A Seismic Survey at the GSW Monitoring Well

Featuring Dr. William J. Domoracki of ESRI, University of South Carolina in Columbia, SC and The Students and Faculty of the GSW Geology & Physics Department

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1. The "Official Field Vehicle" of the Environmental Geophysics Division at ESRI. We are in the process of unloading the seismic equipment. Nice logo!!
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2. A picture showing some of the equipment, Dr. William J. Domoracki and very interested GSW students The black box on the far right is the controller for the downhole geophone, which clamps itself in the borehole for maximum coupling. The middle box (with the yellow top) is a seismograph system. Since the geophone has three-components (one vertical and two horizontal), three of the available 12 channels were used for this procedure. On the left is a laptop computer which records the data.
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3. The first experiment was a Vertical Seismic Profile, or VSP. As the geophone is brought up from the bottom of the well one meter at a time, the geophone is clamped in the well and then the signal is given to the...
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4. ...Source, which in this case is Lori Norton. The steel spindle and plate were set 12 feet from the well and six hammer blows were needed to record the data at each level. It turns out that a hammer source like this is one of the best for shallow seismic surveying.
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5. Students and faculty watching the source at work.
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6. "Fresh" sources are needed at regular intervals. Fortunately, we had plenty on hand that day...

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7. While the survey was going on, this is what the GSW seismic station saw on the afternoon of September 25, 2001. This is a recording from short-period vertical instrument, which is located very close to the monitoring well. The starting time for the survey appears to be around 2:33 EDT (display time starts at 18:30 GMT; one minute per line). The extended breaks are times when the geophone was repositioned in the well.

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8. Karen and Lauren observing as Dr. Domoracki works with the geophone. Notice how close the GSW seismic station -- the short brick building -- is to all the action.
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9. Daniel is the final source for the VSP, as Lori works with the geophone at the well and also watches...
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10. ... a tree in the final stages of falling. It was a windy day, and the tree was creaking ominously as we worked. The tree did not fall while we were out there, but we watched it just the same!!!
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11. Here is the data from the vertical geophone that we collected during the VSP survey. Time is down and the depth decreases to the right. The "0.200" on the time scale actually represents 20 milliseconds. There is a strong first break which will enable the development of a velocity vs. depth curve for the well. Further processing may allow us to distinguish geologic layers near the well and perhaps below it.
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12. New survey, different source. Samantha Slater prepares to give the ground a good thump as Dr. Peavy looks on. The new survey is what is called a walkaway noise test. This survey is usually done before any major seismic work to determine the best source and geophone spacing to use, as well as any potential noise problems.
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13. Students and Dr. Tom Weiland observe the walkaway survey. Actually, this one is more of a "walk-toward "survey, as we are moving towards the geophones at the far end of the field.
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14. Towards the end of the survey, Karen Nowell becomes the source. All the students who participated did a fine job helping out on the survey. Many thanks to all of you!!
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15. Brian Veal helps Karen move the source to the next location.
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16. Here are the results of the walkaway test. Once again, time is downward and distance is across the top, with the far right being closest to the geophones. This noise test did reveal a few reflections from the Clayton Formation beneath the unconsolidated material above. It also revealed a potential problem with surface waves which will have to be addressed if more data are to be collected here and in nearby areas.
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17. After all the fun, you have to clean up. Lee receives instructions from Karen and Allison on just how to reel-in that seismic cable!!!
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18. Lee isn't too sure about the instruction, but he did enjoy a beautiful afternoon outside. Once again, many THANKS to the GSW geology students and faculty who participated in the surveys, and a SPECIAL THANKS to Dr. Bill Domoracki of ESRI and the University of South Carolina for providing us with a great experience.