op ch10 lecture_earth3, earthquakes

Chapter 10: A Violent Pulse: Earthquakes Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak

Chapter 10A Violent Pulse: Earthquakes

©2008 W. W. Norton & Company, Inc.

Portrait of a PlanetThird Edition

earthearth

LECTURE OUTLINE


A Violent Pulse: EarthquakesA Violent Pulse: Earthquakes

Prepared by

Ronald Parker Earlham College Department of Geosciences

Richmond, Indiana

Prepared by

Ronald Parker Earlham College Department of Geosciences

Richmond, Indiana


What Is an Earthquake?What Is an Earthquake? Earth shaking caused by a rapid release of energy.Earth shaking caused by a rapid release of energy.

Due to tectonic stresses that cause rocks to break. Due to tectonic stresses that cause rocks to break. Energy moves outward as an expanding sphere of waves. Energy moves outward as an expanding sphere of waves. This waveform energy can be measured around the globe. This waveform energy can be measured around the globe.

Earthquakes destroy buildings and kill people.Earthquakes destroy buildings and kill people. 3.5 million deaths in the last 2,000 years.3.5 million deaths in the last 2,000 years.

Earthquakes are common.Earthquakes are common.


SeismicitySeismicity Seismicity (earthquake activity) occurs due to…Seismicity (earthquake activity) occurs due to…

Motion along a newly formed crustal fracture (fault).Motion along a newly formed crustal fracture (fault). Motion on an existing fault.Motion on an existing fault. A sudden change in mineral structure.A sudden change in mineral structure. Inflation of a magma chamber.Inflation of a magma chamber. Volcanic eruption.Volcanic eruption. Giant landslides.Giant landslides. Meteorite impacts.Meteorite impacts. Nuclear detonations.Nuclear detonations.


Faults and EarthquakesFaults and Earthquakes Most earthquakes occur along faults.Most earthquakes occur along faults.

Faults are crustal fractures that move rock masses. Faults are crustal fractures that move rock masses. The amount of movement is termed displacement. The amount of movement is termed displacement. Displacement is also called offset, or slip.Displacement is also called offset, or slip.

Markers may reveal Markers may reveal

the amount of offset. the amount of offset.


Earthquake ConceptsEarthquake Concepts Hypocenter (focus) - The spot within the Earth Hypocenter (focus) - The spot within the Earth

where earthquake waves originate. where earthquake waves originate. Usually occurs on a fault surface.Usually occurs on a fault surface. Earthquake waves expand outward from the hypocenter. Earthquake waves expand outward from the hypocenter.

Epicenter – Land surface above the hypocenter. Epicenter – Land surface above the hypocenter.


Faults are like planar breaks in blocks of crust. Faults are like planar breaks in blocks of crust. Most faults slope (although some are vertical).Most faults slope (although some are vertical). On a sloping fault, crustal blocks are classified as:On a sloping fault, crustal blocks are classified as:

Footwall (block below the fault).Footwall (block below the fault). Hanging wall (block above the fault).Hanging wall (block above the fault).

Faults and Fault MotionFaults and Fault Motion


Fault TypesFault Types Fault type based on relative block motion. Fault type based on relative block motion.

Normal fault Normal fault



Reverse faultReverse fault



Thrust fault Thrust fault Special kind of reverse fault.Special kind of reverse fault.



Strike-slip fault Strike-slip fault



Oblique-slip fault Oblique-slip fault A combination of dip-slip and strike-slip.A combination of dip-slip and strike-slip.Most faults display an oblique-slip character.Most faults display an oblique-slip character.PurePure dip-slip or strike-slip are rare. dip-slip or strike-slip are rare.


Faults and Fault MotionFaults and Fault Motion Faults are commonplace in the crust.Faults are commonplace in the crust.

Active faults – Ongoing stresses produce motion.Active faults – Ongoing stresses produce motion. Inactive faults – Motion occurred in the geologic past.Inactive faults – Motion occurred in the geologic past.

Displacement can be visible.Displacement can be visible. Fault trace – A surface tear.Fault trace – A surface tear. Fault scarp – A small cliff.Fault scarp – A small cliff.

Blind faults are invisible.Blind faults are invisible.


Fault InitiationFault Initiation Tectonic forces add stress to unbroken rocks.Tectonic forces add stress to unbroken rocks. The rock deforms slightly (elastic strain). The rock deforms slightly (elastic strain). Continued stress will cause growth of cracks. Continued stress will cause growth of cracks. Eventually, cracks grow to the point of failure. Eventually, cracks grow to the point of failure. When the rock breaks, elastic strain transforms When the rock breaks, elastic strain transforms

into brittle deformation, releasing earthquake into brittle deformation, releasing earthquake energy.energy.


Fault MotionFault Motion Faults move in jumps.Faults move in jumps. Once motion starts, it quickly stops due to friction.Once motion starts, it quickly stops due to friction. Eventually, strain will build up again, causing failure.Eventually, strain will build up again, causing failure. This behavior is termed stick-slip behavior. This behavior is termed stick-slip behavior.

Stick – Friction prevents motion. Stick – Friction prevents motion. Slip – Friction briefly overwhelmed by motion. Slip – Friction briefly overwhelmed by motion.


Fault MotionFault Motion When rocks break, stored elastic strain is released.When rocks break, stored elastic strain is released. This energy radiates outward from the hypocenter.This energy radiates outward from the hypocenter. The energy, as waves, generates vibrations.The energy, as waves, generates vibrations. Vibrations cause motion, as when a bell is rung. Vibrations cause motion, as when a bell is rung. Foreshocks and aftershocks are common. Foreshocks and aftershocks are common.


Amount of DisplacementAmount of Displacement Displacement scale varies from small to large.Displacement scale varies from small to large.

Large events tear huge fault segments 100s of kms long.Large events tear huge fault segments 100s of kms long. Displacement maxima near hypocenter / epicenter.Displacement maxima near hypocenter / epicenter. Displacement diminishes with distance. Displacement diminishes with distance.

Faulting may result in uplift or subsidence.Faulting may result in uplift or subsidence. Changes are measureable using interferometry Changes are measureable using interferometry


Seismic WavesSeismic Waves Body waves – Pass through Earth’s interior.Body waves – Pass through Earth’s interior.

Compressional or Primary (P) waves Compressional or Primary (P) waves Push-pull (compress and expand) motion. Push-pull (compress and expand) motion. Travel through solids, liquids, and gases.Travel through solids, liquids, and gases.Fastest.Fastest.


Seismic WavesSeismic Waves Body waves – Pass through Earth’s interior.Body waves – Pass through Earth’s interior.

Shear or Secondary (S) wavesShear or Secondary (S) waves ““Shaking" motion.Shaking" motion.Travel only through solids; not liquids. Travel only through solids; not liquids. Slower.Slower.


Seismic WavesSeismic Waves Surface waves – Travel along Earth’s surface. Surface waves – Travel along Earth’s surface.

Love waves – S-waves intersecting the surface.Love waves – S-waves intersecting the surface.Move back and forth like a writhing snake.Move back and forth like a writhing snake.

Rayleigh waves – P-waves intersecting the surface.Rayleigh waves – P-waves intersecting the surface.Move like ripples on a pond. Move like ripples on a pond.

These waves are the slowest and most destructive.These waves are the slowest and most destructive.


SeismologySeismology Seismology is the study of earthquake waves.Seismology is the study of earthquake waves. Seismographs - Instruments that record seismicity. Seismographs - Instruments that record seismicity.

Worldwide, they detect earthquakes anywhere on Earth.Worldwide, they detect earthquakes anywhere on Earth.

Seismology reveals size and Seismology reveals size and

location of earthquakes.location of earthquakes.


Seismograph OperationSeismograph Operation A seismograph measures…A seismograph measures…

Wave arrival times Wave arrival times Magnitude of ground motion.Magnitude of ground motion.

Straight line = background.Straight line = background. 11stst wave causes frame to sink (pen goes up). wave causes frame to sink (pen goes up). Next vibration causes opposite motion.Next vibration causes opposite motion. Seismograph preserves a record of wave arrivals.Seismograph preserves a record of wave arrivals.


Seismograph OperationSeismograph Operation Waves always arrive in sequence.Waves always arrive in sequence.

P-waves 1P-waves 1stst.. S-waves 2S-waves 2ndnd.. Surface waves last.Surface waves last.

Wave arrivals areWave arrivals are

captured by the captured by the

seismograph.seismograph.


Locating an EpicenterLocating an Epicenter P- and S-waves travel at different velocities.P- and S-waves travel at different velocities. 11stst arrivals of P- and S-waves varies with distance. arrivals of P- and S-waves varies with distance. A travel-time graph plots the distance of each A travel-time graph plots the distance of each

station to the epicenter.station to the epicenter.


Locating an EpicenterLocating an Epicenter Data from 3 stations can pinpoint the epicenter.Data from 3 stations can pinpoint the epicenter.

A circle is drawn around each station.A circle is drawn around each station.The radius is equal to the distance to epicenter. The radius is equal to the distance to epicenter. Circles around 3 or more stations will intersect.Circles around 3 or more stations will intersect.

The point of intersection is the epicenter.The point of intersection is the epicenter.


Earthquake SizeEarthquake Size Two means of describing earthquake size:Two means of describing earthquake size:

Intensity.Intensity. Magnitude.Magnitude.

Mercalli Intensity Scale.Mercalli Intensity Scale. Intensity – The degree of Intensity – The degree of

shaking based on damage.shaking based on damage. Roman numerals assigned to Roman numerals assigned to

different levels of damage. different levels of damage. Damage occurs in zones.Damage occurs in zones. Damage diminishes in Damage diminishes in

intensity with distance.intensity with distance.


Earthquake SizeEarthquake Size Magnitude – The amount of Magnitude – The amount of

energy released. energy released. Maximum amplitude of motion Maximum amplitude of motion

from a seismogram. from a seismogram. Value is normalized for Value is normalized for

seismograph distance.seismograph distance.

Several magnitude scales. Several magnitude scales. Richter.Richter. Moment.Moment.

Magnitude scales are Magnitude scales are logarithmic.logarithmic. Increases of 1 unit = 10-foldIncreases of 1 unit = 10-fold

increase in ground motion.increase in ground motion.


Measuring Earthquake SizeMeasuring Earthquake Size Earthquake energy Earthquake energy

release can be calculated.release can be calculated. M6.0 – Energy of the M6.0 – Energy of the

Hiroshima bomb.Hiroshima bomb. M8.9 – Annual energy M8.9 – Annual energy

released by all other released by all other earthquakes.earthquakes.


Measuring Earthquake SizeMeasuring Earthquake Size

Small earthquakes are frequent.Small earthquakes are frequent. ~100,000 magnitude 3 / year.~100,000 magnitude 3 / year.

Large earthquakes are rare.Large earthquakes are rare. 32 magnitude 7 earthquakes / year.32 magnitude 7 earthquakes / year.


Earthquake OccurrenceEarthquake Occurrence Earthquakes linked to plate tectonic boundaries.Earthquakes linked to plate tectonic boundaries. Shallow – Divergent and transform boundaries.Shallow – Divergent and transform boundaries. Intermediate and deep – Convergent boundaries.Intermediate and deep – Convergent boundaries.


Earthquake Focal DepthsEarthquake Focal Depths Shallow – 0-20 km.Shallow – 0-20 km.

Along the mid-ocean ridge.Along the mid-ocean ridge. Transform boundaries.Transform boundaries. Shallow part of trenches.Shallow part of trenches. Continental crust.Continental crust.


Earthquake Focal DepthsEarthquake Focal Depths Intermediate and deep earthquakes occur along the Intermediate and deep earthquakes occur along the

subduction trace, the Benioff-Wadati zone.subduction trace, the Benioff-Wadati zone. Intermediate – 20-300 km - Downgoing plate still brittle.Intermediate – 20-300 km - Downgoing plate still brittle. Deep - 300-670 km - Mineral transformations?Deep - 300-670 km - Mineral transformations?

Earthquakes rare below Earthquakes rare below

670 km (mantle is ductile).670 km (mantle is ductile).


Convergent BoundariesConvergent Boundaries Cities near subduction zones have to contend with Cities near subduction zones have to contend with

frequent earthquakes.frequent earthquakes.


Continental EarthquakesContinental Earthquakes Earthquakes in continental crust. Earthquakes in continental crust.

Continental transform faults (San Andreas, Anatolian).Continental transform faults (San Andreas, Anatolian). Continental rifts (Basin and Range, East African Rift).Continental rifts (Basin and Range, East African Rift). Collision zones (Himalayas, Alps).Collision zones (Himalayas, Alps). Intraplate settings (ancient crustal weaknesses).Intraplate settings (ancient crustal weaknesses).


San Andreas FaultSan Andreas Fault The Pacific plate meets the North American plate.The Pacific plate meets the North American plate. The San Andreas is a very active strike-slip fault. The San Andreas is a very active strike-slip fault.

A very dangerous fault; hundreds of earthquakes / yr.A very dangerous fault; hundreds of earthquakes / yr. San Francisco - Destroyed in 1906.San Francisco - Destroyed in 1906. Loma Prieta, 1989, World Series.Loma Prieta, 1989, World Series.


Intraplate EarthquakesIntraplate Earthquakes 5% of earthquakes are not near plate boundaries.5% of earthquakes are not near plate boundaries. Intraplate earthquakes are not well understood.Intraplate earthquakes are not well understood.

Remnant crustal weakness in failed rifts or shear zones?Remnant crustal weakness in failed rifts or shear zones? Stress transmitted inboard?Stress transmitted inboard? Isostatic adjustments?Isostatic adjustments?

Clusters Clusters New Madrid, Mo.New Madrid, Mo. Charleston, S.C.Charleston, S.C. Montral, P.Q.Montral, P.Q.


Earthquake DamageEarthquake Damage Earthquakes kill people and destroy cities.Earthquakes kill people and destroy cities. The damage can be heartbreaking and horrific.The damage can be heartbreaking and horrific. Knowledge improves odds of survival. Knowledge improves odds of survival.


Earthquake DamageEarthquake Damage Ground shaking and displacement.Ground shaking and displacement.

Earthquake waves arrive in a distinct sequence.Earthquake waves arrive in a distinct sequence. Different waves cause different motion. Different waves cause different motion.

P-waves are the 1P-waves are the 1stst to arrive. to arrive. They produce a rapid up-and-down motion.They produce a rapid up-and-down motion.


Earthquake DamageEarthquake Damage S-waves arrive next.S-waves arrive next.

They produce a pronounced back-and-forth motion.They produce a pronounced back-and-forth motion. This motion is usually much stronger than P-waves.This motion is usually much stronger than P-waves. S-waves cause extensive damage.S-waves cause extensive damage.


Earthquake DamageEarthquake Damage Surface waves lag behind S-waves.Surface waves lag behind S-waves.

Love waves are the first to follow.Love waves are the first to follow. Ground writhes like a snake.Ground writhes like a snake.


Earthquake DamageEarthquake Damage R-waves are the last to arrive.R-waves are the last to arrive.

The land surface behaves like ripples in a pond.The land surface behaves like ripples in a pond. These waves may last longer than others.These waves may last longer than others. Cause extensive damage.Cause extensive damage.


Earthquake DamageEarthquake Damage Severity of shaking and damage depends on… Severity of shaking and damage depends on…

Magnitude (energy) of the earthquake. More = more.Magnitude (energy) of the earthquake. More = more. Distance from the hypocenter.Distance from the hypocenter. Intensity and duration of the vibrations.Intensity and duration of the vibrations. The nature of the subsurface material. The nature of the subsurface material.

Bedrock transmits waves quickly = less damageBedrock transmits waves quickly = less damageSediments bounce waves = amplified damage.Sediments bounce waves = amplified damage.


Earthquake DamageEarthquake Damage Effects on buildings.Effects on buildings.

Slabs disconnect.Slabs disconnect.

Facades delaminate.Facades delaminate.

Bridges topple.Bridges topple.

Bridges come apart.Bridges come apart.


Earthquake DamageEarthquake Damage Shaking effects on buildings.Shaking effects on buildings.

Masonry disintegrates.Masonry disintegrates.

Buildings collide.Buildings collide.

Slopes collapse.Slopes collapse.

Earthquake DamageEarthquake Damage

Anchorage, Alaska, 1964 Anchorage, Alaska, 1964


Turkey, 1999 Turkey, 1999


Kobe, Japan, 1995 Kobe, Japan, 1995


Armenia, 1999 Armenia, 1999


Earthquake DamageEarthquake Damage Landslides and avalanches.Landslides and avalanches.

Shaking causes slopes to fail. Shaking causes slopes to fail. Hazardous slopes bear evidence Hazardous slopes bear evidence

of ancient slope failures.of ancient slope failures. Rockslides or snow avalanches Rockslides or snow avalanches

follow earthquakes in uplands. follow earthquakes in uplands. An earthquake started the An earthquake started the

landslide that uncorked Mt. St. landslide that uncorked Mt. St. Helens on May 18, 1980.Helens on May 18, 1980.


Earthquake DamageEarthquake Damage Liquefaction – Waves liquefy HLiquefaction – Waves liquefy H22O-filled sediments. O-filled sediments.

High pore pressures force grains apart reducing friction. High pore pressures force grains apart reducing friction. Liquefied sediments flow as a slurry.Liquefied sediments flow as a slurry. Sand becomes “quicksand”: clay becomes “quickclay.”Sand becomes “quicksand”: clay becomes “quickclay.”

Sand dikes.Sand dikes.Sand volcanoes.Sand volcanoes.Contorted layering.Contorted layering.


LiquefactionLiquefaction Water-saturated sediments turn into a mobile fluid.Water-saturated sediments turn into a mobile fluid. Land will slump and flow. Land will slump and flow. Buildings may founder and topple over intact.Buildings may founder and topple over intact.


Earthquake DamageEarthquake Damage Fire is a common hazard following earthquakes.Fire is a common hazard following earthquakes.

Shaking topples stoves, candles, and power lines. Shaking topples stoves, candles, and power lines. Broken gas mains and fuel tanks ignite a conflagration. Broken gas mains and fuel tanks ignite a conflagration. Earthquakes destroy critical infrastructure such as water, Earthquakes destroy critical infrastructure such as water,

sewer, telephone, and electrical lines as well as roads.sewer, telephone, and electrical lines as well as roads. Firefighters powerless.Firefighters powerless.

No road access.No road access.No water.No water.Too many hotspots.Too many hotspots.

Good planning is Good planning is

crucial to saving lives.crucial to saving lives.


Earthquake DamageEarthquake Damage Earthquake devastation fuels disease outbreaks.Earthquake devastation fuels disease outbreaks.

Food, water, and medicines are scarce.Food, water, and medicines are scarce. Basic sanitation capabilities disabled.Basic sanitation capabilities disabled. Hospitals damaged or destroyed.Hospitals damaged or destroyed. Health professionals overtaxed.Health professionals overtaxed. There may be many decaying corpses.There may be many decaying corpses.


Earthquake DamageEarthquake Damage Tsunamis or seismic sea waves (not Tsunamis or seismic sea waves (not tidaltidal waves). waves).

Tsunamis result when earthquakes change the seafloor.Tsunamis result when earthquakes change the seafloor. Normal faulting drops the seabed; thrusting raises it.Normal faulting drops the seabed; thrusting raises it.

This displaces the entire volume of overlying water.This displaces the entire volume of overlying water.A giant mound (or trough) forms on the sea surface. A giant mound (or trough) forms on the sea surface. This feature may be enormous (up to a 10,000 miThis feature may be enormous (up to a 10,000 mi22 area). area).Feature collapse creates waves that race rapidly away. Feature collapse creates waves that race rapidly away.


Earthquake DamageEarthquake Damage Destructive tsunamis occur frequently - about 1/yr.Destructive tsunamis occur frequently - about 1/yr. Many tsunami disasters dot recorded history.Many tsunami disasters dot recorded history.

94 destructive tsunamis in the last 100 years.94 destructive tsunamis in the last 100 years. 51,000 victims (not including 12/26/04)51,000 victims (not including 12/26/04)

Future tsunami disasters are inevitable.Future tsunami disasters are inevitable. Growing human population in low-lying coastal areas. Growing human population in low-lying coastal areas.

Education about tsunamis can save many lives.Education about tsunamis can save many lives.


Tsunami vs. Wind WavesTsunami vs. Wind Waves Wind wavesWind waves

Influence the upper ~100 m. Influence the upper ~100 m. Have wavelengths of several Have wavelengths of several

10s to 100s of meters. 10s to 100s of meters. Wave height and wavelength Wave height and wavelength

related to windspeed. related to windspeed. Wave velocity maximum Wave velocity maximum

several 10s of kph.several 10s of kph. Waves break in shallow Waves break in shallow

water and expend all stored water and expend all stored energy.energy.

Tsunami wavesTsunami waves Influence entire water depthInfluence entire water depth Have wavelengths of several Have wavelengths of several

10s to 100s of kilometers. 10s to 100s of kilometers. Wave height and wavelength Wave height and wavelength

unaffected by windspeed. unaffected by windspeed. Wave velocity maximum Wave velocity maximum

several 100s of kph.several 100s of kph. Waves come ashore as a Waves come ashore as a

raised plateau of water that raised plateau of water that pours onto the land. pours onto the land.


Tsunami BehaviorTsunami Behavior Tsunamis race at jetliner speed across the ocean.Tsunamis race at jetliner speed across the ocean. They may be almost imperceptible in deep water.They may be almost imperceptible in deep water.

Low wave height (amplitude).Low wave height (amplitude). Long wavelength (frequency).Long wavelength (frequency).

As water shallows, waves As water shallows, waves

slow from frictional drag.slow from frictional drag. Waves grow in height, Waves grow in height,

reaching 10-15 m or more.reaching 10-15 m or more.


TsunamiTsunami Tsunami destruction of the coast depends upon… Tsunami destruction of the coast depends upon…

Offshore bathymetry.Offshore bathymetry.Broad shallows increase amplitude but sap wave energy.Broad shallows increase amplitude but sap wave energy.Quick deep-to-shallow transition – Deadliest condition. Quick deep-to-shallow transition – Deadliest condition.

Waves have maximum energy.Waves have maximum energy. Wave heights are modest.Wave heights are modest. Water pours onto land as a sheet.Water pours onto land as a sheet.

Topography of shore.Topography of shore.Broad, low land – Maximum damage.Broad, low land – Maximum damage.Steep rise of land – Less damage.Steep rise of land – Less damage.


Tsunami RealityTsunami Reality The Indian Ocean TsunamiThe Indian Ocean Tsunami

On December 26, 2004, a strong megathrust earthquake On December 26, 2004, a strong megathrust earthquake (M9.0+) originated in the trench to the west of N. Sumatra. (M9.0+) originated in the trench to the west of N. Sumatra.

The earthquake was the largest in 40 years. The earthquake was the largest in 40 years. Displacement exceeded 15 m; rupture > 1100 km long. Displacement exceeded 15 m; rupture > 1100 km long. The devastating tsunami killed people in 10 countries The devastating tsunami killed people in 10 countries

surrounding the Indian Ocean.surrounding the Indian Ocean.


The Indian Ocean TsunamiThe Indian Ocean Tsunami Killed more people than any tsunami on record.Killed more people than any tsunami on record.

At least 283,106 deaths,14,100 still missing (as of 9/25/07).At least 283,106 deaths,14,100 still missing (as of 9/25/07). 1,126,900 people were displaced.1,126,900 people were displaced.

Record-setting death toll.Record-setting death toll. The earthquake was The earthquake was

so large and the so large and the

tsunami spread fast.tsunami spread fast. Coasts were full of Coasts were full of

Christmas tourists.Christmas tourists.

Source: USGS Earthquake Hazards Program, Source: USGS Earthquake Hazards Program, Most Destructive Earthquakes Most Destructive Earthquakes

http://earthquake.usgs.gov/regional/world/http://earthquake.usgs.gov/regional/world/most_destructive.phpmost_destructive.php//


The Indian Ocean TsunamiThe Indian Ocean Tsunami Destroyed coastlines around the Indian Ocean. Destroyed coastlines around the Indian Ocean. Huge death tolls.Huge death tolls.

Northern Sumatra.Northern Sumatra. Thailand.Thailand. Malaysia.Malaysia. Sri Lanka.Sri Lanka.


The Indian Ocean TsunamiThe Indian Ocean Tsunami Complete devastation below “run-up” elevation.Complete devastation below “run-up” elevation.

Dense coastal development in Banda Aceh hardest hit. Dense coastal development in Banda Aceh hardest hit. Entire communities were erased – buildings and people. Entire communities were erased – buildings and people.


Surviving a TsunamiSurviving a Tsunami Heed natural and official warnings. Heed natural and official warnings.

An earthquake in a coastal setting. An earthquake in a coastal setting. Retreat of water from the shore is sign of an impending Retreat of water from the shore is sign of an impending

tsunami. tsunami.

Expect many waves.Expect many waves. Bigger waves may be next.Bigger waves may be next. Wave arrival may last for hours.Wave arrival may last for hours.

Abandon belongings.Abandon belongings. Get to high ground and stay there.Get to high ground and stay there.

Source: Brian F. Atwater and others, 1999, Surviving a Tsunami – Lessons from Chile, Hawaii and Japan, USGS Circular 1187


Surviving a TsunamiSurviving a Tsunami Expect roads to be impassable.Expect roads to be impassable. Climb a sturdy building or a tree.Climb a sturdy building or a tree. Grab something that floats.Grab something that floats. Expect lots of debris (sediment, wreckage, corpses).Expect lots of debris (sediment, wreckage, corpses). Expect landscape changes.Expect landscape changes.

Source: Brian F. Atwater and others, 1999, Surviving a Tsunami – Lessons from Chile, Hawaii and Japan, USGS Circular 1187


Tsunami PredictionTsunami Prediction Scientific modeling predicts tsunami behavior. Scientific modeling predicts tsunami behavior. Tsunami detection is expanding. Tsunami detection is expanding.

Tsunami detectors are placed on the deep seafloor.Tsunami detectors are placed on the deep seafloor. Sense pressure increases from changes in sea thickness. Sense pressure increases from changes in sea thickness.

Prediction / detection can Prediction / detection can

save 1000s of lives.save 1000s of lives.


Earthquake PredictionEarthquake Prediction Prediction would help reduce catastrophic losses. Prediction would help reduce catastrophic losses. Can we predict earthquakes? Yes and no.Can we predict earthquakes? Yes and no.

They CAN be predicted - long-term (10-100s of years).They CAN be predicted - long-term (10-100s of years). They CANNOT be predicted - short-term (hours-months).They CANNOT be predicted - short-term (hours-months).

Seismic hazards are mapped to assess risk.Seismic hazards are mapped to assess risk. This information is useful for…This information is useful for…

Developing building codes.Developing building codes. Land-use planning.Land-use planning. Disaster planning.Disaster planning.


Earthquake PredictionEarthquake Prediction Long-term predictions. Long-term predictions.

Probability of a certain magnitude earthquake occurring Probability of a certain magnitude earthquake occurring on a time scale of 30 to 100 years, or more.on a time scale of 30 to 100 years, or more.

Based on the premise that earthquakes are repetitive. Based on the premise that earthquakes are repetitive.



Require determination of seismic zones by…Require determination of seismic zones by…Mapping historical epicenters (after ~ 1950).Mapping historical epicenters (after ~ 1950).Evidence of ancient earthquakes (before seismographs).Evidence of ancient earthquakes (before seismographs).

Evidence of seismicity – Fault scarps, sand volcanoes, etc.Evidence of seismicity – Fault scarps, sand volcanoes, etc. Historical records. Historical records.



Recurrence interval – Average time between events. Recurrence interval – Average time between events. Historical records.Historical records.Geologic evidence – Requires radiometric dating of events.Geologic evidence – Requires radiometric dating of events.

Sand volcanoes.Sand volcanoes.Offset strata.Offset strata.Drowned forests.Drowned forests.



Seismic gaps, places that haven’t slipped recently, are Seismic gaps, places that haven’t slipped recently, are more likely candidates. more likely candidates.


Short-term predictions. Short-term predictions. Goal: The location and magnitude of a large earthquake. Goal: The location and magnitude of a large earthquake. Currently no reliable short-range predictions are possible.Currently no reliable short-range predictions are possible. Earthquakes do have precursors. Earthquakes do have precursors.

Clustered foreshocks.Clustered foreshocks.Crustal strain.Crustal strain.Stress triggering.Stress triggering. And, possibly…And, possibly…

Water level changes in wells.Water level changes in wells. Gases (Rn, He) in wells.Gases (Rn, He) in wells. Unusual animal behavior.Unusual animal behavior.

Earthquake PredictionEarthquake Prediction


Preparing for EarthquakesPreparing for Earthquakes We can’t stop them but we can be ready for them. We can’t stop them but we can be ready for them.

Understand what happens during an earthquake.Understand what happens during an earthquake. Map active faults and areas likely to liquefy from shaking.Map active faults and areas likely to liquefy from shaking. Develop construction codes to reduce building failures.Develop construction codes to reduce building failures. Regulate land use to control development.Regulate land use to control development.


Preparing for EarthquakesPreparing for Earthquakes We can’t stop them but we can be ready for them. We can’t stop them but we can be ready for them.

Train the community in earthquake preparedness.Train the community in earthquake preparedness. Run preparedness drills.Run preparedness drills. Educate individuals on safe behavior and responses.Educate individuals on safe behavior and responses. Keep viable stores of emergency supplies. Keep viable stores of emergency supplies.


Chapter 10A Violent Pulse: Earthquakes

©2008 W. W. Norton & Company, Inc.

Portrait of a PlanetThird Edition

earthearth

LECTURE OUTLINE

This concludes the