• stiff, rigid outer rind of the earth
• made up of large blocks called tectonic plates
• mantle
• broken into a dozen or so large plates about another dozen much smaller plates, uneven in size and shape they fit neatly together almost like a mosaic 

• the inner, hotter more easily deformed part of the earth

Earthquakes and ____ account for the majority of deaths from natural disasters 

a. tornadoes

b. hurricanes

c. landslides

d. floods

The continental crust is _____

a. made of granite and about 6 km thick

b. made of basalt and about 6km thick

c. made of granite and about 45 km thick

Earthquakes in subduction zones can reach depths of____

a. 7km

b. 70 km

c. 700 km

d. 7000 km

The seismic waves that often cause the most damage are the____.

a. surface waves

b. secondary (S) waves

c. primary (P) waves

d. shear waves

Because of the bend in the san Andreas Fault as it passes LA, _______

a. the crust beneath the city is broken by many thrust(or reverse) faults

b. the crust beneath the city is broken by many normal (or extensional) faults

c. the crust beneath the city is over 70 km thick

a. the crust beneath the city is broken by many thrust (or reverse) faults

• A reverse fault in which the fault plane is inclined at an angle equal to or less than 45°.
• san andreas fault

reverse faults

move rocks on the upper side of a fault up and over those below

• move on a steeply inclined surface, they move when earths crust pulls apart, during crustal extension
• divergent boundry 

• the average time between earthquakes and faults
• also known as a return period

• pullling a bow taut, bending it out of its normal shape and then releasing it, snap back to its original shape with a sudden release of energy capable of sending an arrow flying
• rocks are elastic, like a spring and can bend when a force is applied

• stress: the forces imposed on a rock
• strain: the change in shape of the rock in response to the imposed stress
• the larger the stress, the greater the strain

• the study of prehistoric fault movements,
• can establish fault movement trends that predate written records
• pattern of earthquakes along fault segments also provides clues to future earthquake activity

• move with a wiggling motion like that of a rhythmically shaking rope and making it hard to stand
• travels through the body of earth/body wave
• destructive because of their motion

• the primary/ compressional waves, come as a sudden jolt
• consist of a strain of compressions and expansions
• comparable to sound waves, however travel at a slower rate
• can travel through the body of earth/ body wave

• arrives after the body waves
• a long series of rolling motions
• travel along earths surface and fade downward
• include love and rayleigh waves, move in perpendicular plane
• generally involve the greatest ground motion so they cause most of all earthquake damage
• inertia keeps people and furniture in place as ground motion yanks building back and forth beneath them

• move in perpendicular planes
• love waves move from side to side
• rayleigh waves move up and down in a motion that somewhat resembles ocean swells 

•  a section of an active fault that has not had recent earthquakes. 
• earthquakes elsewhere on the fault suggest that the gap may have an earthquake in the future

• earthquakes that occur in a sequential manner along a fault over time

• the region above a subduction zone in which the overlying continental plate flexes upward before slip on the subduction zone causes a major earthquake