1. Earthquake Measurement
Chapter 8 Section 2

2. Locating Earthquakes
Seismograph- an instrument that records vibrations in the ground and strength of an earthquake
Seismogram- a tracing of earthquake motion that is created by a seismograph

3. Determining Time and Location of Earthquake
Start time is determined by noting the difference in arrival times of P waves and S waves.
Seismograms is used to find the epicenter
Epicenter- the point on the Earth’s surface directly above the earthquake’s starting point- focus
Focus- the point along a fault at which the first motion of an earthquake occurs

4. S-P Time Method Used to find the epicenter Compare the results of
different seismograms of the same
earthquake and find the common point

5. Measuring Earthquake Strength
Earthquake ground motion
Magnitude increases by 1 unit, measured ground motion becomes 10 times larger
Example: 0.5 on the Richter Scale produces 10x the ground motion as a 0.4. A 0.6 produces a 100x (10 x 10)the ground motion as a 0.4.
Measuring Earthquake Strength

6. Measuring Earthquake Intensity
The degree in which it is felt by people and the damage it causes
Modified Mercalli Intensity Scale to measure
Ranked with Roman numerals I being the lowest ( not felt by most people) and XII being the highest (indicates total damage of an area)