Two Seismographic stations A and B are located 250 km apart on level ground. An earthquake occurred between these two stations and the epicenter is located exactly on the line joining these two stations. The difference in time between P and S wave arrivals was 10 seconds at A and 15 seconds at B. Determine the location of epicenter from these two stations.
Answers
Answer:
Three Types of Waves
Major earthquakes occur when there is rock movement along a fault (crack in the crust). The sudden slippage of huge rock masses sets up shock waves that travel through the earth. The point within the earth where the actual movement takes place is called the focus. As shown in Figure 1, the point on the surface directly above the focus is called the epicenter.
An earthquake epicenter can be located from records made of earthquake waves on devices called seismographs. One type of seismograph is a visible recording machine, shown in Figure 2. A pen draws a pattern of the waves on paper that is attached to a revolving drum. The wave record from a seismograph is known as a seismogram - see Figure 3.
A typical seismogram of an earthquake has three prominent wave patterns. The first waves to arrive are the P-waves (also called "primary" or "push-pull"). They are followed by the S-waves (also called "secondary," "shear," or "shake"). Finally, the L-waves ("long" or "Love") arrive. This investigation contains the seismograms from three different stations for an earthquake. See how accurately you can locate the epicenter of this quake.