Chapter 6.2 Notes: Recording Earthquakes
1. A ____________________ is an instrument that is used to ________________ and
record seismic __________________.
a. A seismograph records _________________ by tracing wave-shaped __________
on a paper or by ______________________ the motion into electronic
________________.
b. A _______________________ consists of three main ______________________
devices that measure _____________________ in the following directions.
i. ____________________ motion of the ground.
ii. ____________________ motion in East-West direction
iii. Horizontal motion in _____________________________ direction
2. Scientists have determined that _________________________ generally produce three
major types of seismic ______________.
a. Each type of wave travels at a different _____________ and causes different
__________________ in the earth’s crust.
i. _________________ waves, or P-waves, move the _______________ and
are therefore the first to be _____________________ by a seismograph.
1. P-waves can travel through ___________ and ________________.
2. The more ____________ the material the faster the ___-wave
travels.
3. P-waves are ________________ waves which means they cause
rock __________________ to move together and apart along the
____________________ of the waves.
ii. __________________ waves, or S-waves, are the second _____________
to be recorded by a seismograph.
1. S-waves can only travel through ______________ material.
2. S-waves are ______________ waves which means that they cause
rock particles to move at _____________ angles to the direction in
which the waves are traveling.
iii. _______________________ waves are created when p-waves and swaves reach the __________________ surface.
1. Surface waves are the _________________ moving waves and are
the _____________ to be recorded on a seismograph.
2. Surface waves travel over the earth’s surface similar to
____________________ waves.
3. Surface waves are __________________ when traveling through
loose earth.
3. Locating an Earthquake
a. The difference between the arrival ____________ of the p-waves and s-waves can
be used to determine the ________________________ of an earthquake.
b. P-waves travel about ______________________ faster than s-waves.
i. Therefore, if the ___________________ arrive shortly after the p-waves
we know that the ________________________ occurred close, and if the
s-waves arrive a ______________ time after the p-waves we know the
earthquake occurred ______________ away.
c. To determine the exact ___________________ of the epicenter scientists
___________ the difference between the __________________ times of the two
waves and compare them to a standard _______________ that turns the times into
distances from the ________________________.
i. In order to determine the _________________ you must have information
from at least three seismograph ________________ at different locations.
ii. __________________ are drawn on a map using the
______________________ recorded.
iii. Where the circles __________________ is the epicenter of the earthquake.
4. Earthquake Measurement
a. ________________________ is a measure of the __________________ released
by an earthquake and is also described as the amount of ______________ motion.
i. Magnitude is measured using the _______________________ scale or the
______________________ _______________________ Scale.
1. The _______________ scale is related to the _________________
of the earthquake while the moment magnitude scale is related to
the ____________________ of the earthquake.
ii. Earthquakes with a magnitude less than a _______ are called
________________________ and are usually not felt by people.
iii. The ____________________ scale expresses the ____________________
of an earthquake, or the amount of ________________________ it causes
through roman numerals and ___________________________ of damage.
1. The Mercalli scale describes an earthquake with a scale from
_____________, where a rating of II is a low ________________.