Applied Geophysics at the Mackay School of Mines
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a folder of selected
high-resolution photos and illustrations;
the photo of the minute.
Professionals and Students Working Together
Mackay faculty and students from the Hydrogeology program examine
seismic survey results from Thomas Creek, south Reno in October 1995.
Hydrogeology graduate programs have attracted many top-notch local
professionals to return to school, such as USGS scientist David Berger
at the center. Although enrolled as a student in the course Geol
492/692, Environmental Exploration Geophysics, Berger operated
USGS-owned surveying equipment during class field exercises. Mackay
partners continually with local government and industry to advance
earth science and engineering. The W. M. Keck Foundation recognized
these partnerships the following year by donating high-resolution
seismic surveying equipment to Mackay that very few institutions
(Photo by J. Louie)
Progressive slices into a 3-d volume of high-resolution seismic
data across the Pahrump Valley fault (PVF) on the Nevada-Calif.
border west of Las Vegas. Mackay's Geol 453/653 Geophysical
Applications class recorded the survey in Spring 1996 during
the class's one-week geophysical field camp. Field operations
were supported by an NSF Geophysics program grant to Prof. J.
Louie; the W. M. Keck Foundation had recently donated the seismic
recorder. The Pahrump Valley fault is seen here as an interruption
in stratigraphy dipping about 80 degrees left (SW) from 24 to
73 m depth in this volume. A lateral stratigraphic pinchout
at 24 m depth is offset at least 18 m in right-lateral strike
slip. Given the 10-450 ka age constraints on the stratigraphy,
our work establishes a fault slip rate above 0.1 mm/yr. The
PVF thus contributes major earthquake hazard to the Las Vegas
region. Las Vegas hazard studies are in the mandate of Mackay's
Seismological Lab, which is chartered for statewide research
and public service. (Illustration by J. Louie)
More about the Pahrump
Valley fault zone....
The Urban Environment
Mackay Geophyiscs major Christine Mann and Geophysics Ph.D. student
Robert Abbott establish geodetic GPS elevation and gravity along South
McCarran Blvd. in Reno. Mackay's new focus on urban environmental and
earthquake hazards required the collection of many new data sets. Since
sedimentary basin depths influence both potential earthquake shaking,
and gravity readings, the U.S. Geological Survey funded the
Seismological Lab to collect 300 gravity readings in Reno and Carson
City during the summer of 1997. Research funding helps support and
retain undergraduate students at Mackay. Such support helped Mann to
choose a Mackay major over a traditional pre-med program; she begins
medical school at Nevada in Fall 2000. (Photo by J. Louie)
Analysis of gravity data collected in the Reno area for effects of
basin sediments. Orange areas have exposed bedrock; blue shows gravity
lows (in mGal) associated with basin depths of as much as 1.5 km. This
work was funded by the U.S. Geological Survey. Surprisingly, the
largest sediment thicknesses in Reno are on the west side of the city,
below West McCarran Blvd. The shaking from local or even distant large
earthquakes can be significantly amplified by this deep basin.
(Illustration by R. Abbott)
More about gravity and
basin depths in Reno....
Basic Research in Earth Science
In a 1995 project Mackay's Seismological Lab teamed up with
the Jet Propulsion Lab and the University of Utah to investigate
Upheaval Dome, in Canyonlands National Park, with NASA funding.
Probing the structure required helicopter placement of seismic
recorders across the extreme topography of the Canyonlands.
Mackay's seismic profiles proved that Upheaval Dome could not
have originated as a salt uplift, and must be the largest
exposed meteor impact structure in the West. (Photo by J. Louie)
More about the Upheaval Dome impact....
Nevada's Unique Tectonics
Nevada Precision Drilling and Blasting places a shot hole for
Mackay's 1998 seismic survey of Dixie Valley, funded by the NSF.
Job Peak is in the background, with the 1954 earthquake scarp
at its base. Louie, Wesnousky, and Caskey used geophysical
surveys to test a hypothesis that the 1954 rupture was along
a low-angle normal fault. Students in Louie's Geol 453/653
Geophysical Applications class performed all fieldwork except
drilling and blasting, as their one-week geophysical field
camp. Mackay students participate in the latest earth-science
research both in class and on the staff of funded projects.
(Photo by J. Louie)
More Dixie Valley photos....
Photo of the 1954 Dixie Valley rupture taken the day after the
earthquake by seismologist Carl V. Steinbrugge. The miner's cabin
rests within the unusually wide fault graben, which is the area
seamed by extensional cracks. Mackay geologists Steve Wesnousky and
S. John Caskey established the constant 15 m width of this graben
over a 50 km length of the fault, suggesting the low-angle normal
rupture. Our Spring 1998 geophysical work confirmed that the
low-angle normal fault extends to 3 km depth, and has maintained
its low angle since basin inception 15-20 million years ago.
Dixie Valley thus contains the world's only proven low-angle
normal fault. (Photo courtesy of the Steinbrugge Archive of
Earthquake Photographs and the U.C. Berkeley Earthquake Engineering
More about the Dixie Valley fault....