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The Earthquake Forecasts the New Progress of Aspect An accidental discovery has brought earthquake scientists one step close

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问题                 The Earthquake Forecasts the New Progress of Aspect
    An accidental discovery has brought earthquake scientists one step closer to being able to predict earthquakes. As part of an effort to measure underground changes caused by shifts in barometric pressure, a team of researchers found that increases in subterranean pressure preceded earthquakes along California’s San Andreas Fault by as much as 10 hours. If follow-up tests advance the findings, earthquake scientists may eventually be able to provide a few hours’ notice for people to find safe haven prior to quakes. "Predicting earthquakes is the final goal for earthquake scientists," says Feng-lin Niu, the research team’s lead author and a Rice University earthquake scientist. "This is a start."
    Reporting in the July 10 edition of the journal Nature, researchers used a high-tech equivalent of a stereo speaker lowered into a bore hole near Parkfield, Calif. , a half-mile deep and five yards from a measuring device. For two months beginning in late 2005, researchers transmitted pulse signals three times per second, from the speaker to the measuring device, calculating travel time between the two stations. Surprised scientists learned the seismic waves slowed dramatically on only two occasions: two hours prior to a magnitude-1 quake, and a startling 10 hours before a magnitude-3 quake.
    The research team theorizes that the immense amount of pressure building along the fault causes small cracks within the rock during the final hours before an earthquake, increasing rock density and slowing the transmission signals. "The more cracks you have, the slower the seismic velocity," says study coauthor Paul Silver, a geophysicist with the Carnegie Institution of Washington. Still unknown is whether there is any significance to the fact that the magnitude-3 quake had a much longer pre-seismic signal than the lower-magnitude quake, or whether it was simply because its magnitude was larger and its center closer to the sensors.
    If scientists can flesh out the new findings during future earthquakes—a two-year study at the same seismically active location begins this September—it could form the basis of a vastly improved early-warning system for quakes. Current earthquake-warning systems give just a few seconds’ notice because they detectonly P-waves, the fast-moving seismic waves that precede the more destructive waves released during a quake. Upgrading to a seismic stress meter, however, is still a long way off. "To use this for earthquake prediction, you need to know the precursor waves have a physical basis (that is, increased pressure and a pending quake) and that it’s repeatable (with a larger sample size of quakes)," Niu says. He also hopes to test whether the stress signals would still be detectable on a larger scale, with the two sensors spaced more than a few yards apart.
    Except a major effort to drill multiple, half-mile-deep bore holes along fault lines, researchers would also need to develop a surface-based detection system capable of filtering out temperature swings, precipitation and other "noise" that could confuse their seismic readings. Says Silver, "we obviously have more work to do, but we’re certainly encouraged because this is what people are looking for."
Which of the following is the best title for this passage?
选项 A、A New Clue in Predicting Earthquakes.
B、Increases in Subterranean Pressure.
C、An Accidental Discovery.
D、The Use of High-Tech Equipment in Earthquake Prediction.
答案A
解析 主旨大意题。本文主要介绍了科学家在测量其他指标时意外地发现了可能对地震加以预报的新方法，故最贴切的答案为[A]。[B]错误，“地下压力上升”只是描述了一个事实，并未揭示其与地震预报的关系，未能反映出文章主题．[C]“一个偶然的发现”未能明确反映文章的主要内容，表达过于空泛；[D]只是说明地震预报中高科技设备的应用，这只是文章中涉及的一个部分，不能够全面地反映出文章的主要内容。
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