Term
|
Definition
vibration of earth produced by the rapid release of energy
often caused by slippage along a fault
energy radiates from focus |
|
|
Term
|
Definition
the sudden release of stored strain in rocks that results in movement along a fault
Earthquakes are vibrations (spring)
stress acting on rock can be stored as energy by the elastic deformation of the rock material
when stress exceeds rock's strenght, rock fractures
|
|
|
Term
|
Definition
| instrument that records earthquake waves |
|
|
Term
|
Definition
record made by a seismograph; reveals seismic waves are elastic energy
2 main types of seismic waves are from rock mass slippage |
|
|
Term
|
Definition
Primary Waves
body wave (interior)
push-pull waves (compress & expand) in direction wave
all materials
changes volume of the material that transmits them
faster |
|
|
Term
|
Definition
secondary waves
shake particles right angles
change the shape of material that transmits them
slower
solids only |
|
|
Term
|
Definition
focus - place within earth where waves originate
epicenter - location on surface directly above focus |
|
|
Term
| shallow focus vs. deep focus |
|
Definition
shallow focus - most common <70km deep
deep focus - >300km
only ocean trench systems
subduction zones |
|
|
Term
| locate the epicenter of an earthquake |
|
Definition
difference in velocities of P & S waves
1. interval between P & S
2. travel-time graph, P-S interval to determine distance
3. distance circle around 3 cities,
center point = epicenter
triangulation |
|
|
Term
|
Definition
path around the outer edge of the Pacific Ocean where the greatest energy is released by earthquakes
Japan, Philippines, Chile Aleutian Islands |
|
|
Term
|
Definition
Seismic belts associated with subduction zones
deep foci
occur along well-defined pathways
represent the boundary between 2 lithospheric plates |
|
|
Term
| magnitude scales vs. intensity scales |
|
Definition
magnitude - mesure of energy released in an earthquake (Richter Scale)
intensity scale - measure of damage (Mercalli Scale) |
|
|
Term
| Earthquake Damage Hazards |
|
Definition
Ground Motion
Faulting
Fire
Mass Movements
Liquefication of Water-Saturated Soil
Seismic Sea Waves/Tsunamis |
|
|
Term
| how are earthquakes waves used to determine the structure of the earth |
|
Definition
| changes in velocity of waves = earth composed of shells of varied compositions |
|
|
Term
oceanic crust vs. continental crust
thickness, rock, age, density |
|
Definition
oceanic crust - thinner, basalt, younger, less dense
continental crust - thicker, upper=granite lower=basalt, older, more dense |
|
|
Term
| Mohorovicic discontinuity |
|
Definition
Lower boundary of the crust
double set of P & S waves
reflections off crust-mantle boundary |
|
|
Term
|
Definition
| higher seismic velocities, don't increase with depth |
|
|
Term
Low velocity zone
asthenosphere |
|
Definition
seismic waves lose speed: layer is less rigid and more plastic that the rest of the mantle
weakness allows plate movement |
|
|
