GEOLOGY

Detailed explanation-1: -Measure the difference in arrival times between the first shear (s) wave and the first compressional (p) wave, which can be interpreted from the seismogram. Multiply the difference by 8.4 to estimate the distance, in kilometers, from the seismograph station to the epicenter.

Detailed explanation-2: -For example, this graph tells you that if an earthquake epicenter is 4000 km away, the P-wave will take 7 minutes to get to you. That is, at your location you will feel the first vi-brations 7 minutes after the rupture occurs at the epicenter.

Detailed explanation-3: -The time difference between the arrival of the P waves and the arrival of S waves increases as the waves travel farther from their origin. This difference in arrival time is called lag time. Scientists can use lag time to find the distance to the epicenter of the earthquake.

Detailed explanation-4: -A P-wave takes 5 minutes to travel from the epicenter of an earthquake to a seismic station.