Earth Science, Tarbuck Chapter 5 Flashcards
What is an Earthquake
is ground shaking caused by the sudden and rapid movement of one block of rock slipping past another along fractures in Earth’s crust
What is a Fault
fractures in Earth’s crust
Why are most faults “locked”
Confining pressure from overlying crust is enormous, leading to the faults to be “Squeezed shut”
Location where slippage begins
Hypocenter or Focus
What is the point directly above the Hypocenter\focus called
Epicenter
Large earthquakes release huge amounts of stored up energy as
Seismic Waves
The energy carried by Seismic Waves causes the material that
transmits them to
Shake
an earthquake generates waves that radiate
Outward in all directions
Describe elastic rebound
Process by which energy is released as an earthquake due to rocks on either side of a transform fault accumulating energy and slowly deforming until their internal strength is exceeded. When this happens, the rocks suddenly move along the fault, releasing the accumulated energy and snapping back to their original shape
What is an aftershock
numerous earthquakes of lesser magnitude following a strong earthquake
What are Foreshocks
Small earthquakes that sometimes precede major earthquakes by days or, in some cases, several years.
Faults associated with _______ and _______ plate boundaries are the source of most large earthquakes.
Convergent and Transform
where one continent is colliding with another, the resulting
compressional forces slice Earth’s crust along numerous large _____ faults
Thrust
in subduction of oceanic lithosphere under another plate, the area of contact between the two plates forms an extensive fault zone, called a ________ fault
Megathrust
What is fault creep
slow, gradual displacement that produce little seismic shaking
Describe Inertia
Objects at rest tend to stay at rest, and objects in motion tend to remain in motion, unless acted upon by an outside force
Records recorded from seismographs is called a
Seismogram
Instruments that detect vibrations from earthquakes
Seismographs or Seismometers
Two types of Seismic Waves
Body waves and Surface Waves
2 types of Body waves
Primary Waves(P waves) and Secondary Waves(S waves)
P waves are ___ waves
Push/Pull
What do P waves do to surrounding rock
They Push(Compress) or Pull(Stretch) rocks in the direction the waves are moving in
What materials can P waves travel through
Solids, Liquids, Gasses due to them resisting the stress of a volume change
What do S waves do to surrounding rock
Shake
P waves change ____ of Material
Volume
S waves change ____ of Material
Shape
S waves cant travel through
Gasses and Liquids due to them not resisting the stress of a shape change
List the different seismic waves from fastest to slowest
P waves, S waves, and the surface waves
Two different types of Surface Waves
Love waves and Rayleigh waves
Love waves move ____
Horizontally
Rayleigh waves _____ along the ground
Roll
What is the difference between surface and body waves
Body waves travel through the inside of Earth while Surface Waves are restricted to traveling throughout the surface of the earth
Which waves are the most destructive waves
Love waves
how to determine distance from epicenter from a seismogram
Distance between P and S waves
the longer the interval between the arrival of the first P wave
and the arrival of the first S wave, the ______ the distance to the epicenter
greater
two fundamentally different measures that describe the size
of an earthquake
Intensity and Magnitude
Describe Mercalli earthquake scale
uses observed property damage to estimate the amount of ground shaking at a particular location
Describe Magnitude Scale
use data from seismographs to estimate the amount of energy
released at an earthquake’s source
Describe how the Richter Scale works
calculated by measuring the amplitude of the largest seismic
wave recorded on a seismogram
Richter Scale has ___ -fold increase in magnitude for an increase of 1 on the Magnitude Scale
10
What is the Amplitude of a seismic wave
the maximum displacement of the ground from its resting position
Which waves most often have the highest amplitudes
Secondary waves or Surface Waves
An increase in a Richter Magnitude means how many times more energy than the last magnitude
32
Why cant the Richter Scale Differentiate between major earthquakes
Richter scale measures a single peak, which can be misleading due to limitations from seismographs
For measuring medium and large earthquakes, seismologists now favor a newer scale called
Moment Magnitude
How is Moment Magnitude Calculated
by determining the average amount of
slip on the fault, the area of the fault surface that slipped,
and the strength of the faulted rock.
For one level increase in moment magnitude an increase of _______ times of energy
32
Describe Liquefaction
transformation of somewhat stable soil into mobile material capable of rising toward Earth’s surface
What are the different things an earthquake can cause
Fire, Ground subsidence and Landslides, Tsunamis,
How do Tsunamis form from earthquakes
Rapid up and Down vertical motion due to slippage at a megathrust fault below water
How do fires form from earthquakes
Earthquakes can sever gas and electricity lines
How does Ground Slippage and Subsidence form from earthquakes
Earthquakes destabilize slopes, loosen soil particles, and trigger liquefaction
The first warning a tsunami often has is
Rapid Withdraw of water from the shore
2 Zones where most seismic activity happens
Circum-pacific belt and Alpine-Himalayan belt
What are intraplate earthquakes
Earthquakes that occur away from plate boundaries
What is a precursor to an earthquake
events or changes that precede an earthquake
Seismic Waves follow a _______ path through earth
Refracted, Reflected, and Diffracted
Describe how a seismic wave is refracted inside the earth
They refract(change direction) when going through boundaries of different layers of the earth
Describe how a seismic wave is reflected inside the earth
Seismic Waves reflect off boundaries between different layers
Describe how a seismic wave is diffracted inside the earth
Seismic waves are diffracted(follow a curved path) around obstacles they encounter
Seismic waves can travel through _________ material faster
Stiff or rigid
