Chapter 10: Chapter 10: Earthquakes (Part 3) (Part 3)
Chapter 10:Chapter 10: Earthquakes (Part 3)(Part 3)Chapter 10:Chapter 10: Earthquakes (Part 3)(Part 3)
IN-CLASS EXERCISEObserve the following objects as I drop them on the floor and answer the following questions:
Objects:- Clay- Rubber Ball- Ice Cube Questions:1) Which of these behaves as a brittle material?2) As a ductile material?3) As an elastic material?4) Which of these material properties best accounts for the generation of earthquakes?
Optional extra credit assignment (20 pts):
The just released movie “The Core” is loadedwith geology, some
of it accurate and some not!
Assignment: Go and see “The Core” and
write a report that separates geological fact from fiction!
Length of write-up: 2 pagesUse illustrations.
Due two weeks from today.
TODAY’S LECTUREDetecting earthquakes.
Determining earthquake intensity and magnitude.
Locating earthquakes.
Earthquake damage (with examples).
In summary: Types of seismic waves
S-wave
Surface-wave
Motion produced by thedifferent wave types
P-wave
Fig. 10.17
W. W. Norton
Arrival timesof earthquake
waves.
Seismology
Seismology
- The study of earthquake “waves”, earthquakes, Earth
AncientChineseseismograph
Instrument torecord seismicwaves
seismic waves
Seismogram - Recording of ground shaking from seismographs
Fig. 10.15
W. W. NortonSeismograph
vs. seismogram
Fig. 10.16
W. W. Norton
Electrostatic device:
For measuring vertical motion…
For measuring horizontal motion…
Earthquake Intensity and Magnitude
Mercalli Intensity Scale
Magnitude
Qualitative scale to convey intensity of ground Shaking & damage at a specific location
An absolute measure of the energy released in an earthquake
Depends on distance to earthquake.& strength of earthquake.
Depends on the amount of elastic energystored in the rocks prior to the earthquakeand the intensity of faulting to releasethat energy.
Earthquake Magnitude & Intensity Magnitude
Intensity
An absolute measure of the energy released in an earthquake.
IntensityMagnitude
A qualitative measure of intensity based on damage.
Locating an Earthquake…
P-waves & S-wave travel at different speeds…
1. Measure time between P and S wave on seismogram.
2. Use travel-time graph to get distance to epicenter.
3. Draw circle on a map with radius of that distance.
4. Three or more circles should intersect at epicenter!
Basic Approach:
Fastest wave: Arrives first!
Fig. 10.18ab
W. W. Norton
Locating an Earthquake…
1. Measure time between P and S wave on seismogram.
2. Use travel-time graph to get distance to epicenter.
3. Draw circle on a map with radius of that distance.
4. Three or more circles should intersect at EQ!
Fig. 10.18c
W. W. Norton
Fig. 10.20
Earthquake Magnitude & Intensity Magnitude
An absolute measure of the energy released in an earthquake.Magnitude is measured at focus and is a non-linear scale…That is, the increase in energy between each step is exponential.
IntensityMagnitude
Fig. 10.21
Earthquake DamageEarthquake Damage
San Francisco, 1906
Intense fireIntense firedamage areadamage area
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
Fig. 10.13ef
W. W. Norton
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
Chapter 10:Chapter 10: Earthquakes (Part 4)(Part 4)Chapter 10:Chapter 10: Earthquakes (Part 4)(Part 4)
CLASS ANNOUNCEMENTS
Midterm 2 is this Friday!
Will cover these text chapters & lectures:
Chapter 7 (Sedimentary Rocks):
Pages 188-199.
Chapter 8 (Metamorphic Rocks)
Interlude B (Rock Cycle)
Chapter 9 (Volcanoes)
Chapter 10 (Earthquakes)
Interlude C (Seeing inside the Earth)
Chapter 11 (Crustal deformation and
mountain building): Pages 319-334.
~50 MC questions. Worth 100 pts.
Review outline will be Posted on web this evening.
TODAY’S LECTUREEarthquake damage (with examples).
Factors that determine the intensity of an earthquake.
Secondary effects of earthquakes.
Videos on selected eartquakes.
Quiz on Chapters 9 and 10.
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sediments3) Fires (rupture of gas lines)3) Fires (rupture of gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
Fig. 10.36a
W. W. Norton
Fig. 10.36b
W. W. Norton
Fig. 10.36c
W. W. Norton
Fig. 10.19
W. W. Norton
Earthquake hazards Along Passive Margins
Charleston, S.C.August 1886
Death toll: 60.Magnitude: ~7
Large Intraplate Earthquakes…New Madrid, Missouri, 1811-12Accounts from fur trappers
& naturalist, John Audubon.Estimated magnitude: >8.5Three main shocks.1500 aftershocks.Activity lasted 53 days.Affected >2.5 million sq. km(1 million acres) Church bells tolled in Boston.Windows rattled, Washington D.C.Thousands of sq. km. subsided to form lakes (St. Francis & Reelfoot Lakes). Large swamps were formed.Mississippi River reversed flowin places.Waves overwhelmed riverboats.Large fissures opened on flood plain of river.Geysers of sand, water and sulfurous geysers were erupted.
What happened?
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sediments3) Fire (ruptured gas lines)3) Fire (ruptured gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
Fig. 10.38d
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sediments3) Fire (ruptured gas lines)3) Fire (ruptured gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
W. W. Norton
High Rise Buildings
Vertical and horizontal ground motion
Mexico City, 1985
Taiwan, 1999 Magnitude 7.6Taiwan, 1999 Magnitude 7.6
Fig. 10.27ab
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Collapse of Building Facades
Collapse of Smaller Multistory Buildings
Fig. 10.28c
J. Dewey, U.S. Geological Survey
Collapse of first floor parking structures
Northridge, CA. 1994 Magnitude: 6.7
Deaths: 61
Seattle 2/28/2001 Magnitude 6.8Seattle 2/28/2001 Magnitude 6.8
Collapse of Building Facades
Types of Earthquakes
Aftershocks Small earthquakes that follow an initial earthquake in same vicinity
Foreshocks
Small earthquakes that sometimes precede a large one by few days
Fig. 10.27cd
W. W. Norton
Elevated Roadways and Bridges
Fig. 10.28b
M. Celebi, U.S. Geological Survey
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sediments3) Fire (ruptured gas lines)3) Fire (ruptured gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
Landslides (slumping)
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sediments3) Fire (ruptured gas lines)3) Fire (ruptured gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
Fig. 10.27fg
W. W. Norton
Behavior of brick structures:
Behavior of water-saturated sediments: Liquefaction
Effects of Earthquakes on Man-made Structures
Anchorage, Alaska, 1964Magnitude: 8.6Death Toll: 131
Fig. 10.30ab
W. W. Norton
Liquefaction of sediments
Turnagain HeightsAnchorage, Alaska 1964
Fig. 10.30c
National Geophysical Data Center/NOAA
Liquefaction
Niigata, Japan 1964.Buildings designed toResist earthquakes,but sited on water-
saturated soil.
Liquifaction of Sediments
San Francisco Bay Area, CA Loma Preita EQ, 1989. Magnitude 7.1
Marina District, San Francisco Loma Prieta EQ, 1989
Magnitude 7.1 Deaths: 63
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sediments3) Fires (ruptured gas lines)3) Fires (ruptured gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
San Francisco 1906 Earthquake: Magnitude 8.3San Francisco 1906 Earthquake: Magnitude 8.3
Fig. 10.32b
U.S. Geological Survey
Ruptured gas main.EQ Magnitude: 6.6
Death toll: 65
San Fernando, CA. 1971
Earthquake Destruction
Important contributing factors:
1) Intensity & duration of shaking 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments2) Soil type (unconsolidated sedimentsor hard bedrock?)or hard bedrock?)3) Building design3) Building design
Other undesirable effects:
1)1) LandslidesLandslides2) Liquifaction of sediments2) Liquifaction of sedimentsFire (rupture of gas lines)Fire (rupture of gas lines)4) Tsunamis (seismic sea waves)4) Tsunamis (seismic sea waves)
Tsunamis (Seismic Sea Waves)
Tsunamis are often called tidal waves, but they are caused by seafloor earthquakes, not the tides!
Travel at speeds of several hundred km/hr. Wave heights <1 m in open ocean, but
upon reaching shallow water, may exceed 65 m.
Fig. 10.34b
Pacific Tsunami Museum
Tsunami, Hilo, HA 1946
Fig. 10.34a
Cecilio Licos, Yasuki Arakaki Collection/Pacific Tsunami Museum
TsunamiHilo, Hawaii, 1946; Death toll: 56
Property damage $25MAfter this, U.S. Coast & Geodetic
Survey established a tsunamiearly warning system.
Tsunami damage:Alaska 1964 earthquake
Earthquake destruction
Tsunami from Chilean earthquake, 1960. Magnitude 9.5
Predicting Tsunamis
Movie:
Tsunami damage in Hawaii, 1960.Originated from Chilean earthquake.Wave arrived 15 hours later.
Tsunamis
Protecting Yourself
Fig. 10.39a
Adapted from Nishenko, 1989 (U.S. Geological Survey).
Earthquake preparedness and how to protect yourself…
See class handout!
Fig. 10.35a
W. W. Norton
How to look for faulting and other evidence of past earthquakes…
Fig. 10.35d
W. W. Norton
How to look for faulting & other evidence of past earthquakes.
Fig. 10.38abc
Adapted from Wesson and Wallace, 1985.
Designing earthquake resistant buildings…
Earthquake prediction
Only long range predictions possible at present (but don’t always work)