Which is one
step that geologists use to find the epicenter of an earthquake?

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.

Electron microscopy (EM) has become an extremely popular method for the ultrastructural study of macromolecules, cells and tissues. An aqueous biological sample is frozen rapidly and irradiated with a beam of electrons. A detector senses how the electrons are scattered and a computer reconstructs the 3D-shape of the molecule.

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