29 terms

Ch 19 Earthquakes

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Terms in this set (...)

Stress
A force that acts on rock to change its shape or volume
Strain
Change in shape of rock due to the stress put on the rock. Subtypes of strain responses: elastic strain, ductile deformation, failure.
Elastic Strain
Temporary change in shape of rock. The rock will go back to its original shape when the stress is gone.
Ductile Deformation
Permanent change in shape of rock due to stress.
Failure (as it pertains to rocks)
Rocks break, causing earthquake.
Fault
Fractures/cracks in Earth's crust where movement occurs when failure and earthquakes occur.
Primary Waves (P-Waves)
Fastest earthquake wave. It starts underground at the focus and can travel through BOTH rock & liquid. AKA "Push-Pull" wave.
Secondary Waves (S-Waves)
Medium speed wave. Arrives 2nd at station. It starts underground at the focus and ONLY goes through SOLIDS. AKA "Side-to-side" wave.
Surface Waves
Slowest wave. Begins on surface at epicenter and causes the most damage.
Focus
The location underground where rock fails/breaks and the earthquake begins. This is where P & S waves start.
Epicenter
Point on earth's surface directly above the focus. This is where the surface waves start.
Refraction
Bending of earthquake waves as they pass from solid to liquid & vice versa.
Shadow Zone
Areas of earth where stations do not detect seismic waves because the waves were blocked or bent by liquid.
Magnitude
Amount of ENERGY released by an earthquake. Measured by the Richter scale. AKA: Strength of an earthquake.
Richter Scale
Measures the strength (magnitude) released by an earthquake. Based on the size of the LARGEST seismic waves. An earthquake can only have ONE value on this scale.
Intensity
Measure of the amount of structural & geological DAMAGE. Measured by the Modified Mercalli Scale.
Modified Mercalli Scale
Measures the intensity or damage in a specific location. Uses Roman numerals I - XII (1-12). Because damage varies based on distance from epicenter, how buildings are made, etc., different locations can have different Mercalli ratings for the same earthquake.
Fracking
When pressurized fluid is used to create fractures/cracks in rock in order to release natural gas or petroleum
Tsunami
Large ocean wave caused by an earthquake on the ocean floor.
Seismometer (AKA Seismograph)
Instrument (machine) that detects earthquakes. Consists of rotating drum, pendulum.
Seismic Risk
Probability or likelihood that a quake will occur in a specific area.
Seismic Gap
A fault that hasn't had a large quake in a long time. In other words there's been a "gap" in earthquake occurance.
Earth's Interior (Layers)
Inner Core: Solid,mainly iron
Outer Core: Liquid, mainly iron
Mantle
Crust
Lithospere: Rocky part made of crust & upper mantle
Normal Fault
Hanging wall "slides" down the slope. (Similar to a person sliding down a hill.) Due to tension pulling plates apart at a Divergent Boundary. Causes lengthening of earth's surface. See Figure 19-3 p.497.
Reverse Fault
Hanging wall is forced "backward" or "up" the slope. Due to compression pushing plates together at a convergent boundary. Results in horizontal shortening of earth's crust. See Figure 19-3 p.497.
Strike-slip Fault
Plates "slip" past each other without moving up or down a slope due to shear (twisting) at a transform boundary. See Figure 19-3 p.497.
Tension
A form of stress due to pulling or stretching apart. (Like stretching a rubberband.) See Fig. 19-1 p.496.
Compression
A form of stress that pushes rock together, causing a decrease in the volume of the rock. See Fig. 19-1 p.496.
Shear
A form of stress that twists. See Fig. 19-1 p.496.