Chp.5) Earthquakes Flashcards
what is an earthquake?
Ground shaking of Earth produced by the rapid release of
energy along faults
earthquakes release (___), a form of energy that travels
through the Earth
seismic waves
location where slippage begins
hypocenter (focus)
point on Earth’s surface directly above the
hypocenter
epicenter
this theory explains that earthquakes occur when rocks on either side of a fault deform and accumulate energy until their internal strength is exceeded, causing a sudden movement along the fault and releasing the accumulated energy
elastic rebound
Earthquakes are often preceded by (___) and
followed by (___)
foreshocks and aftershocks
Earthquakes of lesser magnitude preceding the major
earthquake
foreshock
Earthquakes of lesser magnitude occurring after the major
earthquake. Can occur months or years after a major event
aftershock
(___) boundaries produce some of the largest due to
immense buildup of pressure
convergent
(___) boundaries can produce earthquakes along any of
its numerous branches
transform
(___) boundaries produce small earthquakes
divergent
study of earthquake waves
seismology
seismography
earthquake recording instrument
a record of seismography is called:
seismogram
this type of earthquake wave has push-pull (compressional) motion, can travel through solids, liquids, gas and has the greatest velocity of all earth quake waves
Primary (P) waves
this type of earthquake wave has a shake motion, travels only through solids and is slower than P waves
Secondary (S) waves
this type of earthquake wave has complex motion and has the slowest velocity of all waves
Surface waves
Locating the epicenter of an earthquake requires these 3 steps:
1.) use seismogram from 3 different locations
2.) use time-travel graph to determine distance seismic waves traveled
3.) drawing circles with the radius of distance from each seismic station, you can triangulate approximate epicenter
A measure of the degree of earthquake shaking at a given locale
based on the amount of damage
intensity
The Modified Mercalli Intensity Scale measures
intensity
(___) is measured using the Richter scale
magnitude
(___) is based on the amplitude of the largest seismic wave
magnitude
Each unit of Richter magnitude equates to roughly a (___)-fold
energy increase
32
regarding magnitude, total energy released is measured by these 3 factors
1.) amount of slip on the fault
2.) area of the fault that ruptured the surface
3.) strength of the rock
4 factors the determine structural damage
– Intensity of the earthquake
– Duration of the vibrations
– Nature of the material upon which the structure rests
– The design of the structure
destruction from earthquakes results from these 3 factors
– Ground shaking
– Wave Amplification based on ground material
– Liquefaction of the ground
landslides, fire and (___) can also result from earthquakes
Tsunamis
(___) percent of energy from earthquakes in a few narrow zones
95
true or false
not all plate boundaries produce earthquakes
false
all boundaries do
Study of past earthquakes
Paleoseismology
when a segment of an active fault known to produce significant earthquakes that has not slipped in an unusually long time, this is called a:
seismic gap
Most of our knowledge of Earth’s interior comes from the
study of () and () earthquake waves
P & S
the crust can be as thin as (_) miles in oceanic regions and thick as (__) in some mountainous regions
5 miles
40 miles
Upper crust composed of (___) rocks
granitic
Lower crust is more akin to (___)
basalt
continental crust can be up to (_) billion years old
4
oceanic crust tends to be (___) millions years of age or less
180
Composition of the uppermost mantle is the igneous rock
(___)
peridotite
outer core is composed of (___) alloy
iron-nickel
(___) core behaves like a solid due to extreme pressue
inner
