Answer :
When a seismometer detects an earthquake, the first signal to arrive is usually the pressure wave.
What is a pressure wave in earthquake?
One of the two primary varieties of elastic body waves, known in seismology as seismic waves, is the P-wave. Also known as compressional or compression waves, mechanical longitudinal waves. Pressure waves are the first signal from an earthquake to reach any impacted place or a seismograph since they move quicker than other seismic waves.
Pressure waves are typically too subtle for people to detect, though seismographs can. However, some animals might be able to recognize P-waves before the onset of the S-waves. For any earthquake that was close enough to them to affect them, they would have less than two minutes of notice.
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