ReMi/Refraction Team
Sean Flores
Kristin Kohls
Mahesh Dhar
Preliminary Results of ReMi Seismic Survey:
The following is a summary of preliminary results for the Refraction Micro-tremor survey that occurred during the week
of March 15 to March 19, 2009. The results have been generated via interpretation of data that was analyzed using SeisOpt
ReMi software. Specifically, ReMi Vspect and ReMi Disper were used. The procedure used for producing the models was a
two step process consisting of: (1) using the Vspect program to create a velocity-spectral graph for picking the
velocity/frequency location of the Rayleigh wave front, and (2) importing the picks into ReMi Disper for depth and velocity
modeling.
Line 1:
Line 1 was located in proximity to the 26-Foot Drop hydroelectric power plant on V-Line canal. At the time of the survey the
canal was noted as being empty, with little evidence of recent water flow. Soils were noted as being silty and clayey in nature.
Vegetation was noted as being minimal in juxtaposition to the levee.
What was discovered by our Disper analysis was that the subsurface was comprised of three layers as was modeled to a max
depth of 30 m. Measured down from the surface, the layer depths are 1.8 m and 5.1 m, which overlay a depth-indeterminate
layer. The velocities of the layers are approximately 150 m/s, 185 m/s, and 220 m/s respectively. It is important to note that
the bottom layer was not modeled to its entire depth, as the resolution of the survey did not exceed 30 m in depth.
Line 2:
Line 2 was located perpendicular to line 1 at its midpoint. Line 2 traversed the top of the canal bank and down the South
slope of the bank into the adjacent desert. Water, soil, and vegetation conditions are the same as that noted above under
Line 1.
Our Disper modeling suggests that three layers underlie the survey, with a maximum modeled depth of 15 m. The layer
depths, measured down from the surface, are 1.5 m and 12.1m, which overlie a depth-indeterminate layer. Modeled shearwave velocities are 140 m/s, 200 m/s, and 490 m/s respectively.
Line 3:
Line 3 was located roughly northwest of lines 2 and 3 along the V-line canal bank. Water, soil, and vegetation conditions are
similar to those of lines 1 and 2.
Four layers were modeled at this location with a maximum modeled depth 30 m. The total depths of the layers as measured
from the surface are: 1.1 m, 5.0 m, and 10.6 m, which all overlie a depth-indeterminate layer. Shear-wave velocities of the
layers are 150 m/s, 190 m/s, 158 m/s, and 258 m/s respectively.
Line 4:
Line 4 was located near the V-line Headworks. Soils were noted as being silty and clayey in nature with organics present.
Vegetation at this location consisted of large trees and shrubbery. At the time of the survey the canal was empty and water
was not dammed at the headworks. However, water was flowing in the nearby Carson River.
Three layers were modeled in Disper with a maximum modeled depth of 15 m. Layer depths, as measured from the surface,
are 1.9 m and 4.5 m, which overlie a depth-indeterminate layer. Velocities encountered are 150 m/s, 140 m/s, and 190 m/s
respectively.
Line 5:
Line 5 was located southeast of line 4 along the V-line canal. Soils at this location were silty and clayey in nature with a slight
gravelly component. Vegetation was noted as being sparse, and consisting mostly of desert brush.
In Disper, our team modeled three layers with a maximum overall modeled depth of 30 m. The layer depths as measured
from the surface are 2.0 m and 9.1 m, which overlie a depth-indeterminate layer. Velocities are 105 m/s, 160 m/s, and 300
m/s respectively.
Lines 6, 7, and 8:
Lines 6, 7, and 8 are all adjacent to one another, with 7 starting at the end of line 6, and 8 starting at the end of line 7. Soil
was noted as being silty and clayey in nature at line 6, while lines 7 and 8 had a sand component in addition to the clay and
silt. Line 6 was flanked by a conglomeration of willow trees to south. Line 7 had minimal vegetation located near it. More
willows than line 7 were noted to the south of line 8, but it had less than line 6.
Line 6 was modeled with four layers and a maximum modeled depth 30 m. As measured from the surface, line 6 depths are
1.1 m, 3.0 m, and 6.5 m which overlie a depth-indeterminate layer. Layer velocities are 115 m/s, 125 m/s, 140 m/s, and 330
m/s respectively.
Line 7 was modeled with three layers and a maximum modeled depth of 30 m. Layer depths are noted as being 1.1 m and 6.0
m, which overlie a depth-indeterminate layer. Velocities are 103 m/s, 110 m/s and 270 m/s respectively.
Line 8 was modeled as a three layer structure with a maximum modeled depth of 30 m. Layer depths are recorded as 1.1 m
and 6.4 m, which are superimposed over a depth-indeterminate layer. Recorded velocities are 105 m/s, 119 m/s and 250 m/s
respectively.
Line 9:
Line 9 was located near the Bango Check along the base of small basaltic mountain. Line 9 was a survey conducted on the
Truckee Canal, which at this location, was constructed of large cobbles to boulders with soil infill. Vegetation was noted as
being abundant tumbleweed along the canal. The Truckee Canal was occupied by water at the time of this survey.
Line 9 was modeled as a three layer structure with a maximum modeled depth of 30 m. Layer thicknesses, as measured from
the surface, are 1.1 m and 3.0 m, which overlie a depth-indeterminate layer. Velocities are 169 m/s, 280 m/s, and 421 m/s
respectively.
Line 10
Line 10 was also located along the Truckee Canal near the Bango Check. Line 10 was located north of line 9 along the canal
bank. Water and vegetation were similar to line 9, with the soil conditions changing to sand gravel over cobbles.
Two layers were modeled at this line with a maximum modeled depth of 30 m. Layer depth was noted as 3.0 m overlying a
depth-indeterminate layer. The velocities are 170 m/s and 310 m/s respectively.
For models, please reference the associated excel files. See below for survey line summary.
Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10
Canal Bank (approximate) (m)
2.3
6.6
2.5
1.8
2
2.6
2.8
3.5
10.7
7.7
Layer 1 (Depth) Total (m)
1.8
1.5
1.1
1.9
2.0
1.1
1.1
1.1
1.1
3.0
Layer 1 (Thickness) (m)
1.8
1.5
1.1
1.9
2.0
1.1
1.1
1.1
1.1
3.0
Layer 1 (Velocity)
150 m/s
140 m/s
150 m/s
150 m/s
105 m/s
115 m/s
103 m/s
105 m/s
169 m/s
170 m/s
Layer 2 (Depth) Total (m)
5.1
12.1
5.0
4.5
9.1
3.0
6.0
6.4
3.0
30.0
Layer 2 (Thickness) (m)
3.3
10.6
3.9
2.6
7.1
1.9
4.9
5.3
1.9
i nf
185 m/s
200 m/s
190 m/s
140 m/s
160 m/s
125 m/s
110 m/s
119 m/s
280 m/s
310 m/s
30.0
15.0
10.6
15.0
30.0
6.5
30.0
30.0
30.0
-
Layer 2 (Velocity)
Layer 3 (Depth) Total (m)
Layer 3 (Thickness)(m)
Layer 3 (Velocity)
i nf
i nf
5.6
i nf
i nf
3.5
i nf
i nf
i nf
-
220 m/s
490 m/s
158 m/s
190 m/s
300m/s
140 m/s
270 m/s
250 m/s
421 m/s
-
Layer 4 (Depth) Total (m)
-
30.0
-
-
30.0
-
-
-
-
Layer 4 (Thickness) (m)
-
-
i nf
-
-
i nf
-
-
-
-
Layer 4 (Velocity)
-
-
258 m/s
-
-
330 m/s
-
-
-
-