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Geophysikalische Untersuchungen

Die Datenebene enthält Informationen zu Messgebieten, Profillinien und Messkampagnen geophysikalischer Untersuchungen entsprechend der Fachbereiche getrennt für Geoelektrik, Gravimetrie, Geomagnetik und Seismik. Geoelektrik: Übersicht über lokale Messgebiete, die von verschiedenen Firmen bearbeitet, sowie Untersuchungen, die vom LAGB beauftragt oder selbst durchgeführt wurden. Vor 1990 betreffen die von Firmen durchgeführten Untersuchungen zumeist Messungen des VEB Geophysik Leipzig, nach 1990 Messungen verschiedener Ingenieurbüros, die nach Lagerstättengesetz/Geologiedatengesetz an das LAGB gemeldet wurden. Seismik: Die Profilanlage seismischer Messungen ist unterteilt in 2D-reflexionsseismische Messungen zur Erkundung geologischer Strukturen und der Rohstoffexploration in bis ca. 5 km Tiefe sowie die Messungen der Refraktionsseismik und Weitwinkelreflexionsseismik, welche den Aufbau der Erdkruste in bis zu 40 km Tiefe untersuchen. Die tiefenseismischen Profile werden weiterhin durch die eingesetzten Messmethoden unterschieden. Untersuchungsgebiete reflexionsseismischer 3D-Messungen markieren Gebiete der detaillierten Exploration von mit Hilfe mehrerer Quellen gleichzeitig angeregter seismischer Signale, welche an flächenhaft ausgebrachten Geophonen registriert werden. Gravimetrie und Geomagnetik: Aufgeführt sind die Messgebietsumrisse und Informationen der Regionalmessungen in Sachsen-Anhalt.

Higher frequency data products of the International Monitoring System’s infrasound stations

This dataset consists of data products derived from broadband signal detection lists that have been processed for the certified infrasound stations of the International Monitoring System. More specifically, within the CTBT-relevant infrasound range (around 0.01-4 Hz), this dataset covers higher frequencies (1-3 Hz) and is therefore called the ‘hf’ product. The temporal resolution (time step and window length) is 5 min. For processing the infrasound data, the Progressive Multi-Channel Correlation (PMCC) array processing algorithm with a one-third octave frequency band configuration between 0.01 and 4 Hz has been used. The detected signals from the most dominant directions in terms of number of arrivals within a time window and the product-specific frequency range are summarized at predefined time steps. Along with several detection parameters such as the back azimuth, apparent velocity, or mean frequency, additional quantities for assessing the relative quality of the detection parameters are provided. The dataset is available as a compressed .zip file containing the yearly data products (.nc files, NetCDF format) of all certified stations (since 2003). Further information on the processing and details about the open-access data products can be found in: Hupe et al. (2022), IMS infrasound data products for atmospheric studies and civilian applications, Earth System Science Data, doi:10.5194/essd-14-4201-2022

Deep OCean Test ARray DOCTAR (OBS part)

This is the first deployment of a teleseismic broadband array consisting of 12 three-component stations with an aperture of about 50 km in the deep ocean in about 5000 m water depth. The data can be compared with two other deployments on Madeira and in western Portugal mainland which had similar array layouts and recording time spans (network Y7). The broadband data enable furthermore analysis of the crust and upper mantle beneath the array near to the Gloria fault, a major transform fault in the North Atlantic. Recordings of numerous local and regional earthquakes make a precise location of active structures possible. Waveform data is available from the GEOFON data centre, under network code 3J.

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.

EnvSeis project, Kåfjord

This network of sixteen geophones and six broadbands was installed in Kåfjord, Troms og Finnmark, Norway, to study two rockslides: Njárgavárri and Indre Nordneset. Each study site had three broadbands from September 2023 to June 2025. In addition, were installed and recording: September – November 2023: six geophones on each site; April – August 2024: four geophones at Njárgavárri and ten at Indre Nordneset. The geophones were installed locally around the rockslides while the broadbands were installed one to a few kilometers from the rockslides (except for one of them directly at Indre Nordneset). The geophones in Njárgavárri were first installed as two triangular antennas of four stations each (three in triangle and one in the middle) and were then replaced by a small aperture array around the most active part of the unstable slope. The goal was to record all activities: rock falls, cracking and creeping movements. In Indre Nordneset, the geophone stations were placed in a small aperture array all around the main scarp and surface of failure to record the cracking activity. The geophones are of type 3-D Geophone PE-6/B with DATA-CUBE3 (built-in GPS). The broadbands are of type STS-2.5 with EDR-10 digitizers. Sampling frequency was 400 Hz for geophone stations, 200 Hz broadbands. Gain was at 16 (15.258789 nV/count) for the geophone stations, set on high (100 nV/bit) for the broadband stations. Waveform data is available from the GEOFON data centre, under network code 8I.

Station Explorer - a web application for exploring and accessing seismic station data from EIDA data centres

Station Explorer is a web application for exploring and accessing seismic station data from the federated data centres of the European Integrated Data Archives. It provides researchers, seismologists, and data analysts with an intuitive interface to discover, analyze, and download seismic data from multiple networks. The application features both station-based and event-based data exploration capabilities, with real-time data fetching and interactive visualizations. It is able to present quality metrics obtained from existing data centre web services.

ALOIS: DEPAS ocean-bottom seismometer operations at the western Gakkel Ridge / Lena Trough in 2022-2023

This ocean-bottom seismometer deployment is part of an interdisciplinary project examining the Aurora hydrothermal vent field in an attempt to understand its fluid circulation. A total of 8 ocean bottom seismometers modified for the operation in sea ice covered oceans was deployed around Aurora vent field at the intersection of Gakkel Ridge and Lena Trough in the Fram Strait. The aim of the experiment was to monitor seismicity related to the hydrothermal circulation system and to reveal potentially heat reservoirs devoid of seismicity. The network consisted of 8 DEPAS Lobster type broadband OBS. Instruments were free-fall deployed and spaced by about 5-8 km. Their position at the seafloor is known to within few meters from ultrashort baseline positioning system Posidonia. The OBS recorded continuously at 100 Hz for up to 12 months between end of July 2022 and mid July 2023. One instrument (AUR02) had an unreliable seismometer records due to levelling problems. Skew values were obtained for all stations and ranged between -18 s and 12.3 s. Clock drift in this experiment was partially nonlinear. After the skew correction, a nonlinear time drift for stations AUR02, AUR04, AUR06, AUR08 was determined using noise cross-correlation. A best-fit correction was obtained by using skew-corrected station AUR01 as reference station for stations AUR04 and AUR08, while skew-corrected station AUR03 served as reference for stations AUR02 and AUR06. Station specific phase residuals obtained from a manually picked catalog of 492 events were used to further validate the clock drift corrections. For AUR04 a nonlinear phase residual drift was observed and, subsequently, the applied drift polynomial was manually adjusted to minimize resulting residuals. Waveform data are available from the GEOFON data centre under network code 4V.

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.

DZA short-term seismic network in the Lausitz

A network of 209 continuously running digital seismic stations equipped with short-period geophones (200 stations) and broadband sensors (9 stations) was deployed in an area of ~14 x ~14 km in the Lausitz (Saxony, Germany) for a period of ~5 weeks. The main objectives were 1) to create a 3-D model of the subsurface (shear wave velocity; ambient noise tomography) using the ambient seismic noise field and 2) to investigate the spatio-temporal distribution of the seismic noise (and noise sources). The project is related to the preparations for the construction of a ‘Low Seismic Lab’ (as part of the German Center for Astrophysics, DZA) and potentially the Einstein Telescope. Waveform data is available from the GEOFON data centre, under network code 9I.

Mehr als verschüttete Täler: Dienen Tunneltäler als bevorzugte Fließwege für frisches Grundwasser in der Nordsee?

Die stetig wachsende Bevölkerung führt zu einem steigenden Bedarf an Frischwasser und die Entnahme von Grundwasser ist eine der wichtigsten Quellen diesen Bedarf zu decken. Engpässe in der Frischwasserversorgung haben die Suche Nachweis von frischem Grundwasser unter dem heutigen Meeresboden angetrieben. Die Rolle glazialer Strukturen, welche während der Vergletscherungen entstanden sind, ist jedoch im Hinblick auf das Vorkommen frischen Grundwassers noch wenig bekannt. Insbesondere sogenannte Tunneltäler (TT), welche sich unter den Eisschilden bildeten, könnten von besonderer Relevanz sein. Ihre Ausmaße (bis zu 5 km breit, 400 m tief, 100te km lang) spiegeln die gewaltigen Schmelzwassermengen wider, die den Untergrund unter den Eisschilden durchspülten. Ihre Entstehung und Füllung resultierte in stark durchlässigen Sanden und Kiesen im unteren Teil und feinkörnigen Ablagerungen im oberen Teil dieser Strukturen. Diese Konfiguration begünstigt eine Rolle als bevorzugte Fließwege für offshore Grundwasser. Zur Untersuchung des Potenzials von TT als bevorzugte Fließwege für offshore frisches Grundwasser (OFG), verfolgt dieses Projekt folgende Ziele: (O1) Durch die Kombination von elektromagnetischen und seismischen Daten wollen wir ein strukturgebundenes Widerstandsmodell für mehrere TT erstellen; (O2) Wir wollen die Salzgehaltswerte für verschiedene Architekturen und Tiefen von TT abschätzen; (O3) Aufbauend auf den ersten beiden Zielen wollen wir die Ergebnisse für das gesamte Arbeitsgebiet in ein detailliertes lithologisches 3D-Modell extrapolieren. Die sich daraus ergebende Salzgehaltsverteilung im Untergrund wird dazu beitragen, die Ober- und Untergrenzen des Volumens frischen Grundwassers abzugrenzen und die Grundlage für ein detailliertes Grundwassermodell schaffen. Folgende Schritte sind dazu nötig: (S1) Kartierung und Charakterisierung der räumlichen Heterogenität von TT anhand vorhandener seismischer Daten; (S2) Erstellung eines lithologischen Modells für den Untergrund zwischen Amrum und Helgoland von 0 bis 400 m Tiefe; (S3) Identifizierung vielversprechender Standorte und Durchführung von CSEM-Messungen (Controlled Source Electromagnetic) zur Untersuchung der Verteilung des elektrischen Widerstands im Untergrund (TT); (S4) Kombination von Widerstandsmessungen mit Mehrkanal-Seismikdaten (MCS) zur Ableitung des Salzgehalts der Porenflüssigkeit; (S5) Extrapolation der Ergebnisse für das gesamte lithologische Modell. Tunneltäler existieren in ehemals vergletscherten Regionen weltweit. Gelingt uns der Nachweis von OFG in Tunneltälern, hätte dies erhebliche Implikationen für bisher unbekannte Süßwasserverteilungen und hydrologische Systeme. Die uns zur Verfügung stehenden Daten bieten eine einzigartige Möglichkeit zur Integration von CSEM- und seismischen Messungen bei begrenztem Aufwand. Die Ergebnisse des Projekts werden einen neuen Blick auf offshore Gletscherlandschaften und ihre Rolle im pleistozänen Wasserkreislauf erlauben.

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