TY - JOUR A1 - Degen, Denise A1 - Spooner, Cameron A1 - Scheck-Wenderoth, Magdalena A1 - Cacace, Mauro T1 - How biased are our models? BT - a case study of the alpine region JF - Geoscientific model development : an interactive open access journal of the European Geosciences Union N2 - Geophysical process simulations play a crucial role in the understanding of the subsurface. This understanding is required to provide, for instance, clean energy sources such as geothermal energy. However, the calibration and validation of the physical models heavily rely on state measurements such as temperature. In this work, we demonstrate that focusing analyses purely on measurements introduces a high bias. This is illustrated through global sensitivity studies. The extensive exploration of the parameter space becomes feasible through the construction of suitable surrogate models via the reduced basis method, where the bias is found to result from very unequal data distribution. We propose schemes to compensate for parts of this bias. However, the bias cannot be entirely compensated. Therefore, we demonstrate the consequences of this bias with the example of a model calibration. Y1 - 2021 U6 - https://doi.org/10.5194/gmd-14-7133-2021 SN - 1991-959X SN - 1991-9603 VL - 14 IS - 11 SP - 7133 EP - 7153 PB - Copernicus CY - Göttingen ER - TY - THES A1 - Spooner, Cameron T1 - How does lithospheric configuration relate to deformation in the Alpine region? T1 - Was ist der Zusammenhang zwischen der lithosphärischen Zusammensetzung der Alpen, ihrer Vorländer und deren Deformation? N2 - Forming as a result of the collision between the Adriatic and European plates, the Alpine orogen exhibits significant lithospheric heterogeneity due to the long history of interplay between these plates, other continental and oceanic blocks in the region, and inherited features from preceeding orogenies. This implies that the thermal and rheological configuration of the lithosphere also varies significantly throughout the region. Lithology and temperature/pressure conditions exert a first order control on rock strength, principally via thermally activated creep deformation and on the distribution at depth of the brittle-ductile transition zone, which can be regarded as the lower bound to the seismogenic zone. Therefore, they influence the spatial distribution of seismicity within a lithospheric plate. In light of this, accurately constrained geophysical models of the heterogeneous Alpine lithospheric configuration, are crucial in describing regional deformation patterns. However, despite the amount of research focussing on the area, different hypotheses still exist regarding the present-day lithospheric state and how it might relate to the present-day seismicity distribution. This dissertaion seeks to constrain the Alpine lithospheric configuration through a fully 3D integrated modelling workflow, that utilises multiple geophysical techniques and integrates from all available data sources. The aim is therefore to shed light on how lithospheric heterogeneity may play a role in influencing the heterogeneous patterns of seismicity distribution observed within the region. This was accomplished through the generation of: (i) 3D seismically constrained, structural and density models of the lithosphere, that were adjusted to match the observed gravity field; (ii) 3D models of the lithospheric steady state thermal field, that were adjusted to match observed wellbore temperatures; and (iii) 3D rheological models of long term lithospheric strength, with the results of each step used as input for the following steps. Results indicate that the highest strength within the crust (~ 1 GPa) and upper mantle (> 2 GPa), are shown to occur at temperatures characteristic for specific phase transitions (more felsic crust: 200 – 400 °C; more mafic crust and upper lithospheric mantle: ~600 °C) with almost all seismicity occurring in these regions. However, inherited lithospheric heterogeneity was found to significantly influence this, with seismicity in the thinner and more mafic Adriatic crust (~22.5 km, 2800 kg m−3, 1.30E-06 W m-3) occuring to higher temperatures (~600 °C) than in the thicker and more felsic European crust (~27.5 km, 2750 kg m−3, 1.3–2.6E-06 W m-3, ~450 °C). Correlation between seismicity in the orogen forelands and lithospheric strength, also show different trends, reflecting their different tectonic settings. As such, events in the plate boundary setting of the southern foreland correlate with the integrated lithospheric strength, occurring mainly in the weaker lithosphere surrounding the strong Adriatic indenter. Events in the intraplate setting of the northern foreland, instead correlate with crustal strength, mainly occurring in the weaker and warmer crust beneath the Upper Rhine Graben. Therefore, not only do the findings presented in this work represent a state of the art understanding of the lithospheric configuration beneath the Alps and their forelands, but also a significant improvement on the features known to significantly influence the occurrence of seismicity within the region. This highlights the importance of considering lithospheric state in regards to explaining observed patterns of deformation. N2 - Als Resultat der Kollision zwischen der Adriatischen und Europäischen Platte ist das Alpenorogen durch eine ausgeprägte Heterogenität der Lithosphäreneigenschaften gekennzeichnet, die auf die Geschichte der beiden Platten, ihre Interaktion, Wechselwirkungen mit anderen kontinentalen und ozeanischen Blöcken der Region und strukturell vererbte Merkmale aus früheren Orogenesen zurückzuführen sind. Entsprechend ist zu erwarten, dass die thermische und rheologische Konfiguration der Lithosphäre ebenfalls grundlegend innerhalb der Region variiert. Lithologie und Temperatur-/Druckbedingungen steuern maßgeblich die Festigkeit der Lithosphäre indem thermisch aktiviertes Kriechen die Tiefenlage der spröd-duktilen Übergangszone – die sogenannte brittle-ductile transition (BDT) bestimmt. Diese Tiefenlage kann als untere Grenze der seismogenen Zone betrachtet werden kann, weshalb sie die räumliche Verteilung der Seismizität in der Lithosphärenplatte entscheidend beeinflusst. Trotz der langjährigen und umfangreichen Forschung zur Dynamik und Struktur der Alpen gibt es immer noch verschiedene Hypothesen zum heutigen physikalischen Zustand des Systems und dazu, wie dieser mit der Verteilung und dem Auftreten von Seismizität zusammenhängt. Diese Dissertation hat das Ziel, die Lithosphärenkonfiguration der Alpen zu beschreiben und Zusammenhänge zwischen der Verteilung lithosphärischer Eigenschaften und Deformation, insbesondere der Verteilung der Seismizität abzuleiten. Dies wird durch einen integrierten Modellierungsansatz erreicht, mit dem verfügbare geophysikalische Beobachtungen in 3D Modellen zusammengeführt werden, die die heterogene lithosphärische Konfiguration abbilden. Dazu wird (1) ein mit geologischen, seismischen und gravimetrischen Daten konsistentes 3D-Dichtemodell erzeugt und genutzt, um Lithologien abzuleiten, (2) deren Konsequenzen für das dreidimensionale stationäre thermische Feld zu berechnen und, basierend darauf, schließlich (3) die räumliche Variation der Lithosphärenrheologie zu bestimmen. Diese räumliche Variation der rheologischen Eigenschaften wurde schließlich in Beziehung zur Verteilung der auftretenden Seismizität gesetzt. Die Ergebnisse zeigen, dass die größte Festigkeit innerhalb der Kruste (~1 GPa) und im oberen Mantel (> 2 GPa) oberhalb der Bereiche auftritt, wo Temperaturbedingte Phasenübergänge zu erwarten sind. Für die felsische Kruste umfasst dies den Temperaturbereich bis etwa 400° C, für die mafische Kruste und den lithospärischen Mantel bis etwa 600°, wobei Seismizität jeweils oberhalb dieser Temperaturen auftritt. Zusätzlich wurden Hinweise gefunden, dass diese Festigkeitsverteilung auf vererbte Lithosphäreneigenschaften zurückzuführen ist: so tritt seismische Aktivität in der dünneren und mafischen Adria Kruste (~22,5 km, 2.800 kg m-3, 1.30E -06 W m-3) bei höheren Temperatur (~600° C) auf als in der dickeren und eher felsischen europäischen Kruste (~27.5 km, 2750 kg m−3, 1.3–2.6E-06 W m-3, ~450 °C). Die Beziehung zwischen seismischer Aktivität und Lithosphärenfestigkeit im Bereich der Vorländer zeigt ebenfalls unterschiedliche Trends, die verschiedenene tektonische Randbedingungen wiederspiegeln. Während im Plattenrandsetting des südlichen Vorlands Seismizität in der rheologisch weicheren Lithosphäre in der Umrandung des adriatischen Indentors auftritt, korreliert die auftretende Seismizität im Intraplattensetting des nördlichen Vorlands räumlich mit wärmeren und rheologisch schwächeren Domänen im Bereich des Oberrheingrabens. Somit liefern die Ergebnisse in dieser Arbeit nicht nur ein verbessertes Verständnis der Lithosphärenkonfiguration der Alpen und ihrer Vorländer , sondern auch einen bedeutenden Fortschritt dazu, welche Faktoren Seismizität innerhalb der Region beeinflussen können. Sie zeigen, dass es wichtig ist, die Lithosphärenkonfiguration zu kennen und sie zur auftretenden Deformation in Beziehung zu setzen. KW - Gravity KW - Thermal KW - Rheology KW - Model KW - Alps KW - Alpen KW - Schwerkraft KW - Modell KW - Rheologie KW - Thermisch Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516442 ER - TY - JOUR A1 - Spooner, Cameron A1 - Scheck-Wenderoth, Magdalena A1 - Cacace, Mauro A1 - Anikiev, Denis T1 - How Alpine seismicity relates to lithospheric strength JF - International journal of earth sciences N2 - Despite the amount of research focussed on the Alpine orogen, different hypotheses still exist regarding varying spatial seismicity distribution patterns throughout the region. Previous measurement-constrained regional 3D models of lithospheric density distribution and thermal field facilitate the generation of a data-based rheological model of the region. In this study, we compute the long-term lithospheric strength and compare its spatial variation to observed seismicity patterns. We demonstrate how strength maxima within the crust (similar to 1 GPa) and upper mantle (> 2 GPa) occur at temperatures characteristic of the onset of crystal plasticity in those rocks (crust: 200-400 degrees C; mantle: similar to 600 degrees C), with almost all seismicity occurring in these regions. Correlation in the northern and southern forelands between crustal and lithospheric strengths and seismicity show different patterns of event distribution, reflecting their different tectonic settings. Seismicity in the plate boundary setting of the southern foreland corresponds to the integrated lithospheric strength, occurring mainly in the weaker domains surrounding the strong Adriatic plate. In the intraplate setting of the northern foreland, seismicity correlates to modelled crustal strength, and it mainly occurs in the weaker and warmer crust beneath the Upper Rhine Graben. We, therefore, suggest that seismicity in the upper crust is linked to weak crustal domains, which are more prone to localise deformation promoting failure and, depending on the local properties of the fault, earthquakes at relatively lower levels of accumulated stress than their neighbouring stronger counterparts. Upper mantle seismicity at depths greater than modelled brittle conditions, can be either explained by embrittlement of the mantle due to grain-size sensitive deformation within domains of active or recent slab cooling, or by dissipative weakening mechanisms, such as thermal runaway from shear heating and/or dehydration reactions within an overly ductile mantle. Results generated in this study are available for open access use to further discussions on the region. KW - lithosphere KW - strength KW - rheology KW - 3D-Model KW - Alps KW - seismicity Y1 - 2022 U6 - https://doi.org/10.1007/s00531-022-02174-5 SN - 1437-3254 SN - 1437-3262 VL - 111 IS - 4 SP - 1201 EP - 1221 PB - Springer CY - Berlin ; Heidelberg ER - TY - JOUR A1 - Spooner, Cameron A1 - Scheck-Wenderoth, Magdalena A1 - Cacace, Mauro A1 - Götze, Hans-Jürgen A1 - Luijendijk, Elco T1 - The 3D thermal field across the Alpine orogen and its forelands and the relation to seismicity JF - Global and planetary change N2 - Temperature exerts a first order control on rock strength, principally via thermally activated creep deformation and on the distribution at depth of the brittle-ductile transition zone. The latter can be regarded as the lower bound to the seismogenic zone, thereby controlling the spatial distribution of seismicity within a lithospheric plate. As such, models of the crustal thermal field are important to understand the localisation of seismicity. Here we relate results from 3D simulations of the steady state thermal field of the Alpine orogen and its forelands to the distribution of seismicity in this seismically active area of Central Europe. The model takes into account how the crustal heterogeneity of the region effects thermal properties and is validated with a dataset of wellbore temperatures. We find that the Adriatic crust appears more mafic, through its radiogenic heat values (1.30E-06 W/m3) and maximum temperature of seismicity (600 degrees C), than the European crust (1.3-2.6E-06 W/m3 and 450 degrees C). We also show that at depths of < 10 km the thermal field is largely controlled by sedimentary blanketing or topographic effects, whilst the deeper temperature field is primarily controlled by the LAB topology and the distribution and parameterization of radiogenic heat sources within the upper crust. KW - steady-state KW - thermal-field KW - Europe KW - Alps KW - Adria KW - seismicity Y1 - 2020 U6 - https://doi.org/10.1016/j.gloplacha.2020.103288 SN - 0921-8181 SN - 1872-6364 VL - 193 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Spooner, Cameron A1 - Scheck-Wenderoth, Magdalena A1 - Götze, Hans-Jürgen A1 - Ebbing, Jörg A1 - Hetenyi, Gyoergy T1 - Density distribution across the Alpine lithosphere constrained by 3-D gravity modelling and relation to seismicity and deformation JF - Solid earth N2 - The Alpine orogen formed as a result of the collision between the Adriatic and European plates. Significant crustal heterogeneity exists within the region due to the long history of interplay between these plates, other continental and oceanic blocks in the region, and inherited crustal features from earlier orogenies. Deformation relating to the collision continues to the present day. Here, a seismically constrained, 3-D structural and density model of the lithosphere of the Alps and their respective forelands, derived from integrating numerous geoscientific datasets, was adjusted to match the observed gravity field. It is shown that the distribution of seismicity and deformation within the region correlates well to thickness and density changes within the crust, and that the present-day Adriatic crust is both thinner and denser (22.5 km, 2800 kg m(-3) ) than the European crust (27.5 km, 2750 kg m(-3)). Alpine crust derived from each respective plate is found to show the same trend, with zones of Adriatic provenance (Austro-Alpine unit and Southern Alps) found to be denser and those of European provenance (Helvetic zone and Tauern Window) to be less dense. This suggests that the respective plates and related terranes had similar crustal properties to the present-day ones prior to orogenesis. The model generated here is available for open-access use to further discussions about the crust in the region. Y1 - 2019 U6 - https://doi.org/10.5194/se-10-2073-2019 SN - 1869-9510 SN - 1869-9529 VL - 10 IS - 6 SP - 2073 EP - 2088 PB - Copernicus CY - Göttingen ER -