quarta-feira, outubro 17, 2012

Há 23 anos, o sismo de Loma Prieta afetou a cidade de S. Francisco

The Loma Prieta earthquake, also known as the Quake of '89 and the World Series Earthquake was a major earthquake that struck the San Francisco Bay Area of California on October 17, 1989, at 5:04 pm local time. Caused by a slip along the San Andreas Fault, the quake lasted 10–15 seconds and measured 6.9 both on the moment magnitude scale (surface-wave magnitude 7.1) and on the open-ended Richter Scale. The quake killed 63 people throughout northern California, injured 3,757 and left some 3,000–12,000 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.
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 37.040°N 121.877°W), 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.

Injuries and fatalities
Fifty-seven of the deaths were directly caused by the earthquake; six further fatalities were ruled to have been caused indirectly. In addition, there were 3,757 injuries as a result of the earthquake - 400 severely hurt. The highest number of fatalities, 42, occurred in Oakland because of the Cypress Street Viaduct collapse on the Nimitz Freeway (Interstate 880), where the upper level of 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 a 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.
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.

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. 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. In Santa Cruz, close to the epicenter, 40 buildings collapsed, killing six people. At the Santa Cruz Beach Boardwalk, the Plunge building was significantly damaged. Liquefaction also caused damage in the Watsonville area. For example, sand volcanoes formed in a field near Pajaro as well as in a strawberry field. The Ford's department store in Watsonville experienced significant damage, including a crack down the front of the building. Many homes were dislodged if they were not bolted to their foundations. There were structural failures of twin bridges across Struve Slough near Watsonville. 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. In the Old Town historical district of the city of Salinas, unreinforced masonry buildings were partially destroyed.
The quake caused an estimated $6 billion 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. 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.

Collapse of the Cypress Street Viaduct

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