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EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS. ALASKA 1964: Good Friday Earthquake. Epicenter in Prince William sound. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS. ALASKA 1964: Good Friday Earthquake. 1.) Pacific Plate Under North American Plate

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EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS


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    1. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS ALASKA 1964: Good Friday Earthquake Epicenter in Prince William sound

    2. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS ALASKA 1964: Good Friday Earthquake 1.) Pacific Plate Under North American Plate 2.) Strong ground motion for 3-4 minutes 3.) Downward thrusts followed at 9, 19, 28, 29, 4, and 72 sec. later Hand written notes on setting.

    3. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS ALASKA 1964: Good Friday Earthquake 131 killed, 122 from Tsunami COSTS IN 1964 DOLLARS

    4. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS ALASKA 1964: Good Friday Earthquake DESTRUCTION FROM…. 1.) avalanche 2.) tsunami 3.) landslide 4.) liquefaction PACKAGE DEAL

    5. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Mexico City 1985 Cocos Plate subducting under the N.A. plate Magnitude 8.1 Epicenter Location Overhead Fig. 4.4 Notice seismic gaps

    6. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Mexico City 1985 Collapsed  General Hospital, Mexico City, Mexico(Courtesy USGS DDS21)

    7. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Mexico City 1985 1.) 6-16 story building affected 2.) Resonant frequency/period(1-2sec) same(=) seismic waves(1-2sec) 3.) Lake deposits amplified waves 4.) Coastal villages little damage? WHY?

    8. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Cascadia Subduction Zone 1.) 750 miles long 2.) youthful ocean slab resists subduction = build up of elastic energy 3.) Juan de Fuca plate subducting under N.A. plate Overhead Fig. 4.8

    9. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Cascadia Subduction Zone 1.) About 200 years since last major major event. 2.) Is it “plugged” and subduction stopped? 3.) Volcano activity tell us no. 4.) Is subduction happening smoothly? Probably not 5.) What is the worry???…

    10. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Cascadia Subduction Zone Lets consider the past Last Super Big Quake Jan. 26, 1700 How do we know? 1.) Tree rings from flooded trees that died (ND pg. 104/Fig. 4.11)-subsidence 2.) Japanese records have a tsunami hitting midnight-dawn suggests a Jan. 26 1700 EQ at this location HAPPENED ONCE CAN HAPPEN AGAIN

    11. EARTHQUAKE CASE HISTORIES SUBDUCTION ZONE TECTONICS Seattle Feb. 28, 2001 1.) 6.98 mag. 2.) Focus/hypocenter 33 miles deep WHY? 3.) epicenter 35 mi. SW of Seattle 4.) $2 BILLION in damage 5.) 320 hurt but no deaths (lucky) 6.) since 1970’s EQ code has been in use 7.) Spce needle 600’ high, built to withstand 9.1. Why brick failure?

    12. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS CALIFORNIA - San Andreas Fault 1.) 750 miles long - parallel faults (complex system) 2.) Some sections have creeping motion and others are locked (seismic gap) (ND pg. 109/fig. 4.16)

    13. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS San Francisco 1906 a) ~ 20 ft horizontal motion over up to 265 miles b) mag. 8 60 seconds duration c) wood faired better BUT fire significant type of destruction d) Today - S.F. is a seismic gap-sort of-some activity

    14. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS CALIFORNIA - San Andreas Fault Loma Prieta 1989 (World Series) a) mag 7.1 11 sec duration b) 67 dead - most from freeway collapse c) marina district suffered damage due to artificial fill - saturated in many cases (liquifaction) d.) 18 km deep e.) 11 secs. of shaking f.) 6ft horizontal g.) 4ft. vert. h.) had been seismic gap

    15. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS CALIFORNIA - San Andreas Fault Loma Prieta 1989 Candlestick park Giants homefield advantage? LIQUIFACTION (again)

    16. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS CALIFORNIA - San Andreas Fault Loma Prieta 1989 (World Series) a) mag 7.1 11 sec duration b) 67 dead - most from freeway collapse c) marina district suffered damage due to artificial fill - saturated in many cases (liquifaction) d.) freeways built on muds had resonant frequency BRIDGE FAILURE=PROBLEMS??

    17. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS CALIFORNIA - San Andreas Fault Loma Prieta 1989 Much of the marina district is buld on artificial fill from the 1906 quake LIQUIFACTION RESULTS (again) Marina district “soft” first stories for parking cars along with liquifaction=that

    18. EARTHQUAKE CASE HISTORIES TRANSFORM ZONE TECTONICS Common Patterns for Bay Area Quakes 1.) Common large quakes (6-7) rather than rare large >8 2.) East-west pairings 3.) Northward progression of quakes- ND pg. 118/fig. 4.33

    19. EARTHQUAKE CASE HISTORIES INTERMOUNTAIN SEISMIC BELT DIVERGENT BOUNDARY 1.) Zone of tension=pulling apart 2.) Tensional stress and strain IDAHO WYO UTAH

    20. EARTHQUAKE CASE HISTORIES INTERMOUNTAIN SEISMIC BELT DIVERGENT BOUNDARY Hegben Lake (Near Yellowstone) 1959 1.) 6.3-7.5 mag. 2.) up to 26’ of displacement 3.) Normal faults-tension-pulling apart. 4.) Killer big landslide 5.) Madison River Dammed 53 meters deep

    21. EARTHQUAKE CASE HISTORIES INTERMOUNTAIN SEISMIC BELT DIVERGENT BOUNDARY Borah Peak, Idaho 1983 Location

    22. EARTHQUAKE CASE HISTORIES INTERMOUNTAIN SEISMIC BELT DIVERGENT BOUNDARY Borah Peak, Idaho 1983 1.) 7.3 mag (10 mi. deep) 2.) 9 foot displacement 3.) Normal faults 4.) Borah Peak “grew” by 1 foot

    23. EARTHQUAKE CASE HISTORIES INTERMOUNTAIN SEISMIC BELT DIVERGENT BOUNDARY Borah Peak, Idaho 1983 Thousand Springs Valley 1.) Ground water volcanos carry sediment/sand to surface 2.) 10-20 ft fountains

    24. EARTHQUAKE CASE HISTORIES INTRAPLATE EARTHQUAKES New Madrid, Missouri Dec. 16, 1811 Buried rift=Reelfoot Rift failed splitting= lots o’ cracks= Earthquakes

    25. EARTHQUAKE CASE HISTORIES INTRAPLATE EARTHQUAKES New Madrid, Missouri Dec. 16, 1811 1.) Largest group of clustered events EVER in US 2.) Sand volcanos 3.) Formed two new lakes=subsidence 1.) Lake St. Fancis (37 mi./.62mi) 2.) Reelfoot Lake (19mi/7mi.) 3.) ND pg. 140/fig. 5.15) 4.) Mississipi river had waterfalls where it used to be flat=scarp 5.) Bells rang along eastern seaboard.

    26. EARTHQUAKE CASE HISTORIES INTRAPLATE EARTHQUAKES New Madrid, Missouri Dec. 16, 1811 PROBLEMS 1.) Mississippi Embayment=lots of sandy/mudy water soakedsediments 2.) Amplification, liquifaction 3.) Large population 4.) Oh yeah they tend to BIG!!!!