1989 Loma Prieta earthquake
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| Date | October 17, 1989 |
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| Magnitude | 6.9 Mw |
| Depth: | 18 kilometres (11 mi) |
| Epicenter location: | Forest of Nisene Marks State Park, California |
| Countries/ regions affected |
United States (San Francisco Bay Area) |
| Max. Intensity: | VIII - Destructive |
| Casualties: | 67 killed |
The Loma Prieta earthquake, also known as the Quake of '89 and the World Series Quake, was a major earthquake that struck the San Francisco Bay Area of California on October 17, 1989 at 5:04 p.m. Caused by a slip along the San Andreas Fault, the earthquake lasted approximately 15 seconds and measured 6.9 on the moment magnitude scale (surface-wave magnitude 7.1 on the richter scale).[1] The quake killed 67 people throughout northern California, injured 3,757 people and left some 8,000[2] to 12,000 people homeless.[3]
The earthquake occurred during the warm up for the third game of the 1989 World Series, coincidentally featuring both of the Bay Area's Major League Baseball teams, the Oakland Athletics and the San Francisco Giants. This was the first major earthquake in America to be broadcast on live television.
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[edit] Epicenter
The epicenter of the quake was in Forest of Nisene Marks State Park in Santa Cruz County, an unpopulated area in the Santa Cruz Mountains (geographical coordinates ), approximately 4 km (2-3 miles) north of unincorporated Aptos and approximately 16 km (10 miles) northeast of Santa Cruz. The quake was named for the nearby Loma Prieta Peak which lies 8 km (5 miles) to the northeast in Santa Clara County.
Photo by C.E. Meyer, USGS
[edit] Injuries and fatalities
57 deaths were directly caused by the earthquake, but six further deaths were ruled to be caused indirectly.[4] In addition, there were 3,757 injuries as a result of the earthquake. The highest concentration of fatalities, 42,[5] occurred in the collapse of the Cypress Street Viaduct on the Nimitz Freeway (Interstate 880), where a double-decker portion of the freeway collapsed, crushing the cars on the lower deck. One 50-foot (15 m) section of the San Francisco-Oakland Bay Bridge also collapsed, causing two cars to fall to the deck below, leading to the single fatality on the bridge. The bridge was closed for repairs for a month and one day, reopening on November 18. While the bridge was closed, ridership on Bay Area Rapid Transit and ferry services soared, along with traffic levels on nearby bridges such as the San Mateo Bridge, Richmond-San Rafael and the Golden Gate.
When the earthquake hit, Game 3 of the 1989 World Series baseball championship was just starting. Due to the unusual circumstance that both of the World Series teams (the San Francisco Giants and Oakland Athletics) were based in the affected area, many people had left work early or were staying late to participate in after-work group viewings and parties. As a consequence, the usually crowded freeways were experiencing exceptionally light traffic. If traffic had been normal for a Tuesday rush hour, injuries and deaths could have been higher. The initial media reports failed to take into account the game's effect on traffic and initially pegged the death toll at 300, a number that was corrected in the days after the earthquake.[6]
[edit] Damage
The earthquake caused severe damage throughout the San Francisco Bay Area, most notably in San Francisco and Oakland, but also in many other communities throughout the region, including Alameda, San Mateo, Santa Clara, San Benito County, Santa Cruz, and Monterey Counties. Major property damage in the Marina District 60 miles (95 km) from the epicenter resulted from liquefaction of soil used to fill waterfront properties. Other effects included sand volcanoes, landslides, and ground ruptures. 18,306 homes and 2,575 businesses were damaged. In Santa Cruz, close to the epicenter, 40 buildings collapsed, killing at least six people.
Given the distance between the quake's epicenter and some of the worst-hit areas, geologists were surprised at the severity of the resulting damage. Subsequent analysis indicated that the damage was due to the amplification of the earthquake's Seismic waves by waves reflecting off the deep (about 24 km(15 miles)) discontinuities in the Earth's surface.
The quake caused an estimated $6 billion in property damage, becoming the most expensive natural disaster in U.S. history at the time. It was the largest earthquake to occur on the San Andreas Fault since the great 1906 San Francisco earthquake. Private donations poured in to aid relief efforts and on October 26, President George H.W. Bush signed a $3.45 billion earthquake relief package for California.
[edit] Marina District
Photo by J.K. Nagata, USGS
Extensive damage occurred in San Francisco's Marina District. Several apartment buildings and other multi-story homes were damaged heavily and many expensive homes collapsed. The Marina district was built on filled land made of a mixture of sand, dirt, rubble, and other materials (much of it from rubble bulldozed into the bay after the 1906 San Francisco earthquake), containing a high percentage of groundwater. This resulted in earthquake liquefaction, and the earthquake's shockwaves rippled the ground more severely. Multi-story buildings shook violently and many that had inadequately reinforced garages on the first floor had their heavy upper stories fall into that floor. In some instances, only the top floor was left intact, having spilled into the road, crushing parked cars, trees, and light poles.
Fires raged in some sections of the city as water and gas mains broke. San Francisco's fireboat (the Phoenix) was used to pump salt water from San Francisco Bay through hoses dragged through streets by citizen volunteers. Power was cut to most of San Francisco and was not fully restored for several days.
At the intersection of San Francisco's Beach and Divisadero Streets, a gas main rupture caused a major structure fire. The fire department selected bystanders to help run fire hoses from a distance because the nearby hydrant system failed. Water from the bay was shot at the burning buildings by fireboats similar to those used to put out fires caused by the 1906 earthquake. In collapsed buildings that did not catch fire, rescue teams searched the fallen buildings thoroughly, pulling out survivors from underneath splintered wood and other debris. Most of the apartment structures that collapsed were corner units, with garage doors lined up on the exposed corners. Not originally part of the buildings, but installed some time after the buildings were built, the garage doors weakened the first-story walls, causing the stiff, wood-frame buildings to buckle, crack, and crash into the streets. There were about five deaths from Marina District apartment fires and collapses. One family lost their baby boy who was trapped underneath their collapsed apartment.
[edit] Santa Cruz and Monterey Counties
Photo by C.E. Meyer, USGS
In Santa Cruz, the Pacific Garden Mall was irreparably damaged, with falling debris killing three people. When the earthquake struck, the brick facades of the historic buildings tumbled into the streets, while buildings slammed against one another and crumbled in reaction to the lengthy temblor. 31 buildings were ruined enough to warrant demolishing; seven of which had been listed in the Santa Cruz Historic Building Survey. The four oldest had been built in 1894; the five oldest had withstood the 1906 San Francisco earthquake.[7]
Immediately, a large number of citizens began to work attempting to free victims from the rubble of Ford's Department Store and the Santa Cruz Coffee Roasting Company, both of which had collapsed inward on customers and employees alike. Two police officers crawling through voids in the debris found one victim alive and another dead inside the coffee house. Santa Cruz beach lifeguards assisted in moving the victims. Police dogs were brought in to help locate further victims. A woman was found dead inside Ford's.[8] At the coming of night, public search operations were called to a halt because of unsafe conditions, with fire department personnel continuing their primary search operations by flashlight and generator light. The citizens that had been initially helpful soon became seen by police and fire officials as a hindrance to operations, with frantic coworkers and friends of a coffee house employee who was considered trapped under the rubble continuing their efforts in the dark.[9] Police arrested those who refused to stop searching; this became a political issue in the coming days.[10] The body of the young woman coffee worker was found under a collapsed wall late the next day.[11]
During the first few days following the quake, power was out to most Santa Cruz county subscribers and some areas had no water. Cell phone service remained online, providing a crucial link to rescue workers. Widespread search operations were organized to find possible victims within fallen structures. As many as six teams of dogs and their handlers were at work identifying the large number of damaged buildings that held no victims.
There was significant structural damage to beachfront villas of Capitola Village, when the fireplaces and end-walls of a landmark row-style hotel collapsed onto the sidewalks. The quake claimed a number of lives in Watsonville. Many older wooden structures were knocked off of their foundations and collapsed. Many residents were displaced from their homes. The earthquake also destroyed several buildings in the Old Town district of Salinas. In Monterey, windows were shattered in many homes and businesses and several historical structures were damaged.
[edit] San Francisco-Oakland Bay Bridge
The San Francisco-Oakland Bay Bridge suffered relatively minor damage, as a 50-foot (15 meter) section of the upper deck on the eastern side crashed onto the deck below. The quake caused the Oakland side of the bridge to shift 18 centimeters (7 inches) to the east, and caused the bolts of one section to shear off, sending the small part of the roadbed crashing down like a trapdoor. When that part of the bridge collapsed, a few upper deck motorists drove into the hole but landed safely on the lower deck. Traffic on both decks came to a halt, blocked by the section of roadbed. Police began unsnarling the traffic jam, telling drivers to turn their cars around and drive back the way they had come. Eastbound drivers stuck on the lower deck between the collapse and Yerba Buena Island were routed up to the upper deck and westward back to San Francisco. A miscommunication made by police at Yerba Buena Island directed some of the drivers in the wrong direction; they were directed to the upper deck driving east toward the collapse site. One of the drivers didn't see the gap in time; the car plunged over the ledge and smashed onto the collapsed roadbed. The driver died and the passenger was seriously injured.[12][13] On November 18, the collapsed section was removed and replaced, and the bridge was re-opened.
[edit] Cypress Structure
Photo by H.G. Wilshire, USGS
The worst disaster of the earthquake was the collapse of the Cypress Viaduct in West Oakland. 40 people died and many more were injured.
Built in the late 1950s, the Cypress Viaduct (a small stretch of the I-880 Nimitz Freeway) was a double-decker freeway system that was relatively innovative when it was first constructed. Because little attention had been paid to strengthening it in case of a major earthquake, the freeway was changed very little from when it was built. Like the Marina District, the land the Cypress Viaduct was built on was simply filled marshland. When the earthquake hit, the shaking was amplified in those areas, causing more damage than would have normally occurred if the land were bedrock.
With the combination of outdated earthquake standards and unstable ground, the freeway buckled and twisted to its limits before the support columns failed and sent the upper deck crashing to the lower deck. In an instant, over forty people were crushed in their cars. Cars on the upper deck were tossed around violently, some of them flipped sideways and some of them dangling at the edge of the highway. Appearing as though a "bomb had been exploded on the structure," the gigantic freeway was in ruins, with chunks of concrete in the streets below, steel rebar twisting out, and thick smoke coming out from in between the pancaked roadbeds. Nearby residents and factory workers came to the rescue, climbing onto the wreckage and pulling trapped people out of their mangled cars from under a four-foot gap in some sections. Employees from Pacific Pipe (a now-shuttered factory adjoining the freeway) drove heavy lift equipment to the scene and started using it to raise sections of fallen freeway enough to allow further rescue. Hard-hatted factory workers continued their volunteer operation without stopping night and day until October 21, 1989 when they were forced to halt as President George H. W. Bush and Governor George Deukmejian viewed the damage.[14]
Rebuilding the freeway took eight years. In the meantime, traffic detoured through nearby I-980. Instead of replacing I-880 over the same ground, Caltrans rerouted the freeway further west around the outskirts of West Oakland. Street-level Mandela Parkway now occupies the previous roadbed of the Cypress Structure.
[edit] 1989 World Series
The earthquake had been "predicted" in the morning edition of The San Jose Mercury News in a column by Kevin Cowherd (of The Baltimore Sun). He was discussing the fact that the Oakland Athletics and the San Francisco Giants were playing each other in the 1989 World Series at Candlestick Park that day. The quote from his column read: "... these are two teams from California and God only knows if they'll even get all the games in. An earthquake could rip through the Bay Area before they sing the anthem for Game 3,"— which was precisely when the quake occurred.
It is one of the few times that the onset of an earthquake of such magnitude has occurred during a live network television broadcast. The Series was being televised that year by U.S. network ABC. At the moment the quake struck, sportscaster Tim McCarver was narrating taped highlights of the previous Series game. Viewers saw the video signal begin to break up, heard McCarver repeat a sentence as the shaking distracted him, and heard McCarver's colleague, Al Michaels exclaim, "I'll tell you what -- we're having an earth--." At that moment the feed from Candlestick Park was lost. The network put up a green ABC Sports graphic as the audio was switched to a telephone link. Michaels cracked, "Well folks, that's the greatest open in the history of television, bar none!" accompanied by the cheering of fans who had no idea of the devastation elsewhere. ABC then switched to their "rain delay" backup program, The Wonder Years, while attempting to restore electricity to their remote equipment. After about 15 minutes, and with anchorman Ted Koppel in position in Washington, D.C., ABC began continuous news coverage. Michaels (who had extensive knowledge of the Bay Area from his time as a San Francisco Giants broadcaster), effectively became an on-scene reporter, narrating video shot by the ABC Sports cameras and the Goodyear Blimp from the safety of the TV truck. Michaels was later nominated for an Emmy Award for these news broadcasts.
Fewer than half of the 65,000+ fans had reached their seats, lessening the load on the structure of the stadium. There had also been a seismic strengthening project previously completed on the upper deck concrete windscreen. Fans reported that the stadium moved in an articulated manner as the earthquake wave passed through it, that the light standards swayed by many feet, and that the concrete upper deck windscreen moved in a wave-like manner over a distance of several feet. As soon as the shaking stopped, the assembled crowd, unaware of the tragic destruction just beginning to be revealed around the rest of the Bay Area, roared loudly. A few minutes later they yelled "Let's play Ball, Let's play Ball!" However, the game was called and the Series was postponed for 10 days.
After the shaking subsided, many of the players for both the Athletics and Giants immediately searched for and gathered family and friends from the stands (while still in full uniform) before evacuating the facility altogether.
KGO-TV, the local San Francisco television station of ABC (the national network broadcasting the game) was the first of the local Bay Area television network affiliates to cover the earthquake after the game was postponed (soon afterward, all of the major network stations broadcast continuously for several hours without interruption, providing live news reports and updates) and the coverage was aired live through ABC News.
Because of the importance of the World Series as a national sporting event, many members of local, regional and national broadcast media were in attendance and would later broadcast their observations of the aftermath of the earthquake to their viewers.
[edit] Other notable events
The Goodyear blimp, in San Francisco to cover the World Series, was the first blimp to be airborne over the location of a major earthquake. The pilots of the blimp reported that the blimp bounced during the quake (confirmed by onboard sensors and cameras) almost as if it were on the ground, the first confirmation that the air column above an earthquake is affected by the movement of the ground underneath.
Once the quake ended, the Goodyear blimp became the primary source of visual information, as Bay Area airports were closed. The blimp was the first to report the collapsed section of the Bay Bridge as well as many other major collapses and surveys of damaged areas. The information that the blimp's pilots and cameras provided to emergency workers was crucial to locate the areas of greatest need.
[edit] Effects on transportation
The Loma Prieta earthquake irrevocably changed the San Francisco Bay Area's transportation landscape. Not only did the quake force seismic retrofitting of all San Francisco Bay Area bridges, it caused enough damage that some parts of the region's freeway system had to be demolished. In some cases, the freeways in question had never been completed, terminating in mid-air; in that regard, the quake provided the impetus to deal with regional transportation problems that had gone largely unsolved for decades.
- San Francisco-Oakland Bay Bridge, Interstate 80: The Bay Bridge was repaired and reopened to traffic in just one month. However, the earthquake made it clear that the Bay Bridge, like many of California's toll bridges, required major repair or replacement, for long-term viability and safety. Construction on a replacement for the eastern span would not begin, however, until January 29, 2002. As of 2005, news accounts estimate that the project will not be completed by 2011 due to the California budget crisis. (For discussion, see also San Francisco-Oakland Bay Bridge).
- Cypress Street Viaduct/Nimitz Freeway, Interstate 880: The double-decked Cypress Street Viaduct, Interstate 880 was demolished soon after the earthquake, and was not rebuilt until July 1997. The rebuilt highway was a single- rather than double-decker structure, and was re-routed around the outskirts of West Oakland, rather than bisecting it, as the Cypress Street Viaduct did. The former route of the Cypress Street Viaduct was reopened as the Mandela Parkway.
- Embarcadero Freeway, State Route 480: The earthquake forced the closure and demolition of San Francisco's largely unloved Embarcadero Freeway (State Route 480); this demolition opened up San Francisco's Embarcadero waterfront to new development. The concrete freeway, which ran right along San Francisco's waterfront and had never been completed, was replaced with a ground-level boulevard.
- Southern Freeway, Interstate 280: Seismic damage also forced the long-term closure of Interstate 280 in San Francisco (north of US 101), another concrete freeway which had never been completed to its originally planned route. The highway remained closed for seven years, with its repair facing numerous delays.
- Central Freeway, U.S. Route 101: San Francisco's Central Freeway (part of US 101 and a key link to the Bay Bridge skyway) was another concrete double-deck structure which faced demolition due to safety concerns. Originally terminating at Franklin Street and Golden Gate Avenue near San Francisco's Civic Center, the section past Fell Street was demolished first, then later the section between Mission and Fell Streets. The section from Mission Street to Market Street was rebuilt (completed September 2005) as a single-deck elevated freeway, touching down at Market Street and feeding into Octavia Boulevard, a ground-level urban parkway carrying traffic to and from the major San Francisco traffic arterials that the old elevated freeway used to connect to directly, including Fell and Oak Streets (which serve the city's western neighborhoods) and Franklin and Gough Streets (which serve northern neighborhoods and the Golden Gate Bridge).
- State Route 17: The mountain highway was closed for about 1 month due to landslide. The highway is very close to the epicenter and it crosses the San Andreas Fault.
- State Route 1: In Watsonville, the Struve Slough bridge collapsed on itself with concrete/steel support columns punching through the bridge deck like toothpicks. The highway was closed for several months until it could be demolished and rebuilt. Another section of Highway 1 through Monterey had to be rebuilt following the earthquake as well. Additionally, the bridge carrying Highway 1 over the Salinas River near Fort Ord was damaged and subsequently rebuilt.
- Bay Area Rapid Transit: The BART rail system, which hauled commuters between the East Bay and San Francisco via the Transbay Tube, was virtually undamaged and only closed for post-earthquake inspection. As one of the few ways into San Francisco in the days following the earthquake, ridership increased by 90,000 in the week after the earthquake (from 218,000 to 308,000).
- Transbay Ferries: Ferry service between San Francisco and Oakland, which had ended decades before, was revived during the month-long closure of the Bay Bridge as an alternative to the overcrowded BART. Alameda was a third terminal. The passenger-only service proved popular and still continues as of 2008, with a more recent extension to Vallejo on San Pablo Bay.
[edit] Science of the earthquake
[edit] Magnetic disturbances
The Loma Prieta earthquake was preceded by significant disturbances in the background magnetic field strength nearby. Large increases in extremely low frequency field strength were observed about 7 kilometers from the epicenter, up to two weeks in advance of the actual event. The measurement instrument was a single-axis search-coil magnetometer that was being used for research on radio communications with submarines by Prof. Antony C. Fraser-Smith of Stanford University. Signal strengths 20 times higher than normal were observed on October 3, rising to 60 times normal about three hours before the earthquake.[15]
[edit] Geological data anomalies
A prediction of the Loma Prieta earthquake, by retired geologist Jim Berkland of the U.S. Geological Survey, appeared in a newspaper article four days before the event. The article, entitled "Is 'World Series' Quake Coming?", was published in the Gilroy Dispatch on 13 October 1989.
Berkland based his predictions on anomalies in tidal information, gravitational data, animal behavior, and other sources.[16]
Photo by H.G. Wilshire, USGS
[edit] See also
[edit] References
- ^ USGS. The October 17, 1989, Loma Prieta, California, Earthquake—Selected Photographs
- ^ SFGate.com. AFTER THE FALL: The earthquake shattered the Bay Area, but the cities hardest hit are now mostly rebuilt -- and the scars are hidden deep below the surface. Carl Nolte, Chronicle Staff Writer. Sunday, October 17, 1999
- ^ San Francisco Earthquake History 1915-1989
- ^ Profile of mortality from the 1989 Loma Prieta earthquake using coroner and medical examiner reports.. Disasters. (1994-06). Retrieved on 2006-10-17.
- ^ Cypress Viaduct Freeway.
- ^ 1989: Earthquake hits San Francisco.
- ^ Santa Cruz Public Libraries. Local History. Buildings Demolished in Downtown Santa Cruz as a Result of the Damage from the 1989 Loma Prieta Earthquake
- ^ Santa Cruz Public Libraries. Local History. Photograph Collection: rs009. The front of Ford's Department Store on the corner of Pacific Avenue and Cathcart Street. A woman inside the store died from falling debris during the earthquake. Ford's was later razed. Date: October 18, 1989. Courtesy of Ray Sherrod.
- ^ Santa Cruz Public Libraries. Local History. Log of Emergency Response Operations. Tuesday, October 17, 5:04PM, 15-second earthquake!
- ^ sfmuseum.org. Edward J. Phipps. Overview of Fire Service Responses near the Epicenter of the Loma Prieta Earthquake
- ^ Time magazine. Monday, Oct. 30, 1989. Ed Magnuson. Earthquake (6 of 8)
- ^ An Oral History of the Presidio of San Francisco During the Loma Prieta Earthquake
- ^ Viets, Jack. "They Drove Into Gap: Survivor Recalls Death Of Sister on Bay Bridge", San Francisco Chronicle, The Chronicle Publishing Co, 1989-10-27, p. A21.
- ^ New York Times. Oct 21, 1989 People Moving Gingerly As They Pick Up Pieces
- ^ http://www-star.stanford.edu/~acfs/LomaPrietaPaper.pdf
- ^ Cal Orey, The Man Who Predicts Earthquakes: Jim Berkland, Maverick Geologist--How His Quake Warnings Can Save Lives, (Sentient Publications), ISBN 1-59181-036-1.
[edit] Seismology
- USGS: Loma Prieta
- Simulation of Mercalli Scale ground motion presented as a 75 second animation (Low-Res Quicktime)
- Simulation of Mercalli Scale ground motion presented as a 75 second animation (High-Res Quicktime)
- USGS list of additional Loma Prieta sites
- Selected USGS photographs from the Loma Prieta earthquake
- Progress Toward a safer future since the 1989 Loma Prieta Earthquake
- Additional information on the Loma Prieta Earthquake
- Prof. Antony C. Fraser-Smith, low-frequency electromagnetic precursors to earthquakes
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