An Overview of Seismic Land Streamer Projects at Montana Tech

Downloaded 10/23/14 to 150.131.130.14. Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/

AN OVERVIEW OF SEISMIC LAND STREAMER PROJECTS AT MONTANA TECH Curtis A. Link, Montana Tech, Butte, MT Marvin A. Speece, Montana Tech, Butte, MT Seth J. Betterly, Montana Tech, Butte, MT

Abstract The Geophysical Engineering Department at Montana Tech has conducted a series of land streamer projects over the last several years. Our primary goal was to increase the speed of seismic data collection by dragging streamers of gimbaled geophones rather than using conventional hand-planted spiked geophones. The land streamers implemented at Montana Tech use gimbal-mounted geophones on 24-channel cables with 1m takeout spacing. Our projects included archaeological investigations, void detection, characterization of earthen dams, and imaging abandoned subsurface coal mines. Analysis methods included diving wave tomography, Multi-channel Analysis of Surface Waves (MASW) and Three-Dimensional (3-D) seismic reflection surveying. Early experiments comparing spiked and gimbaled geophones showed high similarity of both amplitude and spectral content for the two geophone types on a variety of surfaces. The exception was a single grass surface for which the gimbaled geophones displayed a consistent phase shift and decreased amplitude. Land streamer data acquisition has proved useful for all of our applications including particularly successful results using diving wave tomography to image voids and archaeological features. Our recent MASW work is focusing on comparing results from data collected with both gimbaled and spiked geophones of different natural frequencies. Using 3-D seismic reflection techniques, we tested a land streamer approach to image abandoned subsurface coal mine workings at a depth of approximately 100m near Belt, Montana. To collect these data we towed an array of four parallel land streamers covering a surface area of 100m by 34m achieving a nominal fold of 24 on 1m bin centers. Typical combined advance and occupation times for each station were less than 30 seconds using a crew of three people. The resulting stacked volume clearly shows the horizontal layering of the sedimentary rock sequence.

Introduction Brief History of Land Streamers. The need to reduce the costs of acquiring land-based seismic data has inspired researchers to investigate the use of a towed land streamer, similar to that used in marine work. In 1974, Kruppenbach and Bedenbender (1976) designed and patented a towed land streamer with gimbaled geophones in which coupling is accomplished through the weight of the geophone housing. An early version of the land streamer using this approach greatly increased the collection rate of quality seismic data on sea ice in arctic North America but no detailed report was ever published (Einarsson et al., 1977). Using a similar design, a land streamer was utilized in Antarctica (Determann et al., 1988) and later an improved version was used in Svalbard and Antarctica (Eiken et al., 1989). In these studies, extensive comparisons between gimbaled geophones and spiked geophones were made and no significant or systematic differences between traces or shot records could be seen. These studies did find that gimbaled geophones are highly susceptible to wind-generated noise at high wind speeds but concluded that this disadvantage is often outweighed by the advantages of speed and economics (Eiken et al., 1989).

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Van der Veen and Green (1998) demonstrated that land streamers could collect high quality seismic data to image the shallow subsurface. They compared data from gimbaled geophones and spiked geophones and found the data practically indistinguishable. Further research found that good coupling could be achieved if the gimbaled geophones were fixed to a long thick rubber mat with the geophones attached to the base of the mat and the cable mounted on the topside (Van der Veen et al, 1999). Miller et al. (2003) found that data from gimbaled geophones weighted by a thick rubber pad compare favorably with data from spiked geophones on sand, asphalt, snow, and grass. In addition, they also found that the rubber pad reduces wind noise. Miller et al. (2005) and Speece et al. (2003) report on using data acquired with a land streamer and diving wave seismic tomography to successfully locate underground manmade features at an archeological site in Egypt. The above cited examples used data collected from 2-D land streamers. A new system developed at Montana Tech utilizes multiple streamers in array form in an effort to make 3-D seismic reflection a viable option for near-surface exploration. This system was successfully used for a high resolution reflection survey over abandoned coal mine workings (Dolena et al., 2005a, 2005b). Land Streamer Projects at Montana Tech. All of the land streamer projects so far at Montana Tech have used 24-channel streamers with 30Hz gimbaled geophones at 1m takeouts. A listing of the projects to date includes: Spiked versus gimbaled geophone comparisons Diving wave tomography Void detection, MSE, Butte, MT Archaeological investigation, Saqqara, Egypt Archaeological investigation, St. Antonio de Padua Mission, California Void detection, Butte, MT Earthen dam characterization, Mike Horse Dam, Lincoln, MT MASW Geophone comparisons, Centennial Av., Butte, MT Dam characterization, Mike Horse Dam, Lincoln, MT 3-D reflection Abandoned subsurface coal mine, Belt, MT. 2-D reflection ANDRILL program, Antarctica (in progress fall 2005) using 60-channel streamer with 25m takeout spacing.

Geophone comparisons Geophone Coupling Experiments Prior to starting our land streamer work, we conducted a series of tests to compare the responses of gimbaled and spiked geophones. Details of this work can be found in Miller et al. (2003). Both the gimbaled and spiked geophones were type SM-7 geophones manufactured by Input/Output Inc. The elements were identical with a natural frequency of 30Hz and coil resistance of 370Ω. The mass of an individual gimbaled geophone is 0.9kg (Figure 1a). In addition to comparing the two geophone types, we also compared results from three streamer configurations (Figure 1b, 1c). Configuration A was the streamer alone. Configuration B incorporated a rubber mat with cutouts for the gimbaled geophones to provide additional weight on the geophones for coupling. An added benefit of the mat is that it provides abrasion protection for the streamer cable and helps reduce wind noise. Configuration C was similar to configuration B but employed an additional rubber mat on top of the entire length of the streamer to further increase the weight for coupling.

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Figure 1: (a) Photograph showing gimbaled (left) and spiked (right) geophones used in the tests. (b) Streamer Configuration A - no mat. (c) Streamer Configuration B - rubber mat with cutouts for individual geophones. We recorded trace data for experiments on four different surfaces: grass, sand, asphalt, and snow. Data were collected using a sledgehammer source with 18m offset. Gimbaled and spiked geophones were almost coincident separated by 15cm. Grass Figure 2a shows results using configuration A (no mat) on grass. The amplitude of the gimbaled geophone was relatively low compared to the amplitude of the spiked geophone; also, a phase shift is evident on the gimbaled trace (top and bottom left). Both of these effects occurred only on grass. For configurations B and C, the phase shift was smaller but still evident and the amplitude of the gimbaled geophone still remained low relative to the planted geophone; however, there was some improvement in the similarity of the spectra compared to configuration A. Sand The sand experiment was conducted on a wet, sandy surface. Raw trace amplitudes were very similar and no phase shift was observed. Configurations B and C showed slightly improved trace and spectrum similarity. Asphalt The asphalt experiment was conducted on a road surface of asphalt pavement (Figure 2b). For this test we replaced the spikes with pavement plates. Data from each type of geophone were nearly identical in this experiment. Changing the streamer configuration had no noticeable effect. Snow For the snow experiment, data for each type of geophone were nearly identical and the various streamer configurations showed little difference.

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(b) Figure 2: (a) Comparison of gimbaled and spiked geophones in grass. Top left plot shows raw trace amplitude for each geophone. Bottom left plot shows normalized trace amplitudes. Note the time lag between the gimbaled geophone (dotted blue line) and the planted geophone (solid red line). Top right plot shows amplitude spectrum for each geophone and bottom right plot shows normalized spectra. (b) Comparison of gimbaled and spiked (pavement plates) geophones on asphalt. Note the similarities of the raw amplitude traces (left) and the amplitude spectra (right).

Diving Wave Tomography Background Standard seismic refraction methods do not typically work well in the presence of the strong lateral variations in subsurface velocity that are often associated with archaeological sites. A solution to this velocity problem is to use seismic diving wave tomography which can accommodate strong lateral changes in velocity. Diving wave tomography requires the use of numerous shot points along a profile

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to maximize the number of wavepaths in the subsurface. A seismic land streamer employing gimbalmounted geophones greatly aids in minimizing the time necessary to mobilize and move receiver spreads. To test land streamer aided, seismic diving wave tomography as a method to detect archaeological features, we collected seismic tomography data at three sites. The first site in Butte, Montana provided us with a well-defined subsurface concrete target (Figure 3a) for use in evaluating the effectiveness of the land streamer survey approach. Results showed high velocity anomalies correlated with the concrete walls and floor and lower velocities in the surrounding fill. At the second site, Mission San Antonio de Padua, California, we observed high velocity anomalies indicating subsurface cobblestone foundation walls corroborated with other geophysical methods. At the third site in Saqqarra, Egypt, we observed an extensive, low velocity anomaly over a feature originally detected using ground penetrating radar with 100MHz antennas. Using seismic tomography, we were able to more than triple the depth of investigation over that obtainable using radar. Moreover, we were able to complete seismic surveys at each site significantly faster than could be done using conventional planted geophones. We used a sledgehammer striking a steel plate as the seismic source at each of the three test sites. Trace data for each shot were recorded with the 24 gimbaled geophone streamer. Each shot record was 100ms in length with a sample period of 0.1ms. The Egypt data were filtered during collection with 8Hz low-cut and 4000Hz high-cut filters. Shot points for all sites were offset by 0.1 m perpendicular to the spread direction to avoid striking the geophones with the sledgehammer. When collecting data in Montana, and California, we used 0.5 m geophone spacing instead of the 1m cable spacing to maximize wavepath coverage in the upper few meters of the subsurface where we expected to image shallow foundation walls. Each seismic profile contained two to four individual spreads, overlapped by fifty percent. To shoot each spread, we located an initial shot 0.5 m off the end of the spread, and then located a shot directly alongside each of the geophones. The final shot for each spread was located 0.5 m off the far end of the spread for a total of 26 shots per spread. We did no vertical stacking of data at these two field sites. In Saqqara, Egypt, we used a geophone spacing of 1m because our target of interest was located deeper than targets at the other two sites. Shooting of the survey was otherwise similar, with shot points off the ends of each spread and alongside each geophone. We vertically stacked nine shots at each shot point at Saqqara. MSE Test Site, Butte, Montana The first site investigation was conducted at the MSE Verification Test Site (MSE VTS) located at the Mike Mansfield Advanced Technology Center in Butte, Montana. The MSE VTS resembles a small concrete basement that has been back filled with native soils from the site (Figure 3a). Although the site contains no archaeological features, the concrete structure provides a well-defined subsurface target with significant lateral velocity contrast. This allowed us to test our system in a controlled environment containing a feature similar to what might be expected at an archaeological site. Figure 3b shows the velocity tomogram and the wavepath coverage diagram for the profile line across the structure. The actual location of the foundation is indicated by the gray rectangles overlain on the middle tomogram plot. The result shows high velocity anomalies associated with the foundation walls at approximately 12.5m and 16.5m along the profile. Wavepath coverage (Figure 3b bottom) near the bottom of the structure is decreased but the tomogram contains a velocity high indicating the floor approximately 8.5m wide at a depth of 4.5m. Initial layout and subsequent moving of the geophone streamer accounted for only minutes of the total survey time. This time was negligible compared with the two hours required to collect the shot data along the profile. Pulling the 24-channel streamer into each new position required only one person.

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Figure 3: (a) Photograph of MSE VTS concrete cell prior to back filling of the site. (b) Results from the MSE VTS investigation: (top) velocity tomogram for profile over cell; (middle) tomogram with overlay indicating target, (bottom) wavepath coverage diagram. Color scales are biased to emphasize shallow anomalies. Wavepath coverage color scale indicates the number of wavepaths traversing each grid cell. Grid cell size is approximately 0.06m by 0.06m. Mission San Antonio de Padua, Monterey County, California The second investigation site was Mission San Antonio de Padua, California, founded in 1771 by Spanish missionaries. The Mission is located within Fort Hunter Liggett Military Reservation in Monterey County, California. The site contains subsurface remnants of several collapsed structures and is situated on quaternary alluvial deposits of varying depth. Based on nearby excavations, the depth of these sediments is greater than our depth of exploration at the site. We collected data along a total of six seismic profile lines (Figure 4a). Orientations of the profile lines were chosen to help delineate buried cobblestone foundation walls presumed to be located within our survey area based on partially exposed walls and a shallow excavation pit to the east (Figure 4a). We expect that the majority of these walls are approximately 1m in both width and depth and that the tops of the walls are located within 1m of the ground surface. Results from profile B-B’ are shown in Figure 4b. This profile intersects two foundation walls of known location and orientation. The middle plot shows the upper 2m of the tomogram to emphasize the shallow, high velocity anomalies resulting from the cobblestone foundations. High velocity anomalies are located on the tomogram at approximately 1m and 7m along the profile (Figure 4b middle arrows). These velocity highs are observed in nearly the exact location of the walls. An additional, weaker velocity anomaly is observed at about 14.5m along the profile. This anomaly correlates with a suspected wall identified at this location by an electrical resistance survey (Reichhardt et al. 2004). Data collection was completed in about eight hours. Movement of the land streamer between spread locations was completed in a matter of seconds and could be accomplished by a single person.

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Because we used a total of 16 spread locations, this resulted in a significant reduction in total survey time.

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(b) Figure 4: (a) Plan view of seismic survey at Mission San Antonio de Padua. Profile B-B’ intersects the foundation walls of a known collapsed structure. (b) (top) P-wave velocity tomogram for Profile B-B’; (middle) upper two meters of velocity tomogram with color scale to enhance velocity anomalies (black arrows indicate actual location of foundation walls); (bottom) wavepath coverage diagram for tomogram - warmer colors indicate greater density of raypaths.

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Djozer’s Step Pyramid, Saqqara, Egypt The third site investigation was in Saqqara, Egypt. Saqqara is one of the principle necropolises of Memphis, an ancient capital of Egypt (Figure 5a). Saqqara is situated at the edge of the desert on a prominent rise that overlooks the Nile valley to the east. The rise is composed of wind blown sand at the surface that is underlain by predominantly flat lying limestones and marls of the Late Eocene Maadi Formation. Perhaps the most remarkable feature at Saqqara is the 3rd Dynasty Pharaoh Djozer’s Step Pyramid (Figure 5b) which was the first monumental structure built entirely of stone.

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Figure 5: (a) Saqqara site map showing major features and the location of the research site (modified from Abdallatif, 1998). (b) Research site at Saqqara showing Djozer’s Step Pyramid. The streamer can be observed fully extended between the two workers. North of Ptahhotep’s tomb is an unexcavated area that we selected as our research site (Figure 5a). A preliminary GPR study of this site yielded numerous, possibly man-made features in the subsurface. The maximum depth of penetration of the GPR when using 100MHz antennas was about 4m. We were interested in following these features to greater depth and so we collected seismic data for diving wave tomography over one of the GPR anomalies. Details of the data acquisition and results for the Saqqara site can be found in Speece et al. (2003) and Miller et al. (2005). We collected data along a west-east profile line consisting of two spreads overlapped by fifty percent and a north-south profile consisting of a single spread. These profiles intersect at a point 16m along the west-east profile and 14m along the north-south profile. While collecting data in Saqqara, the set up and subsequent movement of the land streamer was completed in less than one minute by a single person. Figure 6 shows a composite view of the two velocity tomograms constructed from the Saqqara data. The intersecting tomograms are presented in views from the southwest (Figure 6a) and northeast (Figure 6b). A large, low velocity anomaly is evident in the middle of the west-east profile. The low velocity anomaly is about 25m wide at its base and extends vertically from about 8m depth to about 2m depth. The north-south profile contains a low velocity anomaly beginning at approximately 14m along

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the profile and extending off the north end of the profile. The top of the anomaly is approximately 2m below the ground surface.

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(b) Figure 6: Combined west-east and north-south profile velocity tomograms from Saqqara, Egypt. Note good velocity concurrence between profiles. (a) View from southwest to northeast. (b) View from northeast to southwest. Color scale is biased to emphasized shallow anomalies. Void Detection, Butte, Montana The summer 2004 Montana Tech Geology and Geophysics field camp conducted a survey at the intersection of Wyoming and Copper street in Butte, Montana. The target of the survey was an old vertical mine shaft. Presently, a low point exists at the intersection of these streets where the mine shaft is located. The seismic survey used a four-streamer array of 1m spaced gimbaled geophones. The geophone streamers were towed by a pickup truck using a pulling frame. The survey was conducted by advancing the entire array and corresponding source points in 1m increments. At each stop, we used two source points between the streamers and 1m ahead of the streamer array using a sledgehammer source. Figure 7 shows the resulting P-wave velocity tomogram using data from one of the streamers. The low velocity anomaly (arrow) at 65m occurs at the street intersection, the known location for the old

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mine shaft. Other low velocity anomalies may be associated with heterogeneous fill material under the street.

Figure 7: P-wave velocity tomogram for west to east profile along Copper Street. The low velocity anomaly (arrow) at approximately 65m indicates the location of the mine shaft.

MASW Geophone Natural Frequency Comparisons As part of our work in land streamer applications, we investigated the feasibility of using 30Hz gimbaled geophones in MASW applications. To test this we used five different geophone types at a local test site to compare the effect of geophone natural frequency on MASW inversion. The geophones available were: gimbaled: 30Hz spiked (pavement plates): 30Hz 8Hz 8Hz 4.5Hz We only had six of each type of geophone except the 30Hz gimbaled (24), thus, we had to simulate 24 channel spreads in our investigation by repeating the source at each location and moving the geophones. Figure 8 shows a set of shot records using the same source and geophone locations. Source offset was 10m and geophone spacing was 1m. The test site is a level area of granite derived alluvium over bedrock which occurs at a depth of approximately 25m. The water table is measured at 3.5m in the alluvium. The different frequency content for each geophone type is immediately apparent. Figures 8c and 8e are shot records from spiked and gimbaled 30Hz geophones respectively. Figures 8b and 8d are records from 8Hz spiked and gimbaled geophones. Some of the anomalous traces on the shot record in Figure 8a occur because a 30Hz geophone had to be used for a non-functioning 4.5Hz geophone.

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Figure 8: Set of five shot records recorded at test site in Butte, Montana to compare different frequency geophones for MASW applications. (a) 4.5Hz pavement plate, (b) 8Hz pavement plate, (c) 30Hz pavement plate, (d) 8Hz gimbaled, (e) 30Hz gimbaled. Each record has 24 channels at 1m spacing and 10m shot offset. All shot record lengths are 400ms. Figure 9 shows two preliminary S-wave velocity profiles made from data recorded with the 30Hz gimbaled (Figure 9a) and 4.5Hz spike (Figure 9b) geophones at the test site. The profiles were produced using SurfSeis®. The profiles show clear similarities but contain enough differences that an independent confirmation is required to determine the validity of either one. In particular, the vertically adjacent pair of high/low S-wave velocity anomalies in Figure 9b (4.5Hz data) from about 128m to the end of the profile has the appearance of an inversion artifact.

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Figure 9: (a) MASW S-wave velocity profile from test site using 30Hz gimbaled geophones. (b) MASW S-wave velocity profile from test site using 4.5Hz spiked geophones (pavement plates). Color scales and contour intervals are the same for each plot. Mike Horse Dam, Lincoln, Montana The Mike Horse Dam located near Lincoln, MT, is a tailings impoundment dam from the now abandoned Mike Horse Mine. The tailings dam failed in 1975 allowing lead, copper, and zinc contaminated tailings into the upper Blackfoot River. The dam was rebuilt after the spill but continues

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to leak and recently the U.S. Forest Service recommended that the dam be removed and the area reclaimed. Montana Tech has been working in conjunction with the U.S. Forest Service to characterize the dam using seismic techniques. An initial study used three-component geophones along with the land streamer 30Hz geophones to record P-wave and S-wave data for analysis using diving wave tomography. The S-wave component data were of poor quality and the resulting S-wave inversion was not reliable. Our ultimate goal was to use the P-wave and S-wave tomograms to construct a Poisson’s ratio profile to compare with CPT (cone penetrometer testing) results from the site. Figure 10 shows the delta-t-V inversion result from the P-wave data recorded with the vertical component of the 20Hz three-component geophones. Noted on the plot are the starting and ending depths for a weak zone interpreted from CPT tip stress and sleeve stress measurements. The weak zone location agrees well with a low P-wave velocity zone at the CPT location. The delta-t-V inversion was produced using RayFract™. RayFract’s WET (Wave Equation Tomography) inversion did not work because of a high velocity zone near the surface that gradually decreases with depth, thus violating the conditions for refraction analysis. A coverage plot for the WET raypaths shows very sparse coverage below 2m. The reason the delta-t-V inversion still gives a somewhat reasonable output is that it can handle velocity inversions to some degree.

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Figure 10: P-wave velocity profile from Mike Horse dam using data from 20Hz vertical component of three-component geophones. RayFract™ software was used for the inversion. Low velocity anomalies are interpreted to be weak zones in the dam (comm. U.S. Forest Service). More recently during fall 2005, we recorded short and long offset P-wave data over the entire length of the Mike Horse dam this time using only the land streamer with 30Hz gimbaled geophones. For this work, the profile length was extended from 50m (Figure 10) to the full length of the dam (120m) and the shot spacing was increased from 1m to 2m. A P-wave velocity tomogram constructed from these 30Hz gimbaled geophone data is shown in Figure 11. The plot is shown with the same color scale used in Figure 10 to emphasize the similarity of the 30Hz gimbaled geophone result and the 20Hz spiked geophone result. Note, for example, the low velocity zone similarity in both profiles from 0 to

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10m along the profile at depths from the surface to about 3m. Also, the same high velocity anomaly is imaged at about 20m along the profile at a depth of about 10m. The result shown in Figure 11, as well as showing an extension of the profile in Figure 10, is a more reliable result because of the longer shot offset used to record the data and the WET tomography used to produce the tomogram.

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Figure11: P-wave velocity tomogram from the Mike Horse dam using 30Hz gimbaled geophone data. The tomogram was produced using WET in RayFract™ software. Compare with profile shown in Figure 10.

3-D Reflection Abandoned Coal Mine, Belt, Montana The 3-D seismic reflection method has not been extensively utilized for shallow subsurface investigations because of the relatively high cost of performing 3-D surveys. We have configured our land streamers in a parallel arrangement allowing us to record 3-D seismic reflection data. In a fashion similar to marine work, an All Terrain Vehicle (ATV) tows an array of four parallel seismic cables, or land streamers. Each streamer consists of 24 gimbaled geophones. The ATV drags the array from station to station and shots are taken while the array is stationary. We tested our system near Belt, Montana to characterize abandoned subsurface coal mines. For this survey, our receiver, receiver line, source, and source line spacing were all 1m. In total, we covered a surface area of 100m by 34m and achieved a nominal fold of 24. Typical combined advance and occupation times for each station were less than 30 seconds using a crew of three people. The recorded data contained significant amounts of surface wave energy. However, we were able to suppress the noise using an algorithm designed for surface wave attenuation. Figure 12a is a photograph showing the field setup and equipment. The processed data cube shown in Figure 12b shows the subsurface horizontal layering, however, it is not clear if any of the subsurface passageways were directly below the relatively small survey area. The depth of the coal workings occurs at about 80ms on the seismic data. Details of the data acquisition and results can be found in Dolena et al. (2005a, b).

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(b) Figure 12: (a) Photo showing acquisition system. Four land streamer cables are mounted on hydraulically controlled reels for easy deployment. (b) Cut-away view of brute stack showing layered geology. Traces were balanced for display.

Conclusions Recent land streamer work at Montana Tech has focused on the efficiencies achievable with towed, gimbaled geophone streamers. The gimbaled streamers have proven remarkably effective for acquiring seismic data in traditionally very field intensive investigations such as diving wave tomography and high resolution 3-D surveying. Comparison of data recorded with gimbaled streamer geophones and spiked geophones show very little difference in most applications.

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The land streamer approach thus opens the door to applying innovative seismic methods to investigations that would not have been able to use them previously because of survey acquisition costs or field efficiencies. Downloaded 10/23/14 to 150.131.130.14. Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/

References Abdallatif, T. F., 1998, Magnetic prospection for some archaeological sites in Egypt: Ph.D. thesis, Ain Shams University. Determann, J., Thyssen, F., and Engelhardt, H., 1988, Ice thickness and sea depth derived from reflection seismic measurement on the central part of the Filchner-Ronne Ice shelf: Annals of Glaciology, 11, 14-18. Dolena, T. M., Speece, M. A., Link, C. A., Miller, P. F., and Duaime, T. E., 2005a, A land streamer aided, three-dimensional (3-D) seismic reflection survey, Belt, Montana: Proc. Symposium on the Applications of Geophysics to Engineering and Environmental Problems, 971-978. Dolena, T. M., Speece, M. A., Link, C. A., and Duaime, T. E., 2005b, A land streamer aided, threedimensional (3-D) seismic reflection system: Journal of Engineering and Environmental Geophysics, in review. Eiken, O., Degutsch, M., Riste, P., and Rod, K., 1989, Snowstreamer: an efficient tool in seismic acquisition: First Break, 7, no. 9, 374-378. Einarsson, D., Brooks, L., Bennett, G., and White, A., 1977, Seismic survey on the Beaufort Sea Ice, Geophysics, 42, p. 148. Kruppenbach, J. A., and Bedenbender, J. W., 1976, Towed land cable: US patent no. 3,954,154. Miller, C. R., Allen, A. L., Speece, M. A., El-Werr, A. K., and Link, C. A., 2005, Land streamer aided geophysical studies at Saqqara, Egypt: Journal of Engineering and Environmental Geophysics, 371-380. Miller, C. R., Speece, M., and Link, C, 2003, Modified land streamer configuration for shallow seismic data acquisition: Proc. Symposium on the Applications of Geophysics to Engineering and Environmental Problems, 857-865. Reichhardt, D. K., Hargrave, M. R., Jones, G., Maki, D. L., Miller, C. R., and Speece, M. A., 2004, An assessment of seismic and thermal imaging techniques for archaeological applications: Proc. Symposium on the Applications of Geophysics to Engineering and Environmental Problems, 193-205. Speece, M. A., Miller, C. R., El-Werr, A. K., and Link, C. A., 2003, Land streamer aided, seismic diving wave tomography at an archaeological site, Saqqara, Egypt: Society of Exploration Geophysicists International Exposition and Seventy-Third Annual Meeting 2003 Technical Program Expanded Abstracts, 1255-1258. Van der Veen, M. and Green, A. G., 1998, Land streamer for shallow seismic data acquisition: Evaluation of gimbal-mounted geophones: Geophysics, 63, 1408-1413. Van der Veen, M., Wild, P., Spitzer, R., and Green, A., 1999, Design characteristics of a seismic land streamer for shallow data acquisition: EAGE 61st Conference and Technical Exhibition, paper no. 4-41.

Acknowledgements The National Science Foundation provided financial support for this research through grants DMI-0109095 and DMI-0239071. Landmark Graphics provided ProMAX® software and support through an educational grant.

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