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SO297-land

- Installation of 29 short-period seismometers between Copiapo and Taltal to monitor seismic events - The deployment was between February 2023 and June 2023 - Registering continuously 250 SPS - Onshore component of research cruise SO297 with RV Sonne. Waveform data is available from the GEOFON data centre, under network code 5R.

Horizontal-to-Vertical Spectral Ratios (HVSR) of NW Italy seismic stations elaborated during the "FOCUS-HVNEA" NOA-ILGE project

This data set consists of Horizontal-to-Vertical Spectral Ratios (HVSR) resulting from the application of the software package HVNEA (HV Noise and Earthquake Automatic Analysis) with the aim of comparing them with those resulting from the application of another method, namely STATION (Seismic sTATion and sIte amplificatiON). The results, relative to more than 24,000 HVSR, derive from the processing of 700,000 seismograms recorded over different time periods by 8 stations of the networks IV (Italian Seismic Network), GU (Regional Seismic Network of North Western Italy) and GV (Mobile RSNI). To compare the results of the two methods as accurately as possible, the waveforms were subjected to the same preprocessing already used to elaborate the results stored in the STATION database. To this end, the methodological workflow applied with HVNEA for station IV.MURB involved the selection of segments from continuous recordings for each event reported in the INGV catalogue located within a radius of 120 kilometres from the station. Starting from the automatically picked S-wave onsets, 12-second windows were then extracted and used for the analysis of earthquake recordings. Regarding the noise analysis, it should be noted that STATION again considers 12-second windows selected before the P-wave onset, while HVNEA requires the use of a signal window of at least 60 seconds. A window of 3,600 seconds was used for the analysis. The comparison of the HVSR was performed in the frequency band 0.1–15 Hz. All analysed curves, for both earthquake and noise recordings, show generally similar shapes and identify significant peaks in correspondence of the same frequency ranges, although the amplitudes obtained with STATION are systematically higher than those obtained with HVNEA. To obtain a quantitative comparison, various statistical metrics commonly used to measure the discrepancy between data sets were applied, namely the Mean Squared Error, the Mean Absolute Error and the Pearson Correlation Coefficient. This publication results from work conducted under the transnational access/national open access action at the Site effects Laboratory – INGV L’Aquila supported by WP3 ILGE–MEET project, PNRR–EU Next Generation Europe program, MUR grant number D53C22001400005.

Longterm monitoring of swarm earthquakes in the western Eger rift

The Bohemian Massif (500-250 Ma), the easternmost part of the Variscan orogenic belt, is one of the largest stable outcrops of pre-Permian rocks in Central and Western Europe. This region has persistent geodynamic activity that is clearly linked to upper mantle, and offers a globally unique location for studying intra-continental earthquake swarm (ES) seismicity in combination with deep crust and mantle degassing as well as their interaction with the deep biosphere. The main questions regarding seismicity, microbial life and origin, and heat flow are all linked by the common questions of fluid flow, pathways, and composition. The ICDP project 'Drilling the Eger Rift' aims to develop the most modern, comprehensive laboratory at depth worldwide for the study of ES, crustal fluid flow, mantle-derived CO2 and He degassing, and processes of the deep biosphere. In order to reach a new level of high-frequency, near source, and multi-parameter observation of ES and related phenomena, such a laboratory will comprise of a high-frequency 3D seismic array with a set of four shallow boreholes, combined with modern continuous real-time fluid monitoring at depth (the shallow boreholes) and the study of deep biosphere. Waveform data is available from the GEOFON data centre, under network code 1D.

Methana Magmatic Observational Experiment (MeMaX)

Our group aims to identify evidence of undetected magmatic activity through the identification of microseismic events. We focus on the western Saronic Gulf region within the Aegean Sea. Since 2019, the National Observatory of Athens and the University of Patras have operated six seismic stations on Methana and the nearby Peloponnese mainland.In March 2024, our group deployed an additional 15 remote recording stations from the Geophysical Instrument Pool of GFZ Potsdam across Methana, Aegina, Agistri islands, and the mainland Peloponnese. We use MARK L-4C-3D seismometers in combination with DATA-CUBE3 data loggers equipped with external batteries. This project is part of the MULTI-MAREX initiative funded by the German Federal Ministry of Education and Research (BMBF). Waveform data is available from the GEOFON data centre, under network code 1A.

DEEPEN, Western DAS Branch

From June to August 2021 the DEEPEN project deployed a dense seismic network across the Hengill geothermal area in southwest Iceland to image and characterize faults and high-temperature zones at high resolution. The nodal network comprised 498 geophone nodes spread across the northern Nesjavellir and southern Hverahlíð geothermal fields and was complemented by an existing permanent and temporary backbone seismic network of a total of 44 short-period and broadband stations. In addition, two fiber optic telecommunication cables near the Nesjavellir geothermal power plant were interrogated with commercial DAS-interrogators. The here published dataset contains a subset of the downsampled DAS-recordings from the western fiber optic array. The original data were downsampled from 2000Hz to 250 Hz using the das-convert tool (https://doi.org/10.5880/GFZ.2.1.2021.005). Note that there was a problem with the GNSS timing in the original recorded data which caused significant temporal drift. This has mostly been corrected in the downsampled data, but some residual timing error may exist. Waveform data is available from the GEOFON data centre, under network code 1D, and is fully open.

Data from the GRANU95 seismic refraction experiment

The occurrence of exposed high-metamorphic rocks (granulites) in combination with various gravity anomalies aligned along the direction of Variscan strike characterize a special terrain (Saxothuringikum) which has been sandwiched between two major tectonic units during the Variscan orogeny. Near surface geological studies show evidence that the Saxothuringian zone represents extended crust. Therefore the model of a "metamorphic core complex" is often used to explain the exhumation of the "Saxonian granulites". The thickness of the crust, the geometry of the Moho, and the composition of middle and lower crust that underlie such" metamorphic core complexes" have remained largely unconstrained. Because these physical parameters are critical for understanding the extensional processes acting at depth, we have carried out a seismic refraction experiment in order to resolve the deeper structure of an exposed "granulite-complex". From May 6th to May 13th 1995 a seismic refraction - wide angle reflection experiment was carried out as part of the DFG-priority program: "Orogenic processes – their quantification and simulation at the example of the Variscides". Two lines, A and B, were completed in two deployments (see map in GRANU95_report.pdf). In total 12 shots were fired and over 4500 seismograms were collected using 130 instruments. Only two different types of instruments (Reftek and PDAS) have been used for recording the explosions. All instruments were equipped with a 3-component 1Hz seismometer. The 90 km long NW-SE line (deployment A, 74 instruments) from Leipzig to the Erzgebirge through the Saxonian Granulites was carried out on the 8th and 9th May 1995. Additionally 56 stations were placed symmetrically to shotpoint D along line B (perpendicular to line A). Shots were fired on locations A1, A3, A4, A2 (see map in GRANU95_report.pdf). The station spacing for this deployment was around 1.3 km. The 260 km long SW-NE line (deployment B, 93 instruments) from Dresden to Bamberg, also crossing the Saxonian Granulites was completed from 11th to 13th May 1995. Every second instrument from deployment A was moved to complete line B. Shots were fired on locations B, C, D, E, F, G, H and I (see map in GRANU95_report.pdf) and recorded along line B and line A (perpendicular to line B) at a receiver spacing of about 2.6 km.

Integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system (NEAREST)

The NEARESTproject (Integrated observations from NEAR shore sourcES of Tsunamis:  towards an early warning system) aimed at the identification and characterization of potential near-shore sources of tsunamis in the Gulf of Cadiz. This area is well known from the catastrophic earthquake and tsunami that destroyed Lisbon and several other places mainly along the EastAtlantic coast on November 1st, 1755. One of the project's work packages dealed with monitoring of recent seismic activity in the Gulf of Cadiz area. For this purpose 24 broadband ocean-bottom seismometers (OBS) from the German DEPAS instrument pool were deployed for 11 months in addition to the GEOSTAR multi-parameter deep-sea observatory and two temporary land stations in Portugal. The GEOSTAR observatory and the 24 OBS were deployed and recovered during two expeditions with RV Urania in 2007 and 2008. The OBSs consist of  three‐component Guralp CMG‐40T‐OBS seismometers and HighTech HTI‐04‐PCA/ULF hydrophones. A wide range of signals was recorded, ncluding teleseismic, regional and local earthquakes, and low‐frequency (∼20 Hz) vocalization of fin whales.  The GEOSTAR  observatory was again deployed between 2009 and 2011. The Portuguese temporary land station PDRG was additionally recording during the NEAREST project. Originally, the position of recovery on deck was taken to calculate the mean coordinate of the OBS at depth from deployment and recovery coordinates. In most cases the difference in coordinates between deployment and recovery is very small (table 3 and 4 in Carrara et al., 2008). For two stations, the location at the seafloor could be measured by triangulation (Carrara et al., 2008). Due to experience of other experiments over the years, we finally suggest to use the deployment coordinates as the station coordinates for all stations that could not be tri-angulated. The clocks were synchronized with GPS time before the deployment and if possible again after the recovery. Unfortunately, most of the batteries were empty at the end of the recording period. That either made it impossible to realize the second synchronisation (skew time measurement) or in some case also caused erroneous synchronisations. Therefore, the internal clock drift was estimated by ambient noise analysis (Corela, 2014). The internal clock drifts were corrected using a linear interpolation method. Generally, the data quality is very good, especially for the intended study of local and regional earthquakes. Studies relying on wideband seismological recordings can also be carried out. The sensor package and noise conditions hamper the use for broadband and very broadband applications. Unfortunately, also not all channels operated properly, therefore hampering the use of multi-component methods for the relevant stations. We thank the captain E. Gentile, crew, G. Carrara, and all participants of the R/V URANIA expeditions in 2007 and 2008. We are grateful to all people and institutions involved in the NEAREST project. Waveform data is available from the GEOFON data centre, under network code 9H.

Seismological experiment at Strokkur from 2020

Seismological experiment at Strokkur from 2020" is a seismological experiment realized at the most active geyser on Iceland by Eva Eibl (University of Potsdam) in collaboration with Gylfi P. Hersir formerly at ISOR Iceland. The geyser is part of the Haukadalur geothermal area in south Iceland, which contains numerous geothermal anomalies, hot springs, and basins (Walter et al., 2018). Strokkur is a pool geyser and has a silica sinter edifice with a water basin on top, which is about 12m in diameter with a central tube of more than 20m depth. The aim of the seismic experiment is to monitor eruptions of Strokkur geyser from March 2020 using three broadband seismic stations (Nanometrics Trillium Compact 120s). Sensors were buried at distances of 38.8m (GE4, SE), 47.3m (GE3, SW), and 42.5m (GE2, N) from Strokkur center. Within this time period about 1 month of data is missing due to power outages. At any other times at least one station recorded the eruptions. From this dataset, converted to MSEED using Pyrocko, currently a catalogue of 506,131 water fountains was determined and further investigated in Eibl et al. (2025). In addition, Eibl et al. (2025) assessed the effect of the weather on the system including the bubble trap suspected at around 24 m depth by Eibl et al. (2021). Waveform data are available from the GEOFON data centre, under network code 2Z.

Homogenized regional seismicity catalogue for the Marmara region, northwestern Turkey, for the time in-terval 2021-2023

The dataset is an extended and updated version of the homogenized regional earthquake catalogue of the Marmara region, north-western Turkey, presented in Wollin et al. (2018) and Becker et al. (2023). It is built on the regional Turkish seismicity catalogues provided by AFAD (Disaster and Emergency Management Presidency of Turkey) and KOERI (Kandilli Observatory and Earthquake Research Institute) and spans the time interval 2021-2023. All events available in these two catalogues in the wider Marmara region were combined and duplicate events removed. A total of 2242 events having at least 6 P- and/or S-picks were located using the NLLoc software (Lomax et al., 2000, 2009) in Octtree mode utilizing automatic picks obtained with the PhaseNet algorithm (Zhu & Beroza, 2019) for all available waveforms. The magnitude range is between M0.5 and M5.1 and covers mainly the area 40.00S-41.25S and 27.00E-30.00E which was used as search region for the regional catalogs. The full description of the data and methods is provided in the data description file.

AFG - Active Faults Greece: a comprehensive geomorphology-based 1:25,000 fault database

Greece is Europe’s most seismically active nation, as it is being deformed by an active subduction system and one of the world’s fastest-spreading rifts. Onshore active faults pose seismic hazard that cannot be reliably assessed in the absence of a comprehensive map of potential earthquake sources. Here, we use high-resolution Digital Elevation Models (DEMs), in conjunction with hillshades and slope models, to map and characterise faults in Greece at a scale of 1:25000. The Active Faults Greece (AFG) database records a total of 3815 fault-traces assigned to 892 interpreted faults. Of the AFG traces, 53% were mapped here for the first time, with their geometries and slip-sense constrained by displacement of landscape features. AFG includes >2000 active and 1632 probably active fault-traces, while 30 traces result from historic surface-rupturing earthquakes since 464 BC. About 57% of faults exhibit strong depositional control (DC) on sedimentation patterns, with active faults being characterised by approximately equal numbers of sharp (32%), moderate (29%) and rounded (29%) scarps. AFG is the first fault database in Greece generated using nationwide interpretation of geomorphology and has applications in paleoseismology, seismic-hazard assessment, mineral-resources exploration, and resilience planning. Data Access: - Download archive version via GFZ Data Services (upper left) - Web-Map Server: https://experience.arcgis.com/experience/a6c85b1edf9d4d17a3f01a70cef6d2b2 - GIS Users: https://services2.arcgis.com/T7iULq65Kp9Elquk/arcgis/rest/services/Active_Faults_Greece/FeatureServer - Layerfiles for use in ArcGIS Pro and QGIS: https://noaig.maps.arcgis.com/sharing/rest/content/items/4b93c25b931744dabc4851abf9c8ae38/data

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