Physics of Earthquakes

Question 1

Earthquake

Answer 1

Ground shaking that accompanies sudden movement along a fault, movement of magma underground, a fast-moving landslide, or a large explosion.

Question 2

First Stage of an Earthquake

Answer 2

Energy buildup: Strain accumulates as rock on either side of the fault is pushed in opposite directions (stress).

Question 3

Second Stage of an Earthquake

Answer 3

Rapture and Initial Energy Release: Rock breaks in a rupture zone sends vibrations out through the surrounding rock. Vibrations travel out from the epicenter as Primary and Secondary Waves. (P and S waves)

Question 4

Third Stage of an Earthquake

Answer 4

Continued Release: surface shaking: Earthquake waves reach the surface, traveling as Love and Raleigh waves.

Question 5

Fourth Stage of an Earthquake

Answer 5

Post Event: After shaking ceases, strain builds up, setting the stage for the next earthquake.

Question 6

Primary (P) Waves

Answer 6

Body waves that move by compression and expansion.

Question 7

Secondary (S) Waves

Answer 7

Body waves that move by vertical displacement.

Question 8

Love Waves

Answer 8

Surface waves that move by lateral (sideways) displacement. They decay slowly and are highly destructive.

Question 9

What are Love waves named for?

Answer 9

Mathematician A. E. Love.

Question 10

What is the velocity of a Love wave?

Answer 10

Less than 2.9 kps

Question 11

Raleigh Waves

Answer 11

Surface waves that move by vertical displacement.

Question 12

What is the velocity of a Raleigh wave?

Answer 12

Less than 3.0 kps

Question 13

What are Raleigh waves named for?

Answer 13

Physicist Lord Raleigh

Question 14

What are the 3 stresses that cause geologic formations?

Answer 14

1. Compression
2. Extension
3. Shearing

Question 15

Compression

Answer 15

Rock is pushed together

Question 16

Extension

Answer 16

Rock is stretched

Question 17

Shearing

Answer 17

Rock is wrenched sideways

Question 18

How do earthquakes behave?

Answer 18

1. Initiation
2. Wave travel below the Earth’s surface
3. Wave travel at the Earth’s surface
4. Aftermath

Question 19

Body Waves

Answer 19

Waves travel below the Earth’s surface

Question 20

Surface Waves

Answer 20

Wave travel at the Earth’s surface

Question 21

Aftermath of an Earthquake

Answer 21

Stress buildup and eventual release

Question 22

How are earthquakes measured and located?

Answer 22

1. Instrumentation
2. Measuring scales
3. Locating epicenters and hypnocenters

Question 23

What are the 3 instruments used to measure earthquakes?

Answer 23

1. Seismoscope
2. Vertical Pendulum
3. Seismograph

Question 24

Seismoscope

Answer 24

A mechanical device that detects vibrations from distant earthquakes. It uses a ball falling from a chute into a cup (frog) indicating direction of principle impulse.

Question 25

Vertical Pendulum

Answer 25

A hanging weight attempting to remain motionless while the ground moves below it.

Question 26

Seismograph

Answer 26

A mechanical or electronic device that measures the intensity and frequency of the vibrations associated with an earthquake.

Question 27

What 3 scales are used to measure earthquakes?

Answer 27

1. Mercalli Intensity Scale
2. Richter Scale
3. Moment-Magnitude Scale

Question 28

Mercalli Intensity Scale

Answer 28

Earthquake magnitude scale based on damage to human-made structures. Published by Guiseppe Mercalli (Italian geophysicist) in 1902.

Question 29

Richter Scale

Answer 29

Earthquake magnitude scale based on the peak amplitude of a Wood-Anderson seismogram. Developed by Charles Richter (American geophysicist) in 1935.

Question 30

Moment Magnitude Scale

Answer 30

Earthquake magnitude scale based seismic moment, which is:

1. Total length of fault rupture
2. Depth of rupture
3. Total slip
4. Rock strength

Question 31

What determines how earthquakes behave?

Answer 31

1. Underlying geology
2. Overlying sediments
3. Accumulated Stress
4. Extent and duration of rupture