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Earthquakes/Interior
Earthquakes & the Interior of the Earth
Question | Answer |
---|---|
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 |