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ISNS 4359 Earthquakes and Volcanoes (aka shake and bake)

ISNS 4359 Earthquakes and Volcanoes (aka shake and bake). Lecture 9CA: Historic Earthquakes III & IV. Fall 2005. Historic Earthquakes III & IV. Today we will discuss several major earthquakes: Kobe Japan, 1995 Izmit, Turkey, 1999 Bam, Iran, 2003 New Madrid, US, 1811-1812.

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ISNS 4359 Earthquakes and Volcanoes (aka shake and bake)

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  1. ISNS 4359 Earthquakes and Volcanoes (aka shake and bake) Lecture 9CA: Historic Earthquakes III & IV Fall 2005

  2. Historic Earthquakes III & IV Today we will discuss several major earthquakes: Kobe Japan, 1995 • Izmit, Turkey, 1999 • Bam, Iran, 2003 • New Madrid, US, 1811-1812

  3. Kobe, Japan, 1995 • The effects of any earthquake depend on a number of widely varying factors. These factors are all of: • Intrinsic to the earthquake - its magnitude, type, location, or depth; • Geologic conditions where effects are felt - distance from the event, path of the seismic waves, types of soil, water saturation of soil; and • Societal conditions reacting to the earthquake - quality of construction, preparedness of populace, or time of day (e.g.: rush hour).

  4. Kobe, Japan, 1995 Kobe, Japan, 1995: most expensive earthquake in history • Kobe/Osaka region had a population of 10 million • Magnitude 6.9 earthquake with 50 km long rupture of Nojima fault and 100 seconds of shaking • Tile roofs and little lateral support caused collapse of buildings causing 6,308 fatalities (4571 according to NEIC) • More than 140 fires resulted • State-owned buildings and facilities = 150 billion dollars

  5. Kobe, Japan, 1995 http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html

  6. Kobe, Japan, 1995 Aftershock locations Length of fault indicated by aftershocks-note other faults http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html

  7. Kobe, Japan, 1995 980 gals(cm/sec2)= 1 g acceleration http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.htm http://neic.usgs.gov/neis/eq_depot/world/1995_01_16.htmll

  8. Kobe, Japan, 1995 Note fault break http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html

  9. Kobe, Japan, 1995 http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html

  10. Kobe, Japan, 1995 http://www.seismo.unr.edu/ftp/pub/louie/class/100/effects-kobe.html

  11. Kobe, Japan, 1995 vs. Oakland, California, 20?? Oakland, California, 20?? • Hayward fault has 27% probability of causing magnitude 6.7 or greater earthquake before 2032 • San Francisco Bay region, 62% probability of 6.7 magnitude earthquake on a fault before 2032 • Comparison of Hayward fault and Nojima fault: • Both about 50 km long • Both run through densely populated areas, with large areas of weak ground materials • Both capable of generating magnitude 7 earthquakes

  12. Transform Faults and Earthquakes • Horizontal movements cause major earthquakes • Turkey, 1999: • Segment of North Anatolian fault ruptured for 120 km in magnitude 7.4 earthquake near Izmit, followed weeks later by rupture to the east in magnitude 7.1 earthquake • Residential buildings on soft ground, adding sand to concrete resulted in buildings collapsing during shaking • Some 17,000 dead

  13. Izmit, Turkey 1999 • Turkey, 1999: • Turkey is pushed westward along the North Anatolian fault, which runs for 1,400 km along the Black Sea • Since 1939, the North Anatolian fault has ruptured in 11 earthquakes, from east end of fault to west • Unique, semi-regular pattern • Next event? Probably to west of Izmit, closer to Istanbul • Probably withinnext 30 years

  14. Izmit, Turkey 1999 http://quake.wr.usgs.gov/research/geology/turkey/images/CA-Tu_comp.jpeg

  15. Izmit, Turkey 1999 Mw ≥ 5 http://www.earthquakes.bgs.ac.uk/images/turkey_5plus.jpg

  16. Izmit, Turkey 1999 http://www.earthquakes.bgs.ac.uk/images/turkey_5plus.jpg

  17. Izmit, Turkey 1999 http://quake.wr.usgs.gov/research/geology/turkey/images/CA-Tu_comp.jpeg

  18. Izmit, Turkey 1999 http://quake.wr.usgs.gov/research/geology/turkey/images/CA-Tu_comp.jpeg

  19. Izmit, Turkey 1999 http://pubs.usgs.gov/circ/2000/c1193/c1193.pdf

  20. Izmit, Turkey 1999 http://pubs.usgs.gov/circ/2000/c1193/c1193.pdf

  21. Bam, Iran 2003 • Friday, Dec 26, 2003 at 5:26:52 AM local time • Magnitude (Mw) 6.6 earthquake • Depth of hypocenter = 10 km • At least 30,000 dead, 30,000 injured (dead = 26, 271 according to www.farsinet.com/bam) • 85% of buildings were destroyed

  22. Bam, Iran 2003 http://neic.usgs.gov/neis/world/iran/

  23. Bam, Iran 2003 http://www.usaid.gov/our_work/humanitarian_assistance/disaster_assistance/resources/pdf/iran_pop_Bam123103.pdf

  24. Bam, Iran 2003 Seismicity in Iran since 12/26/03 http://www.iiees.ac.ir/EQSearch/ShowMap.aspx

  25. CO 01

  26. Fig. 1.01 Bam before and after earthquake

  27. U.S. and Canadian Earthquakes • Earthquakes occur throughout North America, not just in California • Occur in clusters, mostly in western North America but also in eastern North America and Hawaii

  28. Western North America: Plate Tectonic-Related Earthquakes • North American plate moves southwest at 2.5 cm/yr • Pacific plate moves northwest 8 cm/yr • Much of Farallon plate has subducted under North America • Western United States uplifted, creating Rocky Mountains, Sierra Nevada, Colorado Plateau • Earthquakes throughout western United States

  29. Intraplate Earthquakes: “Stable” Central United States • Clusters of earthquakes at few locations • Away from active plate edges • Fewer earthquakes, but can be just as large

  30. Intraplate Earthquakes: “Stable” Central United States New Madrid, Missouri, 1811-1812 • Series of earthquakes, with four very large events • Eight considered violent, ten very severe • Total of 1,874 events • Hypocenters beneaththick sedimentsof Mississippi and Ohio Rivers at Mississippi River embayment, near town ofNew Madrid (called ‘Gateway to the West’ before destruction by earthquakes) • Long-lasting effects on topography • Two new lakes • Low cliffs and domes formed • Waterfalls in streams

  31. New Madrid, Missouri, 1811-1812 Seismicity since 1974

  32. New Madrid, Missouri, 1811-1812 • Felt Area • Felt area was largest for any U.S. earthquake • Must consider difference in wave propagation in eastern vs. western North America • Young, tectonically fractured rocks of west coast impede wave propagation and cause wave energy to die out faster than older, more homogeneous rocks of central U.S.

  33. New Madrid, Missouri, 1811-1812 • Magnitudes • Using felt area to estimate magnitudes  8 to 8.3 • Studies of small earthquakes occurring today (aftershocks of 1811-1812 events) in this area can map out the faults • First earthquake on Cottonwood Grove fault, triggered two of following earthquakes on Reelfoot blind thrust • Remaining earthquake difficult to locate

  34. New Madrid, Missouri, 1811-1812 • Magnitudes • Using fault-rupture length estimates from aftershock locations gives smaller moment magnitudes  7.3 to 7.7 • Soft, water-saturated sediment of ground amplifies shaking; accounting for amplification gives magnitudes 7.0 to 7.5

  35. New Madrid, Missouri, 1811-1812 • The Future • 1811-1812 New Madrid earthquakes did not cause great damage because population of area at time was so low • Future earthquakes will affect population of St. Louis, Memphis • Buildings not designed for earthquake shaking • Soft sediments will amplify ground shaking • Very large area will be affected

  36. New Madrid, Missouri, 1811-1812 • The Future • Neotectonic analyses show earthquakes in the area around 500, 900, 1300 and 1600 • Magnitude 7 or higher earthquakes occur here about every 500 years • U.S. Geological Survey forecasts 90% probability of magnitude 6-7 earthquake in next 50 years • Why do earthquakes occur here in middle of continent?  Reelfoot Rift

  37. Reelfoot Rift: Missouri, Arkansas, Tennessee, Kentucky, Illinois • Why do earthquakes follow same linear pattern as deposition of sediments by Mississippi River system? • Linear structural depression underlying New Madrid region  ancient rift valley, Reelfoot Rift • Formed 550 million years ago and since filled with sedimentary rocks and covered with younger sediments

  38. Ancient Rifts in the Central United States • As Pangaea tore apart around 200 million years ago, many rifts formed • Some separated the landmass and formed Atlantic Ocean • Others were failed rifts, left behind weakened zones in continent • Can be reactivated by plate-tectonic stresses • Failed rifts correlate to active faults at the surface

  39. Reactivated Faults and earthquakes • Most shallow earthquakes occur on active faults • those with recent offset in the last 10,000 years. • Inactive faults do not have observed earthquakes or evidence of slip in the last 1.6 million years. • However, some faults have large earthquakes only once every thousands of years. Reactivated faults form when movement occurs along formerly inactive faults due to a change in stress. • Deformation in the New Madrid seismic zone in the central USA is an example of fault reactivation. • Rift structures that formed about 500 million years ago have been responding to recent stresses in the mid-continent

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