Combining Horizontal Strain DAS and Local Seismic Stations in a Full Waveform Attribute Stacking Detector/Locator Algorithm: Verification Test for the Thorbjörn, Iceland, 2020 Unrest Episode

• Main Authors: Heimann, Sebastian, Isken, Marius Paul, Dahm, Torsten
• Other Authors: Jousset, Philippe, Milkereit, Claus, Wollin, Christopher, Dahm, Roman A., Krawczyk, Charlotte M., Horalek, Josef, Hesir, Gylfi P., Blank, Hanna, Erbas, Kemas, Reinsch, Thomas
• Format: Dataset
• Language: English
• Published: 2021
• Subjects: Earthquake Catalog; Geophysics; Distributed acoustic sensing; Earthquake swarm; Iceland
• Online Access: https://zenodo.org/record/6337788; https://doi.org/10.5281/zenodo.6337788

We present a waveform stacking-based earthquake catalog of the seismicity unrest episode in the Svartsengi fissure swarm close to Mt. Thorbjörn, SW Iceland, which started in January 2020 and was still ongoing in January 2021. The magmatic unrest produced more than 5 earthquake swarms comprising thousands of individual events each. We were able to combine local and regional seismic networks with 6 months recording of a 17 km long distributed acoustic sensing (DAS) fibre optical cable with a channel resolution of 4 m. The kHz DAS data were downsampled to 200 Hz and stacked every 64 m. The catalog is based on a migration-based detector / locator technique as for instance implemented in Lassie (Pyrocko). In the accompanying we demonstrate the robustness in a wide variety of applications in seismology. For this dataset, we have extended Lassie to efficiently combine linear ultra-dense sensor arrays with sparse seismological networks. The catalog is in human-readable CSV format, with the timestamp in UTC as seconds from UNIX epoch. The catalog contains all events at all detection levels. In the publication earthquake detections above a threshold of > 400 are shown.