GEOLOGY

EARTH SCIENCE

EARTHQUAKES

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Scientists use the P and S time difference to tell ____
A
the strength of the surface wave
B
the magnitude of quake
C
the distance of the epicenter from station
D
if quake occurred
Explanation: 

Detailed explanation-1: -Use the time difference between the arrival of the P and S waves to estimate the distance from the earthquake to the station. (From Bolt, 1978.) Measure the distance between the first P wave and the first S wave. In this case, the first P and S waves are 24 seconds apart.

Detailed explanation-2: -Using a seismogram, the time difference between the recording of the P wave and the S wave is determined and matched to a corresponding distance value. The single maximum amplitude recorded on the seismogram is calculated and a line is drawn between the amplitude scale and the distance scale.

Detailed explanation-3: -Difference in arrival times between P and S waves can be used to determine the distance between the station and an earthquake. By knowing how far away the quake was from three stations we can draw a circle around each station with a radius equal to its distance from the earthquake.

Detailed explanation-4: -Finding the Epicenter One seismogram indicates the distance to the epicenter. This is determined by the P-and S-wave arrival times. If a quake is near the seismograph, the S-waves arrive shortly after the P-waves. If a quake is far from the seismograph, the P-waves arrive long before the S-waves.

Detailed explanation-5: -As the P and S waves travel out from an earthquake the P waves get progressively farther ahead of the S waves. Therefore, the farther a seismic recording station is from the earthquake epicenter the greater will be the difference in time of arrival between the P and S wave.

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