Continental strike-slip faults often display complex, along-strike geometries with branches and splays, which play an important role in earthquake rupture processes. We use a digital elevation model and a ground-penetrating radar survey to analyse the Awatere Fault in New Zealand and demonstrate that the number of branch faults and the width of the fault zone increases as the fault passes from bedrock to unconsolidated alluvial sediments. With analogue models of a strike-slip fault, we test whether this observation can be reproduced. Each model incorporates a sand body that represents a basin filled with less consolidated sediments above a basement of corn-starch. Fault branch-points repeatedly formed at the basin-basement boundary in the analogue model, indicating that the geometrical complexity of strike-slip faults can be strongly controlled by lateral changes in the properties of the host material. The change of friction coefficient at the material boundary promotes splays and branch fault nucleation and also fosters fault-bend formation. The thicker the sedimentary cover overlying the basement, the wider the zone of deformation. This implies that the lateral passage of faults from bedrock into unconsolidated material leads to a widening of the deformation zone, which is confirmed by the ground-penetrating radar survey across the Awatere Fault. The results of this study have wide application to active strike-slip faults that run into sedimentary basins, as is, e.g., the case for the Newport-Inglewood Fault in the Los Angeles Basin.

The Tauern Window (TW) in the European Alps is one of the largest tectonic windows in the world. Its formation started in the Cretaceous with subduction of the Penninic realm beneath the northern margin of Adria leading to the collision between Europe (Subpenninic) and the Adria margin (Austroalpine). The resulting Penninic and Subpenninic nappe stack was exhumed by ca. 20 km by the approach of the Dolomites Indenter (Eastern Southern Alps) in the Miocene. This last deformation stage resulted in synkinematic N-S shortening of the western TW (ca. 70 km), W-E extension and lateral extrusion towards the east. However, how the Subpenninic core (Venediger Duplex; VD) and the Penninic and Austroalpine nappes (PN and AN, respectively) in the hanging-wall were tectonically stacked, upright folded and emplaced is poorly understood. This study investigates the deformation accommodated by each major tectonic basement unit of the western TW, and contributes to a better understanding of orogenic processes in general.We kinematically restore the cross-section of [1] along the Brenner Base Tunnel (W of the TRANSALP seismic profile) using the software MOVEtm (Petroleum Experts), focusing firstly on the VD. We choose area balancing as minimum criteria, because we do not know how much material was transported out of the plane of cross-section by extension and lateral extrusion. We integrate zircon fission-track data (ZFT) as a temporal constraint and test different geothermal gradients. Petrological data are used to define the maximum depth the VD reached at the time of indentation and as marker for the transition from brittle to viscous conditions of the felsic rocks of the VD (lowest temperature for folding). Finally, we reconstruct the hanging-wall nappes above the restored VD, thereby precisely constraining the position of the AN at that time. The surface samples taken from the AN must have reached thermal conditions between the annealing zones of apatite fission-tracks and ZFT (115°C and 180°C, respectively) as only the former system was reset in the Miocene.We first displace the entire VD down along the Sub-Tauern Ramp below the 300°C isotherm (brittle to viscous transition of felsic rocks). For this, the geothermal gradient of 50°C/km fits well to the petrological data. ZFT ages reveal upright folding of the VD terminated at ca. 17 +/- 2 Ma. Subsequent unfolding of the gneiss cores, while conserving surface area, reveals the model to be extended ca. 70 km to the south (i.e. thus equaling indenter shortening), which means that no material left the plane of cross-section by W-E extension or lateral extrusion. However, the situation for the hanging-wall nappes is different: The total thickness of the northern limbs of the AN and the PN together is twice as much after restoration compared to today. We postulate that the extension on the Brenner Normal Fault mainly caused this tectonic thinning, which is approximately 10 km. References[1] Reiter, F., Freudenthaler, C., Hausmann, H., Ortner, H., Lenhardt, W., & Brandner, R. (2018). Tectonics, 37(12), 4625-4654.

Geothermal heat flow (GHF) is a critical parameter for understanding the thermal structure and dynamics of the lithosphere, providing critical insights into lithospheric thermal evolution and geothermal energy potential. This study investigates the spatial variability of GHF in Germany by applying a Bayesian Markov Chain Monte Carlo method to estimate key thermal parameters, including crustal and mantle thermal conductivities, crustal heat production, and mantle heat flow. The analysis integrates data on surface heat flow, surface temperatures, and the lithosphere-asthenosphere boundary depth. To address the limitations posed by the sparse and uneven distribution of direct borehole measurements, comprising only 595 GHF records, we incorporated a wide range of geophysical and geological constraints, such as gravity, magnetics, seismic velocity, topography, and proximity to faults and volcanic regions. These data sets were analyzed using a Quantile Regression Forest approach that enabled robust GHF estimations, while accounting for uncertainties and providing reliable prediction intervals. This methodology significantly improves upon traditional Curie Point Depth-based methods, providing a more accurate and comprehensive GHF model for Germany. The probabilistic multi-observable approach enhances GHF estimates in Germany, improving constraints on geothermal resources and the lithospheric thermal state.

A comprehensive multi‐method geophysical strategy is used to investigate two faults in the Northern Upper Rhine Graben. Combining industrial 3D seismic data with our own 2D P‐ and S‐wave seismic, electrical resistivity tomography (ERT) and ground‐penetrating radar (GPR), we created comprehensive subsurface images of the faults. 3D seismic data feature structure from 450 m to 4 km deep, whereas high‐resolution 2D P‐wave data complemented this for depths of 50–600 m. S‐wave seismic imaging revealed disrupted layering and syn‐sedimentary features in the range of 5–250 m depth, whereas ERT measurements further supported the identification of offset horizons and showed syn‐sedimentary activity, particularly down to 10 m depth. GPR results remained ambiguous, though they suggested potential geological features related to fault tectonics. Both faults have varying dip angles and offsets in different stratigraphic units, proving that tectonic movement occurred during sedimentation of the Neogene and Quaternary layers. In general, both faults steepen upwards, forming typically listric shapes. They both offset the base Quaternary by about 35 m. Finally, the very‐near‐surface methods show that the faults extend almost up to the Earth's surface, proving their very recent activity. This project highlights the efficiency of multi‐method geophysical surveys in neotectonic research and seismic risk assessment and emphasizes their role in detailed subsurface analysis. It also contributes to our understanding of potential gas migration along fault zones to the Earth's surface.

The Penninic and Subpenninic nappe stack of the Tauern Window (TW) in the European Alps was formed by collision between Europe (Subpenninic) and the Adria margin (Austroalpine), and finally exhumed by the northward push of the Southalpine Dolomites indenter in the Miocene. In this study, we kinematically restore a cross-section along the trace of the Brenner Base Tunnel, concentrating mainly on the Subpenninic nappes (Venediger duplex; VD). We integrate zircon fission-track data (ZFT) as a temporal constraint for the termination of viscous deformation and test different geothermal gradients (GG). P-T-t data are used to define (a) the depth of the brittle-viscous transition (ca. 300 degrees C) and (b) pre-indenter depth. We displace the VD down along the Sub-Tauern ramp below the 300 degrees C isotherm. At that time, a GG of ca. 50 degrees C/km prevailed. ZFT data reveal that viscous conditions allowing folding of the VD started to cease slightly earlier than 17 +/- 0.6 Ma. Unfolding of the VD, while conserving surface area, yield that the model is extended by ca. 70 km (thus equaling indenter shortening), which means that in the westernmost TW, the VD was not significantly affected by W-E extension. Reconstruction of the hanging-wall nappes (Austroalpine and Penninic nappes) above the restored VD reveals that the total pre-indenter thickness of their northern limbs was 25%-48% greater than today. We interpret this as tectonic thinning, which was mainly caused by the Brenner normal fault.

Neotectonic movements pose significant hazards and hold crucial scientific and social relevance, notably in seismic hazard assessment and subsurface utilization. In regions like northern Germany, a presumed aseismic region, understanding these processes remains limited because many faults are buried under sediments. Despite confirmed neotectonic activity, the specifics of these processes and associated structures remain largely unknown. Improving our understanding of neotectonic activity requires investigations of recently-active fault zones, such as the Osning Fault System (OFS) in North Rhine-Westphalia, Germany. Using near-surface geophysics becomes crucial in this endeavour, which so far were not used at the OFS. The OFS stands out as a site of recent and historical seismic activity, experiencing several large earthquakes over the past four centuries. Notably, major earthquakes in 1612 and 1767 with intensities ranging from VI to VII on the MSK scale, emphasize the seismic significance of the OFS. Unlike other faults in the region, the faults of the OFS reach the basement and the fault zone dips north-eastward. Furthermore, the former iceload from Scandinavia influenced the fault system by facilitating glacial isostatic adjustment, which subsequently enabled fault reactivation. The complex nature of the fault system spans various geological phases, prompting a comprehensive investigation approach to understand its regional neotectonic evolution. Our geophysical and geological approach integrates high-resolution 2D P- and SH-wave reflection seismics and retrodeformation of previously-published cross-sections. This is complemented by surface geological maps and limited drilling information. Our aim is to identify and interpret fault geometry and kinematics. While P-wave seismic surveys used for imaging of deep structures often lack high-resolution in the shallow subsurface, the integration of SH-wave reflection seismics compensates for this limitation, offering enhanced resolution, especially at the near-surface. The survey involved three P-wave profiles employing a hydraulically-driven vibrator vehicle and four SH-wave profiles utilizing an electro-dynamic micro-vibrator with varying source point spacing. These seismic profiles successfully delineate fault structures within the Cretaceous formations, revealing previously unidentified extensions of the OFS. Although the P-wave profiles inadequately image the Quaternary layers, there are indications that the faults extend into this formation. The SH-wave profiles, with their superior resolution in the near-surface due to lower wave velocities, confirm these assumptions, revealing further faulting and deformation features within the Quaternary sediments. Interpretation and fault imaging are further enhanced by full waveform inversion of P- and S-wave data, testing of different migration methods for the S-wave data, and seismic attribute analysis. Retrodeformation and balancing of existing cross-sections and the interpreted seismic profiles allows the fault geometry and kinematics to be assessed. We determined which adjustments were necessary to make the profiles more geologically plausible. This combined geophysical and geological approach enabled a more comprehensive interpretation and understanding of the local fault geometry and the neotectonic evolution of the OFS.

In outcrops, the hanging-wall and/or footwall structure around a fault are often exposed, while the underlying fault is poorly resolved. In these cases, it is desirable to estimate the location and shape of the fault at depth, especially if it belongs to an active fault system prone to large earthquakes. The Mw 7.8 Kaikōura earthquake occurred two minutes after midnight on 14th November 2016, causing at least 17 faults in the northeast South Island of New Zealand to rupture, including a number of faults that had not been previously mapped. One of these smaller new faults is the Leader Fault, which at the surface displaces Mesozoic interbedded greywacke and argillite. In outcrop, the fault rupture caused an over 3 m high, 20-30 m wide, and over 120 m long hanging-wall fold to appear at the surface. In September 2022, we used a differential global navigation satellite system to map the topography of the fold. We collected a total of 1493 points over a map area of 4526 m², i.e. an average point density of ca. 1 point per 3 m². The data were meshed into a three-dimensional triangular surface, which was then sectioned into ten cross-sections, each 10 m apart and perpendicular to the fold axes. We present fault-prediction modelling of two of these sections. In the Movetm software (Petroleum Experts), we used two methods of fault prediction; constant heave and constant slip. Both methods require implicit information about the hanging-wall shape, the position of the fault at the surface and the “regional”, i.e. the position of the hanging wall before deformation. Before the modelling, all this information was known apriori; i.e. we mapped the shape of the ground surface, we knew the fault to outcrop at the break of slope at the front of the leading edge, and the regional is an extension of the undeformed footwall. Both modelling techniques require a seed, i.e., a small portion of fault at the surface with a certain angle of dip. We use a horizontal and a 60° dipping seed. We can estimate the fault geometry down to a depth of 20-25 m. For both sections, we predict the fault is steep, greater than 60°. Using a flat seed gives a slightly listric fault geometry, but in any case, the fault is steep down to 20 m depth before flattening out slightly. Compared to a small (15 cm) outcrop of the fault plane (dipping 75° WNW) at the surface at the northern end of the outcrop, the best matches are given by modelling with constant slip. The steep fault geometry is governed by the basement rock that has steep bedding that also dips ca. 70° WNW.

Northern Germany is famous for its numerous Neanderthal (Middle Palaeolithic) archaeological sites and well-preserved palaeoclimate records. Nevertheless, our understanding of how hominins responded to climate fluctuations and adapted to changing environments in this region remains limited because there are only a few reliable, highly-resolved chronological frameworks of long stratigraphic successions. Most of the Middle Palaeolithic sites in this region lack a reliable chronostratigraphy beyond the radiocarbon dating range. In this study, we present a high-resolution optically stimulated luminescence (OSL) chronology derived from a similar to 21 m long sediment core (Li-BPa) that was drilled in close proximity to the known Neanderthal site of Lichtenberg. Quartz OSL dating was applied to the upper 6.5 m of the core. Subsequently, the obtained quartz OSL ages were compared with feldspar post-infrared (IR) IRSL (pIRIR) measured at 290 degrees C (pIRIR(290)), pulsed IR50 (pre-pIRIR(225)), and pulsed pIRIR(225) ages to select a suitable feldspar signal to date older samples. A comparison of the quartz and feldspar ages indicates that only fading-corrected pulsed IR50 (pre-pIRIR(225)) and pIRIR(225) ages agree well with quartz OSL ages. Finally, the age framework of the sediment sequence was established based on the 11 quartz OSL ages and 23 fading-corrected pulsed IR50 (pre-pIRIR(225)) and pulsed pIRIR(225) ages. The resulting Bacon age-depth model agrees with litho- and biostratigraphic designations, indicating that the whole sequence was deposited between ca. 275 ka and ca. 24 ka, corresponding to the Saalian to Weichselian periods.

The Alpine region was shaped by repeated glaciations during the Quaternary, which led to the formation of overdeepened valleys and basins. These features today, hidden below the present-day land surface, host multiple stacked and nested glacial sequences and offer valuable insight into the environmental history and geomorphological evolution of the region. The project Drilling Overdeepened Alpine Valleys (DOVE) of the International Continental Scientific Drilling Program (ICDP) is dedicated to investigating such overdeepened structures around the Alps. Within DOVE, we here focus on the Tannwald Basin in southern Germany. Situated distally within the area formerly occupied by the Rhine Glacier piedmont lobe; it was shaped by multiple glaciations, yet it is located outside the Last Glacial Maximum (LGM) ice extent. Previous seismic imaging and the presence of interglacial pollen sequences indicate a multi-phase infill history. The complex sedimentary architecture observed in a newly drilled core allows for comparison with seismic data and lithological evidence from other sites. On the basis of a lithofacies model that introduces 17 lithotypes, we propose that the basin fill is composed of three lithostratigraphic units that reflect the glacial history of the basin. After the erosion of the Tannwald Basin, a cold-climate, stacked basin-infill sequence recorded sedimentation of two glacial advances, before it was covered by LGM outwash. The sedimentary record includes an extensive basal glacial shear zone with deformed bedrock and several overlying diamict horizons. Further upcore, deformation structures underscore the role of gravitational processes as well as profound glaciotectonics, deforming the sediment deep within the subsurface. While the sedimentary record indicates a rather rapid infill of the depression, further age constraints and detailed investigations of ice-contact sediments will clarify open questions regarding the temporal classification of the deposits.

The Upper Jurassic carbonate aquifer in the German Molasse Basin (S Germany) below Munich is the focus of exploitation of geothermal energy. To implement geothermal wells, meaningful prediction of reservoir quality (e.g., volume, temperature, location of aquifers, porosity, permeability) is required. However, permeability of this aquifer is often highly heterogeneous and anisotropic, as in other karst- and fracture systems. Based on geophysical well logs from six wells, a 3D porosity model, and side-wall cores, we provide a comprehensive characterisation of the reservoir. We investigate the correlation between rock porosity and matrix permeability, and the impact of hyper-facies on fractures and karstification. We locate and analyse hydraulic active zones and compare them with hydraulic inactive zones within equivalent depth ranges, to characterise promising exploration targets. We show that fracture system parameters vary strongly between wells and within a single well. However, we observe local trends between the fracture systems and rock properties. For instance, fracture intensities and compressional wave velocity increase, while porosity decreases, in dolomitic reefal build-ups (massive facies). We observed substantial karstification dominantly within the massive facies. The main indicators for hydraulic active zones in the reservoir seem to be karstification, fractures, and fault zones. Although matrix porosity has neglectable impact on permeability, the identified hydraulic active zones appear more frequently in sections with higher porosity. We conclude, similar to previous studies, that the massive facies is a suitable exploitation target. Despite the favourable conditions within the massive facies, the strongest hydraulic active zones are nevertheless in the bedded facies, often considered as aquitard, directly below the top of the reservoir within the lithostratigraphic group of the Purbeck, at the transition between the Jurassic and the Cretaceous.

This is a dataset of grain-size distribution in sub- and supercritical flow sediments of a Gilbert-type delta from an outcrop in North Germany. Thirteen samples of ca 2.5 kg were dried (at 105°C), and homogenised twice with a sample divider. A representative sample of 1-2 g was then analysed using laser diffraction. The grain-size distribution of the sand has a maximum between fine to medium sand, with a long fine fraction tail down to 0.06 µm and occasional coarse fractions (up to 1.5 mm) in some samples. Specific grain-size distributions correlate with the different sedimentary bedforms from which the samples were taken. This data is important for two reasons: Firstly, sedimentary structures formed by Froude supercritical flows are controlled by grain-size. However, few studies have provided grain-size datasets from the natural record, which often have a much wider grain-size distribution than experimentally-produced supercritical flow deposits. Secondly, the sands were deformed subsequently by disaggregation bands, a type of geological fault that only develops in porous granular materials, i.e. well-sorted, medium sand. The disaggregation bands are indicative of seismic or even aseismic, creeping movement of basement faults.

<p>Neotectonic movements can cause severe hazards and are scientifically and socially relevant, e.g. for seismic hazard assessment, and utilisation of the subsurface. In northern Germany, a presumed aseismic region, little is known about these processes and the associated structures, despite proven neotectonic activity, because many faults are hidden beneath sediments. To improve the knowledge of neotectonic activity, investigations of recently-active fault zones, like the Osning Lineament (OL) in North Rhine-Westphalia, are required.</p> <p>To better understand the neotectonic evolution of the OL, we use near-surface geophysics, which have not been used at the OL so far. We used a combined approach using high-resolution 2D P- and SH-wave reflection seismics. P-wave seismic alone can often not properly image near-surface impressions of faults due to poor shallow resolution, but this gap can be closed using SH-wave reflection seismics, which offers very high resolution, even at shallow depth. Three P-wave profiles were measured with a hydraulically-driven vibrator vehicle (sweep frequency: 20 to 200 Hz) with a source point spacing of 10 m and plugged vertical geophones at 5 m intervals. Additionally, four SH-wave profiles were surveyed using an electro-dynamic micro-vibrator (sweep frequency: 20 to 160 Hz) with a source point spacing of 2 or 4 m and a landstreamer with horizontal geophones at 1 m intervals.</p> <p>The seismic profiles show good results with respect to mapping the fault inventory. In the migrated depth sections of the P-wave profiles, several northward-dipping faults in the Cretaceous formations are recognizable, which are interpreted hitherto unknown extensions of the OL. The Quaternary, with a maximum thickness of 20 to 30 m, is only poorly imaged by the P-wave profiles, but there are nevertheless hints that the faults also extend into the Quaternary. The SH-wave profiles support this assumption, due to their higher resolution close to the surface, because of very-low wave velocities between 150 and 500 m/s. In the Quaternary sediments, further faulting and deformation features are recognizable, enabling a more comprehensive interpretation and understanding of the local fault geometry.</p> <p>In the course of the project, we also carry out a full waveform inversion of the P- and S-wave data to improve the fault imaging. This will be accompanied by testing of different migration methods and seismic attribute analysis.</p>

The Tauern Window in the European Alps has a high tectonic complexity. It is a key area to understand a number of important orogenic processes, including nappe stacking, exhumation, indentation as well as escape tectonics. The polyphase Alpine deformation history of the Tauern Window began with subduction and accretion of the Penninic realm beneath the northern margin of Adria (Austroalpine) in the Cretaceous. Ongoing convergence led to collision between Europe (Subpenninic) and the Adria margin and to the formation of the Penninic and Subpenninic nappe stack in the southward dipping orogenic wedge from Eocene to early Oligocene. The W-E trending Periadriatic Fault System (PFS) located within the Adriatic units south of the Tauern Window was active as dextral strike-slip fault at this time, as indicated by the deformation of the Eocene and Oligocene Periadriatic intrusions [1]. Indentation of the Dolomites Indenter (Eastern Southalpine) bent the primarily PFS and finally caused this fault system to be sinistrally offset by the NNE-SSW striking Giudicarie fault system in the Miocene. This last deformation stage (D5 after [2]) caused strong N-S shortening (~65 km) of the western Tauern Window in front of the Dolomites Indenter, accompanied by lateral extrusion towards the east of at least ~100 km involving major strike-slip faults (e.g., Inntal Fault, PFS, SEMP). W-E extension further led to the formation of the Katschberg and Brenner Normal Fault (on the eastern and western borders of the Tauern Window, respectively). The latter, perhaps in combination with slab break-off and mantle upwelling, led to rapid exhumation of the Tauern Window.Balancing a cross-section is an excellent tool to analyze the kinematic evolution of mountain belts. Therefore, we collected a structural dataset along a N-S trending cross-section through the western Tauern Window based on the Brenner Base Tunnel profile [3]. Before balancing, however, basic assumptions have to be typically considered: (1) Whether plane-strain deformation is applicable, which means that no material should move lateral into or out of the cross-section plane (2) Conservation of the area (or volume), and (3) line-length should be preserved. Hence, such a balancing is not simply possible in the western Tauern Window because of the last deformation stage (D5 after [2]), when contemporaneous N-S shortening, W-E extension, and vertical uplift led to penetrative deformation and non-plane strain conditions, respectively. We focus on the restoration of the last deformation stage; first with plane-strain and second with non-plane, oblate strain. The results reveal the effect of the W-E extension on the nappe geometry in the footwall of the Brenner Normal Fault – a topic that is controversially discussed. This is the basis for further backward restoration that needs to incorporate all the tectonic movements out of the cross-section plane, and will be carried out as balancing in 3-D at a later stage of the project. References[1] Pomella, H. et al. (2011). International Journal of Earth Sciences, 100(8), 1827-1850.[2] Schmid, S. M. et al. (2013). Swiss Journal of Geosciences, 106(1), 1-32.[3] Brandner, R. et al. (2008). Geo Alp, 5, 165-174.

Neotectonic movements can cause severe geohazards and thus require examination for seismic hazard assessment, and utilisation of the subsurface for e.g. nuclear-waste disposal sites and geothermal exploitation. In northern Germany, very little is known about these processes and the associated structures, despite proven neotectonic activity, because many faults are hidden beneath sediments.The Osning Lineament (OL) in North Rhine-Westphalia is a recently-active fault zones. Three major earthquakes and seven other macro-seismic earthquakes occurred at the OL during the last 400 years. The strongest earthquakes occurred in 1612, 1767, and 1770, with an estimated intensity of VI to VII on the MSK scale. The OL is a unique fault system compared to other faults in northern Germany. The faults of the OL reach the basement, whereas in the north of the Lower Saxony Basin, most faults are decoupled from the basement by salt. Furthermore, the OL dips to the northeast and therefore the vector of the fault plane points towards the former iceload from Scandinavia, enabling glacial isostatic adjustment to occur on the faults. Additionally, the OL has had a history of multiphase reactivation in the geological past.To better understand the neotectonic evolution of the OL on a regional scale, we carried out a 2D retrodeformation using already existing large-scale cross sections along the lineament, which are based on surface geological maps and sparse drilling information. Balancing of these cross-sections verifies whether the fault geometry and kinematics derived from surface data are justified or need to be revised. Retrodeformation is also used to suggest the path of the fault(s) at greater (seismogenic) depth. Later on, retrodeformation will also be performed including new, highly-detailed seismic profiles and a joint interpretation will be carried out to improve the understanding of the past evolution of the Osning Lineament.

The quality of geothermal carbonate reservoirs is controlled by, for instance, depositional environment, lithology, diagenesis, karstification, fracture networks, and tectonic deformation. Carbonatic rock formations are thus often extremely heterogeneous, and reservoir parameters and their spatial distribution difficult to predict. Using a 3D seismic dataset combined with well data from Munich, Germany, we demonstrate how a comprehensive seismic attribute analysis can significantly improve the understanding of a complex carbonate reservoir. We deliver an improved reservoir model concept and identify possible exploitation targets within the Upper Jurassic carbonates. We use seismic attributes and different carbonate lithologies from well logs to identify parameter correlations. From this, we obtain a supervised neural-network-based 3D lithology model of the geothermal reservoir. Furthermore, we compare fracture orientations measured in seismic (ant-tracking analysis) and well scale (image log analysis) to address scalability. Our results show that, for example, acoustic impedance is suitable to identify reefs and karst-related dolines, and sweetness proves useful to analyse the internal reef architecture, whereas frequency- and phase-related attributes allow the detection of karst. In addition, reef edges, dolines, and fractures, associated with high permeabilities, are characterized by strong phase changes. Fractures are also identified using variance and ant tracking. Morphological characteristics, like dolines, are captured using the shape index. Regarding the diagenetic evolution of the reservoir and the corresponding lithology distribution, we show that the Upper Jurassic carbonate reservoir experienced a complex evolution, consisting of at least three dolomitization phases, two karstification phases, and a phase of tectonic deformation. We observe spatial trends in the degree of dolomitization and show that it is mainly facies-controlled and that karstification is facies- and fault-controlled. Karstification improves porosity and permeability, whereas dolomitization can either increase or decrease porosity. Therefore, reservoir zones should be exploited that experienced only weak diagenetic alteration, i.e. the dolomitic limestone in the upper part of the Upper Jurassic carbonates. Regarding the fracture scalability across seismic and well scales, we note that a general scalability is, due to a combination of methodological limitations and geological reasons, not possible. Nevertheless, both methods provide an improved understanding of the fracture system and possible fluid pathways. By integrating all the results, we are able to improve and adapt recent reservoir concepts, to outline the different phases of the reservoir's structural and diagenetic evolution, and to identify high-quality reservoir zones in the Munich area. These are located southeast at the Ottobrunn Fault and north of the Munich Fault close to the Nymphenburg Fault.

The Brenner Fault (BF) is an extensional low-angle fault in the eastern Alps that borders the western edge of the Tauern Window. The BF was instrumental in the exhumation of the latter, allowing the formation of the tectonic window by the uplift of the footwall. It consists of a wide shear zone, dipping to the west by an angle of 25-30°, overprinted by a brittle and steeper fault zone with a few metres thickness. Exhumation and cooling history of its footwall has been investigated by several low temperature thermochronometry approaches, which have defined the Neogenic deformation history, using the zircon and apatite U-Th/He dating methods (Wolff et al. 2021). Because of the lack of thermochronological methods able to date the thermal history of the rocks during Quaternary, the most-recent knowledge of this fault activity has not yet been defined. New studies have shown the possible application of ESR dating on quartz as an ultralow-temperature thermochronometer, characterized by a closure temperature of 30°-90°C, and dating range of 103-107 years that is therefore a useful tool to reconstruct the tectonic deformation of the upper crust during the Quaternary. In this work, we show new structural data and the first results of ESR thermochronometry on quartz applied to rocks of BF collected across both the shear and fault zones. An en-echelon system of normal faults can be distinguished within the continuous N-S striking main fault, suggesting the probable start of brittle deformation or a following deformation phase overprinted the previous one. Moreover, ESR measurements of ten samples collected across the BF show that the ESR ages of quartz get younger toward the Tauern Window, in accordance with fission track and (U-Th)/He ages. The ESR ages indicate the Quaternary exhumation of the BF, i.e. the youngest activity of the BF. Our results promise the successful application of ESR thermochronometry in defining the youngest deformation histories of Neogenic faults in the Alpine chain.

<p>Lithospheric flexure is the primary mechanism for the development of normal faults in foreland basins. While the tectonic regime defines the overall fabric of such flexure-induced faults, mechanical heterogeneity of the sedimentary sequence and pre-existing faults exert a major control on the geometry of the individual faults. Interpretation of 3-D seismic reflection data in the central part of the German Molasse Basin, a northern Alpine foreland basin, reveals a normal fault network that exhibits varying degrees of vertical segmentation. Two major faults oriented parallel to the strike of the Alpine orogen are characterised by geometrically coherent displacement of deeper Mesozoic strata and shallower Cenozoic strata. In contrast, another major fault system, oriented obliquely to the orogenic strike, shows an along-strike variation in geometric coupling between deeper and shallower structural levels. Although a thoroughgoing fault in the northeast, it bifurcates laterally to the southwest, with the deep and shallow segments decoupling across a southeastwardly-thickening, mechanically-weak layer. To establish the geometric evolution of these faults and understand to what extent it was governed by mechanical stratigraphy and structural inheritance, we here analyse throw distribution on the faults and variations in stratal thicknesses across the faults. High-resolution throw mapping indicates a general updip decrease in throw for the orogen-parallel faults, whereas the obliquely-oriented fault, in its coupled portion, has two throw maxima separated by a throw minimum at the mechanically incompetent interval. These results, together with syn-kinematic strata observations, show that the former faults initiated with the onset of the Cenozoic foreland flexure and grew upward by radial propagation, whereas the latter fault formed by an oblique reactivation of precursory Mesozoic faults and developed in the Cenozoic as a segmented structure. We hypothesise that the coupling of its deep and shallow segments to the northeast was established by a dip-linkage mechanism, which was inhibited further to the southeast as the mechanical barrier thickens. The reactivation of the pre-existing structures explains the non-optimal orientation of the younger fault segments at a shallower level, with the former acting as kinematic attractors for the latter faults. This study demonstrates how a detailed fault kinematic analysis can help to decipher the effect of multi-layered mechanical stratigraphy and structural inheritance on the spatial evolution of individual flexure-induced faults.</p>

Hidden, blind faults have a strong seismic hazard potential. Consequently, there is a great demand for a robust geological indicator of neotectonic activity on such faults. Here, we conduct field measurements of disaggregation bands above known underlying blind faults at several locations in Central Europe. We observe that the disaggregation bands have the same orientation as that of the faults, indicating their close connection. Disaggregation bands develop in unconsolidated, near-surface, sandy sediments. They form by shear-related reorganization of the sediment fabric, as a consequence of grain rolling and sliding processes, which can reduce the porosity. Using an analogue shearing experiment, we show that disaggregation bands can form at a velocity of 2 cm h −1 , which is several orders of magnitude slower than seismogenic fault-slip velocities. Based on the field data and the experiments, we infer that disaggregation bands can form in the process zone of active blind faults and serve as an indicator of neotectonic activity, even if the fault creeps at very low slip velocity. Disaggregation bands could open a new path to detect hidden active faults undergoing aseismic movements.

The subsurface dissolution of soluble rocks can affect areas over a long period of time and pose a severe hazard. We show the benefits of a combined approach using P-wave and SH-wave reflection seismics, electrical resistivity tomography, transient electromagnetics, and gravimetry for a better understanding of the dissolution process. The study area, “Esperstedter Ried” in northern Thuringia, Germany, located south of the Kyffhäuser hills, is a large inland salt marsh that developed due to dissolution of soluble rocks at approximately 300 m depth. We were able to locate buried dissolution structures and zones, faults and fractures, and potential fluid pathways, aquifers, and aquitards based on seismic and electromagnetic surveys. Further improvement of the model was accomplished by analyzing gravimetry data that indicates dissolution-induced mass movement, as shown by local minima of the Bouguer anomaly for the Esperstedter Ried. Forward modeling of the gravimetry data, in combination with the seismic results, delivered a cross section through the inland salt marsh from north to south. We conclude that tectonic movements during the Tertiary, which led to the uplift of the Kyffhäuser hills and the formation of faults parallel and perpendicular to the low mountain range, were the initial trigger for subsurface dissolution. The faults and the fractured Triassic and lower Tertiary deposits serve as fluid pathways for groundwater to leach the deep Permian Zechstein deposits, since dissolution and erosional processes are more intense near faults. The artesian-confined saltwater rises towards the surface along the faults and fracture networks, and it formed the inland salt marsh over time. In the past, dissolution of the Zechstein formations formed several, now buried, sagging and collapse structures, and, since the entire region is affected by recent sinkhole development, dissolution is still ongoing. From the results of this study, we suggest that the combined geophysical investigation of areas prone to subsurface dissolution can improve the knowledge of control factors, hazardous areas, and thus local dissolution processes.