| Date | October 17, 1989[1] |
|---|---|
| Duration | 15 seconds |
| Magnitude | 6.9 Mw[1] |
| Depth | 11 miles (18 km)[1] |
| Epicenter | [1] |
| Countries or regions | United States (San Francisco Bay Area), (Santa Cruz County, California) |
| Max. intensity | Mostly V (strongly felt) to VII (light damage), with localized areas experiencing IX (heavy damage) to X (extreme damage)[1] |
| Casualties | 63 killed,[2] 3,757 injured[3] |
The Loma Prieta earthquake, also known as the Quake of '89 and the World Series Earthquake,[4] was a major earthquake that struck the San Francisco Bay Area of California on October 17, 1989, at 5:04 p.m. local time. Caused by a slip along the San Andreas Fault, the quake lasted 10–15 seconds[1] and measured 6.9 on the moment magnitude scale[5] (surface-wave magnitude 7.1) or 6.9 on the open-ended Richter Scale.[1] The quake killed 63[2] people throughout northern California, injured 3,757[3] and left some 3,000-12,000[1][6][7][8] people homeless.
The earthquake occurred during the warm-up practice for the third game of the 1989 World Series, featuring both of the Bay Area's Major League Baseball teams, the Oakland Athletics and the San Francisco Giants. Because of game-related sports coverage, this was the first major earthquake in the United States of America to have its initial jolt broadcast live on television.[9]
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The epicenter of the quake was in the Forest of Nisene Marks State Park in Santa Cruz County, an unpopulated area in the Santa Cruz Mountains (geographical coordinates ),[1] approximately 2–3 miles (3–5 km) north of unincorporated Aptos and approximately 10 mi (16 km) northeast of Santa Cruz. The quake was named for the nearby Loma Prieta Peak which lies 5 mi (8 km) to the northeast in Santa Clara County.[10]
Fifty-seven of the deaths were directly caused by the earthquake; six further fatalities were ruled to have been caused indirectly.[2] In addition, there were 3,757[3] injuries as a result of the earthquake—400 severely hurt.[1] The highest number of fatalities, 42,[12] occurred in the City of Oakland because of the failure of the Cypress Street Viaduct on the Nimitz Freeway (Interstate 880), where a double-deck 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, leading to the single fatality on the bridge. Three people were killed in the collapse of the Pacific Garden Mall in Santa Cruz, and five people were killed in the collapse of a brick wall on Bluxome Street in San Francisco.[4]
When the earthquake hit, the third game of the 1989 World Series baseball championship was just beginning. Because of 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 contained 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 estimated the death toll at 300, a number that was corrected to 63 in the days after the earthquake.[13]
The earthquake caused severe damage in some very specific locations in the San Francisco Bay Area, most notably on unstable soil in San Francisco and Oakland. Oakland City Hall was evacuated after the earthquake until US$80M seismic retrofit and hazard abatement work was complete in 1995.[14] Many other communities sustained severe damage throughout the region located in Alameda, San Mateo, Santa Clara, San Benito, Santa Cruz, and Monterey counties. Major property damage in San Francisco's Marina District 60 mi (97 km) from the epicenter resulted from liquefaction of soil used to create waterfront land. Other effects included sand volcanoes, landslides, and ground ruptures. Some 12,000 homes and 2,600 businesses were damaged.[1] In Santa Cruz, close to the epicenter, 40 buildings collapsed, killing six people.[15] At the Santa Cruz Beach Boardwalk, the Plunge building was significantly damaged.[16] Liquefaction also caused damage in the Watsonville area.[17] For example, sand volcanoes formed in a field near Pajaro as well as in a strawberry field.[17] The Ford's department store in Watsonville experienced significant damage, including a crack down the front of the building.[17] Many homes were dislodged if they were not bolted to their foundations.[17] There were structural failures of twin bridges across Struve Slough near Watsonville.[17] In Moss Landing, the liquefaction destroyed the causeway that carried the Moss Beach access road across tidewater basin, damaged the approach and abutment of the bridge linking Moss Landing spit to the mainland and cracked the paved road on Paul's Island.[18] In the Old Town historical district of the city of Salinas, unreinforced masonry buildings were partially destroyed.[19]
The quake caused an estimated $6 billion[1] in property damage, becoming one of the most expensive natural disasters 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.[10] 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.[8]
Four people died in San Francisco's Marina District, four buildings were destroyed by fire, and seven buildings collapsed.[9] Another 63 damaged structures were judged too dangerous to live in.[9] Among the four deaths, one family lost their infant son who choked on dust while trapped for an hour inside their collapsed apartment.[4]
The Marina district was built on filled land made of a mixture of sand, dirt, rubble, waste, and other materials containing a high percentage of groundwater. Some of the fill was rubble discarded after the 1906 San Francisco earthquake but most was sand and debris laid down in preparation for the 1915 Panama-Pacific International Exposition, a celebration of San Francisco's ability to rebound after its terrible catastrophe in 1906.[20] After the Exposition, apartment buildings were erected on the filled land. In the 1989 earthquake, the water-saturated unconsolidated mud and sand suffered liquefaction, and the earthquake's vertical shock waves rippled the ground more severely.[8]
At the intersection of Beach and Divisadero Streets in San Francisco, a natural gas main rupture caused a major structure fire.[21][22] The fire department selected bystanders to help run fire hoses from a distance because the nearby hydrant system failed. Water from the bay was pumped by a fireboat, Phoenix, to engines on the shore and used to douse the burning buildings.[23][24] The apartment structures that collapsed were older buildings that included ground floor garages, which engineers refer to as a soft story building.[25]
In Santa Cruz, the Pacific Garden Mall was severely damaged, with falling debris killing three people, half of the six earthquake deaths in the Santa Cruz and Monterey Counties.[15] Some 31 buildings were damaged enough to warrant demolition, seven of which had been listed in the Santa Cruz Historic Building Survey.[26] The four oldest had been built in 1894; the five oldest had withstood the 1906 San Francisco earthquake.[26]
Immediately, a number of civilians began to work to attempt to free victims from the rubble of Ford's Department Store and the Santa Cruz Coffee Roasting Company—both buildings had collapsed inward on customers and employees alike.[15] Two police officers who crawled through voids in the debris found one victim alive and another dead inside the coffee house.[27] Santa Cruz beach lifeguards assisted in moving the victims.[27] Police dogs were brought in to help locate further victims.[27] A woman was found dead inside Ford's.[28] The civilians who had been initially helpful soon were viewed by police and fire officials as a hindrance to operations, with frantic coworkers and friends of a coffee house employee who was thought trapped under the rubble continuing their efforts in the dark.[27] Police arrested those who refused to stop searching; this became a political issue in the coming days.[29] The body of a young woman coffee worker was found under a collapsed wall late the next day.[30]
During the first few days following the quake, electric power was out to most Santa Cruz county subscribers and some areas had no water. Limited phone service remained online, providing a crucial link to rescue workers.[29] 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.[29]
The quake claimed one life in Watsonville;[29] a driver who collided with panicked horses after they escaped their collapsed corral.[31] In other Santa Cruz and Monterey county locations such as Hollister, Boulder Creek and Moss Landing, a number of structures were damaged, with some knocked off of their foundations.[32] Many residents slept outside their homes out of concern for further damage from aftershocks, of which there were 51 with magnitudes higher than 3.0 in the following 24 hours, and 16 more the second day.[32] The earthquake damaged several historic buildings in the Old Town district of Salinas, and some were later demolished.[33]
The San Francisco – Oakland Bay Bridge suffered relatively minor damage, as a 76-by-50-foot (23 × 15 m) section of the upper deck on the eastern cantilever side crashed onto the deck below. The quake caused the Oakland side of the bridge to shift 7 in (18 cm) to the east, and caused the bolts of one section to shear off, sending the 250-short-ton (230 t) section of roadbed crashing down like a trapdoor.[34] When that part of the bridge collapsed one car drove into the hole, resulting in the death of the driver. 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 emergency workers at Yerba Buena Island routed some of the drivers the wrong way; they were directed to the upper deck where they drove eastward toward the collapse site.[4] One of these drivers did not see the open gap in time; the car plunged over the edge and smashed onto the collapsed roadbed. The driver died and the passenger was seriously injured.[21][35] Caltrans removed and replaced the collapsed section, and re-opened the bridge on November 18.[8]
The worst disaster of the earthquake was the collapse of the two-level Cypress Street Viaduct of Interstate 880 in West Oakland. The failure of a 1.25-mile (2.0 km) section[36] of the viaduct, also known as the "Cypress Structure" and the "Cypress Freeway",[4] killed 42 and injured many more.[37]
Built in the late 1950s, the Cypress Street Viaduct, a stretch of Interstate 880, was a double-deck freeway section made of nonductile reinforced concrete[38] that was constructed above and astride Cypress Street in Oakland. Roughly half of the land the Cypress Viaduct was built on was filled marshland, and half was somewhat more stable alluvium.[7] Because of new highway structure design guidelines—the requirement of ductile construction elements—instituted following the 1971 San Fernando earthquake, a limited degree of earthquake reinforcement was retrofitted to the Cypress Viaduct in 1977. The added elements were longitudinal restraints at transverse expansion joints in the box girder spans, but no studies were made of possible failure modes specific to the Cypress Viaduct.[38] When the earthquake hit, the shaking was amplified on the former marshland, and soil liquefaction occurred.[32]
During the earthquake, 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, 41 people were crushed to death in their cars. Cars on the upper deck were tossed around violently, some of them flipped sideways and some of them were left dangling at the edge of the highway. Nearby residents and factory workers came to the rescue, climbing onto the wreckage with ladders and forklifts[11] and pulling trapped people out of their mangled cars from under a four-foot gap in some sections. Some 60 members of Oakland's Public Works Agency left the nearby city yard and joined rescue efforts.[36] 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 pause as U.S. President George H. W. Bush and California Governor George Deukmejian viewed the damage.[39] The stubborn efforts of the rescue workers were rewarded just after dawn on October 21 when survivor Buck Helm was freed from the wreckage, having spent 90 hours trapped in his crushed car under the rubble.[40] Dubbed "Lucky Buck" by the local radio, Helm lived for another 29 days on life support, but finally succumbed to respiratory failure at the age of 57.[41]
Rebuilding the freeway took 11 years.[42] In the meantime, traffic was detoured through nearby Interstate 980, causing increased congestion.[42] Instead of rebuilding Interstate 880 over the same ground, Caltrans rerouted the freeway further west around the outskirts of West Oakland to provide better access to the Port of Oakland and the San Francisco – Oakland Bay Bridge, and to meet community desires to keep the freeway from cutting through residential areas.[43] Street-level Mandela Parkway now occupies the previous roadbed of the Cypress Structure.[43]
The 1989 Loma Prieta earthquake was one of the few times that the onset of an earthquake of such magnitude has occurred during a live network television broadcast, and as a result, the first moments of the earthquake were seen around the world as it happened. 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—."[31] At that moment, the feed from Candlestick Park was lost.[44] 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.[45] ABC then switched to their "rain delay" backup program, Roseanne, while attempting to restore electricity to their remote equipment. With anchorman Ted Koppel in position in Washington, D.C., ABC News began continuous coverage of the quake about 5:40 p.m. (Al Michaels, in the process, became a de facto on site reporter for ABC), at the same time as CBS News.[46] NBC News also began continuous coverage, with Tom Brokaw, about an hour later.[46] KGO-TV, a local affiliate of ABC, later won a Peabody Award for their news coverage, as did radio station KCBS (AM).[47]
In Los Angeles, ABC owned and operated station KABC chose not to air the network feed. It aired its own coverage, anchored by Mark Coogan. However, some network footage was incorporated into its coverage.
Fewer than half of the more than 62,000 fans[4] had reached their seats by the time of the quake, and the load on the structure of the stadium was lower than maximum.[48] There had also been a seismic-strengthening project previously completed[49] 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. Electrical power to the stadium was lost, forcing the game to be postponed. The series did not resume for 10 days.[48]
After the shaking subsided, many of the players on both teams immediately searched for and gathered family[48] and friends from the stands before evacuating the facility.
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 viewers around the world.[50] In addition to broadcast news, many photojournalists were present, and a collection of their photos was released as the book Fifteen Seconds: The Great California Earthquake of 1989, which was published soon after the quake to raise money for the victims.[50]
The Goodyear blimp was aloft above the ballpark to provide aerial coverage of the World Series. Blimp pilot John Crayton reported that he felt four bumps during the quake.[51]
Immediately following the earthquake, San Francisco Bay Area airports closed to conduct visual inspection and damage assessment procedures. San Jose International Airport,[52] Oakland International Airport and San Francisco International Airport all opened the next morning.[53] Massive cracks in Oakland's runway and taxiway reduced the usable length to two-thirds normal, and damage to the dike required quick remediation to avoid flooding the runway with water from the bay.[54] Oakland Airport repair costs were assessed at $30 million.[54]
San Francisco Municipal Railway (Muni) lost all power to electric transit systems when the quake hit, but otherwise suffered little damage and no injuries to operators or riders.[55] Cable cars and electric trains and buses were stalled in place—half of Muni's transport capability was lost for 12 hours. Muni relied on diesel buses to continue abbreviated service until electric power was restored later that night, and electric units could be inspected and readied for service on the morning of October 18.[55] After 78 hours, 96 percent of Muni services were back in operation, including the cable cars.[55]
The earthquake changed the Bay Area's automobile transportation landscape. Not only did the quake force seismic retrofitting of all San Francisco Bay Area bridges,[56] it caused enough damage that some parts of the region's freeway system had to be demolished.[38] Damage to the region's transportation system was estimated at $1.8 billion.[32]
The Loma Prieta earthquake was preceded by disturbances in the background magnetic field strength as measured by a sensor placed in Corralitos, California, about 4.5 miles (7 km) from the epicenter.[60] From October 5, a substantial increase in background noise was measured in the frequency range 0.01–10 Hz.[60] The measurement instrument was a single-axis search-coil magnetometer that was being used for low frequency research by Antony C. Fraser-Smith of Stanford University.[60] Signals in the range .01–.5 Hz rose to exceptionally high levels about three hours before the earthquake.[60] Though this pattern gave scientists new ideas for research into potential precursors to earthquakes, more recent studies have cast doubt on the connection, attributing the observations before the Loma Prieta quake to either an unrelated and more geographically widespread magnetic disturbance[61] or to sensor malfunctions.[62]
