gravity janice kukuk rob ghigieri ross whitmore
TRANSCRIPT
Gravity
Janice KukukRob Ghigieri
Ross Whitmore
http://sciencefun.wordpress.com/2008/04/
Takehome Message
• Bolstered NE portion of the Truckee Meadows Basin (TMB) Gravity dataset
• Hidden Valley Sub-basin
Purpose
• Learn how to use a Gravimeter
• Fill data gaps in TMB dataset
• Profile a smaller sub-basin in Hidden Valley
Location
Methods
• LaCost and Rhomberg Gravimeter
• Grav2d
• GM-SYS
• Trimble GPS
• Theodolite
Results for Prater
1 1.5 2 2.5 3 3.5 4-0.50.00.51.01.52.02.53.03.54.0
DepthSlab
Distance East, km
Basi
n T
hic
kn
ess
, km
Tolerance 1mGal
Density contrast -0.5 g/cc
~14 mGal anomaly
W E
Distance in km
Grav2d
GM-SYS
Results for Hidden Valley
0 0.5 1 1.5 2 2.5 3 3.5 4-0.50.00.51.01.52.02.53.03.54.0
DepthSlab
Distance East, km
Basi
n T
hic
kn
ess
, km
Tolerance 2 mGal
Density contrast-0.33 g/cc
-6 mGal Anomaly
W E
Grav2d
GM-SYS
Distance in km
Comparison of results Prater
1 1.5 2 2.5 3 3.5 4-0.50.00.51.01.52.02.53.03.54.0
DepthSlab
Distance East, km
Basi
n T
hic
kn
ess
, km
(Modified from Widmer et al., 2007)
W E
Comparison of results Hidden Valley
0 0.5 1 1.5 2 2.5 3 3.5 4-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
DepthSlab
Distance East, kmB
asi
n T
hic
kn
ess
, km
W E
Error
• Non-equilibrated spring
• Terrain corrections
• Elevation error
• Inconsistent temperature
• User error
• Instrument drift
Future Work
• Verification of Hidden Valley anomaly
• Completion of D’Andrea pkwy line to bolster dataset
Takehome Message
• Bolstered NE portion of the Truckee Meadows Basin (TMB) Gravity dataset
• Hidden Valley Sub-basin
References • Abbot, R.E., and Louie, J.N., 2000, Depth to bedrock using
gravimetry in the Reno and Carson City, Nevada, Area basins: Geophysics, V. 65, p. 430-450.
• Anderson, J., Su, F., Zeng, Y., 1999, Seismic Hazards in the vicinity of Las Vegas and Reno: Final Technical Report GS# 1434-HQ-97-GR-03044 (paper copy, 15 p.)
• Telford, W.M., Geldhart, L.P., and Sheriff, R.E., 1990, Applied Geophysics: New York, Cambridge University Press, 770 p.
• Widmer, M.C., Cashman, P.H., Benedict, F.C., Trexler, J.H., 2007, Neogene through Quaternary stratigraphy and structure in a portion of the Truckee Meadows Basin; a record of recent tectonic history: Geological Society of America Abstracts with programs, v. 39, no. 4 p.9