TomTime

 

TomTime provides:
• Output formatted as input for the 3-D tomography software GeoTomCG.
• Reads all common seismograph formats.
• Versatile filtering and display options.
• Economical, only $400 (academic $300).
• Instrucciones sumarias en español e inglés.
Summary instructions in Spanish and English.

Display features. The display below shows traces 34 to 51 from a 146-trace seismograph file. Red squares are auto-picks. Blue dots and arrows are final picks, which usually can be left at the auto-pick positions with good data. Green and blue-green amplitude dots (hard to see in this printout) are on the three peaks following the time pick. Trace 35 was labeled dead, so the time is 0. The magnified display in the small box (trace 45) allows more accurate examination of auto-picks and manual repicking, if necessary.

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Overlaying traces. TomTime contains features such as filtering and overlaying of traces to help obtain accurate time picks and amplitudes, even in noisy data. The display below contains three files of VSP data collected with a 3-D geophone set. The first three channels were collected with a P-wave source. The next three channels were collected with an S-wave source moving in one direction. The last three channels, shown overlain in red on channels 4-6, were collected with the S-wave source moving the in opposite direction. Channels that were not of interest were marked dead, and their time and amplitudes set to 0.

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TomTime provides automatic picking (and manual repicking if necessary) of traveltimes and amplitudes for all common seismograph waveform files. Output is in the format used for input by the 3-D tomographic program GeoTomCG. The user can choose whether output files provide times and amplitudes, or just times. Times picked with automatic picking are first-breaks or first-peaks, and amplitudes are on the first, second, and third peaks following the time pick. (These amplitudes must be processed before being used as input for GeoTomCG.) Minimum and maximum time limits can be set to guide the auto-picking. Times and amplitude positions can be reset manually. TomTime can also write and read ASCII files of the waveforms, which allows data to be examined with a spreadsheet.

TomTime contains features to help obtain accurate time picks and amplitudes, even in noisy data. These features include versatile filtering and display options. Filtering options include smoothing with Parzen filters, low-cut filters from 10 Hz to 600 Hz, high-cut filters from 10 Hz to 2000 Hz, and notch filters. Frequency spectra for individual and selected combinations of traces can be plotted to help decide what filters to use and to estimate wavelengths. Frequency spectra can be saved in a file for spectral decomposition in attenuation investigations.

An optional coordinate file can reduce the need for manual entry of 3-D source and receiver coordinates. The user can assign each source and receiver position an identifying integer, and prepare a coordinate file that lists each source and receiver position and the corresponding identifier only once. Another display option allows measured or calculated times from a GeoTomCG data file to be displayed on the traces. TomTime reads the coordinates in the GeoTomCG data file and matches them with those in the TomTime coordinate file. It then displays the times from the data file on the appropriate traces.