1. Japan Earthquake and TsunamiEarthquake

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

3. 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.

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

5. What is an earthquake?

6. Release of stored energyenergy 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 boundary

7. JapanJapan moved eastward 8 feet

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

9. 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

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

12. 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

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

14. Response to stress Brittle: rock breaksDuctile: rock folds

15. 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

16. Fast/cold versus slow/warm

18. 1906 San Francisco Earthquake: fast movement causes offset Marin County, 16 feet of offset Offset: amount of displacement

19. Calaveras Fault: creep causes deformation

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

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

22. Japan is part of the Ring of Fire

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

24. 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.

25. Tectonic Setting: complex

26. 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. Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05:46:23 UTC Japan Trench

27. 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 Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05:46:23 UTC What does the pink line represent?

28. 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. Images courtesy of the US Geological Survey Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05:46:23 UTC JAPAN Seismicity Cross Section across the subduction zone showing the relationship between color and earthquake depth.

29. Globally, this is the 4th largest earthquake since 1900. Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN Friday, March 11, 2011 at 05:46:23 UTC Chile 1960 Alaska 1964 Sumatra 2004 Chile 2010 Japan 2011 Russia 1952 Ecuador 1906 Alaska 1965

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

31. Worldwide SeismicitySeismicity

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

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

34. Phil Stoffer, USGS geologist

35. Cold, brittle crust breaks and movesbreaks 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

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

37. Older rocks on top of younger rocks

38. Strike-slip faults

39. North Anatolian Fault, Turkey

42. 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.

43. 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

44. LIDAR image, similar location

45. 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.

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

47. 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

48. 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

49. Understand the relation between tectonic setting, stress, and fault type Tectonic settingStressFault