Earthquake

2.  Earthquakes
 An earthquake is the vibration of Earth
produced by the rapid release of energy
 An earthquake (also known as
a tremor or temblor) is the result of a
sudden release of energy in
the Earth's crust that creates seismic waves
 Earthquakes strike suddenly, without
warning

3.  The plates break free causing the ground to
shake
Most earthquakes occur at the boundaries where the plates meet

4. An earthquake is just like throwing a
stone in a pond of water

6. • Focus is the point within Earth
where the earthquake starts.
• Epicenter is the location on
the surface directly above the
focus.
• Faults are fractures in Earth
where movement has
occurred.

8. Cause of Earthquakes
 Elastic Rebound Hypothesis
• Most earthquakes are produced by the
rapid release of elastic energy stored in
rock that has been subjected to great
forces.
• When the strength of the rock is
exceeded, it suddenly breaks, causing the
vibrations of an earthquake.

9. Elastic Rebound Hypothesis

10. Cause of Earthquakes
 Aftershocks and Foreshocks
• An aftershock is a small earthquake that
follows the main earthquake.
• A foreshock is a small earthquake
that often precedes a major
earthquake.

11. The vibrations are called SEISMIC WAVES

12. Measuring Earthquakes
 Historically, scientists have used two different types of
measurements to describe the size of an earthquake
—intensity and magnitude.
 Richter Scale
• Based on the amplitude of the largest
seismic wave
• Does not estimate adequately the size of very large
earthquakes
• Each unit of Richter magnitude equates to
roughly a 32-fold energy increase

13. Measuring Earthquakes
Measuring Earthquakes
 Momentum Magnitude
• Derived from the amount of displacement that occurs along
the fault zone
• Moment magnitude is the most widely used measurement for
earthquakes because it is the only magnitude scale that
estimates the energy released by earthquakes.
• Measures very large earthquakes

14. Earthquake Waves
Measuring Earthquakes
 Seismographs are instruments that
record earthquake waves.
 Surface waves are seismic waves that
travel along Earth’s outer layer.
 Seismograms are traces of amplified,
electronically recorded ground motion
made by seismographs.

15. •The study of earthquake waves is known as SEISMOLOGY
•The experts who study the pattern of earthquakes are known as
SEISMOLOGISTS
•The machine which records the intensity of earthquake is known as
SEISMOGRAPH

16. The recordings of the SEISMOGRAPH are converted into the actual intensity
of the quake by using RICHTER SCALE

17. Thank you