Download Chapter 11 Part 3

CHAPTER 11
Earthquakes: Part 2
Learning Objectives:
1) I can explain what causes an
earthquake, what happens when one
occurs, as well as the different types
of hazards associated with them.
2) I can distinguish the four kinds of
seismic waves: P-wave, S-waves,
Rayleigh waves, and Love waves
3) I can match different earthquake focal
mechanisms to the type of faulting, and I
can relate them to different types of plate
boundaries.
Learning Objective 3 I can match different earthquake focal mechanisms to the type of faulting,
and I can relate them to different types of plate boundaries.
Most earthquakes occur on plate boundaries, but some earthquakes occur within plates
Copyright © 2014 John Wiley & Sons, Inc. All
rights reserved.
Learning Objective 3 I can match different earthquake focal mechanisms to the type of faulting,
and I can relate them to different types of plate boundaries.
Divergent plate boundaries: Seismicity (i.e., earthquake activity)
is typically shallow and low in magnitude.
?
normal
faulting
?
strike-slip
faulting
Copyright © 2014 John Wiley & Sons, Inc. All
rights reserved.
Learning Objective 3 I can match different earthquake focal mechanisms to the type of faulting,
and I can relate them to different types of plate boundaries.
Convergent plate boundaries:
seismicity can extend to great
depths along the subducting
plate, i.e., along the
Wadati-Benioff Zone.
?
reverse
faulting
is typical in
the mantle
Seismicity in back of the
Tonga Trench
Learning Objective 3 I can match different earthquake focal mechanisms to the type of faulting,
and I can relate them to different types of plate boundaries.
Transform plate boundaries: seismicity is frequent and can
be hazardous in highly populated areas.
??
strike-slip faulting is typical
CHAPTER 11
Earthquakes: Part 3
Learning Objectives:
1) I can identify the seismic characteristics of
Earth’s major layers.
2) I can relate earthquake magnitude to the relative
energy released and to the number of earthquakes
that occur.
3) I can use seismographs to locate and earthquake
and estimate its magnitude.
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers.
The seismic record around the world tells us the earth is layered.
Copyright © 2014 John Wiley & Sons, Inc. All
rights reserved.
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers and identify some structures found by seismic tomography
P-wave and
S-wave shadow zones
confirm the presence of
a liquid outer-core
no core
Slower seismic waves
Faster seismic waves
Faster seismic waves
Slower seismic waves
forward and back pushing
& pulling
Contraction
no S waves in liquid
outer core
S waves
side-to-side shear
P waves
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers and identify some structures found by seismic tomography
Reflections and refractions confirm the presence of
discontinuities in rock density inside the Earth
2) Lithosphere:
defines the
tectonic plate.
4 5 6 7 8 9 10
seismic velocity (km/s)
S waves velocity = 0
1) Coremantle
boundary
(2900 km
deep)
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers and identify some structures found by seismic tomography
Reflections and refractions confirm the presence of
discontinuities in rock density inside the Earth
2) Lithosphere:
defines the
tectonic plate.
6
7
P wave velocity
(km/s)
8
9
mafic & intermediate
rocks
low seismic velocity
higher seismic velocity
ultramafic rocks
(super dark chocolate)
4 5 6 7 8 9 10
seismic velocity (km/s)
S waves velocity = 0
1) Coremantle
boundary
(2900 km
deep)
3) Mohorovicic Discontinuity or “Moho”:
base of the crust:
• ~ 7 km beneath oceanic basins
• ~ 20 to ~70 km beneath continents
CHAPTER 11
Earthquakes: Part 3
Learning Objectives:
1) I can identify the seismic characteristics of
Earth’s major layers.
2) I can relate earthquake magnitude to the relative
energy released and to the number of earthquakes
that occur.
3) I can use seismographs to locate and earthquake
and estimate its magnitude.
Learning Objective 3: I can relate earthquake magnitude to the relative energy
released and to the number of earthquakes that occur.
Question 1: How many times more energy is released by a magnitude 7
earthquake compared to a magnitude 6 earthquake?
A) 56,000,000 times more
B) 1,800,000 times more
C) 32 times more
D) 2 times more
Learning Objective 3: I can relate earthquake magnitude to the relative energy
released and to the number of earthquakes that occur.
Richter
Question 3: Which are more frequent, magnitude 5 earthquakes or magnitude
6 earthquakes?
A) magnitude 5 earthquakes are more frequent
B) magnitude 6 earthquakes are more frequent
Learning Objective 3: I can relate earthquake magnitude to the relative energy
released and to the number of earthquakes that occur.
Richter
Question 4: How much more frequent are magnitude 5 earthquakes
compared to magnitude 6?
A) 10 times more
B) 100 times more
C) 1000 times more
D) 100 times less
CHAPTER 11
Earthquakes: Part 3
Learning Objectives:
1) I can identify the seismic characteristics of
Earth’s major layers.
2) I can relate earthquake intensity to the effects felt
and relate earthquake magnitude to the relative
energy released.
3) I can use seismographs to locate and earthquake
and estimate its magnitude.
Learning Objective 4: I can use seismographs to locate and earthquake and estimate
its magnitude.
Learning Objective 3: I can relate earthquake magnitude to the relative energy
released and to the number of earthquakes that occur.
The earthquake Intensity Scale (Modified Mercalli)
measures effects on people and buildings.
Earthquake Prediction:
We cannot predict
WHEN the earth will
break but we can
estimate where hazards
are more and less likely.
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers.
Seismologists use seismic tomography to image structures in Earth
Subducting Gorda and
Juan de Fuca Plates
Yellowstone
mantle plume
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers.
Seismic tomography is used to image the Earth’s interior like a CT scan
(see http://www.youtube.com/watch?v=Hrto0nIP8nk)
Red = slow seismic waves, low density, hot
Blue =fast seismic waves, high density, “cool”
Learning Objective 2: I can identify the seismic characteristics of Earth’s major
layers.
Tomography images of the
Hawaiian mantle plume
Red = slow seismic waves, low density, hot
Green= normal mantle
Blue =fast seismic waves, high density, “cool”
NW
Kilauea
SE
NW
SE