Despite the amount of research focused on the Alpine orogen, significant unknowns remain regarding the thermal field and long term lithospheric strength in the region. Previous published interpretations of these features primarily concern a limited number of 2D cross sections, and those that represent the region in 3D typically do not conform to measured data such as wellbore or seismic measurements. However, in the light of recently published higher resolution region specific 3D geophysical models, that conform to secondary data measurements, the generation of a more up to date revision of the thermal field and long term lithospheric yield strength is made possible, in order to shed light on open questions of the state of the orogen. The study area of this work focuses on a region of 660 km x 620 km covering the vast majority of the Alps and their forelands, with the Central and Eastern Alps and the northern foreland being the best covered regions.
Knowledge of groundwater flow is of high relevance for groundwater management and the planning of different subsurface utilizations such as deep geothermal facilities. While numerical models can help to understand the hydrodynamics of the targeted reservoir, their predictive capabilities are limited by the assumptions made in their set up. Among others, the choice of appropriate hydraulic boundary conditions, adopted to represent the regional to local flow dynamics in the simulation run, is of crucial importance for the final modelling result. In this publication we present the hydrogeological models to obtain results to quantify how and to which degree different upper hydraulic boundary conditions and vertical cross boundary fluid movement influence the calculated deep fluid conditions Therefore, we take the central Upper Rhine Graben area as a natural laboratory. The presented three models are set up with different sets of boundary conditions. The Reference Model uses the topography as upper hydraulic pressure surface of 0 kPa. In model S1, a subdued replica of the topography, which was built on the base of hydraulic head measurements is applied as the upper hydraulic boundary condition and in model S2 vertical cross boundary flow is implemented.
Based on our results, we illustrate in the landing paper that for the Upper Rhine Graben specific characteristics of the flow field are robust and insensitive to the choice of imposed hydraulic boundary conditions, while specific local characteristics are more sensitive. Accordingly, these robust features characterizing the first order groundwater flow dynamics in the Upper Rhine Graben include: (i) a regional groundwater flow component descending from the graben shoulders to rise at its centre; (ii) infiltration of fluids across the graben shoulders, which locally rise along the main border faults; (iii) the presence of heterogeneous hydraulic potentials at the rift shoulders. The configuration of the adopted boundary conditions influence primarily calculated flow velocities and the absolute position of the upflow axis within the graben sediments. In addition, the choice of upper hydraulic boundary conditions exerts a direct control on the evolving local flow dynamics, with the degree of influence gradually decreasing with increasing depth.
With respect to regional flow modelling of basin hosted, deep water resources, the main conclusions derived from this study are: (i) the often considered water table as an exact replica of the model topography (Reference Model) likely introduces a source of error in the simulations in regional hydraulic modelling approaches. Here, we show that these errors can be minimized by making use of a water table as upper boundary condition derived from available hydraulic head measurements (model S1). If the study area is part of a supra-regional flow system - like the central Upper Rhine Graben is part of the whole Upper Rhine Graben - the in- and outflow across vertical boundaries need to be considered (model S2).
This report describes the passive seismic data acquired by the TOPASE network deployed over Rittershoffen geothermal field (Alsace, France). The monitoring period extends from March 2013 to November 2014, which includes the stimulation of the first well of the doublet, the drilling of the second well and well tests. These data were acquired using 31 Earth Data Loggers PR6-24 and MARK-SERCEL L-4C-3D 1 Hz seismometers of the Geophysical Instrument Pool Potsdam (GIPP), which were provided to the KIT-AGW-Geothermal research division.
The Alps are one of the best studied mountain ranges in the world, yet significant unknowns remain regarding their crustal structure and density distribution at depth. Previous published interpretations of crustal features within the orogen have been primarily based upon 2D seismic sections, and those that do integrate multiple geo-scientific datasets in 3D, have either focused on smaller sub-sections of the Alps or included the Alps, in low resolution, as part of a much larger study area. Therefore the generation of a 3D, crustal scale, gravity constrained, structural model of the Alps and their forelands at an appropriate resolution has been created here to more accurately describe crustal heterogeneity in the region. The study area of this work focuses on a region of 660 km x 620 km covering the vast majority of the Alps and their forelands are included, with the Central and Eastern Alps and the northern foreland being the best covered regions.Surface GenerationAll referenced data was integrated to constrain sub-surface lithospheric features including: previous regional scale gravitationally and seismically constrained models of the TRANSALP study area, the Upper Rhine Graben, the Mollasse Basin and the Po Basin; continental scale integrative best fit models (EuCRUST-07 and EPcrust); and seismic reflection depths from numerous published deep seismic surveys (e.g. ALP’75, EGT’86, ALP 2002 and EASI). The software package Petrel was used for the creation and visualisation of the modelled surfaces in 3D, representing the key structural and density contrasts within the region. All surfaces were generated with a grid resolution of 20 km x 20 km using Petrel’s convergent interpolation algorithm. During interpolation, a hierarchy of data source types was used in the case of contradiction between the different data sources and was as follows: 1. regional scale, gravitationally and seismically constrained models; 2. regional scale, seismically constrained models; 3. individual seismic reflection surfaces and interpreted sections; 4. continental scale, seismically constrained, integrative best fit models. No subduction interfaces were modelled. Topography and bathymetry were taken from ETOPO1 and the LAB from Geissler (2010).Gravity ModellingThe generated surfaces and the calculated free-air anomaly from the global gravity model EIGEN-6C4, at a fixed height of 6 km above the datum were used in the 3D gravity modelling software IGMAS+ for the constrained of lithospheric density distribution. The layers of the generated model were split laterally into domains of different density, to reflect the heterogeneous nature of the crust within the region. Densities used in the initial structural model were derived from empirical P wave velocity to density conversions (Brocher, 2005) from the input seismic data sources. The densities were then modified, through multiple iterations, until the resulting model produced a gravity field within ± 25 mGal of the observed one. Surfaces generated as part of the integration work were not modified.FilesThe surface depths, thicknesses and densities of the model can be found as tab separated text files for each individual layer of the model (Unconsolidated Sediments, Consolidated Sediments, Upper Crust, Lower Crust and Lithospheric Mantle). The columns in each file are identical: the Easting is given in the “X COORD (UTM Zone 32N)”, Northing in the “Y COORD (UTM Zone 32N)”, the top surface depth of each layer is given as TOP (m.a.s.l), the thickness of each layer is given as THICKNESS (m), and the bulk density of that layer is given as DENSITY (Kg/m^3).
We present a 3-D lithospheric-scale model covering the area of Germany that images the regional structural configuration. The model comprises 31 lithostratigraphic units: seawater, 14 sedimentary units, 14 crystalline crustal units and 2 lithospheric mantle units. The corresponding surfaces are integrated from previous studies of the Central European Basin System, the Upper Rhine Graben and the Molasse Basin, together with published geological and geophysical data. The model is a result of a combined workflow consisting of 3-D structural, gravity and thermal modelling applied to derive the 3-D thermal configuration.The top surface elevations and thicknesses of corresponding layers of the 3-D-D model are provided as ASCII files, one for each individual layer of the model. The columns in each file are identical: the Easting is given in the “X COORD (UTM Zone 32N)”, the Northing is in the “Y COORD (UTM Zone 32N)”, the top surface elevation of each layer is given as "TOP (m.a.s.l)", the thickness of each layer is given as "THICKNESS (m)".