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It's hard to imagine that anything good could come out of an earthquake. But after the shaking stops, the planet sometimes reveals some of its secrets or confronts seismologists with entirely new questions. The 1994 Northridge earthquake in Southern California continues to drive research more than four years after the magnitude-6.7 earthquake, which killed 61 people and caused more than $40 billion in damage. The direct cause was a previously unknown fault nine miles beneath Northridge, a town in the San Fernando Valley. It was a "blind" fault, one that doesn't break the surface and make itself visible. (See animations below.) To seismologists, the quake drove home the point that the thicket of known and unknown local faults in the Los Angeles Basin may represent a hazard at least as great as the main San Andreas fault to the east. Though Northridge would normally be considered "moderate" on the earthquake magnitude scale, it did tremendous physical damage. In fact, it was the costliest natural disaster in U.S. history. And, inexplicably, the shaking was unusually strong in certain spots. Sherman Oaks and Santa Monica, for instance, suffered greater damage than some towns much closer to the earthquake's epicenter. |
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