Beschreibung: SO277 OMAX served two scientific projects. The objectives of the first project, SMART, were to develop multi-disciplinary methodologies to detect, quantify, and model offshore groundwater reservoirs in regions dominated by carbonate geology such as the Mediterranean Sea. To this end we acquired controlled-source electromagnetic, seismic, hydroacoustic, geochemical, seafloor imagery data off Malta. Preliminary evaluation of the geophysical data show that there are resisitivity anomalies that may represent offshore freshwater aquifers. The absence of evidence for offshore springs means that these aquifers would be confined and that it will be difficult to use them in a sustainable manner. The objective of the second project, MAPACT-ETNA, is to monitor the flank of Etna volcano on Sicily which is slowly deforming seaward. Here, we deployed six seafloor geodesy stations and six ocean bottom seismometers for long-term observation (1-3 years). In addition, we mapped the seafloor off Mt. Etna and off the island of Stromboli to constrain the geological processes that control volcanic flank stability.

Beschreibung: Gas hydrate dynamics may impact the global carbon cycle and global warming. They may be used as a possible future energy source, but their dynamics may also influence slope stability. Therefore, their occurrence, formation, dissociation, and mobilization are of high interest. The quantification of gas hydrates in continental margins, either by drilling or geophysical methods, is the bases to understanding gas hydrate dynamics. To provide estimates of the gas hydrate saturation the common methodology reaches from the simple detection of gas hydrates by seismic imaging to more sophisticated approaches using the combination of geological, geochemical and geophysical methods. While most geophysical experiments use empirical relationships like Archie’s Law to derive saturations from remotely sensed data, a coupling of rock physics and geophysics by effective medium modeling offers new perspectives to directly invert for porosity, gas and gas hydrate saturations. We apply a joint elastic and electric approach by using a self-consistent approximation/differential effective medium model (SCA-DEM) on data from downhole P-wave velocity and induction sensors, recorded in a sedimentary setting at Formosa Ridge south-westoff Taiwan. In a first step, we construct a background model and derive porosity distributions from the data. Subsequently, we invert the complete borehole dataset for gas and gas hydrate saturations. A sensitivity analysis shows how the joint elastic andelectric approach is able to distinguish between gas and gas hydrate saturations and thereby overcomes the widely observed disagreement in saturation levels between seismic and electromagnetic methods. This approach lays the foundation to directly derive saturation levels from an existing joint geophysical electromagnetic and seismic dataset at Formosa Ridge.

Beschreibung: Volcanic eruptionsand earthquakes in the Christiana-Santorini-Kolumbo rift have repeatedly triggered devastating tsunamis including the 1600 BC Late Bronze Age eruption of Santorini, the 1650 eruption of Kolumbo and the 1956 Amorgos earthquake. The Late Bronze Age eruptiontsunami affected large areas of the eastern Mediterranean and contributed to the demise of the Minoan culture on Crete, while the effects of the 1650 Kolumbo and the 1956 Amorgos tsunamis were limited to the islands around the Christiana-Santorini-Kolumborift. Although intensively studied in recent decades, the potential tsunami source parameters of these events remain poorly constrained. The THESEUS project aims to parameterize various potential source parameters associated with these tsunami events using marine high-resolution reflection seismics. For this purpose, we conducted high-resolution 2D and 3D reflection seismic surveys as well as ocean-bottom seismometer refraction seismic experiments covering the Christiana-Santorini-Kolumbo rift during expedition POS538 onboard RV Poseidon in October 2019. Here, we present the first results of the ongoing analysis of our P-Cable 3D seismic dataset, which covers most of the Kolumbo volcanic edifice and a prominent fault zone to the north. In addition, we present 2D seismic profiles covering the Santorini Caldera and pyroclastic flow deposits associated with the Late Bronze Age eruption

Beschreibung: The goal of core-log-seismic integration is to glean new scientific understanding from diverse datasets that span the millimeter to kilometer scale. Germany plays an important role in international scientific drilling, with major core curation and data management centres, as well as broad expertise in seismicdata acquisition, borehole logging and sediment core investigations. Springboarding from this solid foundation, we propose to establish a virtual Core-Log-Seismic Integration Research Centre to act as a nucleus for conceiving and running research projectsthat harvest the untapped potential of hundreds of scientific boreholes. We envisage that scientists from Germany, in collaboration with key international partners, should work closely together and provide the critical mass and long-term expertise to sustain the research centre. We see this an ideal way to foster collaboration within Germany and globally.In this presentation we will describe this new initiative and provide some examples of on-going and developing research projects that are underpinned by core-log-seismic integration methods. The examples will include investigations into submarine landslide processes (offshore New Zealand), gas hydrate formation (offshore Taiwan) and continental collision (onshore Sweden).

Beschreibung: Driven bysignificant economic benefits, the hydrocarbon industry developed sophisticated methods for the integration of geophysical and geochemical measurements with direct core observations. However, these techniques were developed primarily for sedimentary settings and have been applied only seldom in metamorphic settings. One outstanding example for comprehensive geophysical and borehole data integration is the COSC-1 borehole in the central Scandinavian Caledonides. It was drilled in 2014 and resulted in an extensive dataset to shed light on deformation during continental collision. Our study combines data from downhole logging and zero-offset vertical seismic profiling at COSC-1, with 2D and 3D seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. We show that there are powerful tools to distinguish between mafic and felsic lithologies in log-core correlation but that metamorphic settings bear special challenges for core-log-seismic integration. In contrast to sedimentary basins, reflections in the Seve Nappe Complex are not as distinct but we can link several of them to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. It appears that in spite of the metamorphic overprint around 417+/-9 Ma, the original configuration of the volcanic passive margin is partly preserved in the Seve Nappe Complex and it thus outlasted continent-continent collision including the nappe emplacement. Integration of borehole and three-dimensional geophysical data reveals lithological changes that can then be extrapolated in three dimensions to arrive at a better understanding of the compositionand geometry at mid-crustal levels. Furthermore, our results suggest that mid-crustal reflectivity at COSC-1 is primarily a function of pre-orogenic lithological variations which has to be considered when deciphering mountain building processes.

Beschreibung: SEG and the German Geophysical Society (DGG) held their first joint workshop in early March at DGG's 2021 Annual Meeting. The workshop was part of a new cooperative aim between DGG and SEG to promote engagement between the societies, to foster growth in geophysics, and to expand the community of scientists and engineers tackling important geophysical problems. The 2021 workshop theme, “Scientific Drilling,” was chosen because scientific drilling provides access to rocks and fluids in the subsurface that are essential for ground truthing interpretations from geophysical data and geologic interpretation, for providing samples and in-situ data for detailed characterization, and for providing inputs to models. Consequently, the workshop aimed to attract interest across many subfields of geophysics.