Question

Which steps do geologists use to find the epicenter of an earthquake? Check all that apply.

Answer 1

Answer:

They draw circles around the epicenter from three locations.

Explanation:

Geologists use triangulation method to determine the epicenter of an earthquake.

The epicenter of an earthquake is a point on the earth surface directly above the focus. The focus is the point beneath the surface where the earthquake occurs.

To determine the epicenter of an earthquake, we simply draw three circles whose point of intersection will be the epicenter. How do we now draw the circle?

From a seismogram obtained from 3 stations, we can deduce the time it takes a wave to travel. We simply compare the time lag between the first occurrence of the s-waves and that of the p-waves. Now that we have the time, we can determine the distance travelled by the wave. Since we know that the velocity of waves are constant, we simply use the relationship between velocity and time to find the unknown distance.

Using the distance as the radius, we draw three circles from different seismograph stations on a map. The point where the three circles intersects marks the epicenter of the earthquake.

Answer 2

Answer:

Option (1), (2), (3) and (4)

Explanation:

Earthquakes refers to the sudden shaking of the earth. It releases a certain amount of energy. During an earthquake, seismic P and S waves are generated that travels through the interior of the earth.

The seismographs that are located near the epicenter records the data during an earthquake. This data is then used to draw 3 circles around those 3 seismographs. The point where these 3 circles intersects is the location of the earthquake epicenter.

The arrival of P wave and S waves are also carefully observed. The P waves travels faster than the S waves, so they are recorded first in the seismograph. This difference between the arrival of these two waves are marked that is helpful for the determination of the epicenter.

The intensity of an earthquake is determined by the amount of damage it causes. It is measured by using a scale known as the Mercalli's intensity scale.

Hence, the correct answers are options (1), (2), (3) and (4).