Science Year 1991 [antikvár]

Geologists have learned a great deal about earthquakes and how to protect buildings and other structures from their destructive force. Earth's Deadly Movements BY ELDRIDGE M. MOORES t was 5:04 p.m. on Oct. 17, 1989, and the third game of baseball's World Series between the San Francisco Giants and the Oakland Athletics was about to begin at San Francisco's Candlestick Park. Geologist Marty Giaramita was sitting in the bleachers. Suddenly, he felt a vibration and heard a loud rocking and clicking sound moving toward him from the left. As he stood up to see what was causing the commotion, the bleacher seats around him began to rock violently. He felt as if he were shooting the rapids of a river—while standing up in the raft. Giaramita had experienced one of the most devastating of all nature's forces—an earthquake. The quake that rocked San Francisco, as well as nearby cities such as Santa Cruz, was the latest in a series of large earthquakes that have occurred along California's San Andreas Fault. This huge break in Earth's crust extends more than 1,200 kilometers (750 miles) from off the coast of northwestern California to the southeastern part of the state near the Mexican border. The October quake—named the Loma Prieta quake after a nearby mountain—began about 97 kilometers (60 miles) southeast of San Francisco in a section of the fault that passes through the Santa Cruz Mountains. This earthquake killed at least 62 people and caused an estimated $6 billion in damage. Earthquakes are among the most powerful events on Earth. One large earthquake may release more energy than six hydrogen bombs. Earthquakes occur everywhere in the world except in areas where the bedrock is very old and stable, such as Antarctica and central Canada. Opposite page: Rescuers search for survivors in a collapsed section of the double-decked Nim-itz Freeway in Oakland after an earthquake jolted northern California on Oct. 17, 1989. drei