XII. EARTHQUAKES

A. BASICS

1. Definition
2. Causes:
   1. human factors
   2. magma
   3. faults (elastic rebound and energy release) (fig. 14.4)
3. Location:  (fig. 14.2)
   1. epicenter,
   2. hypocenter (focus), depth, origin underground,
   3. scarp, surface break (rupture)

B. SEISMIC WAVES:

1. recording - seismograph, seismogram (fig. 14.6)
2. surface waves (damage)
3. body waves - (fig. 14.7)
   1. P-waves, compression, primary waves, fastest
   2. S-waves, shear, secondary waves, slower, not through liquid

C. LOCATION

1. time - distance graph (fig. 14.8)
2. arrival time of S & P waves,
3. three stations to locate (fig. 14.9)

D. SIZE

1. magnitude, 0-10?,
   1. Richter scale (fig. 14.11)
      • used for small to medium sized quakes (up to around M7)
      • amplitude, ground motion, 10X amplitude, 30X energy,
   2. moment magnitude scale,  
   used for very large quakes (greater than M6.5)
   • complex to measure
2. intensity,
   1. Mercalli scale, I-XII (Table 14.2),
   2. damage done and amount of shaking,
   3. subjective, used for insurance, city planners, construction
      

E. DAMAGE

1. ground rupture,
2. ground motion,
3. fire,
4. landslides,
5. tsunamis, (fig. 14.16)
6. liquefaction