The warning system works by detecting primary waves, which spread from the epicenter of a quake and travel faster than the destructive shear waves.

预警系统的工作原理是探测最初从震中传出的地震波，其速度要比破坏性的剪切波快。

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Primary waves are identical in character to sound waves. The ground is forced to move forwards and backwards as it is compressed and decompressed.

主要波跟声波的特征相同，当地面被加压或减压时强迫向前和向后移动。

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Since the primary waves travel more quickly than the comparatively sluggish secondary waves, the system picks up on the magnitude and speed at which the quake is approaching, and beams the data over fiber optic networks to emergency relay stations setup in corporate towers, governmental buildings, hospitals, and transportation venues such as railways.

ENGADGET: Japan Meteorological Agency develops earthquake warning system