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  • 1
    Publication Date: 2022-02-16
    Description: Abstract
    Description: Between early 2018 and late 2019 the STIMTEC hydraulic stimulation experiment was performed at ca.~130 m below surface at the Reiche Zeche underground research laboratory in Freiberg, Saxony/Germany. The project aimed at gaining insight into the creation and growth of fractures in anisotropic and heterogeneous metamorphic gneiss , to develop and optimise hydraulic stimulation techniques and to control the associated induced seismicity under in situ conditions at the mine-scale. These aspects of failure and associated seismicity are important for the development of enhanced geothermal energy systems. A combined seismic network consisted of 12 single-component acoustic emission sensors (sensitivity 1-100 kHz) and three single-component Wilcoxon accelerometers (sensitivity 50 Hz-25 kHz) were installed in boreholes drilled into the test volume, surrounding the stimulation site (Figure 1). A stimulation borehole with 63 m length was drilled with 15° northward inclination. This data set of 314 active ultrasonic transmission (UT) measurements is supplementary to Boese et al. (2021, in review), which introduces the STIMTEC experiment and its active measurement campaigns. This data set was used to derive an anisotropic velocity model for the STIMTEC rock volume. The active seismic data provided here are from six boreholes (BH09, BH10, BH12, BH15, BH16, BH17) as shown in Figure 1. of the associated data description. There are three tables provided as metadata that contain the STIMTEC sensor coordinates, event information of the 314 UT measurements and the UT picks. The UT measurements were recorded with a sampling rate of 1 MHz and results from an automatic stack of 1024 UT pulses generated by the ultrasonic transmitter and recorded by the STIMTEC sensors. The UT measurements are saved in binary file format (fsf file format). Fsf-files can be processed with FOCI software: https://www.induced.pl/software/foci Each fsf file contains 32768 samples, which corresponds to 0.032768 seconds. All UT event files were manual inspected and phase arrivals identified. These are stored in the fsf-file header as well as in the table STIMTEC_UT_picks.csv.
    Keywords: Ultrasonic transmission ; Acoustic emission sensor ; velocity calibration ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 EARTHQUAKES 〉 SEISMIC PROFILE 〉 SEISMIC BODY WAVES ; In Situ/Laboratory Instruments 〉 Magnetic/Motion Sensors 〉 Accelerometers 〉 ACCELEROMETERS
    Type: Dataset , Dataset
    Location Call Number Expected Availability
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  • 2
    Publication Date: 2022-12-06
    Description: Other
    Description: Earthquakes associated with fluid injection in various geo-energy settings, such as shale gas and deep geothermal energy, have shelved many projects with great potential. However, the injection-rate dependence of earthquake nucleation length, i.e., the slowly slipping (creeping) fault length in preparation for a subsequent earthquake (Kaneko & Lapusta, 2008), remains elusive. In this study, we take a step towards this issue by performing fluid injection experiments on low-permeability granite samples containing a critically stressed sawcut fault at different local injection rates (0.2 mL/min and 0.8 mL/min) and confining pressures (31 MPa and 61 MPa) (c. f., Ji & Wu, 2017; Wang et al., 2020). An array of local strain gauges and acoustic emission (AE) hypocenter locations were used to monitor the precursory slip of critically stressed faults before injection-induced stick-slip failure (c. f., Passelègue et al., 2020; Wang et al., 2020). The nucleation length was determined for each injection-induced stick-slip event, and its dependence on effective normal stress and injection rate was explored. Herein, we compile the processed data obtained from the experiments in four Excel worksheets. The full description of the methods is provided in Ji et al. (2022).
    Keywords: Injection-induced seismicity ; Injection rate ; Earthquake nucleation length ; Fluid injection ; Hydraulic stimulation ; Fault slip ; EARTH SCIENCE 〉 SOLID EARTH 〉 ROCKS/MINERALS/CRYSTALS 〉 IGNEOUS ROCKS ; geological process 〉 seismic activity 〉 earthquake
    Type: Dataset , Dataset
    Location Call Number Expected Availability
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