Earthquakes Flashcards
Most earthquakes occur along what plate boundary?
Most earthquakes occur along active plate boundaries
Seismic Energy
Energy that radiates from fault movement via earthquakes
elastic rebound theory
The deformation that results from application of a stress
Strain
The deformation that results from application of a stress.
The release of seismic energy is explained by what theory
Elastic Rebound Theory
Brittle Deformation
A style of strain in which an object suddenly breaks, fractures, or otherwise fails in a different way than ductile deformation.
Focus
Initiation point of an earthquake or fault movement.
The place where the initial offsetting rupture takes place between the fault blocks is called the focus.
The earthquake focus, also called hypocenter, is the initial point of rupture and displacement of the rock moves from the hypocenter along the fault surface.
Offset
Amount of movement during a faulting event.
seismic stress causes continuous, gradual displacement between the fault blocks called…….
Fault Creep
After an initial earthquake, continuous application of stress in the crust causes elastic energy to begin to build again during a period of inactivity along the fault. The accumulating elastic strain may be periodically released to produce small earthquakes on or near the main fault called____
Foreshocks
Foreshock
An earthquake that sometimes occurs before the larger mainshock.
The main release of energy during the major earthquake is known as the_________
Mainshock
Mainshock
Largest earthquake in an earthquake sequence.
Focus is also known as
Hypocenter
epicenter
The epicenter is the location on the Earth’s surface vertically above the focus. This is the location that most news reports give because it is the center of the area where people are affected
The location at the surface directly above the focus of an earthquake, typically associated with strong damage.
amplitude
Height or depth of a wave from the middle point.
Magnitude
A measure of earthquake strength. Scales include Richter and Moment.
Wave amplitude indicates the ________ or height of earthquake motion.
Wave amplitude indicates the magnitude or height of earthquake motion.
Wavelength
The distance between any two repeating portions of a wave (e.g., two successive wave crests).
_________is the number of repetitions of the motion over a period of time, cycles per time unit.
Wave frequency
When waves combine in sync, they produce _____________, where the influence of one wave adds to and magnifies the other.
When waves combine in sync, they produce CONSTRUCTIVE INTERFERENCE, where the influence of one wave adds to and magnifies the other.
If waves are out of sync, they produce __________, which diminishes the amplitudes of both waves.
If waves are out of sync, they produce DESTRUCTIVE INTERFERENCE, which diminishes the amplitudes of both waves.
If two combined waves have the same amplitude and frequency but are one-half wavelength out of sync, the resulting destructive interference can _____________
If two combined waves have the same amplitude and frequency but are one-half wavelength out of sync, the resulting destructive interference can ELIMINATE EACH WAVE.
These processes of wave amplitude, frequency, period, and constructive and destructive interference determine the _____ and ______ of earthquakes.
These processes of wave amplitude, frequency, period, and constructive and destructive interference determine the MAGNITUDE and INTENSITY of earthquakes.
What type of inference?
Constructive Interference
What constructive waves look like
What type of interference
Destructive
If two combined waves have the same amplitude and frequency but are one-half wavelength out of sync, the resulting destructive interference can ___________.
if two combined waves have the same amplitude and frequency but are one-half wavelength out of sync, the resulting destructive interference can ELIMINATE EACH WAVE
Seismic waves
are the physical expression of energy released by the elastic rebound of rock within displaced fault blocks and are felt as an earthquake
Seismic waves occur as what two kinds of waves?
Seismic waves occur as body waves and surface waves
Body Waves
Seismic waves that travel through the Earth, mainly P waves and S waves.
Body waves pass underground through the Earth’s interior body and are the first seismic waves to propagate out from the focus.
Body waves include which waves?
Body waves include primary (P) waves and secondary (S) waves
___________ are the fastest body waves and move through rock via compression, very much like sound waves move through air.
P waves are the fastest body waves and move through rock via compression, very much like sound waves move through air.
Rock particles move forward and back during passage of the ______ waves, enabling them to travel through solids, liquids, plasma, and gases
Rock particles move forward and back during passage of the P waves, enabling them to travel through solids, liquids, plasma, and gases
S waves
Second-fastest seismic wave that has a sheer motion
Because ___ waves are restricted to lateral movement they can only travel through solids but not liquids, plasma or gases
S Waves
P-waves are compressional or shear
Compressional
S waves are compressional or shear.
Shear
During an earthquake what do body waves do?
During an earthquake, body waves pass through the Earth and into the mantle as a sub-spherical wave front. Considering a point on a wave front, the path followed by a specific point on the spreading wave front is called a seismic ray and a seismic ray reaches a specific seismograph located at one of thousands of seismic monitoring stations scattered over the Earth. Density increases with depth in the Earth, and since seismic velocity increases with density, a process called refraction causes earthquake rays to curve away from the vertical and bend back toward the surface, passing through different bodies of rock along the way.
Refraction
Waves that change direction due to changing speeds, typically caused by a change in density of the medium
seismic velocity increases with ____
seismic velocity increases with density
__________ are produced when body waves from the focus strike the Earth’s surface.
SURFACE WAVES are produced when body waves from the focus strike the Earth’s surface.
because of their complex horizontal and vertical movement, ________ waves are responsible for most of the damage caused by an earthquake.
because of their complex horizontal and vertical movement, SURFACE WAVES are responsible for most of the damage caused by an earthquake.
Raleigh Waves
Surface waves take the form of rolling waves called Raleigh Waves
-Raleigh waves cause rock particles to move in a direction opposite to that of water particles in ocean waves.
Surface waves take the form of side to side waves called _________
Love waves
Which travels slower surface waves or body waves?
Surface waves
because of their complex horizontal and vertical movement, _______ waves are responsible for most of the damage caused by an earthquake
because of their complex horizontal and vertical movement, SURFACE waves are responsible for most of the damage caused by an earthquake
Love Waves
Surface waves that have a side-to-side motion.
______waves produce predominantly horizontal ground shaking and, ironically from their name, are the most destructive.
LOVE waves produce predominantly horizontal ground shaking and, ironically from their name, are the most destructive.
______ waves produce an elliptical motion with longitudinal dilation and compression like ocean waves
Rayleigh waves produce an elliptical motion with longitudinal dilation and compression, like ocean waves.
Description how induced seismicity happens
Earthquakes known as induced seismicity occur near natural gas extraction sites because of human activity. Injection of waste fluids in the ground, commonly a byproduct of an extraction process for natural gas known as fracking, can increase the outward pressure that liquid in the pores of a rock exerts, known as pore pressure. The increase in pore pressure decreases the frictional forces that keep rocks from sliding past each other, essentially lubricating fault planes. This effect is causing earthquakes to occur near injection sites, in a human induced activity known as induced seismicity.
induced seismicity
Earthquakes that occur due to human activity.
What is the focus of an earthquake?
Where the actual rupture of rock occurs in the subsurface producing the earthquake
The focus is where the actual rupture of rock begins that releases energy that travels outward as seismic waves
Which seismic wave type travels the fastest?
P-waves
P-waves travel fastest, then S-waves, and finally surface waves, which include Love and Rayleigh waves.
Two types of surface waves
Love waves (side to side) and Raleigh Waves (rolling)
Which seismic wave type is most damaging?
Surface (Love and Rayleigh) waves are the most dangerous, with the ironically-named Love waves causing the most damage.
What attributes do p-waves have?
Compressive
High Frequency
Low Amplitude
Fastest waves
Attributes of S-Waves
Secondary waves Shear Low Frequency High Amplitude 2nd fastest wave
Which waves are the second fastest?
S-Waves
What kind of wave?
P Wave
What type of wave?
S wave
What type of wave?
Love Wave
What type of wave>
Rayleigh wave
