Download 25.1 Notes

EQ notes 25.2
Earthquake
-A sudden movement or vibration of the ground that occurs when
rocks slip or slide along cracks in the Earth
- corresponds closely with plate boundaries
-usually shallow EQ’s (70km or lower) occur at divergent boundaries
-deep EQ’s (70km or more) occur at convergent boundaries
FAULTS
-crack in the Earth’s crust where rock has moved
CAUSES
-Energy is released along a fault
-caused by forces applied to rocks along plate boundaries
DEFORMATION
-Caused by forces applied to objects
-Stress on a object is the force/unit area that acts
on that object
4 types of STRESS
1- compression (comes together)
2- tension (pulls apart)
3- shearing (moves opposite ways)
4- torsion
(twists)
Types of deformation
Elastic deformation occurs when stress is applied and
the object snaps back to its original shape.
Plastic or Inelastic deformation occurs when stress is
applied and the object DOES NOT snap back to original
position
ENERGY RELEASE
Elastic Rebound- EQ occur when a rock
that has been stressed releases
strain energy and moves along the fault.
SEISMIC WAVES
- Point of ORIGIN from an EQ is called the FOCUS
- Point on SURFACE above focus is the EPICENTER
SEISMIC WAVES CONT.
P-waves (primary)- Compressional waves that, move
through material by squeezing and stretching in the same
direction as the wave is moving. EX- a spring
S-waves (secondary)- Transverse waves move materials at
right angles to the wave direction. EX- a rope
Surface waves- move on the surface like ocean waves
move vertically and horizontally
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es
1002page01.cfm
EQ MEASUREMENT
Richter Scale- magnitude scale,
measures the energy
released during an EQ
Mercalli Scalemeasures EQ intensity
Seismograph- records ground
vibration during an EQ
EQ DAMAGE
• Nearly all EQ damage comes from buildings
and human made objects.
• Can cause tsumanis
• In the middle of nowhere an EQ does not
cause much damage at all