Question

Choose one of the recording stations
and measure the computed distance
on the map scale (the scale of the map
in Figure 3 is 1.5 cm: 200 km). Set
your compass for that computed
distance.​

Answer 1

Answer:

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.

Figure 1: Earthquake epicenter and focus

Answer 2

Recording channels and measure calculated distance  map scale is:

• Select one of the recording stations and measure the calculated distance on the map scale (map scale 1 cm: 70 km).
• Set your compass at that computer level.

• Calculate the landmark distance from each station using a formula:       d = TD x 100 km 8 seconds.

• When: d = distance (km)
• TD = Time difference in the arrival time of P-wave and S-wave (seconds) 7.

• Select one of the recording stations and measure the calculated distance on the scale (map scale 1 cm: 100 km).

• Set your compass on the channel you choose.
• Draw a circle.