Measuring the force of earthquakes

seismic gaps

areas on active faults where a major earthquake hasn't occurred in a long time

foreshocks

mini-quakes that usually occur before a major earthquake

Which of the following are signs that an earthquake may occur?

changes in water levels in wells foreshocks changes in the magnetic properties of rocks

The area where rock layers first move along a fault is the _____ of an earthquake.

focus

seismograph

instrument used to record and measure vibrations from earthquakes or earth tremors

triangulation

process used to locate the epicenter of an earthquake

Richter scale

scale of magnitude based on the size of seismic waves produced by an earthquake

Mercalli intensity scale

scale that measures the effects or severity of an earthquake

seismology

scientific study of earthquakes

Which of the following is the point underground where rock layers first move during an earthquake?

Focus

Which of the following represents the most powerful earthquake?

Great Chilean, 9.5

seismogram

a record of the time and intensity of the energy waves produced by an earthquake

Match the earthquake measuring instrument with its correct description. 1. Richter scale 2. moment magnitude scale 3. Mercalli intensity scale

3 measures effects of an earthquake; measurement can vary from place to place 1 measures strength of an earthquake; measurement is based on the size of seismic waves 2 measures strength of larger earthquakes; measurement is based on multiple variables

1. foreshocks 2. magnitude 3. Mercalli intensity scale 4. moment magnitude scale 5. Richter scale 6. seismic gaps 7. triangulation

7process used to locate the epicenter of an earthquake 2measure of the total amount of energy released during an earthquake 3 scale that measures the effects or severity of an earthquake 4 newer magnitude scale that measures the amount of moved (displaced) rock along a fault to determine the strength of an earthquake 5scale of magnitude based on the size of seismic waves produced by an earthquake 1 mini-quakes that usually occur before a major earthquake 6areas on active faults where a major earthquake hasn't occurred in a long time

A seismograph records an earthquake, but scientists do not feel it. The earthquake has a magnitude _____.

< 2.0

Which of the following describes the relationship between P and S waves and the epicenter?

The farther away the P and S waves are on a seismogram, the further the epicenter.

Triangulation is a process to locate an earthquake. Which statements are true regarding this process?

You must know the difference in the times that S waves and P waves arrive at a seismograph station to determine the distance to the epicenter. You should draw a line from the center of the seismograph station to the epicenter to show its location. Three seismograph distances must be mapped with circles and the point where they intersect is the epicenter.

magnitude

measure of the total amount of energy released during an earthquake

moment magnitude scale

newer magnitude scale that measures the amount of moved (displaced) rock along a fault to determine the strength of an earthquake