Earthquakes Flashcards
Which side of a Popsicle stick breaks first,
and why?
The upper side.
Do rocks break more easily under tension
or compression?
Why is the 1906 San Francisco
earthquake considered “one of the most
significant earthquakes of all time”?
How are the meanings of “elastic” and
“plastic” deformation different?
What is an epicenter? Explain.
The point on the surface closest to the earthquake focus
What is an earthquake focus? Explain.
Calculation question. If an earthquake
occurs 240 km from a city, will the S or P
wave reach the city first? How long will it
take for a P-wave to reach it (assuming a
straight line distance from the focus)?
How long will it take the S-wave to reach
the city? Hint: Look at the notes for the
approximate speeds of the P and S waves? Solution is given at the end of this document.
Should damage increase, decrease, or
stay about the same with increasing
distance from an earthquake?
What are the various types of seismic
waves? Compare and contrast properties
of these waves – direction in which the
ground moves, speed of wave, damage
potential.
Which type of earthquake wave typically
causes the most damage to man-made
structures?
What caused most of the damage during
the San Francisco of 1906?
What is an “inertial mass”? How does it
respond during an earthquake?
What is a seismograph? How does a
seismogram differ from a seismograph?
What kind of information can be
determined from “reading” a
seismogram? Give an example.
What are “first arrivals”? Give an
example.
What is the “amplitude” of a seismic
wave? Give an example.
amount of ground shaking recorded by a seisometer. The length between the center of the line and the top of th
What are the names of the three scales of
earthquake measurement, and what does
each measure?
P wave, S wave, Surface wave
Calculation question. If one earthquake
has a Richter magnitude of 3, and
another 5, how much “bigger” in
amplitude (amount of ground shaking) is
the 5 event compared to the 3 event?
x102
Calculation question. If one earthquake
has a Richter magnitude of 4.5, and
another 6.5, how much more energy was
released in the 6.5 event compared to the
4.5 event?
x103 or 100x
Calculation question. If one earthquake
has a Richter magnitude of 4.5, and
another 6.5, how many of the 4.5 earthquakes would be needed to equal the energy of a single 6.5 event?
What were some consequences of the
1994 Northridge earthquake? Describe
details.
Elevated highways were toppled, $20 billion losses, 57 dead, 4th costliest disaster in US history.
As ground amplitude increases, does
damage to buildings and structures
increase, decrease, or stay about the
same? Explain.
buildings and strucutres receive less damage if they are above solid bedrock. The looser the sediment, the worse the damage.
How might a sizable earthquake make an
average home or apartment a deadly
place to be during the event?
The furniture and other items can fall on top of you.
Buildings can’t be protected from
earthquake damage, right? Explain.
They can be to an extent. With friction pendolum bearings.
What is liquefaction and how is it a risk for
some structures?
When the earthquake causes the ground to liquify. Loss of soil strength during earthquake.
What is a “tsunami”? How are tsunamis
caused by earthquakes?
seismic sea waves caused by earthquakes under water. A subuduction plate dives down underneath the subduction zone. Check notes for picture.
What is the estimated Richter Magnitude
of the Indonesian (Sumatran) earthquake
of 2004, and why was it (in part) so
deadly throughout the Indian Ocean?
9.3
250,000 people died because there was no warning system.
Calculation question. Suppose an
undersea earthquake causes both a
tsunami and P-waves, starting at the
same location. If the tsunami travels at
400 mph through the ocean, and the P
wave travels at 6 km/sec through the
lithosphere, which wave would first hit a
distant coastal city some 1,000 miles
away?
What was Iben Browning’s earthquake
prediction? Did it come true?
Earthquakes triggered by lunar gravity because the moon will be closer to the earth then in a very long time, and gravitational stress will cause a 6 to 6.5 earthquake on Dec. 2-3 1990.
No eathquake happened.
What were the scientific ideas behind
Browning’s earthquake prediction? Was
the science “good” or “bad”? Explain.
Is earthquake “prediction” an important
part of current earthquake research?
Explain.
Where was the largest known earthquake
to have occurred in Alabama, and how big was it? How do we know?
What’s the difference between an
earthquake “forecast” and an earthquake
“prediction”? Explain.
About how fast is the San Andreas Fault
moving, based on data at Wallace Creek?
1.4 in a year
Calculation question. If the San Andreas
Fault is moving at an average rate of 2
inches per year, about how far (in miles)
will land on one side of the fault be moved
in 100,000 years?
Compared to California, the risk of
earthquake activity in Alabama is a) more,
b) about the same, c) less. Defend your
choice by citing relevant evidence.
If another earthquake of the same size as
the San Francisco 1906 earthquake were
to occur again today, how (and why)
would damage and other effects be
different (if at all) from those that occurred
in 1906? Explain.
Is the distribution of earthquakes
“random” across the face of the globe? If
not, what controls where most
earthquakes occur?
