EGS Collab Experiment 2: Continuous Broadband Seismic Waveform Data

Description

Two broadband seismometers were installed on the 4100 level and recorded for the duration of EGS Collab Experiment #2. Inspired by published data from similar instruments installed in the Aspo Hard Rock Lab, these long-period instruments aimed to measure the tilting of the drift in response to the injection of fluid into the testbed. One instrument was installed underneath the wellheads in Site A (aka the "battery" alcove) and the other was installed along the east wall of the drift, south of Site B. Due to the feet of gravel (ballast) laid along the floor of the drift, we were unable to anchor the sensors directly to the rock. As a result, the coupling of the sensors to the experiment rock volume is likely poor. In addition, there are a number of noise sources that complicate the interpretation of the data. For example, sensor BBB is installed adjacent (within 3 ft) to the rail line that runs towards the Ross shaft. Trains (motors) run along this line almost daily and produce a large signal in these data. Careful extraction of periods of interest, as well as filtering for specific signals, is necessary. The sensors are Nanometrics Trillium Compact Posthole seismometers, sensitive down to 120 seconds period. They were installed as close to the drift wall and as deep as we could manually excavate (only about 1 ft or so). The holes were leveled with sand and the sensors were placed on a paver before backfilling with sand. The hole was then covered by a bucket filled with insulation to improve the sensor's isolation from daily temperature variations, which are minor but present due to drift ventilation from the surface. Data were recorded on Nanometrics Centaur digitizers at 100 Hz. The full response information is available in the StationXML file provided here, or by querying the sensors through the IRIS DMC (see links below). These instruments were provided free of charge through the IRIS PASSCAL instrument center. The network code is XP and the station codes are BBA and BBB. The waveform data can be queried through the IRIS FDSN server using any method the user likes. One convenient option is to use the Obspy python package: https://docs.obspy.org/packages/obspy.clients.fdsn.html

Resources

Name Format Description Link
22 Picture of the location of sensors BBB, south of Site B. https://gdr.openei.org/files/1422/BBB_site.jpg
22 Picture of the installation of site BBB, prior to covering with insulation and bucket. https://gdr.openei.org/files/1422/BBB_installation.jpg
22 Picture of the installation of site BBA, prior to covering with insulation and bucket. https://gdr.openei.org/files/1422/BBA_installation.jpg
21 Location of the network metadata. You can download the data from this site. http://ds.iris.edu/mda/XP/?timewindow=2022-2022
21 Link to the IRIS GMAP service showing the locations of the sensors in this network. This link will also allow downloading of network metadata. http://ds.iris.edu/gmap/#network=XP&starttime=2022-01-19T00:00:00&endtime=2022-12-31T23:59:59&planet=earth
21 International Federation of Digital Seismograph Networks (FDSN) site for the EGS Collab 4100L (XP) seismic network. This page includes metadata and a separate DOI that should be used to cite the actual data recorded by this network - i.e. to cite the data at the link "IRIS Network Page for Data Download." https://www.fdsn.org/networks/detail/XP_2022/

Tags

  • geophysics
  • experiment
  • egs
  • tilt
  • surf
  • egs-collab
  • sanford-underground-research-facility
  • monitoring
  • 4100-level
  • fracturing
  • stimulation
  • broadband
  • characterization
  • seismic
  • hydraulic
  • waveforms
  • waveform
  • geothermal
  • experiment-2
  • energy
  • continuous

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