin section of Founders’ Rock, Paul
Renne evaluated it. Doris Sloan and Peggy Hellweg, who both have led countless tours along various
sections of the fault, were always at my beck and call to find answers to whatever question I had when
putting this guide together. Without the help of Samantha Teplitzky from UC Berkeley’s Earth Sciences
and Map Library I would not have found old maps and pictures. I thank all of them for their generosity.
Cover Picture
In urban areas it is sometimes difficult to perform geological research. The native landscape has been
highly altered by human activity, like building roads, houses, sports facilities and many other
structures. Geologic features are covered over by infrastructure or hidden inaccessibly on private
property. Aerial or satellite photography sometimes helps to reveal the underlying landscape, but often
enough such images show very little of interest to the Earth scientists, like in the top panel of our cover
picture. A 3D-scanning technique called Lidar (Light detection and ranging) uses laser beams to scan a
region mostly from aircraft. Using numerical calculations researchers can then strip such scans of
buildings and vegetation to gain a detailed image of the hidden landscape. The lower panel of our cover
shows such a Lidar image of the same area as the satellite picture above. The imagery covers the area of
much of the tour described in this pamphlet, from the California Memorial Stadium on the left to the
track field of Clark Kerr Campus on the right. The red line indicates the location of the Hayward Fault.
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Introduction
The University of California, Berkeley is – according to the author’s knowledge – the only major
university in the world, whose campus is intersected by a dangerously active earthquake fault. The
Hayward Fault, a branch of the San Andreas Fault system in the San Francisco Area of northern
California, cuts through the eastern part of campus, most prominently through the playing field of the
University’s football arena, the California Memorial Stadium. Ranked by the latest probabilistic hazard
analysis (UCERF-3) as the most dangerous earthquake fault in the greater San Francisco region, the
Hayward Fault is thought to be able to generate magnitude 7.5 earthquakes, capable of causing
significant damage. At the same time, some sections of the Hayward Fault are in constant motion.
Across campus the fault creeps along aseismically by a few millimeters a year.
The fact that UC Berkeley is located on the Hayward Fault was not intentional. At the time the first
students and faculty occupied the campus, in 1873, the science of seismology was in its infancy. Earth
scientists were still oblivious to the causes of earthquakes, phrases like earthquake fault had not even
been invented and the concept of plate tectonics would be almost a century away. Nevertheless, since
the university’s founding Berkeley faculty has played a major role in advancing the science of
earthquakes and of seismic monitoring. In fact the first seismometer network in the western hemisphere
was set up by Berkeley scientists in 1887. After adapting many times to advances in technology, it is still
in operation today in northern California and southern Oregon as the Berkeley Digital Seismic
Network. In addition, the Berkeley Seismological Laboratory (BSL) operates several local seismic
networks.
Despite the fact that the Hayward Fault is one of the best studied earthquake faults in the world, it
remains rather elusive. We are not talking about the lack of reliable earthquake prediction but instead
about uncertainties in the exact location of the fault. Figure 1 shows a topographic map of the foothill
area of East Berkeley with UC Berkeley’s stadium prominently displayed. While many details in this
map are not relevant for our tour, the important information is contained in the colored lines crossing
the map. Each line represents the estimate made by one researcher or group of scholars as to the
location of the fault. In some areas, these locations vary by more than 1000 ft. The reader may keep
these uncertainties in mind, when looking at maps of the locations of our tour stops, as in figures 2 and
5.5. There we show the fault as a single straight line for reasons of simplicity.
Fig. 1: Topographic map with locations of the Hayward Fault as different researchers see it. Each color represents a
different geologic investigation. In some sections, the fault locations differ by 1000 ft.
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In the following, we highlight some of the major features of the Hayward Fault on campus. We
will visit sites where the continuous aseismic creep along the fault is tearing at buildings,
structures and roads, we will see examples of how the University mitigates some of the risk posed
by the seismic hazard and we will look at methods to monitor the seismic activity of the fault.
This pamphlet is designed as a guide for a walking tour to the points of interest as they are shown
on the maps in figures 2 and 5.5. The numbering of these points on the maps is consistent with
their nomenclature in the text. Paragraphs set in italic font and underlain in light grey explain how to get
from one point of interest to the next.
Fig. 2: Map of the eastern part of UC Berkeley’s campus showing points of interest along the Hayward Fault
This tour is designed as a walking tour. Taken in its entirety the tour will take about 2.5 hours,
depending, of course, how much time one spends at each stop. The tour can also be broken up in
sections to be taken at different times. During our walk, we will mostly stay on UC Berkeley’s
property or on public roads. However at point 6 we will be looking at private property. Please
respect the privacy of the owner and his neighbors and avoid loud noise. A word of caution: As
the Hayward Fault runs along the foot of the Berkeley Hills, we will encounter several steep climbs
and stairways during our walk. Be prepared by wearing sensible shoes and by carrying some
drinking water and perhaps a snack. You are welcome to take as many pictures or videos as you
want.
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The tour starts on the north side of the Mining Circle at the base of the impressive stairs leading to the Hearst
Memorial Mining Building, point 1 in figure 2. Walk into the building and stop in the grand lobby, the Memorial
Gallery.
1.
Hearst Memorial Mining Building
Because UC Berkeley was founded in a merger between the public Agricultural, Mining, and
Mechanical Arts College and the private College of California, mining played an important role in the
curriculum of the young university. After all, the California Gold Rush of 1849 had caused a
mining boom in the state which lasted for many decades. In the early 1900’s more than 15 percent
of the 3000 students then enrolled in Berkeley majored in mining, making UC Berkeley’s College of
Mining the largest school of its kind in the world. However, in the beginning the UC miners did
not have their own building on campus. That changed in 1907 when the Hearst Memorial Mining
Building, designed by New York architect John Galen Howard, opened its doors. The building was
financed and gifted to the university by the widow of George Hearst, a U.S. Senator who had made
his vast fortune in silver mining in several western states. In all its Beaux Art splendor, particularly
in its grand, three story lobby, the building has been called “the architectural gem of the entire UC
system.” But however beautiful, the building is located less than 800 ft away from the Hayward
Fault and in its original state it constituted a major risk in a strong earthquake. Hence, between
1998 and 2003, it underwent a massive renovation and seismic retrofit. The College of Mining was
integrated into the College of Engineering in 1942 and the building is now home to the Department
of Materials Science and Engineering.
Fig. 1.1: The Hearst Memorial Mining Building and a cutaway of its new underpinnings
after the major seismic retrofit. Note the moat surrounding the building
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1.1
Memorial Gallery
At first glance this impressive, three
story atrium style lobby seems like an
earthquake nightmare. You are
surrounded by brick walls accentuated
by a vaulted tiled ceiling topped by
beautiful glass domes. Every textbook on
seismic engineering will tell you that
unreinforced masonry, or brick, is the
most vulnerable of all construction
methods when shaken by seismic waves.
Usually the thin layers of mortar holding
the bricks together fail under vibrational
load and the brick walls collapse. This
was indeed the grave risk the building
constituted until its retrofit.
Fig. 1.2: The impressive lobby of the
Hearst Memorial Mining Building
In order to make the brick walls safe, they were reinforced with steel bars. The ceiling, however, posed a
much greater challenge. Its tiles were produced more than 110 years ago by the “Guastavino Fire Proof
Construction Company”. Their patented system allowed self-supporting vaulted ceilings to be built.
The interlocking terracotta tiles were held together by layers of mortar. During the retrofit, much of the
mortar was replaced by a mesh of fiberglass and wire. Nearly invisible polymer pins now connect every
tile to the new backing. This is the only time such a Guastavino tile system was ever seismically
strengthened. In addition, during the retrofit, the vinyl flooring added to the gallery in the 1960’s was
removed to reveal the original herringbone-pattern of yellow bricks.
Now walk a few steps through the glass doors opposite the entrance to the Memorial Gallery and look at the wall
of pictures. They show the various phases of the original construction and of the seismic retrofit.
1.2
Seismic Base Isolation
The entire building was raised from its original foundation by several feet and a new foundation
system was constructed underneath, including the steel piers shown in figure 1.1. A new platform
was constructed as the base of the building. A total of 134 circular columns made of a rubber and
steel composite were placed between the platform and the foundation in order to mechanically
separate the building above from the ground below (see figures 1.3 and 1.4). Each of these circular
columns is called a seismic base isolator and is approximately 4 ft in diameter and 2 ft high. The
composite is compressed between two round steel plates and it acts – in simple terms – like a shock
absorber. While the ground underneath moves in an earthquake, the base isolators mostly absorb
these horizontal vibrations and thereby minimize the seismic forces acting on the building. Such
passive structural vibration isolation technique is common for big buildings in earthquake prone
areas. For example, the City Halls in San Francisco, Oakland and Los Angeles were similarly
retrofit and now rest on base isolators.
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Fig. 1.3: The left panel shows in a sketch how seismic base isolation works. A base isolator mechanically separates a
building from its foundation anchored in the ground. When the ground vibrates in an earthquake, the rubber and
steel laminate absorbs much of the movement and prevents the building from shaking. The right panel shows a
base isolator underneath the raised Hearst Memorial Mining Building during its installation in 2000.
Fig. 1.4: A total of 134 base isolators in the subbasement of the
Hearst Memorial Mining Building, like the two shown here, keep
the floor of the building (above) seismically separated from the ground (below).
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Leave the building through the main entrance and walk down the stairs in front of the building. Turn right and
walk a short distance downhill. Then turn right again around the corner and walk about 100 ft along the west side
of the building until you reach the walkway leading to the side entrance. Turn right and walk until you almost
reach the door and stop directly under the “underpass”. You are now standing on the moat.
1.3
The Moat
The seismic base isolators protecting the Hearst Memorial Mining Building from underneath are
designed to absorb horizontal ground movement of up to 28 inches in any direction. When the ground
moves by that amount, the building will essentially not move at all and stays in place. But that applies
only to forces underneath the building. What would happen if the outer walls of the building were still
directly connected to the ground as in any ordinary building? The ground shaking would still affect the
building despite the base isolators, because the ground vibrations would excite the outer walls from the
sides. The best way to prevent the walls from being shaken is to separate them entirely from direct
contact with the ground – and the easiest way to achieve that is to dig a deep trench around the
structure, in short, to protect the building with a moat like a medieval fortress. That is exactly what the
engineers have done with the Hearst Memorial Mining Building. It is completely surrounded by such a
trench, which, unlike the classic moats, is dry and not filled with water. All around the building the
trench is covered by dark grey concrete slabs, except at the western side entrance, where one can look
into the moat through the iron bars at the underpass.
Retrace your steps to the stairs in front of the building and continue uphill for a short distance. Turn left around
the corner of the building, walk about 100 ft on the street along its east side. Walk until you reach a heavily
secured steel gate on the right (eastern) side of the street. This is the Lawson Adit, point 2 in figure 2.
2.
Lawson Adit
In order to prepare its graduates for their professional lives in and around mines, UC Berkeley’s College
of Mining could not just rely on teaching theory. The students had to learn how to lay out and construct
a mine, how to blast their way into
rocks, how to shore up the hollows
they created. Perhaps most
importantly they had to learn how to
adapt to hours of hard work
underground in dark, wet and
poorly ventilated conditions. Hence
in 1916 Frank Probert, a newly
appointed Professor of Mining,
started his students in digging a
demonstration and teaching mine on
campus. He did not have to venture
far from the Hearst Memorial
Mining Building, because the foot of
the Berkeley Hills lies just a few a
dozen feet to the east. The mine
entrance – where you are standing
now – is right across from the
northeastern door of the building.
Fig. 2.1: Students in front of the Lawson Adit
before a mine rescue exercise.
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Over the years, classes of the students dug a 200 ft long horizontal adit eastward into the hills to
provide “sound, practical training in drilling, drifting, blasting, timbering, and mine surveying” as the
classes were advertised in the catalogue.
Students also had to become familiar with the technical language miners use. The word “adit” describes
a horizontal passage leading into a mine – in contrast to a “shaft”, which is a vertical passage. Adit is also
different from a “tunnel”, which has both an entrance and an exit. The adit here was named after
Andrew Lawson, a Berkeley geologist who lead the team of eminent scientists studying the aftermath of
the Great San Francisco Earthquake of 1906. Starting in 1914 Lawson was also the Dean of the College of
Mining for four years.
In the late 1930’s when new campus
buildings were planned east of
Gayley Road, questions were raised
about the stability of the slopes after all, the Hayward Fault was
only a few yards away from the
proposed building sites. In order to
investigate the geologic conditions,
UC Berkeley geologist George
Louderback had the adit extended
by 700 ft until it reached the
Hayward Fault. He was surprised
by what he found:
– near what is now Stern Hall and
Foothill Student Housing the fault
was split into at least two branches,
– the traces were defined by a
peculiar mix of serpentine and
metamorphic rocks.
Fig. 2.2: Original plan for the Lawson Adit from 1916
He also discovered several accumulations of rounded cobbles similar to those found in Strawberry
Canyon further to the southeast. Louderback interpreted these as exposures of the offset of Strawberry
Creek, indicating a displacement of more than 600 ft north along the Hayward Fault (see also section 5).
After Louderback’s extension, the adit was eventually abandoned. Today much of it has collapsed and it
is deemed unsafe to enter the mine. However, the Berkeley Seismological Laboratory (BSL) has plans to
place a seismic monitoring station into the adit.
Walk back to the Mining Circle and take a very sharp, almost 180 degree turn to the left. Then walk across the
parking lot of Donner Laboratory until you reach a stairway. Climb the stairs to the top and turn left. After about
20 yds, Founders’ Rock is on your right.
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3.
Founders’ Rock
UC Berkeley’s lore has it that the campus and by default the entire University of California system was
founded on April 16th, 1860, at this unique rock outcrop now hidden under trees and behind bushes at
the corner of Hearst Avenue and Gayley Road. Never mind that the actual founding of the University
happened on March 23rd, 1868, when then Governor Henry Haight signed into law the Charter Act,
which the State Assembly had passed a few weeks earlier. And also ignore that the commemorative
plaque inserted into the rock does not mention UC Berkeley at all but one of its predecessors, the
College of California. Nevertheless, this location is special to the University, being the highest point
above sea level in the northeast corner of the original campus. The view across campus and over the San
Francisco Bay must have been spectacular before Cory Hall was built in 1950 obstructing the overlook.
And the oddly shaped outcrop itself is definitely worthy of being called Founders’ Rock.
Fig. 3.1: Founders’ Rock at the corner of Hearst Avenue and Gayley Road.
While its north and east sides are thickly covered with moss and lichen, the west side reveals the rock’s
origin. It is a reddish volcanic rock very rich in silica. Such rocks with high silica content are called
rhyolite. Looking at it from up close it seems to be volcanic ash baked together with small fragments of
other volcanic material. These two observations make Founders’ Rock a “volcanoclastic welded tuff”
with rhyolitic composition.
But where does this strange outcrop come from, when there is no volcano in sight anywhere on
campus? One plausible hypothesis is based on the fact that Founders’ Rock is very similar to a rock type
from the Jurassic period, which was quarried for decades in the Leona Quarry at the upper end of
Hegenberger Road in Oakland, the so-called Leona rhyolite. The tectonic movement of the Hayward
Fault, so the hypothesis goes, carried the rock to its current location almost 10 miles northwest of the
quarry. It this is true, then Founders’ Rock formed when dinosaurs still roamed the planet, which
predates the founding of the University by a mere 150 million years.
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Confirming this hypothesis, however, is not that easy. Figure 3.2
shows what geologists call a “thin section” of a small piece of
Founders’ Rock. It is less than a tenth of an inch thick and molded
into clear plastic, so that light can shine through it. The section
reveals the reddish color of the rock, but also shows clear veins
which are filled with mineral called calcite. When the author of this
guide asked Paul Renne, the Director of the Berkeley Geochronolgy
Center, to determine the age of this rock, he responded: “This rock
has a tortured history. It is completely recrystallized and
metasomatized, to the point that I can’t tell what kind of rock it was
originally. It may have undergone major deformation and brittle
shear but the texture is so heavily overprinted with carbonate and
other secondary minerals that even this is hard to say.” It seems
that for right now Founders’ Rock shall remain an enigma.
Fig. 3.2: Thin section of a small
piece of Founders’ Rock
Walk southeast on Gayley Road until you reach the intersection with Stadium Rim Way, where you turn left. Walk
uphill to the end of the parking garage under the Maxwell Family Field across from Bowles Hall. Turn right at the
stop sign there and walk towards the stadium. At the end of the parking row on your left an asphalted walkway
leads gently uphill. Get on this walkway. Just before you reach to top of the walkway, you’ll see a concrete box
with a steel lid on your right. This is our stop 4 in figure 2.
4.
Seismic Borehole Station CMSB
A key element to understanding and classifying the behavior of an earthquake fault is to monitor its
seismic activity. The BSL operates several extensive networks of
seismometers in Northern California. One of these networks
covers the Hayward Fault. Currently, you are standing in front
of one of the most important components of this network, where
a seismometer is sunk into a borehole, which penetrates directly
into the active fault. This borehole is almost 600 ft deep, which
its bottom is about 150 ft below sea level. The seismometer is one
of the few seismic sensors in the world deployed directly into an
active fault. The station is named “CMSB” after the California
Memorial Stadium.
Typically seismometers are placed in small concrete vaults
directly on or at a maximum of a few feet below the ground.
There are however special seismometers which can be placed
deep into water filled boreholes. They are of a slim, cylindrical
design capable of withstanding several thousand pounds of
water pressure. The latest seismometer sunk into this borehole is
shown inside the red ellipse in figure 4.1 during its deployment
in August 2016.
There are two reasons why seismologists deploy seismometers
in deep boreholes. At depth the seismic noise (ground
vibrations) generated by the footsteps of thousands of football
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Fig. 4.1: Borehole Seismometer
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fans or by cars and trucks driving by is greatly reduced, which makes for clearer recordings of even the
smallest earthquakes (see figure 4.3). A deep deployment also brings the seismometer closer to the
earthquake sources, which further increases its detection capability.
Like any other seismometer, such borehole sensors can be overwhelmed, when a strong earthquake
occurs close by. They clip and the data they collect become useless to seismologists. In order to still be
able to “catch” strong local earthquakes, BSL engineers have placed an additional sensor into the
concrete vault built around the wellhead of the borehole. Such accelerometers (see figure 4.2) are also
called strong motion sensors, because they are designed to record strong earthquakes with a high
fidelity.
Together, the highly sensitive borehole sensor and the
accelerometer at the surface are able to record the full
spectrum of the earthquakes which are expected in the
Berkeley section of the Hayward Fault.
Fig. 4.2: A view into the concrete vault at the wellhead.
An example of a recording of a very small earthquake is
shown in figure 4.3. The epicenter of this quake with a
magnitude of 1 was about 900 yards north of the
borehole at the westernmost edge of the Lawrence
Berkeley National Laboratory. The quake occured on
the Hayward Fault at a depth of more than 5 miles.
Fig. 4.3: Recording of a micro-earthquake with magnitude 1 by the borehole seismometer at CMSB.
The time marks along the horizontal axis are in seconds. The P-waves arrives between 18:28:34 and 18:28:35,
the S-waves follow a second later.
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5.
The California Memorial Stadium
The California Memorial Stadium, like the Hearst Memorial Mining Building (see section 1), was
designed by John Galen Howard. It is a tribute to UC Berkeley alumni who died in World War I. It is
located at the base of the Berkeley Hills directly at the mouth of Strawberry Canyon. This spot on the
easternmost part of the campus was chosen after a more convenient location in downtown Berkeley was
rejected by local merchants. When construction of the sports arena commenced in December 1922 the
University’s administration was fully aware that the future stadium would straddle the Hayward Fault.
Fig. 5.1: A view upstream of Strawberry Canyon around 1870 along what is now
Centennial Drive. Panoramic Hill occupies the right side of this photograph.
How did the landscape in this area look, before the first dirt was excavated? Strawberry Canyon
was still largely undeveloped, except for a dairy farm where the Botanical Garden is located today.
On Panoramic Hill to the south of the creek, Fredrick Law Olmsted, the landscape architect of
Golden Gate Park and New York’s Central Park fame, had – at the University’s request – laid out a
gracious residential neighborhood. At the base of the Berkeley Hills where Strawberry Creek
encountered the Hayward Fault its straight downhill flow was blocked by a shutter ridge,
transported there by the right lateral movement of the Hayward Fault. As a consequence, the creek
turned sharply to the northwest for about 1100 ft, before it resumed its westward downhill flow.
As with many other creeks on the west side of the East Bay Hills the bed of Strawberry Creek is an
offset stream channel.
Howard managed to squeeze the large stadium with its more than 72,000 seats right into the
depression caused by the erosion of Strawberry Creek where its bed bends to the northwest. This
was exactly the spot for which Frank Soulé, who would later become the first dean of UC
Berkeley’s College of Civil Engineering, had in 1875 proposed to dam Strawberry Creek into a
reservoir to secure the drinking and irrigation water supply for the growing campus (see figure
5.2). The plan for the reservoir, however, never came to fruition.
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Fig. 5.2: Map of the Strawberry Creek area by Frank Soulé from 1875. The fault is highlighted in red.
The area where Soulé proposed a drinking water reservoir is marked in blue. This is exactly the spot
where the stadium was built 48 years after this map was drawn
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To build the stadium Howard made use of the natural bowl shape. In addition he cut away a section of
what is now Tightwad Hill at the base of the Berkeley Hills. It consists of sandstone from the Great
Valley Sequence of the Cretaceous period. For their work the engineers used hydraulic mining
techniques similar to those developed during the Californian Gold Rush. The newly created slope was
turned into the foundation for the bleachers on the east side of the field. At the same time Strawberry
Creek was diverted into a 4 ft diameter culvert. It initially runs under the stadium and then turns west
(downhill) where the parking garage below Maxwell Family Field is today. After a total length of 1450
ft the culvert daylights near the Women’s Faculty Club (blue circle in figure 2). From there Strawberry
Creek runs through campus as a lovely gurgling brook. Because the capacity of the culvert proved
insufficient during the Christmas Floods of 1964, a larger bypass was constructed under Stadium Way.
Fig. 5.3, left panel: A view from the northwest of the construction site in early 1923. The ditch seen in the lower
left is the offset bed of Strawberry Creek, which also marks the fault line of the Hayward Fault. Right panel:
opposite view to the northwest in an earlier phase of the construction. Horse drawn carriages were used to remove
excess excavation material. The Campanile can be seen faintly in the upper left.
Because the approximate location of the Hayward Fault, its potential for significant earthquakes were
known at the time of construction, Howard adapted the design of the stadium accordingly. He placed
expansion joints in the stadium exterior walls mainly at the points where the wall intersected the fault.
We will see examples at points 5.2 and 5.4 on this tour. Despite the enormous engineering challenges,
the construction of the stadium was finished in only 11 months. The arena opened on November 24th,
1923, just in time for the Big Game against Stanford, which, by the way, the Bears won 9-0.
Over the next eight decades the Beaux Art façade of the exterior wall of the football arena became one of
UC Berkeley’s iconic symbols. In 2006 the stadium was even placed as a landmark on the National
Register of Historic Places (ref# 06001086). In the meantime the tectonic movement along the Hayward
Fault tugged relentlessly on the structure – with dire consequences. Columns in the interior had bent
and bulged, façades had cracked and during a seismic safety study the stadium received a rating of
“poor”, which means that the building had become an “appreciable life hazard” during an earthquake.
Hence in early 2010 the University’s Board of Regents approved the retrofit and the complete
renovation of the stadium.
During this reconstruction, which cost an estimated $445 million, the stadium was entirely gutted. Only
the exterior wall had to be left untouched because of the stadium’s status as a protected landmark (see
figure 5.4). The bleachers and all athletic and spectator facilities were completely rebuilt according to
the latest seismic mitigation techniques. The old press box was demolished and a new structure built in
its place, independent of the rest of the stadium.
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Fig. 5.4: During the renovation from 2010 to 2012 the stadium was entirely gutted except for the exterior wall.
This areal view from the east is looking over the stadium towards campus. When this picture was
taken the construction of the new press box had not yet commenced.
The newly renovated stadium, as we see it today, opened on September 1st, 2012 when the Cal Bears
hosted the University of Nevada’s Wolf Pack team as the season opener. This time, the Bears lost 31-24.
As of this writing not even five years have passed since the reopening of the stadium, but the Hayward
Fault has already been tirelessly at work. At the following stops we will see some of the effects which
the fault creep of a few millimeters per year has already had on the rebuilt stadium. Some signs are still
rather subtle, but given the unstoppable movement of the tectonic plates under northern California, the
small cracks and movements visible today will grow larger with each passing year.
5.1
5.2
5.3
5.4
5.6
5.5
Fig. 5.5: The Hayward Fault crosses the stadium and its surroundings along the yellow line. The orange arrows
indicate the right lateral character of the fault movement. The numbered red arrows point to stops during the
stadium tour.
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Horst Rademacher
From the borehole continue the walkway uphill for a few steps until you reach a flight of concrete stairs. Walk
down a few of these stairs, but not farther than the first platform. Stop there. This is our initial point of interest in
the stadium.
5.1
Stairway on North Side of Stadium
The stairway on which you are standing was built
during the stadium’s renovation in 2012. If you walked
the whole length of the stairway, you would not find
any cracks in the concrete steps or in the wall holding
the hand rail, except here on the first platform from the
bottom. There are several subtle, cracks crossing the
base of the platform. Much more noticeable, however,
are the cracks where at least three handrail supports are
set into the concrete wall (see figure 5.6). The reason for
these cracks is not shoddy workmanship durin
