Timing issues on the Hussar low-frequency experiment

Kevin W. Hall, Gary F. Margrave

Nanometrics Trillium compact seismometers were deployed at a nominal 200 meter station spacing from flag 564 (southwest end of line) to flag 264 for the Hussar low-frequency experiment. Three component data was acquired continuously on Nanometrics Taurus recorders at a two millisecond sample rate for the duration of the survey. The Taurus recorders were synchronized to GPS time. Two INOVA (ARAM) Aries recorders and an INOVA Scorpion recorder logged dates and times for each shot in their respective observer's logs. However, time of shot does not match between these recorders for a given shot, and is not consistent between recorders for the time difference between subsequent shots. We speculate that the Aries time of shot is a file creation time. It is shown that the times derived from the Scorpion shot identification number (UNIX time stamp) are the best choice for extracting shot gathers from the seismometer continuous data, by visual inspection of observer's log times (converted to Coordinated Universal Time) plotted over the vertical component of seismometer data recorded at flag 524 for all sources at flag 524.