GEOLOGY

Detailed explanation-1: -With increasing distance from the earthquake the time difference between the arrival of the P waves and the arrival of the S waves increases. This basic approach to locating quakes is illustrated using an example of an earthquake near Mexico.

Detailed explanation-2: -The graph shows that the S-waves need about 12 minutes: 40 seconds to travel the same distance. Therefore, if the time separation between the arrival time of the P-and S-waves is 5 minutes:40 seconds, the epicenter must be 4000 km away.

Detailed explanation-3: -The speed at which seismic waves travel depends on the properties of the material that they are passing through. For example, the denser a material is, the faster a seismic wave travels (SF Table 7.1). P waves can travel through liquid and solids and gases, while S waves only travel through solids.

Detailed explanation-4: -the difference in arrival times for P-and S-waves; this difference is used to determine the distance between the epicenter and the seismograph station.

Detailed explanation-5: -The speed of P waves and S waves increases as they travel deeper into the Earth’s mantle . They travel through the Earth in curved paths, but they change direction suddenly when they pass through the boundary between substances in different states.