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Earthquakes & the Interior of the Earth

General description of internal forces Solids cohere together, earthquakes are produced by the rapid release of elastic energy stored in rock that has been deformed by differential stress.
Description of cohesive force Holds molecules together, exists between 2 sides of a fault, stress must be large enough for earthquake to overcome this
What are the interior layers of the earth? From inside: Inner core, outer core, mantle, crust
Moho discontinuity? Actual boundary between crust & mantle, separates both oceanic crust and continental crust from underlying mantle
Shadow zone? Area void of seismic waves, S-waves do not go through outer core because it is liquid, seismographs cannot detect an earthquake after its seismic waves have passed through the Earth, refracted by liquid
Liquefaction? Unconsolidated materials are saturated with water- earthquake vibrations can turn stable soil into a mobile fluid
Sand geysers? Indication of liquefaction
Intensity of earthquake Degree of shaking at a given locale based on observations
Magnitude? Data from seismic records show amount of energy released
Seismograms Drawings of seismic activity, record obtained from seismograph
Richter scale Logarithmic scale based on powers of 10
Moment magnitude scale More accurate than Richter scale because it measures total energy released
Mercalli scale Scale based on roman numerals 1-12, eyewitness reports
Surface waves? Stay at surface
P-wave Body wave, travels through solids liquids & gases, first wave to show up, push-pull/compressional wave, push-squeeze then pull-stretch in direction of wave, represents volume
S-wave Second wave to show up, does not go through liquid, if S-wave takes a long time to show up after P-wave then epicenter is father, represents shape
L-wave Love wave, surface wave, fastest surface wave, moves the ground from side-to-side, confined to the surface of the crust, horizontal movement
Rayleigh wave Rolls along the ground just like a wave rolls across a lake or an ocean, moves the ground up and down, and side-to-side in the same direction that the wave is moving, surface wave
Focus? Point of breakage deep in earth, origin of an earthquake
Epicenter? Most energy of an earthquake, point at surface directly above focus
Time-path The amount of time that it takes for a seismic wave to pass through the earth is dependent on the material that it encounters along its path, seismic waves travel faster through denser/solid material
Triangulation A method of determining the direction of an earthquake and precise location, 3 arcs merging to show epicenter
Seismographs Instruments that record earthquake waves
Seismology Study of seismic activity and earthquake waves
Seismic wave Massive amount of energy released during an earthquake
Tsunami Japanese word for a seismic sea wave, subduction zone earthquake that happens beneath the ocean and creates destructive waves, deep wave wave, water recedes when trough (low area) lands first
Precautions during a tsunami Small room like a closet with door frame, get away from glass or anything that can fall on you, stay in car if you are in traffic
Historical earthquakes 1)San Francisco 1906, 2)New Madrid Missouri 1811-1812
Earthquake belts 1)Circum-Pacific "Ring of Fire" = biggest, 2)Mid-Atlantic ridge, 3)Alpine-Himalayan (Alpide)
Local causes of earthquake activity? Volcano- earthquakes cause vibration
Normal fault Tensional force (pulling apart), Downblock going down
Reverse fault Compressional force(pushing together), Upblock going up leaving a hanging wall
Thrust fault Downblock going down at an angle and upblock stays the same
Lateral fault Both blocks traveling opposite directions but side by side
Horst and graben topography Horst=high point, graben=valley, zigzag pattern
Hanging wall Hanging wall block is always above the fault plane or resting/hanging on top of the foot wall block
Foot wall Foot wall block is always below the fault plane and is shaped like a foot
Density of crust Sedimentary rock = 2.5g/cm3 (continental and least dense), Granitic rock = 2.7g/cm3 (continental and least dense), Basalt = 3g/cm3 (ocean floor), Mantle = 3.3g/cm3 (most dense)
Rock structures Position of rock layers
Top layer is Youngest
Bottom layer is Oldest
Name of space between rock layers Bedding plane
Type of structure based on: 1)Amount of force applied, 2)Rate of force applied, 3)Kind of rock acted upon
Surface v Deep Pressure Surface breaks but deep pressure bends, Deep pressure causes material to bend due to uniform pressure and also hotter temperature
Fracture Any break or rupture in rock along which no appreciable movement has taken place
Fault A break in rock mass along which movement has occurred
Anticline A fold in sedimentary strata that resembles an arch
Syncline A linear downfold in sedimentary strata and the opposite of anticline
Elastic body? Can change shape or volume but recovers to original shape when force is removed like a rubber band
Elastic limit? Breaking point
Foreshocks Small earthquakes that precede a major earthquake
Aftershocks Small tremors that follow an earthquake
Tension (force) Going apart
Compression (force) Coming together
Shearing (force) Scissor-like movement and rocks twisted
Buoyancy (force) Upward force
Isostacy State of balance
Density of rocks: LEAST Sedimentary rock- igneous rock- basalt- mantle MOST
Created by: kbkari