[unav_all] Mendenhall postdoc opportunity - Quantitative 3D analysis of the Northern San Andreas faut

[Gerald W. Bawden]

Here is a unique opportunity to help resolve the active tectonics in  
northern California through the analysis of very high-resolution  
GeoEarthScope airborne LiDAR imagery.



32. Application of newly acquired airborne LiDAR data for  
quantitative analysis of landforms associated with active faults in  
northern California

Airborne LiDAR (Light Detection And Ranging, also known as Airborne  
Laser Swath Mapping, or ALSM) data have revolutionized the study of  
landforms associated with active faults in a variety of tectonic  
settings by providing high-resolution (<1 m under ideal  
circumstances) Digital Elevation Models (DEMs). The high measurement  
density of airborne LiDAR data allows the ground surface, even in  
heavily vegetated regions, to be imaged (known as a “bare earth”  
DEM), and therefore has been especially useful in locating previously  
unknown faults in the Pacific Northwest and in refining the positions  
of active fault strands along part of the northern San Andreas Fault.  
GeoEarthScope (GeoES), an NSF-funded program administered by UNAVCO,  
has just completed (April, 2007) the acquisition of airborne LiDAR  
data along most of the major, active, strike-slip faults in northern  
California. This acquisition has imaged >1500 square kilometers in  
swaths 1 to 2 km wide centered on the most significant faults of the  
region. The USGS has been centrally involved in the planning and  
implementation of this data acquisition. Along with its partners, the  
USGS has provided funding as well as expertise and other resources in  
support of this effort because of the great potential of these data  
to provide new insights into these hazardous earthquake faults. These  
data are expected to be the highest-resolution LiDAR data collected  
along any active fault to date, and once processed will be freely  
available at no cost to any user (estimated time of availability is  
autumn, 2007).

The GeoES northern California LiDAR acquisition provides an  
unprecedented opportunity to advance the understanding of the major  
active faults and evaluate the earthquake hazards they present. For  
the first time, these data will provide exceptionally clear images of  
the ground surface beneath the vegetation canopy along the San  
Andreas, San Gregorio, Calaveras, Paicines, Rodgers Creek, Maacama,  
Hayward, and Green Valley Faults. The dense forest canopy above most  
of these fault zones has hampered the accurate mapping of active  
fault traces in northern California, and the acquisition of LiDAR  
data will reveal the fault traces with extraordinary clarity. Even  
more importantly, the LiDAR data will provide the opportunity to  
locate paleoseismic sites in forested regions where slip-rate and pre- 
historic earthquake chronologies can be acquired. Because the LiDAR  
data are digital, they provide the additional opportunity for  
innovative quantitative geomorphic analyses of landforms associated  
with active faults. LiDAR data in southern California have been used  
to locate and digitally quantify offsets of small stream channels  
that are displaced by one or more earthquakes, and we anticipate  
similar opportunities in northern California. These data can be used  
to define offsets of geomorphic features that can provide information  
about coseismic slip, and may provide slip-rate estimates when  
evaluated in concert with other paleoseismic data. In addition, the  
long-term complexity of fault-zone activity is recorded in landforms  
associated with and adjacent to the faults, and these will be imaged  
in great detail as a result of the new LiDAR data acquisition. Thus,  
exploration of this rich dataset will provide new and unexplored  
means of evaluating fault-zone complexity and long-term fault  
development. The topography of fault systems of Northern California  
contains a rich record of both the horizontal and vertical  
deformation field, and quantitative analyses of LiDAR data should  
elucidate the spatial patterns of this deformation. By comparing  
topographic metrics such as topographic steepness and residual relief  
along fault zones and considering them within the context of  
differences in the underlying bedrock lithologies, these metrics may  
reveal differences in the rates of vertical deformation related to  
restraining fault geometries and plate-normal convergence. Rates of  
plate-normal convergence are currently not uniquely resolved by  
geodetic measurements in northern California, and so analysis of  
LiDAR data has the potential to shed light on the relative influence  
of restraining fault geometries vs. transpression on the long-term  
vertical deformation of the plate margin in Northern California.

http://geology.usgs.gov/postdoc/2009/opps/opp32.html

Proposed Duty Station: Menlo Park, CA

Areas of Ph.D.: Geology, geophysics, neotectonics, tectonic  
geomorphology, GIS, remote sensing

Qualifications: Applicants must meet one of the following  
qualifications: Research Geologist, Research Geophysicist, Research  
Geochemist

(This type of research is performed by those who have backgrounds for  
the occupations stated above. However, other titles may be applicable  
depending on the applicant's background, education, and research  
proposal. The final classification of the position will be made by  
the Human Resources specialist.)

Research Advisor(s): Carol Prentice, (650) 329-5690,  
cprentice at usgs.gov; George Hilley (Stanford University), (650)  
723-2782, hilley at pangea.stanford.edu; Gerald Bawden, (916) 278-3131,  
gbawden at usgs.gov; David Phillips (UNAVCO), (303) 381-7471,  
dap at unavco.org

Human Resources Office contact: Erica Settlemyer, (916) 278-9383,  
esettlemyer at usgs.gov


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