faults and folds part 2 diastrophism processes breaking & warping earth

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

1989 LOMA PRIETA, CALIFORNIA EARTHQUAKEMAGNITUDE 7.1 ON THE SAN ANDREASDavidson et al

Classroom Resources

Cal Memorial Stadium

1989 LOMA PRIETA, CALIFORNIA EARTHQUAKE

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

1989 LOMA PRIETA, CALIFORNIA EARTHQUAKE

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

Faulting

Relationship Between Stress and Strain under high Temps or Pressure

Folding

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