Chp 11 Earthquakes

Question 1

What are Earthquakes?

Answer 1

They are a sudden release of energy that has been built up in the earth’s crust.

Question 2

Explain the elastic rebound theory.

Answer 2

It is a theory that explains the accumulation of energy and its sudden release during earthquakes.

Question 3

State Notes about the elastic rebound theory:

Answer 3

• Earthquakes can be caused by forces far away from the source.
  This is because due to the rigid nature of the tectonic plates, they build up stresses even far away from edges where the initial movement occurs.
• This movement over time builds up stress.
• When the accumulated stress exceeds the strength of the rock at the fault line , it releases this energy.

Question 4

What is the focus (or hypocenter) of the earthquake?

Answer 4

It is the point of initial breakage and movement along the fault.

Question 5

What is the Epicenter?

Answer 5

It is a point on the Earth’s surface directly above the focus.

Question 6

What are Seismic waves?

Answer 6

They are the form in which energy of the earth quake is released.

Question 7

What are the types of Seismic Waves?

Answer 7

• Surface waves:
  They travel along the surface of the Earth away from the epicenter.
• Body Waves:
  Travel outward from the focus in all directions through the Earth’s interior.

Question 8

What are the Types of Body Waves?

Answer 8

There are two types of Body waves:

• Primary Waves:
  They travel through solids. They are about 1.7 times faster than S-waves.
  They propagate in the same direction of motion.
• Secondary Waves:
  They travel only through solids.
  They propagate along the Z-axis, perpendicular to the direction of movement.

Question 9

What are the properties of Surface Waves?

Answer 9

• Slowest moving
• largest amplitude
• Most destruction
• complex rotational motion
• they have greatest periods

Question 10

Explain the two measurements of the describe the size of the earthquake?

Answer 10

1. Intensity: a measure of the degree of earthquake shaking at a given locale based on the amount of damage.
2. Magnitude: Estimates the amount of energy released at the source of the earthquake.

Question 11

What is one Intensity Scale?

Answer 11

Mercalli Intensity scale

Question 12

What is the drawback of intensity scales?

Answer 12

It is that destruction may not be a true measure of the earthquake actual severity.

Question 13

What is an important note about the magnitude of earthquakes?

Answer 13

They use a logarithmic scale so a unit increase in the magnitude corresponds to 10 fold increase in the amplitude of motion.

Question 14

What are the magnitude scales of earthquakes?

Answer 14

• Richter scale
• Moment magnitude

Question 15

Where can you expect the worst effects of the earthquake?

Answer 15

Close to the epicenter you can expect the wrost.