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

IN-CLASS EXERCISE Observe 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 loaded with 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 pages Use illustrations. Due two weeks from today.

TODAY’S LECTURE  Detecting 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 the different wave types P-wave

Fig W. W. Norton Arrival times of earthquake waves.

Seismology - The study of earthquake “waves”, earthquakes, Earth Ancient Chinese seismograph Instrument to record seismic waves seismic waves Seismogram - Recording of ground shaking from seismographs

Fig W. W. Norton Seismograph vs. seismogram

Fig W. W. Norton Electrostatic device:

For measuring vertical motion… For measuring horizontal motion…

Earthquake Intensity and Magnitude l Mercalli Intensity Scale l 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 energy stored in the rocks prior to the earthquake and the intensity of faulting to release that energy.

Earthquake Magnitude & Intensity l Magnitude lIntensity An absolute measure of the energy released in an earthquake. Intensity Magnitude 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 ab 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 c W. W. Norton

Fig

Earthquake Magnitude & Intensity l 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. Intensity Magnitude

Fig

Earthquake Damage San Francisco, 1906

Intense fire damage area San Francisco 1906 Earthquake: Magnitude 8.3

Fig ef W. W. Norton

San Francisco 1906 Earthquake: Magnitude 8.3

Chapter 10:(Part 4) Chapter 10: Earthquakes (Part 4)

CLASS ANNOUNCEMENTS Midterm 2 is this Friday! Will cover these text chapters & lectures: Chapter 7 (Sedimentary Rocks): Pages 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 ~50 MC questions. Worth 100 pts. Review outline will be Posted on web this evening.

TODAY’S LECTURE  Earthquake 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 l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments 3) Fires (rupture of gas lines) 4) Tsunamis (seismic sea waves)

Fig a W. W. Norton

Fig b W. W. Norton

Fig c W. W. Norton

Fig W. W. Norton Earthquake hazards Along Passive Margins Charleston, S.C. August 1886 Death toll: 60. Magnitude: ~7

Large Intraplate Earthquakes… New Madrid, Missouri,  Accounts from fur trappers & naturalist, John Audubon.  Estimated magnitude: >8.5  Three 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 flow in 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 l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments 3) Fire (ruptured gas lines) 4) Tsunamis (seismic sea waves)

Fig d

Earthquake Destruction l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments 3) Fire (ruptured gas lines) 4) Tsunamis (seismic sea waves)

W. W. Norton High Rise Buildings Vertical and horizontal ground motion

Mexico City, 1985

Taiwan, 1999 Magnitude 7.6

Fig ab W. W. Norton Collapse of Building Facades Collapse of Smaller Multistory Buildings

Fig c J. Dewey, U.S. Geological Survey Collapse of first floor parking structures Northridge, CA Magnitude: 6.7 Deaths: 61

Seattle 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 cd W. W. Norton Elevated Roadways and Bridges

Fig b M. Celebi, U.S. Geological Survey

Earthquake Destruction l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments 3) Fire (ruptured gas lines) 4) Tsunamis (seismic sea waves)

Landslides (slumping)

Earthquake Destruction l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments 3) Fire (ruptured gas lines) 4) Tsunamis (seismic sea waves)

Fig fg W. W. Norton Behavior of brick structures: Behavior of water-saturated sediments: Liquefaction Effects of Earthquakes on Man-made Structures

Anchorage, Alaska, 1964 Magnitude: 8.6 Death Toll: 131

Fig ab W. W. Norton Liquefaction of sediments Turnagain Heights Anchorage, Alaska 1964

Fig c National Geophysical Data Center/NOAA

Liquefaction Niigata, Japan Buildings designed to Resist earthquakes, but sited on water- saturated soil.

Liquifaction of Sediments San Francisco Bay Area, CA Loma Preita EQ, Magnitude 7.1

Marina District, San Francisco Loma Prieta EQ, 1989 Magnitude 7.1 Deaths: 63

Earthquake Destruction l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments 3) Fires (ruptured gas lines) 4) Tsunamis (seismic sea waves)

San Francisco 1906 Earthquake: Magnitude 8.3

Fig b U.S. Geological Survey Ruptured gas main. EQ Magnitude: 6.6 Death toll: 65 San Fernando, CA. 1971

Earthquake Destruction l Important contributing factors: 1) Intensity & duration of shaking 2) Soil type (unconsolidated sediments or hard bedrock?) 3) Building design l Other undesirable effects: 1)Landslides 2) Liquifaction of sediments Fire (rupture of gas lines) 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 b Pacific Tsunami Museum Tsunami, Hilo, HA 1946

Fig a Cecilio Licos, Yasuki Arakaki Collection/Pacific Tsunami Museum Tsunami Hilo, Hawaii, 1946; Death toll: 56 Property damage $25M After this, U.S. Coast & Geodetic Survey established a tsunami early warning system.

Tsunami damage: Alaska 1964 earthquake Earthquake destruction

Tsunami from Chilean earthquake, Magnitude 9.5 Predicting Tsunamis Movie:

Tsunami damage in Hawaii, Originated from Chilean earthquake. Wave arrived 15 hours later. Tsunamis

Protecting Yourself

Fig a Adapted from Nishenko, 1989 (U.S. Geological Survey). Earthquake preparedness and how to protect yourself… See class handout!

Fig a W. W. Norton How to look for faulting and other evidence of past earthquakes…

Fig d W. W. Norton How to look for faulting & other evidence of past earthquakes.

Fig abc Adapted from Wesson and Wallace, Designing earthquake resistant buildings…

Earthquake prediction l Only long range predictions possible at present (but don’t always work)