NLL-SSST-coherence high-precision earthquake location catalog for the 2025 Santorini-Amorgos earthquake swarm

Hypocenter catalog files and visualization of high-precision, NLL-SSST-coherence earthquake locations for the 2025 Santorini-Amorgos Greece earthquake swarm and background seismicity 2024-01-01 to 2025-03-23).

NLL-SSST-coherence (Lomax and Savvaidis, 2022; Lomax and Henry, 2023; Lomax et al., 2024) is an enhanced, absolute-timing earthquake location procedure which 1) iteratively generates spatially varying travel-time corrections to improve multi-scale location precision and 2) uses waveform similarity to improve fine-scale location precision.

Relocations performed with phase arrival data available from Institute of Geodynamics of the National Observatory of Athens (NOA-IG)

The initial seismic velocity model is a smoothed combination of two velocity models:Above 2.5 km depth:Hooft, E. E. E., Heath, B. A., Toomey, D. R., Paulatto, M., Papazachos, C. B., Nomikou, P., et al. (2019). Seismic imaging of Santorini: Subsurface constraints on caldera collapse and present-day magma recharge. Earth and Planetary Science Letters, 514, 48–61. https://doi.org/10.1016/j.epsl.2019.02.033Below 2.5 km depth:Brüstle, A. (2013). Seismicity of the eastern Hellenic Subduction Zone. Retrieved from https://hss-opus.ub.ruhr-uni-bochum.de/opus4/frontdoor/index/index/docId/1127

Visualizations include surface fault traces from NOAFAULTs geospatial database of active faults of Greece: https://doi.org/10.5281/zenodo.3483135

This repository contains:

Full catalog in CSV format:CSV file data columns correspond to selected fields of the of NonLinLoc Hypocenter format output http://alomax.free.fr/nlloc/soft7.00/formats.html#_location_hypphs_

Selected visualization imagesAnimated 3D view of relocated seismicity (ellipsoid semi-major axis length ≤ 4 km):  V_Santorini_NE_Seismicity_NLL-SC_se4_movie_*.mp4Map view of all relocated seismicity (3904 events):  *_coherence.pngMap view of relocated seismicity (ellipsoid semi-major axis length ≤ 4 km):  *_coherence_se4.pngProfile view from azimuth N135°E of relocated seismicity (ellipsoid semi-major axis length ≤ 4 km):  *_coherence_se4_fromAz135.pngProfile view from azimuth N225°E of relocated seismicity (ellipsoid semi-major axis length ≤ 4 km):  *_coherence_se4_fromAz225.pngMatrix of NLL-coherence maximum absolute coherences between event pairs:  *_waveform_coherences.png (event index corresponds to those in the CSV catalog)

Selected statistical plots In the distance_time_*.png plots, events with M≥4.5 are highlighed with blue circles.