Earthquakes

Question 1

Which side of a Popsicle stick breaks first,
and why?

Answer 1

The upper side.

Question 2

Do rocks break more easily under tension
or compression?

Question 3

Why is the 1906 San Francisco
earthquake considered “one of the most
significant earthquakes of all time”?

Question 4

How are the meanings of “elastic” and
“plastic” deformation different?

Question 5

What is an epicenter? Explain.

Answer 5

The point on the surface closest to the earthquake focus

Question 6

What is an earthquake focus? Explain.

Question 7

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.

Question 8

Should damage increase, decrease, or
stay about the same with increasing
distance from an earthquake?

Question 9

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.

Question 10

Which type of earthquake wave typically
causes the most damage to man-made
structures?

Question 11

What caused most of the damage during
the San Francisco of 1906?

Question 12

What is an “inertial mass”? How does it
respond during an earthquake?

Question 13

What is a seismograph? How does a
seismogram differ from a seismograph?

Question 14

What kind of information can be
determined from “reading” a
seismogram? Give an example.

Question 15

What are “first arrivals”? Give an
example.

Question 16

What is the “amplitude” of a seismic
wave? Give an example.

Answer 16

amount of ground shaking recorded by a seisometer. The length between the center of the line and the top of th

Question 17

What are the names of the three scales of
earthquake measurement, and what does
each measure?

Answer 17

P wave, S wave, Surface wave

Question 18

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?

Answer 18

x10²

Question 19

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?

Answer 19

x10³ or 100x

Question 20

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?

Question 21

What were some consequences of the
1994 Northridge earthquake? Describe
details.

Answer 21

Elevated highways were toppled, $20 billion losses, 57 dead, 4th costliest disaster in US history.

Question 22

As ground amplitude increases, does
damage to buildings and structures
increase, decrease, or stay about the
same? Explain.

Answer 22

buildings and strucutres receive less damage if they are above solid bedrock. The looser the sediment, the worse the damage.

Question 23

How might a sizable earthquake make an
average home or apartment a deadly
place to be during the event?

Answer 23

The furniture and other items can fall on top of you.

Question 24

Buildings can’t be protected from
earthquake damage, right? Explain.

Answer 24

They can be to an extent. With friction pendolum bearings.

Question 25

What is liquefaction and how is it a risk for some structures?

Answer 25

When the earthquake causes the ground to liquify. Loss of soil strength during earthquake.

Question 26

What is a “tsunami”? How are tsunamis caused by earthquakes?

Answer 26

seismic sea waves caused by earthquakes under water. A subuduction plate dives down underneath the subduction zone. Check notes for picture.

Question 27

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?

Answer 27

9.3 250,000 people died because there was no warning system.

Question 28

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?

Question 29

What was Iben Browning’s earthquake prediction? Did it come true?

Answer 29

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.

Question 30

What were the scientific ideas behind Browning’s earthquake prediction? Was the science “good” or “bad”? Explain.

Question 31

Is earthquake “prediction” an important part of current earthquake research? Explain.

Question 32

Where was the largest known earthquake to have occurred in Alabama, and how big was it? How do we know?

Question 33

What’s the difference between an earthquake “forecast” and an earthquake “prediction”? Explain.

Question 34

About how fast is the San Andreas Fault moving, based on data at Wallace Creek?

Answer 34

1.4 in a year

Question 35

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?

Question 36

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.

Question 37

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.

Question 38

Is the distribution of earthquakes “random” across the face of the globe? If not, what controls where most earthquakes occur?