faults and folds part 2 diastrophism processes breaking & warping earth

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  • Faults and FoldsPart 2Diastrophism Processes Breaking & Warping Earth

  • Faults and FoldsExtension - Normal faulting (part 1)Compression - Thrust faulting (part 1)Transform Strike-slip faultingFolding from Compression

  • PACIFICNORTH AMERICASan Andreas Fault, Carrizo Plain36 mm/yr3. Transform Strike-slip faulting

  • Classroom Resource

  • Online Videos1906 San Francisco Earthquakehttp://serc.carleton.edu/NAGTWorkshops/visualization/collections/SanFran1906.html

  • 1906 S.F. Quake


  • Classroom Resources

  • Cal Memorial Stadium


    The two level Nimitz freeway collapsed alonga 1.5 km section in Oakland, crushing cars

    Freeway had been scheduled for retrofit to improve earthquake resistance


    Houses collapsed in the Marina district of San Francisco

    Shaking amplified by low velocity landfillStein & Wysession 2003 2.4-10 (USGS)

  • Over time, slip in earthquakes adds up and reflects the plate motion

    Offset fence showing 3.5 m of left-lateral strike-slip motion along San Andreas fault in 1906 San Francisco earthquake

    ~ 35 mm/yr motion between Pacific and North American plates along San Andreas shown by offset streams & GPS

    Expect earthquakes on average every ~ (3.5 m )/ (35 mm/yr) =100 years

    Turns out more like 200 yrs because not all motion is on the San Andreas

    Moreover, its irregular rather than periodic

  • EARTHQUAKE RECURRENCE IS HIGHLY VARIABLEReasons are unclear: randomness, stress effects of other earthquakes on nearby faultsM>7 mean 132 yr s 105 yrSieh et al., 1989Extend earthquake history with paleoseismologyS&W 1.2-15

  • In general, the most destructive earthquakes occur where large populations live near plate boundaries. The highest property losses occur in developed nations where more property is at risk, whereas fatalities are highest in developing nations.

    Estimates are that the 1990 Northern Iran shock killed 40,000 people, and that the 1988 Spitak (Armenia) earthquake killed 25,000. Even in Japan, where modern construction practices reduce earthquake damage, the 1995 Kobe earthquake caused more than 5,000 deaths and $100 billion of damage. On average during the past century earthquakes have caused about 11,500 deaths per year.

    The earthquake risk in the United States is much less than in many other countries because large earthquakes are relatively rare in most of the U.S. and because of earthquake-resistant construction

  • San Andreas FaultHelps SetTopography

  • More Dangerous: LA riddled with unknown faults

  • San Bernardino MountainsSan Andreas faultSan Jacinto faultCucamonga fault

  • Recent mudslide scarsCucamonga fault scarp

  • SAN ANDREAS FAULTPads for 47 new homes

  • Classroom ResourcesShaking Wet Sand Italy Example

  • Highest LiquefactionPotential

  • (adjacent to the San Andreas fault)

  • Classroom ResourcesWhat will happen when a big one hits the Inland Empire

    Animation of the future quake

  • Landforms of a Strike-Slip Fault

  • Classroom ResourceSpin Around QTVR at Offset Drainage, Wallace Creek, San Andreas Fault

  • Strike-Slip Faulting elsewhere, too in Turkey & Levant

  • Quake in Turkey

  • Quake in Turkey

  • 4. Folding from Compression

  • Relationship Between Stress and Strain at low Temps and Pressure or Sudden Stress


  • Relationship Between Stress and Strain under high Temps or Pressure


  • Monocline single bend

  • Flat- lyingFlat- lyingSingle bend

  • Anticline foldfrom: http://earth.leeds.ac.uk/learnstructure/index.htm

  • Folded Rocks, Hwy 23 Newfoundland, New JerseySource: Breck P. KentAdjacent Anticline and Syncline

  • Anticlines and OilEarly USA petroleum exploration, e.g. Pennsylvania anticlines

  • Folded Rock Before Erosion

  • Folds Erode Creating Flatirons (hard layers on side of anticline fold)

  • Fold Erosion creates Hogbacksfrom a side of the fold

  • Banff, Canada

  • Classroom ResourceQTVR spin arounds to see hogbacks and monoclines (Waterpocket, San Rafael Swell)

  • Folded Rock After ErosionEroded Anticline, older rocks in center. Syncline is opposite.

  • Topography may be opposite of Structure Anticline Before/After ErosionNotice center rock oldest

  • Topography may be opposite of Structure Syncline Before/After ErosionNotice center rock youngest

  • Synclinal RidgeHard strata last preserved at the bottom of the syncline, holding up the weaker rock

  • Synclinal Mountain, Canada

  • Synclinal Mountain, Mt Everest

  • Lazy Path of Rivers: Erode rock in the weak strata creating strike valley

  • Namibia: Most of the streams (dry washes) flow between hogbacksBut Ugab River cuts across the hard layers (hogbacks). Why? How?

  • Why didnt the Susquehanna River go around the fold? Why did it go through?Transverse Streams that cut right across fold belts & horsts

  • How did the Columbia River get through the Cascades?

  • How did this stream cross the Anticline in the Zagros Mountains?

  • Overflow of an ancient lake most common explanation in the westAncient Lake Roosevelt Overflowed

  • Lake Overflow led to Grand Canyon Formation

  • Classroom ResourceModeling how streams get across uplifts

  • Imagery seen in this presentation is courtesy of Ron Dorn and other ASU colleagues, students and colleagues in other academic departments, individual illustrations in scholarly journals such as Science and Nature, scholarly societies such as the Association of American Geographers, city,state governments, other countries government websites and U.S. government agencies such as NASA, USGS, NRCS, Library of Congress, U.S. Fish and Wildlife Service USAID and NOAA.cs