Title: Active and Neotectonic Structures 1) What's the difference? 2) Methods in active tectonics 3) Methods in neotectonics 4) Implications for structural geology 5) Consequences for Society
1Active and Neotectonic Structures1) What's the
difference?2) Methods in active tectonics3)
Methods in neotectonics4) Implications for
structural geology5) Consequences for Society
2Time scales
- Tectonics- study of large scale deformations and
Earth evolution processes at scales of millions
to tens of millions of years focus of this class - Neotectonics thousand to tens of thousand years
- Active tectonics happens during a person's
lifetime
3Uniformitarianism
- Present is key to the past
Or is it?
4Methods in Active tectonics
- 1) Seismology
- 2) Measuring recent movements
- Surveying
- GPS techniques
- Radar interferometry
5Earthquakes occur all the time- all over the
world They produce ground motion (seismic
waves), that we can measure
6gt3000 seismological observatories around the
world, continuously recording seismic waves
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11How long did it take seismic waves to travel from
Alaska to Tucson?
12Real-time action Real-time measurement- what
can we learn from seismology about structural
geology??
1) Location and depth of faulting
(brittle-ductile transition) 2) fault plane
solutions- orientation of fault and sense of
slip- geometry and kinematics 3) Energy release-
size of fault, rupture characteristics-
unidirectional, bidirectional, chaotic?
13Seismic hazard
Bad destruction of property and life
Good? Funding for geology?
14What do we need to know, in order to predict
earthquakes??
15(1) aseismic movements that occur in between
earthquakes
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17The wave of the future-GPS Global Positioning
System
Satellite navigation system
18Accurate and precise knowledge of motion over
timescales of years
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20What we are learning from GPS1) Plate tectonic
assumptions OK- but only to first order- Within
plate deformation can be huge2) How continents
deform during orogenesis- diffuse? plate
like?3) What parts of faults are slipping vs.
what parts are "locked" up- important for EQ
predictions4) unprecedented knowledge of recent
movements on Earth
21GPS is great, but requires lots of stations and
time to wait around. Scientists are greedy- we
want more data on ground motion and with less
effort- is it possible?
22Scientific advancements are simply awesome!
Wide-area, high-precision surveying from Space
Satellites beam microwave radiation (radar) down
on Earth
23The Earth reflects back to the satellite
microwaves of different phases that yield X,Y,Z
information.
24Two passes of a satellite with imaging radar over
the same area produce two images. The difference
between two images provides the displacement
field over the entire area (often, 100 km 100 km)
between the time of the two passes.
25A simple, schematic example
26A real example- ground motion due to an
earthquake in a thrust belt
27Movement of glaciers over six days- think about
how many GPS stations would be required to
provide this kind of detailed information
28Displacement due to an EQ in Turkey. Can also
determine displacement in between EQ's!
29Landers Earthquake
30This technique is called InSAR- for
Interferometric Synthetic Aperture Radar. The
potential is endless!
31- It is estimated that a magnitude 8 or larger
earthquake in a major metropolitan area, such as
Los Angeles or Tokyo would cause more than 40,000
fatalities, up to 250,000 injuries, and 100
billion dollars in damage
What else do we need to know to be able to
predicts earthquakes?
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33- Study the earthquake cycle- recurrence intervals
of major events through neotectonic studies - 1) study deformed historic sites of known ages
(Great Wall of China) - 2) Paleoseismology
- 3) offset geomorphologic surfaces surface dating
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35Paleoseismology
San Gorgonio, CA
36Paleoseismology results for one fault system
37Fault-scarp profiling- gives displacement and
age as well as other interesting info regarding
structure
38Laser theodolite for surveying. Gary
Axen wishes that a satellite would fly over and
beam down those microwaves!
39A cheaper way to fly!
40Neotectonic mapping
400 m in 10000 yrs
40 mm per year
Long term plate motion- 5 cm/yr
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42 The scarp hidden by the waterfall is about 7
meters high. The bridge failed where it crosses
the fault to the right a few hundred meters, out
of the frame of the photo. It is being
reconstructed in the same location.
43Assignment Visit the following
website http//quake.wr.usgs.gov/research/index.h
tml http//quake.wr.usgs.gov/research/deformation
/modeling/index.html Surf around. Check out the
cool animations! Download 4 of your favorite
geology-related images. Then email to me
(pkapp_at_geo.arizona.edu). This will be graded as
a "What is it quiz".