Chapter 10:(Part 3) Chapter 10: Earthquakes (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

W. W. Norton

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)