Notes Chapter 12 Earthquakes
Section 12.1 – How and where earthquakes happen
Earthquakes

____________________of Earth's crust caused by a sudden ______________of _______

usually _________________ along a ______________(moveable break in Earth's crust)

affect large areas
 most ________________natural disaster
 __________________________that builds up between 2 __________________________

Large earthquakes have occurred in San Francisco, ___________________________,
______________________and Japan.
Why earthquakes happen

_________________ rebound
 friction between plates __________________ movement along boundary
(_________________)
 _______________ causes the plates to _______________ (change shape)
 stress becomes great enough to ____________________ the frictional force
and the _____________________...EARTHQUAKE!
 plates _____________________________ to original shape, but in a new
location relative to each other
Anatomy of an Earthquake

______________ - location along a fault WITHIN Earth where earthquake waves
originate

____________________ - point on Earth's SURFACE directly above focus

__________________ - large fracture in earth along which movement occurs
Seismic Waves

released energy in the form of ______________________

Earth's interior affects the __________________________________

____________________________ - area where no seismic waves from a particular
earthquake can be detected
Body & Surface Waves

_______________ waves
 _____ waves (primary or compression waves)
 _____ waves (secondary or shear waves)

__________________ waves
 travel along the __________________ cause ground and anything on it to
move; ___________________ moving, but can cause ______________________

Love waves - ___________________________

_________________ waves – _____________________ motion
P waves vs. S waves

P waves
 ________________ waves and ________ detected
 push and pull __________________ to the direction waves are traveling
 ___________ travel through _______________________________________.

S waves
 _______________ than P waves
 move rock in a _____________________________ motion perpendicular to
wave motion
 can travel through __________________ only
Section 12.2 – Studying earthquakes
Recording Earthquakes

________________________________ - study of earthquakes and seismic waves s

_______________________________ - instrument that records earthquake waves

produce ___________________________ (tracing of earthquake motion) the larger
the _____________________ the bigger the earthquake
Locating an Earthquake

uses the __________________________ of P and S waves

___________________ lag time indicates an earthquake __________________ away

lag-time graph shows relationship between P & S wave travel time and _________
distance

today, computers perform complex calculations to locate epicenter

before computers, 3 seismograph recordings were needed to locate epicenter
 radius of circle = distance from station to epicenter point where all circles
intersect indicates epicenter
Magnitude

total amount of __________________ released during an earthquake

determined by measuring the amount of ___________________________ caused by
an earthquake

moment magnitude
 uses the _____________________________________ that fault blocks move to
determine the magnitude (the larger the number the stronger the quake)
 largest recorded earthquake is 9.5
 2.5 and lower not usually felt by humans
Intensity

amount of damage caused by an earthquake

earthquake's intensity depends on it
 magnitude
 distance between epicenter and affected area
 local geology
 duration
 human infrastructure

measured on modified Mercalli scale (Roman numerals I-XII)
Section 12.3 – Earthquakes and Society
Destruction of Quakes

depends on __________________________________________ to a populated area

_______________________ damage
 intensity, duration of vibration, type of ground beneath building, design
or structure

_____________________ (large ocean waves generated by quakes) sudden drop
or rise in ocean floor or underwater landslide increase in height as they
approach shore

__________________________ (broken power or gas lines)

_______________________ (triggered by vibrations)

__________________________ (broken dams/levies)
Earthquake Safety

before


be ___________________________
during
___________________
 indoors - stand in doorway or _________________ a desk/table, stay
__________________ from windows and heavy furniture
 car - _______________ the car in a safe place

after
 be ______________________
wear closed toe shoes
Predicting Earthquakes

__________ reliable way

Methods of prediction
 __________________________ - zones of low earthquake activity
 ___________________ – little earthquakes before big ones
 __________________________ – tilting, strain, cracks
 Monitor _________________________________ from strained or fractured rock