1989 Loma Prieta earthquake

Loma Prieta earthquake

UTC time	??
Magnitude	7.1 Mw
Epicenter	Aptos, California
Areas affected	United States (San Francisco bay area)
Casualties	67 killed

The Loma Prieta earthquake, also known as the Quake of '89, was a major earthquake that struck the San Francisco Bay Area of California on October 17, 1989 at 5:04 p.m. The earthquake lasted approximately 15 seconds and measured 6.9 on the moment magnitude scale (surface-wave magnitude 6.1). The quake killed 67 people throughout northern California, injured 3,757 people and left more than 12,000 people homeless

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 on poop

Epicenter

The epicenter of the quake was in Forest of Nisene Marks State Park, an unpopulated area in the Santa Cruz Mountains (geographical coordinates 37.04°N 121.88°W / 37.04; -121.88), near 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.

Although much of the damage and most of the fatalities occurred in the San Francisco/Oakland area, geologists/seismologists estimate the earthquake's intensity near the epicenter at between 6.9 and 7.1 on the Richter Scale. The communities nearest the epicenter are all in Santa Cruz County.

Injuries and fatalities

67 deaths were directly caused by the earthquake, but six deaths were ruled to be indirectly caused by the temblor. In addition, there were 3,757 injuries as a result of the earthquake. The highest concentration of fatalities, 42, 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, the popular "Battle of the Bay" was just starting and 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.

Damage

The earthquake caused major damage as far away as the Marina District in San Francisco, 95 km (60 miles) away from the epicenter. It 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 that occurred in the areas more distant 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 2575 businesses were damaged. In the area close to the epicentre, 40 buildings collapsed in Santa Cruz (killing at least six people).

Given the distance between the quake's epicenter and the Bay Area, 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.

Marina District

Extensive damage occurred in San Francisco's Marina District, where many expensive homes built on filled ground collapsed (much of the fill came from rubble which was bulldozed into the bay following the 1906 San Francisco earthquake). Fires raged in some sections of the city as water 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.

In San Francisco's Marina District, several apartment buildings and other multi-story homes were damaged heavily. Because the land the Marina neighborhood sat on was filled land, the earthquake's shockwaves rippled the ground with more severity. The mixture of sand, dirt, rubble, and other materials used to make up the artificial ground contained a high percentage of groundwater which resulted earthquake liquefaction. Multi-story buildings shook violently and many that had inadequately reinforced garages on the first floor experienced their heavy upper stories falling onto that floor. In some instances, only the top floor was left intact, having spilled into the road, crushing parked cars, trees, and light poles. At the intersection of San Francisco's Beach and Divisadero Streets, there was a major structure fire, due to a gas main rupture. Bystanders were selected by the fire department 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 various 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, the garage doors that were installed quite some time after the buildings' initial construction weakened the first-story walls, causing the stiff, wood-frame buildings to buckle, crack, and crash into the streets. There were about five deaths that occurred from Marina District apartment fires and collapses. One family lost their baby boy who was trapped underneath their collapsed apartment.

Santa Cruz and Monterey Counties

Deaths in downtown Santa Cruz occurred when brick storefronts and sidewalls in the historic downtown (what was then called the Pacific Garden Mall) tumbled down on people exiting the buildings. 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 busineses and several historical structures were damaged.

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 poured into the streets, while buildings self-destructed by slamming against one another in reaction to the lengthy trembler. During the first several days, the power was out and some areas had no water. The historic streets all over coastal Santa Cruz county were filled with debris, rescue workers, and concerned evacuees. Modern downtown Santa Cruz was effectively rebuilt from scratch, much as San Francisco was rebuilt after the 1906 earthquake.

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 motorists fell into the hole, but landed safely on the lower deck, preventing them from falling into the bay. A miscommunication made by the police directed some of the drivers on the bridge in the wrong direction; instead of driving away from the collapse site, they were directed toward the collapse site. One woman captured on videotape a car going down into the hole, shortly after remarking how the police had sent her the wrong way and she had seen the hole. 23-year-old Anamafi Moala Kalushia, a one-month newlywed, had picked up her brother, Lesisita Halangahu, from San Francisco International Airport. Anamafi Moala Kalushia approached the collapse site too quickly to stop, drove the car off the ledge and smashed onto the collapsed roadbed. Halangahu was pulled to safety and eventually recovered from multiple compound fractures to both his legs. Anamafi Moala Kalushia died shortly after plunging off the upper deck. She was the only fatality on the bridge. On November 18, almost exactly one month after the earthquake, the collapsed section was removed and replaced, and the bridge was re-opened.

Failed support columns and collapsed upper deck of the Cypress Viaduct

Cypress Structure

By far, the worst disaster of the earthquake was the collapse of the Cypress Viaduct in west Oakland, right across the bay from San Francisco. In a strange twist of events, traffic was significantly light as most Bay Area fans had either flocked to game three of the 1989 World Series or to their homes to watch the game on television. As a result, rush-hour traffic was surprisingly minimal.

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 the limits before the support columns failed and sent the upper deck crashing to the bottom deck. In an instant, over forty people were crushed in their cars, with nowhere to go when the earthquake hit. 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, cars on the upper deck thrown around, and thick smoke coming out from in between the pancaked roadbeds. Nearby residents and factory workers came to the rescue, bravely 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. Police arrived soon after and told most residents to stop their rescue efforts, a move that has been widely criticized. 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.

According to engineers, the structure's weak support columns were not designed to withstand a large amount of movement. As a result, the columns exploded outward, thrusting the upper deck onto the one below. Cars on the lower deck were crushed "like beer cans," some of them being flattened to their axles. Cars on the upper deck were tossed around violently, some of them flipped sideways and some of them dangling near the edge of the highway. Cranes were used to retrieve the cars from the upper deck. Paramedics pulled the crushed victims out of their mutilated cars. In total, 40 people died in this incident. The street-level Mandela Parkway stands where the deadly freeway once stood.

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, Roseanne, 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.

See also: Major League Baseball on ABC

Fortunately, 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 as loud as if a game-winning double had been hit. 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. During this time, many Bay Area residents felt the Series should be canceled altogether out of respect for the lives lost and damage sustained, but the World Series was resumed.

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.

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.

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 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 2007, with a more recent extension to Vallejo on San Pablo Bay. Ferry service has also been extended to Marin County, with service to Sausalito and Larkspur.

Science of the earthquake

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.

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 unproven sources. His theories and methods are controversial, and are considered unreliable by mainstream scientists.

References

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

Images

• KPIX-TV San Francisco live coverage of 1989 Loma Prieta Earthquake