DOI: 10.5281/zenodo.10438514
title: Microseismic event catalogue for the April 2022 third stimulation at FORGE Enhanced Geothermal System (Utah, US) generated applying a semblance-based detection method to DAS data

description: The dataset contains microseismic event detections for the third stimulation stage (started on 21 April 2022 at 13:48:22 UTC) performed at FORGE Enhanced Geothermal System (Utah, US) (EGIUU, 2022). We created the catalogue of detections using the semblance-based detection method described in Porras et al. (2024).  We applied the detector only to the optical fibre in the observational well 78B-32 (EGIUU, 2022). 

The catalogue contains events detected from 21 April 2022 at 13:00 UTC to 22 April 2022 at 13:00 UTC and is compared with the Short-Term Average/Long-Term Average catalogue created by Silixa LLC for the same time interval (EGIUU, 2022).

The semblance-based detection method detects 2187 events in comparison to the 1169 events reported in the Silixa LLC catalogue. Notice that both catalogues are declustered by removing detections less than 0.7 seconds apart (we keep the earliest detection in case of two or more events within 0.7 seconds). We inspect for common events in both catalogues by considering a time interval of ± 0.6 seconds from the detection time of the events in our catalogue (in the case of more than one event we keep only the closest detection). We find 1086 common events, 83 events only contained in the Silixa's catalogue, and 1101 events only contained in the catalogue from Porras et al. (2024). We manually inspect all the detected events and classify as false detection 6 out of the 1086 events common to both catalogues, 64 out of the 83 events only in the Silixa's catalogue, and 116 of the 1101 events only in the catalogue from Porras et al. (2024).  False detections, in addition to noise where no clear P and/or S-waves are visible, include codas of microseismic events (e.g. the same event is picked multiple times especially in the cases where the events occur across two files), and seismic events not related to the FORGE stimulation. In summary, our catalogue contains 2187 microseismic events with 122 potential false detections (5.6 %), while the Silixa's catalogue contains 1169 microseismic events with 70 potential false detections (6.0 %).

In this data repository we also include a catalogue "microseismicity_catalogue.csv" with the detection times, the catalogue to which the detection belong (i.e., common detection to both Silixa's catalogue and the catalog from this study, only the Silixa's catalogue, only the catalogue from this study), and a description of the detection (i.e., real event, or false detection). We also upload the figures of all the detections where the figure name correspond to the detection time. The figures are obtained using the original sampling rate of the data (i.e., 4 kHz) and applying a Frequency-Wavenumber (FK) filter to remove the K=0 and unwanted energy (an example of the used F-K filter is also included in this repository). Traces in the figures have amplitudes normalized between -1 and 1.    

For additional details about the method used to obtain the catalogue we refer the reader to Porras et al. (2024)

References:

EGIUU, Energy and Geoscience Institute at the University of Utah. (2022). Utah FORGE: Well 16A(78)-32 2022 Stimulation Silixa Microseismic Report [data set]. Retrieved from https://dx.doi.org/10.15121/1893532.

Porras, J., Pecci, D., Bocchini, G. M., Gaviano, S., De Solda, M., Tuinstra, K., Tognarelli, A., Lanza, F., Stucchi, E., and Grigoli, F. (2023). A Semblance-based Microseismic Event Detector for DAS Data. Geophysical Journal International, ggae016, https://doi.org/10.1093/gji/ggae016