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Near-surface Seismic Investigation of Barringer (Meteor) Crater, Arizona
Soumya Roy1 and Robert R. Stewart1
Department of Earth and Atmospheric Sciences,
University of Houston, Houston, TX 77204 Email: [email protected]
1
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117
Near-surface Seismic Investigation of Barringer (Meteor) Crater, Arizona
1
Soumya Roy1 and Robert R. Stewart1
Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204
Email: [email protected]
ABSTRACT
We investigated the shallow subsurface of Barringer (Meteor) Crater, Arizona using highresolution seismic methods. The seismic surveys were conducted in May, 2010 during a joint
expedition by the University of Houston, the University of Texas at Austin, and the Lunar and
Planetary Institute (LPI). We performed compressional (P)-wave refraction analysis on the
seismic data and found P-wave velocities of 450–2,500 m/s for a 55-m deep model. Away from
the crater rim (toward the south), the shallow P-wave low-velocity layers thin. We also estimated a
near-surface, shear (S)-wave velocity structure using a surface-wave inversion method. S-wave
velocities vary from 200–700 m/s for the top 16–20 m, increasing to 900–1,000 m/s at 38-m depth.
We interpret a prominent change in S-wave velocity (at around 500–600 m/s) as the transition
from the ejecta blanket (a sheet of debris thrown out of the crater during the impact) to the bedrock Moenkopi sandstone. The ejecta is characterized as unconsolidated, low velocity, and low
density. This S-wave transition takes place at a depth range of 12–20 m near the crater rim with a
thinning away from the crater rim. This consistent P-wave and S-wave structure is interpreted as
the ejecta blanket. Ultrasonic measurements on hand samples collected during the expedition give
a range of P-wave velocities of 800–1,600 m/s for the Moenkopi. Predicted bulk densities from
estimated S-wave velocities using modified Gardner’s equation fall in the range of 1.8–2.5 gm/cm3,
with low-density materials (ejecta) underlain by high-density materials (bedrock). These density
results, along with available drilling information and residual gravity anomalies, also support the
thinning of the ejecta blanket.
Introduction
Barringer (Meteor) Crater, situated near Winslow,
Arizona, was excavated some 49,000 years ago by the
collision of a high-velocity iron-nickel meteorite with the
Colorado Plateau. The impact energy was equivalent to
10 MT of TNT, creating a crater with a diameter of
approximately 1.2 km (Kring, 2007). The crater rim rises
some 30–60 m above the surrounding plain and encircles
an approximately 180-m deep bowl-shaped depression.
The near-surface of the crater is fractured, brecciated,
and unconsolidated, having mixed debris of different
strata and meteoritic materials. A number of questions
remain unanswered about this impact structure including its asymmetry, depths and orientation of fractures,
thickness of ejecta blanket (the layer of debris thrown
out of the crater during the impact), and rock properties. We undertook a suite of geophysical measurements in May, 2010 to attempt to answer some of these
questions. The University of Houston, the University
of Texas (Austin), and the Lunar and Planetary Institute (LPI) led a joint geophysical expedition at the
JEEG, September 2012, Volume 17, Issue 3, pp. 117–127
crater site. In this paper, we present seismic, ultrasonic
and gravity results. The primary goals of this work are
to: a) obtain the near-surface seismic velocity structure,
and b) estimate the ejecta blanket thickness. In addition, this study also addresses some broader seismic
and planetary surface issues as: a) whether seismic
waves can propagate through brecciated materials, b)
the development of general survey methodologies to
determine ejecta thicknesses in various craters, c) how
to image near-surface faults associated with the impact
mechanism, and d) where to drill for rock physics
purposes.
Geological Setting of Barringer Crater
Barringer (Meteor) Crater is categorized as a
simple crater (a small impact structure with a relatively
smooth bowl-shaped depression, no central uplift, and
the depth of the crater much less than the diameter).
Figure 1(a) shows a schematic diagram of the final stage
of a simple crater. The present day stratigraphy (a
normal upper Grand Canyon sequence) near the Meteor
118
Journal of Environmental and Engineering Geophysics
Figure 1. (a) Schematic diagram (French, 1998; Kring, 2007) showing the final stage of a simple crater, such as
Barringer Crater, and (b) schematic diagram of the stratigraphy at Barringer Crater (modified after Shoemaker et al.,
1974; Kring, 2007).
crater consists of white Coconino sandstone overlain
by the very thin Toroweap sandstone, followed by the
yellowish Kaibab dolomite and minor sandstone, and
then the red Moenkopi siltstone at the top. The impact
created an inverted or overturned stratigraphy so that
the layers immediately exterior to the rim are stacked
in the opposite order in which they normally occur.
The overturned layers (‘‘ejecta blanket’’) extend to a
distance of one to two kilometers outward from the
crater’s edge. Thus, the entire sequence around the
crater from the top to bottom is the ejecta blanket
(debris from Coconino-Kaibab-Moenkopi) underlain
by the bedrock Moenkopi-Kaibab-Coconino (Fig.1(b)).
The ejecta blanket also contains other materials (e.g.,
fragments of meteorites, recent alluvium) mixed with the
excavated debris (Kring, 2007).
Physical Properties of the Geological Units
Early studies (Walters, 1966; Watkins and Walters, 1966; Ackermann et al., 1975) characterized some
of the physical properties of the Barringer Crater units.
The near-surface of the crater is unconsolidated, dry
with a low bulk density. Hence, a low near-surface
velocity is also expected. A summary of the average
thicknesses and range of the bulk densities for different
near-surface units obtained from previous work and
drilling results is provided in Table 1.
Bulk densities are often predicted from P-wave
velocities (VP), using Gardner’s relationship (Gardner
et al., 1974). We predicted average bulk densities from VP
(obtained from ultrasonic transmission measurements
during the expedition) using Gardner’s relationship r 5
0.23 VP 0.25, where r is the bulk density in gm/cm3 and VP
is the P-wave velocity in ft/s. Ranges of VP values from the
ultrasonic measurements are also given in Table 1 along
with predicted bulk densities. Details of the ultrasonic
transmission method and results are provided later. It is
also possible to predict bulk densities from S-wave
velocities (VS) using a modified Gardner’s relationship
(Dey and Stewart, 1997; Potter and Stewart, 1998). The
modified Gardner’s relationship for VS can be represented
as r 5 aVSb, where r is the bulk density in gm/cm3, VS is
the S-wave velocity in ft/s, a 5 0.37 and b 5 0.22 (Potter
and Stewart, 1998). The results regarding predicted
densities from VS are also discussed later in the paper.
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Roy and Stewart: Seismic Investigation of Barringer Crater, Arizona
Table 1. Summary of the ranges of average thicknesses, average P-wave velocities, and dry bulk densities of different
units at the Barringer Crater from previous work (Walters, 1966; Watkins et al., 1966; Kring, 2007) and ultrasonic
measurements from May, 2010.
Target units
Average
thicknesses (m)
Average P-wave
velocities (m/s) from
ultrasonic measurements
Bulk densities
(gm/cm3) from
drill cores
Predicted bulk
densities (gm/cm3) from
P-wave velocities
Ejecta blanket
Moenkopi formation
Kaibab formation
0–26
12.3
73
N/A
800–1,600
2,530–3,720
1.87–2.17
2.19–2.48
2.12–2.68
N/A
1.65–1.96
2.19–2.42
Geophysical Surveys at the Crater
We performed a set of test seismic surveys on the
southern portion of the crater (Fig. 2(a)). One set
of experiments was performed using a 4.5-kg (10-lb)
sledgehammer as the source, and another set of
experiments was performed using a 40-kg (88-lb)
accelerated weight drop (AWD). For the NW-SE
trending seismic line 1, the source was the sledgehammer
(hence, we name seismic line 1 as hammer line) and the
receivers were planted vertical geophones. The hammer
line is 66-m long (34 receiver stations with 2-m
intervals). For the N-S trending seismic line 2, the
source was a truck-mounted AWD (hence, we name
seismic line 2 as AWD line) and receivers were again
planted vertical geophones. The AWD line is 645-m long
(216 receiver stations with 3-m intervals). The starting
position of the AWD line is approximately 600-m away
from the center of the crater. All vertical geophones used
in this survey have a natural frequency of 14 Hz. A
summary of the seismic acquisition parameters is
provided in Table 2.
Gravity surveys were conducted along five different survey lines on the southern part of the Meteor
crater. One of the main gravity lines is exactly along the
AWD seismic line. The gravity line starts closer to the
rim and overlaps with 0–570 m portion of the AWD line
(0–645 m). Gravity stations were 30-m apart. At every
station, three readings of 60-s each were recorded using
a Scintrex CG-5 gravimeter. Some initial gravity results
along the AWD seismic line are discussed here and in
Turolski (2012). In addition, we performed ultrasonic
transmission measurements (using a James Instrument
V-meter) on a number of hand specimens during the
expedition to estimate the P-wave velocities of different
lithologies.
Figure 2(b) shows an overlay map of the seismic
lines and the approximate locations of several rotary
drill-holes (marked as stars) from Roddy et al. (1975).
The ‘‘South Line’’ and the ‘‘South East Line’’ (Roddy
et al., 1975) indicated in the drill-hole location map
Figure 2. (a) Satellite image showing the location of
Barringer (Meteor) Crater and seismic lines used in this
study. (b) Overlay image of the Meteor Crater with
seismic lines and approximate locations of several drillholes (marked in stars) from the rotary drilling program
of Roddy et al. (1975). The drill-hole lines (‘‘South Line’’
and ‘‘South East Line’’) and available drill-holes (marked
as stars with surrounding white circles) from the same
drilling program closest to the seismic lines are also
plotted (Google Earth plots).
120
0.25
0.5
1,000
3,000
66
645
34
216
2
3
Planted vertical
Planted vertical
10-lb (4.5-kg) Sledgehammer
88-lb (40-kg) Accelerated Weight Drop
Hammer
AWD
2
3
Receiver
interval (m)
Receiver type
Source type
Source
interval (m)
(Fig. 2(b)) are the nearest drill-hole lines to our seismic
lines. We used ejecta blanket thickness results from
this drilling program to compare our results during
interpretation.
Methodology
Seismic line
Table 2.
Summary of acquisition parameters for different seismic lines at Barringer Crater.
Total
receivers
Receiver spread
length (m)
Record
length (ms)
Sample
interval (ms)
Journal of Environmental and Engineering Geophysics
One of the main objectives of this paper is to create
a high-resolution, near-surface velocity structure and
hence to try to identify different layers. We gave special
emphasis to estimating the S-wave velocity (Vs)
structure as no S-wave velocity structure has been
determined for the Barringer Crater. We applied the
surface-wave (Rayleigh wave or ground-roll) inversion
method to obtain the S-wave velocity structure (using
the Multichannel Analysis of Surface Waves (MASW)
method from Park et al., 1998; Park et al., 1999; Xia
et al., 1999). MASW is based on the frequencydependent properties of surface waves to create dispersion curves (phase velocity versus frequency plots). These
dispersion curves are inverted for the fundamental (and
higher) modes to obtain the near-surface Vs structure.
We undertook careful assessment of the offset and
spread lengths used in our multi-mode MASW inversion
(Park et al., 2001; Park and Ryden, 2007; Park, 2011).
The higher modes have greater velocities than the
fundamental mode at a particular frequency; hence,
they have longer wavelengths and can penetrate deeper.
Using higher modes may provide improvement in
velocity estimations (Wisén et al., 2010).
We also used a P-wave refraction analysis method.
In this method, we first pick the first-break arrival times
of the raw shot gathers, generate an initial VP model,
and then an iterative travel-time tomography is performed. In the tomographic technique, rays are traced
through an iteratively updated velocity model with the
goal of minimizing the difference between calculated
and observed travel times. This procedure produces the
final VP structure. We used the Geometrics SeisImager
refraction software for this purpose.
Results
During the expedition, P-wave velocities for
Moenkopi and Kaibab hand samples were measured
on the interior slopes of the northern rim of Meteor
Crater using ultrasonic transmissions with the field
portable V-meter (Table 3). Rock types were identified
by D. Kring (LPI). Measured VP values are in the range
of 815–1,570 m/s (measuring errors varying from 4–9%)
for Moenkopi samples and 2,560–3,705 m/s (measuring
errors varying from 2–9%) for Kaibab samples. The
probable reasons of the variations in VP values are: 1)
the samples are weathered differently, 2) the samples are
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Roy and Stewart: Seismic Investigation of Barringer Crater, Arizona
Table 3. Ultrasonic measurements of Moenkopi and Kaibab hand specimens showing approximate ranges of Pwave velocities.
Rock formation
Moenkopi 1
Moenkopi 2
Moenkopi 3
Kaibab 1
Kaibab 2
Thickness (mm)
41.42
32.40
34.03
68.65
32.44
6
6
6
6
6
1.0
1.0
1.0
1.0
1.0
of very irregular shapes and sizes, and 3) measurement
errors. Nevertheless, the values give a general idea of the
P-wave velocities of the different lithologies at the crater
and help to understand the seismic results.
We then performed a detailed study of the seismic
raw shot gathers. Shot gathers from different seismic
lines are shown in Fig. 3. Figure 4 shows a series of
amplitude spectra for different raw shot gathers from
hammer and AWD lines. Hammer-seismic data show
the dominance of higher frequencies (around 100 Hz)
compared to AWD data (around 50 Hz) for a nearoffset range. However, for the middle to far offsets, the
amplitude spectra share a comparable range of frequencies for both hammer and AWD lines. For the AWD
case, the weight of the source is greater and produces
more energy. This increase in energy is observed in the
Figure 3. (a) A raw shot gather from seismic line 1
(hammer line), and (b) a raw shot gather from seismic line
2 (AWD line) at Barringer Crater, Arizona (AGC
applied). The trends of first break picks are shown by
solid lines.
Transit time (ms)
50.8
25.82
21.675
18.53
12.675
6
6
6
6
6
0.8
1.4
0.6
0.15
0.65
P-wave velocity (m/s)
815
1,255
1,570
3,705
2,560
6
6
6
6
6
33
106
89
81
210
amplitude spectra (Fig. 4) as AWD data show higher
true amplitude values.
Next, we undertook P-wave refraction analysis for
the 645-m long AWD line. We used a minimum VP of
450 m/s and maximum of 3,000 m/s for a 55-m deep
model for the travel-time tomography. The minimum
and maximum VP values are based on the initial analysis
of first-break picks for several raw shot gathers along
with ultrasonic results. We find a final P-wave velocity
model with a range of VP values varying from 450 m/s to
2,500 m/s up to 55-m depth (Fig. 5).
Surface-wave inversion (MASW) was next applied
to estimate the S-wave velocities. We used the SurfSeis
3.0 (Kansas Geological Survey) software package.
Careful selections of offset ranges have been made to
avoid (as much as possible) the mixing of different
modes. For the hammer line, the most useful offset
range from the source is 9–55 m, whereas the offset
range is longer (10.5–82.5 m) for the AWD line. The
dispersion curves from single raw shot gathers for
selected offset ranges are shown in Fig. 6. The AWD
line is richer in lower frequencies than the hammer line
(Fig. 4), and thus provides more robust low-frequency
velocity information (Fig. 6).
The final step in the surface-wave inversion
method is to invert the dispersion curves using
fundamental (and higher modes) for S-wave velocity.
The inversion of one dispersion curve corresponding
to one shot gather produces a 1-D S-wave velocity
structure at the center of the selected offset spread.
Multiple 1-D velocity profiles along a seismic line are
then merged into a 2-D velocity profile. Such 2-D Swave velocity profiles for the hammer and the AWD line
are shown in Fig. 7. The VS structure from the hammer
line (Fig. 7(a)) shows a range of velocities from 200–
700 m/s up to 16.5-m depth and increases to 1,000–
1,200 m/s below that. The 2-D S-wave velocity
structure for the AWD line shows a range of velocities
from 300–1,000 m/s up to 38-m depth and increases to
1,200–1,300 m/s below that (Fig. 7(b)). S-wave velocities increase away from the crater rim, as with the Pwave results. The deeper velocity structures from the
AWD line, compared to the hammer-seismic line, are
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Journal of Environmental and Engineering Geophysics
Figure 4. (a)-(c) Amplitude spectra with true amplitude values for seismic line 1 (hammer line) and seismic line 2 (AWD
line) for different source-receiver offset ranges.
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Roy and Stewart: Seismic Investigation of Barringer Crater, Arizona
Figure 5. A 2-D P-wave velocity model estimated using
travel-time tomography for the 645-m long AWD seismic
line. The black dotted line indicates the trend of lowvelocities (the interpreted ejecta blanket). Approximate
outcrops or surface lithologies along the AWD line are
also plotted at the top of the velocity profile. The velocity
model is plotted from the ground surface (0 m).
obtainable because of more deeply penetrating and
propagating source energy.
Interpretation
In this section, we interpret the velocity models to
identify different stratigraphic layers and ejecta blanket
thickness. Previous work identified the transition from
the ejecta blanket to the Moenkopi based on changes in
P-wave velocities from refraction surveys and changes
in physical properties from drill cores (bulk density,
Young’s and Shear modulus).We compare our estimates
with one seismic refraction survey (Ackermann et al.,
1975) and several drill core results (Watkins and
Walters, 1966; Roddy et al., 1975).
Ackermann et al. (1975) showed a low-velocity
layer of 500–750 m/s for the top 15 m (roughly
consistent with the ejecta blanket thickness) followed
by an intermediate velocity zone of 750–1,500 m/s from
P-wave refraction analysis. They suggested all velocities
less than 1,500 m/s indicate unconsolidated, fractured
materials. We estimated P-wave velocities of 450–2,500 m/
s for up to 55-m depth with low-velocity layers tapering
away as we move southward. We interpret this as
the thinning of the low-velocity, unconsolidated ejecta
blanket away from the crater rim. We also obtained Pwave velocities of 800–1,600 m/s for the Moenkopi hand
specimens from ultrasonic measurements during the
expedition. These values are in the neighborhood of
the Ackermann et al. (1975) and our P-wave refraction
results.
In addition to interpreting P-wave velocities, we
also estimated the ejecta blanket thickness from S-wave
velocities (the first attempt to do so to our knowledge at
Barringer Crater) along with the prediction of bulk
densities. We identified prominent S-wave velocity
changes (at around 500–600 m/s) at depths varying
from 15–20 m near the crater rim (up to 800–900 m from
the center of the crater, i.e., 200–300 m from the
beginning of the AWD line) on the southern flank. We
interpret this change as the transition from the ejecta
blanket to Moenkopi. As we move further away from
the crater rim, similar to the P-wave results the VS
values also increase. A summary of the depths of
transition from the ejecta blanket to the Moenkopi
obtained from previous studies are provided in Table 4,
along with the results obtained from the surface-wave
inversion method.
We also predicted bulk densities from VS (using
modified Gardner’s relation), which are in the range of
1.8–2.5 gm/cm3 (Fig. 8(a)). Closer to the crater rim,
a transition from lower densities (ejecta) to higher
densities (bed-rock) is calculated at depths varying from
15–20 m. Densities increase at around 800–900 m
distance from the crater center, indicating the consolidation of materials and thinning of low-density ejecta
materials. These predicted bulk densities are in the range
of density values from previous drilling results (Tables 1
and 5) and consistent with seismic results.
The residual gravity anomaly results along the
AWD line from Turolski (2012) show a low in the
gravity field near the rim, then a rise (at around 800–
900 m from the center of crater) followed by another
decrease at the end (Fig. 8(b)). The initial decrease
probably indicates low-density unconsolidated materials
(ejecta blanket), followed by an increase in densities.
This is consistent with our predicted density results.
Turolski (2012) interpreted the gravity field decrease at
the end of the line as an effect of dipping beds.
We also received LiDAR (Light detection and
ranging) data to better estimate the crater’s topography.
The airborne LiDAR data were acquired by the National
Center for Airborne Laser Mapping (NCALM). The
resulting topographic maps have a horizontal resolution
of 25 cm and a vertical resolution of 5 cm. The last 100 m
of the AWD line do not overlap the LiDAR data,
therefore they were extrapolated using a second-order
polynomial fit (Turolski, 2012). The P- and S-wave
velocity models are re-plotted along with actual elevations. The P- and S-wave velocity models along with
elevations and distances from the center of the crater are
shown in Figs. 9(a) and 9(b). The probable transition
from the ejecta blanket to Moenkopi is also marked
(dotted black line). Figure 9(c) shows a composite plot of
the transition depths from: 1) the ‘‘South Line’’ (Roddy
124
Journal of Environmental and Engineering Geophysics
Figure 6. Dispersion curves for single shot gathers from (a) the hammer line for an offset range of 9–55 m from the
source, and (b) the AWD line for an offset range of 10.5–82.5 m from the source. The plots also show phase velocity picks
for the fundamental and first higher modes.
et al., 1975), 2) the 2-D S-wave velocity profile, and 3) the
2-D P-wave velocity profile along the AWD line with
reference to the actual elevations.
We identify the consistent trend of thinning of the
ejecta blanket as we move away from the crater rim in:
1) 2-D velocity models for P- and S-wave (velocities
increase with distance from the crater rim), and 2) 2-D
density model and residual gravity field studies (density
increases away from the crater). The surface lithological
expression is mostly alluvium. Debris from the Moenkopi and some occasional patches of the Kaibab and
Coconino at surface are observed along the AWD line.
Conclusions
A seismic investigation of the shallow subsurface
was undertaken for Barringer (Meteor) Crater, Arizona.
We produced both P- and S-wave near-surface velocity
models. We estimated P-wave velocities of 450–
2,500 m/s for a 55-m deep model. The P-wave velocity
structure shows some thinning of the low-velocity layer
as we move away (southward) from the crater rim.
P-wave velocities (varying from 800–1,600 m/s) of
Moenkopi hand specimens obtained from ultrasonic
measurements are consistent with the refraction results.
Using surface-wave inversion (MASW), we obtained
S-wave velocities from 200–700 m/s for the top 16 m,
increasing to 900–1,000 m/s at 38-m depth. We found a
prominent change in S-wave velocities (at around 500–
600 m/s), which we interpret as the transition between
the overlying ejecta blanket and the underlying bed-rock
Moenkopi. This transition is observed at a depth range
varying between 12–20 m near the crater rim (up to 800–
900 m from the center of the crater) and tapers away
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Roy and Stewart: Seismic Investigation of Barringer Crater, Arizona
Figure 7. The 2-D S-wave velocity profiles determined from the surface-wave inversion for (a) the hammer line (the
profile is of 22–42 m from the total of 0–66 m line), and (b) the AWD line (the profile is of 51–609 m from the total of
0–645 m line). Approximate outcrops or surface lithologies along the AWD line are also plotted at the top of the velocity
profile. Dashed lines show our interpretation of the transition from the ejecta blanket to bed-rock Moenkopi. The velocity
models are plotted relative to ground surface (0 m).
(transition depth as shallow as 5 m and less) as we move
southward. The tapering trend of low-velocity layers for
both P- and S-wave velocity models is caused by the
expected thinning of the ejecta blanket away from the
crater rim, along with some local topographic effects
and local surface lithologies. Predicted bulk densities
from S-wave velocities (using a modified Gardner’s
relation) fall in the range of 1.8–2.5 gm/cm3, which are
consistent with the drilling results and some residual
gravity anomaly results. We have successfully identified
different lithological layers based on seismic velocity
variations (especially S-wave), estimated the ejecta
Table 4. Summary of the depths of transition from the ejecta blanket to the bedrock Moenkopi from Roddy et al. (1975)
and surface-wave inversion method close to the crater rim (up to 800–900 m from the center of the crater).
South-East line (Roddy et al., 1975)
Hammer line
South line (Roddy et al., 1975)
AWD line
10–19.5 m
10–14 m
13.5–18 m
15–20 m
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Journal of Environmental and Engineering Geophysics
Figure 8. (a) A 2-D bulk density profile (from the AWD
line) predicted from the modified Gardner’s equation using
Vs and plotted relative to the ground surface (0 m), (b) the
residual gravity anomaly over the same portion of the
AWD line as the density profile (Turolski, 2012).
Table 5. Summary of the dry bulk densities at different
depths for different lithological units and the depth of
transitions (Watkins and Walters, 1966 and modified
after Kring, 2007).
Drill core: MCC-4; Location: South side of the crater, 10 m
from the crater rim
Depth (m)
Dry bulk
density (gm/cm3)
Lithology
8.2
9.3
10.7
16.0
20.0
21.0
2.18
2.18
2.19
2.44
2.48
2.68
Ejecta-sandstone
Ejecta-sandstone
Moenkopi-sandstone
Moenkopi-sandstone
Moenkopi-shaly sandstone
Kaibab-dolomite
Figure 9. The 2-D a) P-wave and b) S-wave velocity
models plotted with reference to actual elevation and
interpreted thickness of ejecta blanket. c) The figure
shows the transition depths (from the ejecta blanket to the
bed rock Moenkopi) from: 1) previous work (drill cores
from Roddy et al., 1975), 2) P-wave refraction analysis,
and 3) surface-wave inversion method with reference to
actual elevation profile.
blanket thickness, and also identified the thinning of the
low-velocity ejecta blanket as we move away from the
crater rim. Near-surface seismic methods as outlined
above may be useful in the study of other meteorite
impact structures and planetary expeditions.
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Roy and Stewart: Seismic Investigation of Barringer Crater, Arizona
Acknowledgments
We thank the University of Houston field crews
(especially Mr. Bode Omoboya, Mr. Li Chang, Mr. Arkadiusz
Turolski, and Ms. Tania Mukherjee) for their assistance in
acquiring the data and their analysis. We are also appreciative
of Dr. D.A. Kring of the Lunar and Planetary Institute for
helping coordinate the Meteor Crater surveys, along with the
generous staff at the Meteor Crater Museum. Dr. K. Spikes
and Ms. Jennifer Glidewell, from The University of Texas at
Austin, participated in Meteor Crater surveys.
References
Ackermann, H.D., Godson, R.H., and Watkins, J.S., 1975, A
seismic refraction technique used for subsurface investigations at Meteor Crater, Arizona: Journal of Geophysical Research, 80, 765–775.
Dey, A.K., and Stewart, R.R., 1997, Predicting density using
Vs and Gardner’s relationship: in Research Report:
Consortium for Research in Elastic Wave Exploration
Seismology, Ch. 9.
French, B.M., 1998, Traces of catastrophe: A handbook of
shock-metamorphic effects in terrestrial meteorite
structure, Contribution No. 954, Lunar and Planetary
Institute, 120 pp.
Gardner, G.H.F., Gardner, L.W., and Gregory, A.R., 1974,
Formation velocity and density – the diagnostic basics
for stratigraphic traps: Geophysics, 39, 770–780.
Kring, D.A., 2007. Guidebook to the geology of Barringer
Meteorite Crater, Arizona (a.k.a. Meteor Crater), Field
guide for the 70th Annual Meeting of the Meteoritical
Society.
Park, C.B., Miller, R.D., and Xia, J., 1998, Imaging dispersion
curves of surface waves: in Expanded Abstracts: 68th
Annual International Meeting, Society of Exploration
Geophysicists, 1377–1380.
Park, C.B., Miller, R.D., and Xia, J., 1999, Multichannel
analysis of surface waves: Geophysics, 64, 800–808.
Park, C.B., Miller, R.D., and Xia, J., 2001, Offset and
resolution of dispersion curve in multichannel analysis
of surface waves (MASW): in Proceedings of the
Symposium on the Application of Geophysics to
Engineering and Environmental Problems, SSM-4.
Park, C.B., and Ryden, N., 2007, Offset selective dispersion
imaging: in Proceedings of the Symposium on the
Application of Geophysics to Engineering and Environmental Problems.
Park, C.B., 2011, Imaging Dispersion of MASW Data – Full
vs. Selective Offset Scheme: Journal of Environmental
and Engineering Geophysics, 16(1), 13–23.
Potter, C.C., and Stewart, R.R., 1998, Density predictions
using VP and VS sonic logs: in Research Report:
Consortium for Research in Elastic Wave Exploration
Seismology, Ch. 10.
Roddy, D.J., Boyce, J.M., Colton, G.W., and Dial, A.L. Jr., 1975,
Meteor Crater, Arizona, rim drilling and thickness,
structural uplift, diameter, depth, volume, and mass-balance
calculations: in Proc. Lunar Science Conf. 6th, 2621–2644.
Shoemaker, E.M., and Kieffer, S.W., 1974, Guidebook to the
geology of Meteor Crater, Arizona: Meteoritical Society, 37th Annual Meeting, Arizona State University
Centre for Meteorite Studies, Tempe, Arizona, 66 pp,
reprinted in 1988.
Turolski, A., 2012, Near-surface geophysical imaging of complex structures: Meteor Crater, AZ and Jemez Pueblo,
NM: M.S. thesis, University of Houston, Houston, Texas.
Walters, L.A., 1966, In situ physical properties measurements:
in Investigation of in situ physical properties of surface
and subsurface site materials by engineering geophysical
techniques, annual report, fiscal year 1966, Watkins, J.S.
(ed.), NASA Contractor Report (CR)-65502 and USGS
Open-File Report 67-272, 7-24.
Watkins, J.S., and Walters, L.A., 1966, Laboratory physical
property measurements on core and surface samples
from six lunar analog test sites: in Investigations of in
situ physical properties of surface and subsurface site
materials by engineering geophysical techniques, annual
report, fiscal year 1966, Watkins, J.S. (ed.), NASA
Contractor Report (CR)-65502 and USGS Open-File
Report 67-272, 259-267.
Wisén, R., Boiero, D., Maraschini, M., and Socco, L.V., 2010,
Shear wave velocity model from surface wave analysis—
A field case example: in Expanded Abstracts: 72nd
European Association of Geoscientists and Engineers
Conference and Exhibition, M045.
Xia, J., Miller, R.D., and Park, C.B., 1999, Estimation of nearsurface shear-wave velocity by inversion of Rayleigh
wave: Geophysics, 64, 691–700.