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We have completed the last year of our research titled "Reflectivity from Noise". There are five developments sponsored in our ACS grant since the beginning of the project.

1.

We utilize scattered energy which is considered as noises to go beyond the law of signal-to-noise enhancement, where N is the number of geophones that record seismic data. Our numerical experiments validate that the signal-to-noise ratio can be improved by where. Here T is the total recording time of a trace and is the dominant period of the source wavelet. Four 120-channel field tests were conducted at the following locations:

a.Utah steam tunnel

b.Tucson, Arizona San Xapher experimental mine

c.Moab, South Utah

d.Nevada, a gold mine in northern Nevada

The application for this new methodology is for a variety of uses, including detecting trapped miners in lost mines and for detecting the location of hydro-frac sources. In both applications the noises coming from the subsurface (trapped miners or hydro-frac) are recorded with the receivers on the surface. These noises will be used to find the trapped miner location or transformed to reflectivity in hydro-frac example.

We also validated the super-resolution properties of multiple scattering in a seismic field experiment, in this case scattering signals are assumed to be noises, but we used them to increase the resolution of the results 6 – 10 times. Perhaps the first time this has been done using field seismic data. I (Schuster) have included the results in my new book "Seismic Interferometry".

2.

We have developed a new method to image VSP and SSP data using the interferometry concept. We use the VSP data to migrate below salt without needing to know the velocity model. In this research we used the multiple reflections which are considered as noises and transform them to reflectivity data. This is an important improvement over the previous breakthrough of Calvert et al. (2004) who created virtual seismic sources from VSP data but were restricted to imaging data around the well. We have broken that restriction. An extended abstract discussing all these results is presented in the 2008 SEG annual meeting committee.

3.

In this research, we were able to extract inexpensive RVSP (reverse vertical seismic survey) and SSP (surface seismic survey) surveys from passive data. Passive data is considered as noises. Two sets of passive data were collected: a.At Tooele Army Depot (TEAD), Utah using a crane-driven hammer drill as a source of noises and two overlapping lines of geophones along the ground to record noises generated by the hammer drill. Despite the high level of ambient noise at this army base, the raw data traces show clear reflection arrivals even though the events overlap from different source excitations. The traces were autocorrelated and a gapped prediction error filter was applied to these data and the result was a RVSP shot gather with no overlapping events and a high signal-to-noise ratio. These RVSP records were then correlated and summed for different source positions in depth to give a virtual surface seismic profile data. Strong coherent surface waves prevented the formation of visible reflection arrivals so the next step is careful surface wave filtering. Nevertheless, the clear RVSP records obtained after deconvolution of 10-second records suggest the possibility of using hammer-drill sources to collect 3D RVSP data in environmentally delicate areas where vibroseis trucks are not allowed (e.g., towns or cities). If the surface waves are removed then it is likely that these RVSP data can be used to extract a virtual 3D SSP survey. b.At gold mine in Wyoming. Noises due to drilling three boreholes are recorded using 120 receivers at 5 m receiver-interval. The maximum depth of each borehole was around 70 m from ground surface. The collected VSP noises are used to generate virtual SSP shot gathers. The same procedure described in point (a) is followed. The final results of this part are not yet ready for publication and it will be a part of the master degree for Qiong Wu.

4.

In the seismic interferometry book I described the theory and practice of seismic interferometry, with an emphasis on applications in exploration seismology. Some of the results and publications mentioned in this report are included in the book.

5.

Another test of the time reversal mirror concept to identify the location of trapped miners from noises was conducted in mid-July 2009 in an active Nevada coal mine. The mine tunnel was at a depth of 200 – 230 m below the ground surface, and 72 receivers were planted on the rocky surface along 90 m line. A hammer strike at the mine wall was used to generate seismic wave, while the mine was in partially working mode. The operation of the mine and the weak signals coming from the hammer made the receiver on the ground surface record nothing but noises. We selected 28 locations inside the mine 3 m apart. The subsequent seismic noises were recorded by the receivers on the surface to give both SOS records and the calibration records. Applying the TRM concept to these noises showed that we were able to identify the locations of 23 out of the 28 SOS locations within accuracy of 3 m.

We have acknowledged the support of ACS in all publications that are mentioned in this report: "The American Chemical Society is acknowledged for their 2007-2009 grant ACS-45408-AC8."