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Poster Panel 00 – Earthquake Loma Prieta Strikes San Francisco Bay Area, Santa Cruz
The 6.9 Loma Prieta earthquake occurred on October 17, 1989, severely shaking the San Francisco and Monterey Bay areas. The epicenter was in the Santa Cruz Mountains near Loma Prieta peak, about 60 miles southeast of San Francisco and about 14 miles northeast of Santa Cruz.
“The 1989 Loma Prieta earthquake ended decades of tranquility in the San Francisco Bay region. It was a wakeup call to prepare for the potentially even more devastating shocks that are inevitable in the future. Since 1989, the work of the U.S. Geological Survey and other organizations has improved understanding of the seismic threat in the Bay region, promoted awareness of earthquake hazards, and contributed to more effective strategies to reduce earthquake losses. These efforts will help reduce the impact of future large quakes in the San Francisco Bay region.”
- Robert Page, U.S. Geological Survey
image caption: Oakland: Collapsed sections of Interstate Highway 880
photo: H.G. Wilshire, U.S. Geological Survey
Poster Panel 01 - Earthquake Loma Prieta - Quake Details
The Loma Prieta earthquake suddenly jolted the San Francisco and Monterey Bay areas at 5:04 p.m. on a Tuesday afternoon. Felt differently – with differing effects – in various parts of the region, the shaking lasted 10 to 15 seconds, and was of a very high magnitude, registering 6.9 on both the moment magnitude and the open-ended Richter scales. Damage was significant in Northern California, causing 63 deaths, injuring 3,757, and displaced 3,000 to 12,000 others.
caption: Shake Maps - Loma Prieta Earthquake
Poster Panel 02 - Earthquake Loma Prieta - Overview of Damage
The most costly damage caused by the Loma Prieta quake was recorded in urban areas, especially Oakland, San Francisco, and Santa Cruz. 41 deaths occurred in the structural failure of the double-decked section of highway I-880 that routed traffic to and from the San Francisco-Oakland Bay Bridge. The bridge itself suffered the collapse of a roadway section that killed one motorist. Building failure in the Marina District of San Francisco caused 5 more fatalities, and Santa Cruz sustained the catastrophic collapse of the Pacific Garden Mall, which killed 3 people.
Poster Panel 03 - Earthquake Loma Prieta - Oakland Damage
Oakland sustained some of the worst damage in the Loma Prieta quake with the collapse of the Cypress Street freeway viaduct. Built in the 1950s, this stacked roadway was not designed to withstand the severe shaking unleashed by a strong quake like Loma Prieta. Additionally, it had been built on loose soils and - due to variations in the earth’s crust - was geologically situated to receive focused energy from the quake’s epicenter. 41 people died in the collapse, and many more were injured.
The quake occurred a few minutes after 5pm on a weekday, but on this particular day two San Francisco teams were playing in a World Series game in San Francisco, and the fact that many people had already made their way to the game – or otherwise had avoided the freeway – was credited with keeping deaths and injuries as low as they were.
Poster Panel 04 - Earthquake Loma Prieta - Official Response
Aside from obvious rescue efforts that went on for days – notably at the collapsed Cypress freeway collapse in Oakland where one motorist was saved from his crushed vehicle only to die a few days later – most official governmental response centered on immediate and long-term safety concerns for the region.
The day after the quake, congressional committees requested that the National Institute of Standards and Technology (NIST) investigate earthquake damage, including the dramatic collapse of transportation infrastructure on both I-880 and the San Francisco - Oakland Bay Bridge. NIST dispatched a team to the Bay Area, where it conducted a rigorous investigation from October 18 through October 26, 1989.
Poster Panel 05 – The Official National Institute of Safety Report
The official NIST report on the Loma Prieta quake concluded that most structures in the regions affected sustained little serious damage, thanks to modern building codes and standards. Many structures, however, did not do well at all – specifically buildings and highways constructed of concrete and masonry that had not been designed to the latest codes, and which had not been subsequently strengthened. Of 65 earthquake-related deaths, collapsing structures caused 62. Landslides caused two additional fatalities, and fire claimed a single victim.
The NIST report provided the foundation upon which design improvements and construction practices would be recommended in the future for buildings and so-called lifeline structures, like freeways and buildings.
Poster Panel 06 - Immediate Effects of the Loma Prieta Quake on Hayward
The City of Hayward did not suffer much in terms of direct physical damage from the Loma Prieta quake. There was some cracking discovered at the old City Hall on Mission Boulevard, as well as a couple of structures on the Cal-State campus, but overall, infrastructure issues were minimal.
The city’s biggest problem was the need to absorb a high volume of traffic, as drivers looked for alternate routes across the Bay, due to the closure of the Bay Bridge. Since the San Mateo Bridge was the most obvious alternative for many East Bay residents, cars soon flooded Hayward surface streets looking for the best approach to the bridge.
The city was forced to embark on a series of scheduled traffic-flow accommodations to improve the new commute priorities dictated by the Loma Prieta quake (see newspaper clippings, below).
source: Hayward Fire Department
Poster Panel 07 - Long-Term Effects of Loma Prieta on Hayward: Warren Hall
Warren Hall - CSUEB’s iconic 13-story administration building - became one of the long-term casualties of the Loma Prieta quake. Built in 1971, and dedicated to campus booster E. Guy Warren in 1980, it suffered no critical structural issues at the time of the 1989 temblor. However, engineering studies in the aftermath of Loma Prieta produced a better understanding of how structures behave in serious quakes, and highlighted serious deficiencies in many Bay Area structures, including Warren Hall.
Because of these newly revealed shortcomings, as well as the building’s siting less than 700 yards from the Hayward Fault, the CSU Seismic Review Board named Warren Hall as the least earthquake-safe building in the Cal-State University system of campuses. It was eventually abandoned (administration offices moving to the current Student Administration Building), and demolished on August 17, 2013.
source: CSUEB Archives
Poster Panel 08 - Long-Term Effects of Loma Prieta on Hayward: City Hall
Dedicated on October 18, 1969, the “new” Hayward City Hall building was one of two high rises in Hayward that eventually had to be demolished because of safety concerns raised by the Loma Prieta quake [the other being Warren Hall, see adjacent panel].
Built on the site of the former Hayward Union High School on Foothill Boulevard, the new City Hall was intended to anchor a revitalized downtown Hayward. The building had been partially retrofitted to address seismic concerns at the time of the 1989 quake, but new knowledge gleaned about building behavior from Loma Prieta forced city administrators to vacate the building.
After the quake, city offices relocated to temporary quarters in the industrial district west of Hesperian Boulevard, while the construction of the current City Hall at B and Watkins Streets began, incorporating special seismic features that were a direct result of Loma Prieta’s lessons.
source: Hayward Area Historical Society
Poster Panel 09 - Earthquake Loma Prieta - Santa Cruz Damage
The epicenter of the Loma Prieta quake was located in the Santa Cruz Mountains in Nisene Marks State Park, less than 10 miles northeast of Santa Cruz.
Liquefaction of unconsolidated soil contributed to major property damage in Santa Cruz, including the Pacific Garden Mall - the entire historic district of shops sustained significant damage, and a collapsing structure resulted in the deaths of two people.
Los Gatos and Watsonville were other nearby communities in close proximity to the epicenter that also suffered damage. Most of the more than 1,000 recorded landslides and rock falls caused by the quake occurred in this epicentral zone in the Santa Cruz Mountains. One slide on nearby Highway 17 disrupted traffic for over a month.
Poster Panel 10 - Earthquake Loma Prieta - San Francisco Damage
San Francisco sustained major damage in the Marina District, and to the Embarcadero Freeway. The intensity of the quake caused liquefaction of the soil in the Marina District, a residential neighborhood constructed on the land filled site of the 1915 Panama-Pacific International Exposition. The 1989 quake thus caused many of the homes in the Marina to collapse because of the soil configuration, and firefighters had to pump water directly from the Bay to fight a resulting firestorm, since many of the city’s water mains were damaged as well.
A major legacy of the quake for San Francisco was the eventual demolition of the quake-damaged Embarcadero Freeway that had obscured the city’s view of the Bay for decades. Anti-freeway groups were finally able to pressure the Board of Supervisors to vote in favor of demolition because of the quake damage.
Poster Panel 11 - Earthquake Loma Prieta - Lessons Learned
Since the Loma Prieta shock, the U.S. Geological Survey (USGS) and cooperating organizations have intensified efforts to understand earthquake hazards and apply this new knowledge to reducing future losses. Greater attention has been focused on the Nation's urban regions threatened by strong earthquakes, because these areas have the most people at risk, the largest inventory of structures, and the densest and most complex infrastructure. Communication of earthquake-hazard information to the public and to those in business and government responsible for decisions and actions has also been strengthened.
Poster Panel 12 - Major Bay Area Quakes: 1868 Hayward Earthquake
One of the most destructive earthquakes in California history occurred on the Hayward Fault in the San Francisco East Bay on October 21, 1868. While not heavily populated at the time, there was extensive damage throughout the Bay Area.
Taking into account recent evidence that the Hayward Fault has shaken the region numerous times in the past, USGS scientists regard the Hayward Fault as a “tectonic time bomb.” They predict a quake in the 6.8 to 7.0 ranges could occur at any time.
Realizing the severe consequences such a large quake could cause in such a densely populated metro area – hundreds of deaths, thousands homeless – several organizations have stepped-up their efforts to help communities in the Bay Area to prepare for this inevitable event.
Poster Panel 13 - Major Bay Area Quakes: 1906 San Francisco Earthquake
The California earthquake of April 18, 1906 is regarded as a turning point in the understanding of earthquake behavior. It ruptured the northern end of the San Andreas Fault from San Juan Bautista to Cape Mendocino, and caused large horizontal displacements.
At a time when the understanding of plate tectonics was a half-century in the future, the significance of the fault’s behavior was not recognized in 1906, although one contemporary scientific formulation based on the quake is still held today: the elastic-rebound theory of the earthquake source.
The quake leveled much of the city east of Van Ness Avenue. Additionally, fire from a damaged chimney in the hours after the initial shaking spread rapidly causing more damage.
Poster Panel 14 – Major Bay Area Quakes: 2014 South Napa Earthquake
On the morning of August 24th, 2014 at 3:20 a.m., a major earthquake shook the Napa Valley, north of the San Francisco Bay Area. The 6.0 temblor was the largest to hit the Bay Area since the Loma Prieta earthquake in 1989. Although the shaking only lasted between 10 and 20 seconds, over 200 people were injured and considerable damage occurred to homes and businesses throughout Napa and Solano counties. Many of the historic masonry structures in downtown Napa were particularly hard hit by the shaking.
An experimental early warning system developed by the University of California at Berkeley successfully detected the P-waves generated by the earthquake and gave seismologists 10 seconds advance warning before more destructive shaking was felt.
Poster Panel 15 – Earthquake Loma Prieta – Los Gatos Damage
While there were few communities in the bay Area that were unaffected by the Loma Prieta quake, Los Gatos in the South Bay was among the hardest hit.
As in other areas of Santa Cruz County, Los Gatos suffered from being built on a floodplain that is subject to liquefaction when an earthquake strikes. Many residences that were not bolted down moved off their foundations, resulting in destroyed homes.
Many masonry buildings in downtown Los Gatos suffered major damage, while many others evidenced minor distress, including shattered windows throughout the city’s downtown area. The downtown was strewn with bricks and masonry by the quake. Luckily there were no fatalities, though one car was crushed by falling bricks. Many residents camped outside their homes following the earthquake.
Poster Panel 16 – Earthquake Loma Prieta - Watsonville Damage
The Watsonville area in the Pajaro Valley just southeast of Santa Cruz sustained major damage from soil liquefaction – evidenced in numerous sand volcanoes in a nearby strawberry field.
In downtown Watsonville, older, unreinforced buildings suffered varying degrees of damage: a large crack in the façade of Ford’s department store was dramatic evidence of how inadequately engineered buildings can behave on shifting soil.
Similarly, many homes that had not been properly bolted to their foundations jumped off their footings, causing severe damage in many cases. Additionally, the twin bridges crossing Strove Slough collapsed when the quake struck, pushing the bridge’s steel support columns through the deck of the bridge. The highway was closed for several months to effect needed repairs.
Watsonville also witnessed a fatality when a driver ran into several horses that had panicked and escaped their corral.
Poster Panel 17 – Looking Ahead – Earthquake Probabilities
The year after the 1989 Loma Prieta shock, a panel of scientists reassessed the earthquake threat to the San Francisco Bay region. Their conclusions were published in the USGS report Probabilities of Large Earthquakes in the San Francisco Bay Region, California. They projected 2-in-3 odds for one or more destructive earthquakes (magnitude 7 or larger) to strike the Bay region in the period 1990 to 2020.
Studies made since that 1990 report have added much new information for determining earthquake probabilities. Geologists have uncovered new evidence for the dates and amounts of slip of prehistoric earthquakes on the Hayward, San Andreas, and other active Bay region faults and for the amounts of movement on those faults over past millennia.
These data are incorporated in a new USGS report that estimates the locations, sizes, and probabilities of damaging Bay region earthquakes during the next 30 years (2000 to 2030).
The Great California Shakeout
graphic: Drop, Cover, Hold On
"Are You Ready to ShakeOut?"
"This document was printed under a grant from FEMA's Grant Program Directorate, U.S. Department of Homeland Security. Points of view or"
"opinions expressed in this document are those of the authors and do not necessarily represent the official position or policies of FEMA's"
"Grant Programs Directorate or the U.S. Department of Homeland Security."
"We’re all in this together…"
" On the third Thursday of October each year, you"
"can join the millions of Californians who will “Drop, Cover, and Hold On” in The Great California ShakeOut, the largest earthquake drill ever!"
" As described below, major earthquakes may happen where you work, live, or travel in"
"California. The ShakeOut is our chance to practice how to protect ourselves, and for everyone to become prepared. The goal is to prevent disasters from becoming catastrophes."
" Why is a “Drop, Cover, and Hold On” drill important? As with anything, to act quickly you must"
"practice often. You may only have seconds to protect yourself in an earthquake before strong shaking knocks you down, or something falls on you."
" Other preparedness information is on the back of this flyer and is online at"
" Everyone can participate! Individuals, families, businesses, schools, government agencies,"
"community groups, and other organizations are all invited to register."
" Register now at www.ShakeOut.org"
"This section of the San Andreas Fault in central"
"California is how most people picture faults. But many faults do not reach the surface, are under the ocean along the coast, or are covered by streets or buildings. No matter where we are in California, we must be prepared!"
"California is earthquake country!"
" California experiences earthquakes as large as"
"the 1994 Northridge or 1989 Loma Prieta quakes (or larger) twice each decade, on average."
" All areas of California have experienced"
"earthquakes in the past and will do so again in the future. There are hundreds of faults throughout the state that can have large earthquakes."
" There is a 50% chance of a magnitude 7.5 or"
"greater earthquake somewhere in California in the next 30 years (www.scec.org/ucerf)."
" While some areas and certain faults have a higher chance of earthquakes than others, the risk anywhere in California is high when compared to most areas of the country."
"The Seven Steps to Earthquake Safety"
"From Putting Down Roots in Earthquake Country, available at www.earthquakecountry.org"
"1. Identify earthquake hazards in your home, and check if you are in a tsunami hazard zone: You should secure anything heavy enough to hurt you if it falls on you, or anything that will be a significant loss if it breaks. Move heavy objects to lower locations, strap your water heater and top heavy furniture to walls, and securing electronics and valuables to tables. Do you live, work, or travel near the coast? Find out what areas are at risk of a tsunami."
"2. Create a disaster plan: Plan now what each person in your household will do before, during and"
"after an earthquake. Have a meeting place and an out-of-state contact. Learn basic first aid. Plan how to deal with the risk of fire, potential lack of utilities and basic services, and aftershocks. For those with functional or mobility needs, identify people who can assist you where you regularly spend time. Learn the natural and official warnings of a tsunami and know how to respond."
"3. Create disaster supplies kits: Everyone should have personal disaster supplies kits, which are"
"useful for many emergencies. Keep one kit in your home, one in your car, and a third at work. Your home should have a larger household kit with supplies to last three days to one week."
"4. Identify and fix your building’s weaknesses: There are several common issues that can limit a"
"building's ability to withstand earthquake shaking, such as inadequate foundations, unbraced cripple walls, soft first stories and unreinforced masonry. Seek professional retrofitting advice if your building has these issues."
"5. During earthquakes–Drop, cover and hold on: Drop to the floor, take cover under a sturdy"
"desk or table, and hold on to it firmly. If no table is nearby, drop to the floor near an interior wall and cover your head and neck with your arms and hands. Face away from windows or mirrors. Do not leave a building during an earthquake. If you use a wheelchair or have other mobility impairments, protect your head and neck with a pillow or your arms if you are able. Learn more at www.dropcoverholdon.org, including what to do in different situations. Everyone can practice what to do during earthquakes in the Great California ShakeOut (www.ShakeOut.org)."
"6. After earthquakes–Check for injuries and damage: Remain calm and take care of yourself first. If you live on the coast in a tsunami inundation zone, immediately walk to higher ground or inland away from the coast. If you are in a safe area, help others and check for damage. Learn in advance what to do about fire, leaking gas, electrical dangers, and chemical spills. Aftershocks may cause additional damage so be ready to drop, cover, and hold on."
"7. When safe, continue to follow your disaster plan: If you evacuated coastal areas - stay away"
"until officials permit you to return. When possible, if you cannot stay in your home, take your disaster kit and get to a safe location. Listen to a portable radio for news, and call your out-of-state contact. Begin your recovery by organizing your financial papers and documenting any damage."
"The Earthquake Country Alliance is a statewide partnership of earthquake experts,"
"emergency managers, business and community leaders, and others working to help"
"Californians prepare for earthquakes. Visit www.earthquakecountry.org/alliance."
"The California Emergency Management Agency is a proud leader and partner in the"
"Earthquake Country Alliance. Learn more about disaster readiness, and about"
"CalEMA’s programs and responsibilities at www.calema.ca.gov."