faulting landforms from side- by-side (transform) motion strike-slip faulting and landforms
TRANSCRIPT
Faulting landforms from side-by-side (transform) motion
Strike-slip faulting and landforms
PACIFIC
NORTH AMERICA
San Andreas Fault, Carrizo Plain
36 mm/yr
Transform – Strike-slip faulting
Online Videos
1906 San Francisco Earthquake
http://serc.carleton.edu/NAGTWorkshops/visualization/collections/SanFran1906.html
1906 S.F. Quake
1989 LOMA PRIETA, CALIFORNIA EARTHQUAKEMAGNITUDE 7.1 ON THE SAN ANDREAS
Davidson et alDavidson et al
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 landfill
Stein & 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, it’s irregular rather than periodic
EARTHQUAKE RECURRENCE IS HIGHLY VARIABLEReasons are unclear: randomness, stress effects of
other earthquakes on nearby faults…
M>7 mean 132 yr 105 yr
Sieh et al., 1989
Extend earthquake history with paleoseismology S&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
Fault
Helps Set
Topography
More Dangerous: LA
riddled with unknown faults
San Bernardino Mountains
San Andreas fault
San Jacinto fault
Cucamonga fault
Recent mudslide scars
Cucamonga fault scarp
SAN ANDREAS FAULT
Pads for 47 new homes
Highest LiquefactionPotential
(adjacent to the San Andreas fault)
Landforms of a Strike-Slip Fault
Strike-Slip Faulting elsewhere, too in Turkey & Levant
Quake in Turkey
Quake in Turkey
Ancient San
Andreas-like Fault
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.