GeoTomCG 3-D tomographic Windows software from GeoTom, LLC

· 3-D and 2-D tomographic inversions for velocity or attenuation.

· Many years of program development guided by processing field data.

· Versatile methods for using site information for more reliable results.

· Plots for quality control of data and optional data weighting.

· Displays showing goodness of fit for traveltimes and calculated velocities.

· Economical, only $600 (academic $500).

· Instrucciones sumarias en español e inglés.

Summary instructions in Spanish and English.

GeoTomCG can process and display 2-D and 3-D crosshole or VSP seismic or radar data. The display above shows calculated seismic velocities from a dam in Taiwan being investigated for earthquake damage¹. S and R indicate source and receiver positions, respectively. The crosshatch pattern indicates areas with few raypaths. The investigators reported that the seismic velocities were consistent with results obtained by other geophysical methods.

The display to the left shows a 3-D display of the calculated velocities in the dam. The 3-D displays can be rotated and tilted. Low velocity zones inside a 3-D volume can be displayed with a cutoff velocity. Only zones where the velocity is below the cutoff velocity are colored.

GeoTomCG can export results for display by commercial 2-D and 3-D graphics programs such as Surfer®, Voxler®, Tecplot®, and SlicerDicer®. A 3-D display from Tecplot of results calculated by GeoTomCG is shown to the right. This display shows questionable locations (velocity 3.0 to 3.6 m/ms, green-yellow) in the dam in Taiwan¹.

¹Application of Elastic Wave Tomography for Dam Safety. Sheng-Hsung Hsieh, Chih-Hsin Hu, Chih-Hsien Hsieh , Jen-Kai Huang, Cheng-Yang Yen, Wen -Lung Chi, and Chao-Ming Lin. Presented at SAGEEP 2012, Tucson, AZ, USA, Mar. 25-29, 2012, Poster Session Two, Wed. Mar. 28. hsung@hckgeo.com.tw, H.C.K. Geophysical Company

GeoTomCG features and options

Traveltimes (or amplitudes) can be processed to calculate velocities (or attenuation). Sources and receivers can be anywhere within a 3-D grid. Anisotropy can be specified for each grid point. Raypaths can be straight or curved. An option allows the influence of data on the inversion to be weighted according their specified quality.

Options for using site information to improve the reliability of results include:
1. Maximum and minimum calculated velocities.

2. Constant velocity in user-selected areas or volumes in the grid.

3. Groups of nodes with similar velocities, such as horizontal layers or vertical columns.

4. Constraints that take into account the uncertainty in site knowledge.

5. Adjustable damping and smoothing to reduce small-scale variations in calculated velocity.

GeoTomCG runs under Windows and provides graphical displays of velocities, raypaths, raypath densities, slowness residuals, and other parameters for inspecting results and preparing reports. Displays can be copied and pasted with the Windows clipboard. Quality control plots include traveltime vs. distance, residual vs. raypath angle, velocity vs. raypath angle, common-source and common-receiver gathers, and others. Text files of 3-D results and 2-D slices of the 3-D grid can be read by commercial 3-D and 2-D visualization programs. Results can be compared by differences or ratios. Examples with files allow the user to practice traveltime and amplitude data processing. The time and amplitude picking program TomTime, described in a separate information sheet, provides output in a format read by GeoTomCG.

Client data processing

GeoTom has many years of experience processing clients’ tomographic data. That experience and the familiarity with the programs as the developer provide efficient and reliable data processing. Clients can provide traveltimes (or amplitudes) picked by the client or seismograph files for GeoTom to pick times (or amplitudes). Processing amplitudes is more complex than processing traveltimes and the reliability of results can be adversely affected by scattering at interfaces.

Customers’ comments
Over 100 copies have been sold worldwide, with many favorable comments from users. Julian Ivanov of the Kansas Geological Survey wrote, "GeoTomCG is very well designed and organized 3-D Tomography software. It is very user friendly! My needs as a customer were very well anticipated and met. Time-consuming tasks, like model building, are automatically handled. Also, I've been very pleased with the prompt and efficient customer support." Jim Hasbrouck of Hasbrouck Geophysics, Inc. wrote, "The combination of TomTime and GeoTomCG has provided efficient, robust and accurate processing and interpretation of the numerous surface to borehole seismic and crosshole seismic surveys that I have conducted. Questions on the operation of the programs or methods for improved results have always been addressed in a timely and helpful manner by Dr. Tweeton. I highly recommend the use of these computer programs for applicable projects."

To purchase

The commercial price for the program, documentation, and eight hours of support is $600. The academic price is $500. GeoTomCG can be purchased from GeoTom or from these resellers:

Sensors & Software Inc, Mississauga, Ontario Canada, 1-800-267-6013 or 905 624-8909, e-mail sales@sensoft.ca.
GISCO, St. Louis Park, MN, phone 1-800-523-1526 or 952 929-8000, e-mail Daryl.Tweeton@giscogeo.com.

Olson Instruments, Wheat Ridge, CO, (303) 423-1212, e-mail info@OlsonInstruments.com.

Geotomographie, Neuwied, Germany, fax 49 2631 778136, e-mail TFechner@geotomographie.de.

Geo2X - W_GeoSoft, Oulens, Switzerland, fax 41 21 881 48 00, e-mail jacques.jenny@geo2x.com.

Idrogeostudi, Catania, Italy, fax 39 095 433222, e-mail foresta@idrogeostudi.com (exclusive reseller for Italy).

P.A.S.I. srl, Torino, Italy, fax 39 011 658646, e-mail info@pasisrl.it (for customers outside of Italy).

GeoTom, LLC Tomographic software E-mail sales@geotom.net

13785 Diamond Path and data processing Website www.geotom.net

Apple Valley, MN 55124 USA Phone or fax (1) 952 423-3838