Why is earthquake prediction a challenge for scientists

Reliable predictions require precursors – some kind of signal in the earth that indicates a big quake is on the way. The signal has to happen only before large earthquakes and it has to occur before all big quakes.

Explanation:

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.