The system is designed to rapidly detect the initiation of an earthquake, and it can determine how big the earthquake is and where it is located. The system can also issue a warning to people immediately through TV, short messages and emails. If quakemonitoring stations are about 30 km apart, the system can issue warning information about 10 seconds after a quake happens below ground.
As earthquakes cannot be predicted, getting people to safety quickly before the destructive Swaves arrive can decrease casualties and reduce damage. Experts estimate that casualties could be reduced by 14 percent with a threesecond advance warning of an earthquake, and 39 percent with a 10second warning. And the few seconds of warning can also help a train driver slow down to avoid possible derailment, and give a shutdown signal to chemical factories or nuclear plants to prevent potential leaks and fires.
But the system has its limitations. The Swaves generally move at a speed of 3.5 km per second, which means before the warning is issued, Swaves have already spread in a radius(半径)of 35 km from the epicenter. The area within the 35km radius of the epicenter called the “blind area” cannot be warned. The system cannot play a role in small quakes, either.
Unit 3
Ⅰ.1. A 考查被动语态。sounds和drop之间存在被动关系,应用被动语态形式。本句讲的是一般性的情况,应用一般现在时态。句意:在美国一些地方的英语口语中,词尾的“r”音省掉了。
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