ReMi Applied GeophysicsSpring Break 2010
Fariha IslamGretchen Schmauder
Question
• Can the ReMi method be used to locate faults in the Reno Basin?
Area Geology
• NE trending faults• Lacustrine, fluvial, and alluvial fan
deposits• Tertiary volcanic basement• Active hot springs
Abbott and Louie (2000)
Project Constraints
• Sedimentary cover can be greater than 1000 meters thick (Abbott and Louie, 2000).
• ReMi method typically used to depths less than 100 meters.
ReMi Method
• Surface wave velocity spectral analysis used to determine shallow earth structures
– Typically used to determine IBC site classification, rippability, void detection, and fault mapping.
ReMi Method
Fundamental Mode Rayleigh Wave
Transect 3 along lakeside dr.
ReMi Survey
Transect 4 along lakeside dr.
Survey location
Scott et al. (2004)
20 Transects along Manzanita Ln and adjacent streets
First order: shear velocity correlates to surficial geology
Tr ansect 14 Vs30 Model
-200
-150
-100
-50
00 500 1000 1500
Shear Wave Vel ocity (m/ s)
Depth
(m
)
Vs30 = 827 m/ s
NEHRP C l ass B
Tr ansect 2 Vs Model
-200
-150
-100
-50
00 100 200 300 400 500
Shear Wave Vel ocity (m/ s)
Depth
(m
)
Vs30 = 301 m/ s
NEHRP C l ass D
Tr ansect 5 Vs Model
-200
-150
-100
-50
00 500 1000
Shear Wave Vel ocity (m/ s)
Depth
(m
)
Vs30 = 407 m/ s
NEHRP C l ass C
Frary (2009)
Abbott and Louie (2000)
Second order: shear velocity correlates to depth to bedrock
Third order: correlation between shear velocity and faults?
Conclusions
• Transect velocity models reflect regional geology and depth to bedrock
• Correlation between velocity models and faults is inconclusive
• Indication that the alluvium has a lower shear velocity due to faulting
Further Work
• Additional ReMi lines south of Manzanita Lane to verify higher velocity in alluvium
• Better constraint on area faulting
references