Long-period transients (tilt signals) on continuous broadband seismograms recorded during meter-scale hydraulic fracturing experiments at Äspö Hard Rock Laboratory

Cite as:

Niemz, Peter; Milkereit, Claus; Zang, Arno (2021): Long-period transients (tilt signals) on continuous broadband seismograms recorded during meter-scale hydraulic fracturing experiments at Äspö Hard Rock Laboratory. GFZ Data Services. https://doi.org/10.5880/GFZ.2.1.2021.007

Status

I N R E V I E W : Niemz, Peter; Milkereit, Claus; Zang, Arno (2021): Long-period transients (tilt signals) on continuous broadband seismograms recorded during meter-scale hydraulic fracturing experiments at Äspö Hard Rock Laboratory. GFZ Data Services. https://doi.org/10.5880/GFZ.2.1.2021.007

Abstract

This dataset contains processed (downsampled, rotated to local Äspö96 coordinate system, cut) broadband seismograms from two seismometers (Trillium Compact 120s), showing long-period transients on the horizontal components recorded during multiple hydraulic fracturing experiments in the Äspö Hard Rock Laboratory (HRL). Furthermore, the dataset contains extracted tilt time series and the injection parameters of the experiment to allow reproducing the results of Niemz et al. (2021).

The seismic waveforms were recorded during meter-scale hydraulic fracturing experiments in the Äspö Hard Rock Laboratory (HRL) in Sweden (Zang et al., 2017). This dataset only contains a subset of the data recorded during the experiments, monitored by a complementary monitoring system. The two seismometers contained in this dataset (A89 and A8B) were located in galleries adjacent/close to the injection borehole (see Fig. 2 in Niemz et al., 2021). The experiments were conducted at the 410m-depth level of the Äspö HRL. Each of the six experiments (HF1 to HF6) consisted of multiple stages with an initial fracturing and three to five refracturing stages (see injection parameters contained in this dataset). The six injection intervals were located along a 28m-long injection borehole. The borehole was drilled sub-parallel to the minimum horizontal compressive stress direction. The distance of the two seismometers to the injection intervals in the injection borehole is between 17 m and 29 m for sensor A89 and 52 m to 72 m for sensor A8B. A89 and A8B correspond to BB1 and BB2 in Niemz et al., 2021. For more details regarding the experimental setup, see Zang et al., 2017; Niemz et al., 2020; and Niemz et al., 2021.

The records of the two seismometers show long-period transients that correlate with the injection parameters. These transients are the response of the seismometers to a tilting of the gallery floor. The extracted tilt time series provide independent insight into the fracturing process during the hydraulic stimulations (Niemz et al., 2021).

Authors

Niemz, Peter;GFZ German Research Centre for Geosciences, Potsdam, Germany;Institute of Geosciences, University of Potsdam, Potsdam, Germany
Milkereit, Claus;GFZ German Research Centre for Geosciences, Potsdam, Germany
Zang, Arno;GFZ German Research Centre for Geosciences, Potsdam, Germany;Institute of Geosciences, University of Potsdam, Potsdam, Germany