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Comprehensive data set of in-situ hydraulic stimulation experiments for geothermal purposes at the Äspö Hard Rock Laboratory (Sweden)

This data set contains measurements of an underground hydraulic fracture experiment at Äspö Hard Rock Laboratory in May and June 2015. The experiment tested various injection schemes for rock fracture stimulation and monitored the resulting seismicity. The primary purpose of the experiment is to identify injection schemes that provide rock fracturing while reducing seismicity or at least mitigate larger seismic events. In total, six tests with three different injection schemes were performed in various igneous rock types. Both the injection process and the accompanied seismicity were monitored. For injection monitoring, the water flow and pressure are provided and additional tests for rock permeability. The seismicity was monitored in both triggered and continuous mode during the tests by high-resolution acoustic emission sensors, accelerometers and broadband seismometers. Both waveform data and seismicity catalogs are provided.

Source parameters of Acoustic Emissions from triaxial experiments on Westerly granite, Aue Granite and Flechtigen Sandstone

This dataset is supplementary material to "What controls the presence and characteristics of aftershocks in rock fracture in the lab?" by Joern Davidsen, Thomas H. W. Goebel, Grzegorz Kwiatek, Sergei Stanchits, Jordi Baro and Georg Dresen (Davidsen et al., 2021). The dataset contains source parameters of acoustic emission events recorded during triaxial fracture and friction (stick-slip) experiments performed on two Westerly Granite samples, Aue Granite and Flechtigen Sandstone. Basic seismic catalog associated with each experiment contains origin time, hypocentral location in local Cartesian coordinate system of the sample, acoustic-emission derived magnitude and polarity coefficient (a simplified measure of mechanism type: shear, pore opening or collapse). Extended catalog information is available for selected experiments including information whether event is background seismicity, trigger of following events or triggered by preceding events. In addition, we provide information on focal mechanisms calculated in each experiment using full moment tensor inversion. Focal mechanism catalogs include information on strike, dip and rake of two nodal planes, and percentage of isotropic, clvd and double-couple components of the full moment tensor. The detailed description of catalog is provided in the data description file which is also included in the zip folder of the data.

Frequency-dependent quality factors of S-coda waves from active ultrasonic transmission measurements in the STIMTEC project, URL Reiche Zeche, Germany

Mean S-wave coda quality factors (mean-Qc) were estimated from active ultrasonic transmission (UT) measurements acquired during the STIMTEC project in the URL Reiche Zeche (Saxony, Germany). We used S-coda waves of 88 selected UT measurements carried out in 3 differently oriented boreholes (BH10, BH12, BH16) to estimate the spatial change of the coda quality factor in the targeted rock volume, an anisotropic metamorphic gneiss. We also analysed temporal variation in attenuation before and after hydraulic stimulations performed in two boreholes (BH10, BH17). We formed in total 8 UT groups (see data table "2022-004_Blanke-and-Boese_mean_UT_event_locations") from neighbouring UT measurements within different depths and from separated time intervals (see also Tab. 1 in Blanke et al. 2023), and compare mean-Qc estimates of centre frequencies ranging 3-21 kHz of octave-width frequency bands. Our results show a characteristic frequency-dependence and we find that mean-Qc estimates reveal temporal-variations of attenuation more significantly than those obtained from velocity measurements. The temporal variations are strongly connected to hydraulic stimulation activities resulting in a reduction of the coda quality factor where AE events occurred. Analysis of mean-Qc estimates after a temporal resting phase (with no activity in the rock volume) suggests that frequencies > 15 kHz indicate healing of small-scale fractures induced by injections. The study shows that coda analysis is a powerful tool for the detection of damage zones and for monitoring changes of the local fracture network within reservoirs important for exploitation or underground storage of gases and liquids.

JAGUARS – Mining induced picoseismicity associated to gold mining

This dataset presented herein originates from the JAGUARS (The Japanese German Underground Acoustic Emission Research in South Africa) project, which took place from 2007 to 2009 in Mponeng Gold Mine, South Africa. Project partners included Ritsumeikan University, Earthquake Research Institute University of Tokyo and Tohuku University in Japan, the German Research Center for Geosciences Potsdam and Gesellschaft für Materialprüfung und Geophysik GMuG mbH in Germany, as well as the Council for Scientific and Industrial Research in Johannesburg, Seismogen CC in Cartonville, Anglo Gold Ashanti Ltd and the Institute of Mining Seismology in the Republic of South Africa. This publication forms part of the Geo-INQUIRE initiative (HORIZON-INFRA-2021-SERV-01 call, project number 101058518). It is cross-referenced on the EPISODES Platform (https://episodesplatform.eu/?lang=en#episode:JAGUARS (not yet existing)), which is managed by the EPOS TCS AH (European Plate Observing System Thematic Core Service Anthropogenic Hazards). Within the EPISODES Platform, the datasets are consolidated into an “episode” titled “JAGUARS: Mining induced picoseismicity associated with gold mining”. The EPISODES Platform offers open access to the integrated research infrastructures of the EPOS TCS AH, enabling users to download data and utilize a range of basic online visualization tools to graphically represent and process the datasets directly within their personal workspace.

Acoustic Emission and Seismic moment tensor catalogs associated with triaxial stick-slip experiments performed on Westerly Granite samples

The dataset contains source parameters of acoustic emission (AE) events recorded during triaxial friction (stick-slip) experiments performed on the Westerly Granite sample WgN05. In addition we provide raw waveform data of AE events recorded in triggered mode with a network of 16 AE sensors. Basic seismic catalog associated with the stick-slip experiment contains origin time, hypocentral location in local Cartesian coordinate system of the sample (with associated uncertainties), and AE-derived magnitude. In addition, for a subset of AEs we provide full moment tensors. This catalog include information on fault parameters (strike, dip and rake of the two nodal planes), percentage of isotropic, compensated linear vector dipole and double-couple components of the full moment tensor, P, T, B axes orientations in the coordinate system of the sample, uncertainty assessment, as well as the six independent moment tensor components. Finally, we provide a time series of axial stress values as presented in the Kwiatek et al. (2023) as well as the coordinates of the AE sensors. The catalog and parametric data is supplemented with the raw waveform recordings stored in HDF5 format from 16 acoustic emission sensors placed on the surface of the sample.

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