Japan Earthquake and Tsunami What happened Large earthquake

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Japan Earthquake and Tsunami

Japan Earthquake and Tsunami

What happened? • Large earthquake • Earthquake hazards: – Tsunami – Ground shaking –

What happened? • Large earthquake • Earthquake hazards: – Tsunami – Ground shaking – Liquefaction – Landslides • People and structures in the way of the hazards = catastrohe

Note: • Japan is a developed country: per capita income is $32, 433 •

Note: • Japan is a developed country: per capita income is $32, 433 • Well prepared for earthquakes in terms of monitoring, education, and preparedness • 8, 000 fatalities and 12, 000 missing Japan was prepared. The earthquake and tsunami caused so much destruction that emergency services and education of population were not enough to save many lives.

Today’s lecture • What is an earthquake? – Causes of earthquakes – Foreshocks and

Today’s lecture • What is an earthquake? – Causes of earthquakes – Foreshocks and aftershocks – Earthquake terminology – Fault classification

What is an earthquake?

What is an earthquake?

Release of stored energy • Elastic rebound theory explanation to how earthquakes occur •

Release of stored energy • Elastic rebound theory explanation to how earthquakes occur • Plate movement concentrates energy in crust • When the stored energy exceeds the strength of the crust, the crust ruptures • The rupture generally occurs along faults because this is the weakest point • Japan’s earthquake was produced on a plate boundary

Japan moved eastward 8 feet

Japan moved eastward 8 feet

How Faulting Generates Earthquakes • Movement on the fault causes a release in energy

How Faulting Generates Earthquakes • Movement on the fault causes a release in energy • As the energy passes through an area, the vibration is felt • The energy is transferred through the earth and man-made structures • The bigger the amount of slip the more energy released and therefore, the more vibrations are produced

Causes of Earthquakes • Tectonic stress (most common) • Water added under pressure •

Causes of Earthquakes • Tectonic stress (most common) • Water added under pressure • Geothermal gradient (variation due to boundary) • Rock type • Fast/cold versus slow/warm rate and temperature

Causes of Earthquakes • Stress accumulation and energy release at plate boundaries.

Causes of Earthquakes • Stress accumulation and energy release at plate boundaries.

Types of Stress (think of plate boundaries) • Compressional stress- crust shortens • Tensional

Types of Stress (think of plate boundaries) • Compressional stress- crust shortens • Tensional stress- crust thins • Shear stress- one piece of crust slides past another piece of crust

Stress: causes rock to change volume or shape Permanently deformed Maximum strength before rupture

Stress: causes rock to change volume or shape Permanently deformed Maximum strength before rupture or failure If stress is released the material will return to the original shape • Strain measures the amount of deformation

Response to stress Brittle : rock breaks Ductile: rock folds

Response to stress Brittle : rock breaks Ductile: rock folds

Geothermal gradient • Quartz makes a transition from brittle to ductile at about 350

Geothermal gradient • Quartz makes a transition from brittle to ductile at about 350 degrees centigrade • This is to a depth of about 12 miles in California

Fast/cold versus slow/warm

Fast/cold versus slow/warm

Fast/cold versus slow/warm

Fast/cold versus slow/warm

1906 San Francisco Earthquake: fast movement causes offset Offset: amount of displacement Marin County,

1906 San Francisco Earthquake: fast movement causes offset Offset: amount of displacement Marin County, 16 feet of offset

Calaveras Fault: creep causes deformation

Calaveras Fault: creep causes deformation

Elastic Rebound Theory: Reid, 1906 Elastic Rebound Theory earthquake • Stress is added to

Elastic Rebound Theory: Reid, 1906 Elastic Rebound Theory earthquake • Stress is added to the crust • Strain is accumulated and deformation occurs • Stress exceeds the frictional strength of the fault plane then rupture occurs

The San Andreas fault: right lateral strike-slip Strike-slip Fault Example (which way is the

The San Andreas fault: right lateral strike-slip Strike-slip Fault Example (which way is the window relative to the manure pile? ) Fault scarp 1906 San Francisco Earthquake

Japan is part of the Ring of Fire

Japan is part of the Ring of Fire

Ring of Fire: trenches and associated subduction zones that surround the Pacific Ocean

Ring of Fire: trenches and associated subduction zones that surround the Pacific Ocean

Tectonic Plates Tectonic plates may be composed of oceanic crust, continental crust or both

Tectonic Plates Tectonic plates may be composed of oceanic crust, continental crust or both types of crust. Describe the extent of the North American plate and the Pacific plate.

Tectonic Setting: complex

Tectonic Setting: complex

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05: 46: 23 UTC This earthquake was the result of thrust faulting along or near the convergent plate boundary where the Pacific Plate subducts beneath Japan. This map also shows the rate and direction of motion of the Pacific Plate with respect to the Eurasian Plate near the Japan Trench. The rate of convergence at this plate boundary is about 83 mm/yr (8 cm/year). This is a fairly high convergence rate and this subduction zone is very seismically active. Japan Trench

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05: 46: 23 UTC This earthquake occurred 130 km (80 miles) east of Sendai, Honshu, Japan and 373 km (231 miles) northeast of Tokyo, Japan. Images courtesy of the US Geological Survey What does the pink line represent?

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05: 46: 23 UTC The map on the right shows historic earthquake activity near the epicenter (star) from 1990 to present. As shown on the cross section, earthquakes are shallow (orange dots) at the Japan Trench and increase to 300 km depth (blue dots) towards the west as the Pacific Plate dives deeper beneath Japan. Seismicity Cross Section across the subduction zone showing the relationship between color and earthquake depth. Images courtesy of the US Geological Survey

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011

Magnitude 9. 0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05: 46: 23 UTC Globally, this is the 4 th largest earthquake since 1900. Great (M > 8) Earthquakes Since 1900 9. 7 Chile 1960 Alaska 1964 9. 2 Sumatra 2004 Magnitude Russia 1952 8. 7 Japan 2011 Ecuador 1906 Chile 2010 Alaska 1965 8. 2 7. 7 7. 2 1900 1920 1940 1960 Year 1980 2000 2020

Foreshocks and aftershocks • Relative measurement • Foreshocks: smaller earthquakes before the main event;

Foreshocks and aftershocks • Relative measurement • Foreshocks: smaller earthquakes before the main event; – a portion of the fault moves • Aftershocks: larger earthquakes after the main event; – Adjustment of the fault plane

Worldwide Seismicity

Worldwide Seismicity

Classification of Faults Fault scarp: a portion of the fault plane exposed after an

Classification of Faults Fault scarp: a portion of the fault plane exposed after an earthquake Fault plane: described by an area; length x width; where movement occurs • Based on relative movement along the fault plane Focus or hypocenter: point of movement initiation

Epicenter • Point on the Earth’s surface directly above the hypocenter or focus •

Epicenter • Point on the Earth’s surface directly above the hypocenter or focus • The earthquake is generally named after the epicenter USGS

Phil Stoffer, USGS geologist

Phil Stoffer, USGS geologist

Cold, brittle crust breaks and moves • • Compressional stress causes reverse faults Extensional

Cold, brittle crust breaks and moves • • Compressional stress causes reverse faults Extensional stress causes normal faults Shear stress causes strike-slip faults Oblique movement on strike-slip faults occurs when there is also vertical slip along the fault plane

Thrust Fault Waterton Lakes National Park, Alberta, Canada Alps A close-up of the thrust

Thrust Fault Waterton Lakes National Park, Alberta, Canada Alps A close-up of the thrust plane at this location. The rocks underlying the fault plane are intensely deformed

Older rocks on top of younger rocks

Older rocks on top of younger rocks

Strike-slip faults

Strike-slip faults

North Anatolian Fault, Turkey

North Anatolian Fault, Turkey

Identification of faulting • Rocks along fault may be ground up or polished •

Identification of faulting • Rocks along fault may be ground up or polished • Ground up rocks are easier to erode so often depressions on the Earth’s surface are indicative of active faults.

Identification of faulting • Rocks along fault may be ground up • ground up

Identification of faulting • Rocks along fault may be ground up • ground up rocks are easier to erode, so linear gullies or valleys form Fault trace of the San Andreas Fault

LIDAR image, similar location

LIDAR image, similar location

Prince William Sound, 1964 Alaska earthquake, marine terrace exposed Flat surface formed by wave

Prince William Sound, 1964 Alaska earthquake, marine terrace exposed Flat surface formed by wave action below sea level. Uplifted above sea level during the earthquake.

Uplifted marine terraces, California coast north of Santa Cruz Michael Rymer, USGS

Uplifted marine terraces, California coast north of Santa Cruz Michael Rymer, USGS

Identification of faulting • Offset is the distance of displacement along the fault plane

Identification of faulting • Offset is the distance of displacement along the fault plane • Offset features such as offset streams, roads, fences are indicative of movement • Changes in topography

Identification of faulting • Fault Scarp produced by fault movement • When fault plain

Identification of faulting • Fault Scarp produced by fault movement • When fault plain rises higher than the Earth’s surface • Hector Mine Earthquake, 1999 • Mojave Desert

Understand the relation between tectonic setting, stress, and fault type Tectonic setting Stress Fault

Understand the relation between tectonic setting, stress, and fault type Tectonic setting Stress Fault