1,720,972 research outputs found
Inferring the lithospheric thermal structure from satellite gravimetry
Full text linkThis doctoral dissertation is aimed at obtaining regional surface heat flow estimates on stable continental lithosphere from satellite-derived global models of the Earth static gravity field, using variations in crustal thickness as a gravity-derived thermal constraint. The heat transported across the Earth surface, arising from its cooling interiors, senses a wide assortment of phenomena, from near-surface paleoclimatic perturbations to the driving forces of plate tectonics and mantle dynamics. Surface heat flow (SHF) is sensed with borehole measurements of temperature and conductivity - this implies that it is a costly observable, highly depending on logistic and financial constraints, on previous exploration interest and on availability of data. Different components superimpose on the SHF signal: over continents, at regional scales, most of the static signal can be explained by a partition between a basal flow through the crust-mantle boundary and the contribution of radioactive heat production (RHP). The generation of continental crust through magmatic differentiation significantly enriched it with radioactive elements. The indirect estimation of their concentration is a non trivial task, since it does not directly affect petrophysical quantities by a significant amount. However, other processes concur in affecting sensible quantities: empirical relationships from velocity and density to heat production have developed and tested satisfactorily. In addition, multi-observable modelling is regularly employed to improve the understanding on the subsurface distribution of temperature and thermal parameters. The gravity field is particularly sensitive to variations in crustal thickness, arising from the significant density contrast at the Moho. Compared with the problematically sampled SHF, gravity data benefits from a more uniform coverage. While terrestrial data still suffers from data availability issues, models derived from satellite gravimetry missions provide an unprecedented spatial homogeneity. The global gravity models derived from the European Space Agency GOCE mission provide a ppm-level accuracy for g with a resolution of about 70 km at the Earth surface. These models have already shown promising results in global crustal thickness modelling. This basis provided the motivation to assess how satellite gravity data could contribute to thermal modelling. I devise and test a strategy to constrain the crustal RHP using a gravity-derived Moho and the available heat flow data, with the aim of overcoming the issues with SHF interpolation over no-data areas. The strategy is supported by a 3D finite-difference based thermal forward model, developed ad-hoc for the project, and a gravity data reduction strategy, to isolate the Moho undulation signal. It is supported by a global reduction modelling scheme which includes a Monte Carlo error propagation of model uncertainties, complemented by a series of validation tests against spatial-domain forward modelling of test mass distributions. The tested strategy, albeit relying on a simplified uniform model of error distribution, proved fit for purpose at the target resolution (maximum degree and order of 300, aimed at data reduction of satellite-only models) and may be easily scaled. An application test in Central-Eastern Europe is presented in the last chapter. It integrates data from a satellite-only GGM, reductions with a mixed spatial- and spectral-domain modelling scheme, and heat flow measurements. It resulted in a 3D lithospheric model of temperature and thermal parameters, fitting available data and providing added information respect to the structure of the lithosphere. The modelled thermal regime is coherent with what geological inference expects and with other models of the area, keeping into account the limitations of a method which relies on as little a-priori data as possible, by design. The gravity-derived Moho is benchmarked against existing crustal models in the area
An assessment of the impact of Next Generation Gravity Missions on earthquake signal retrieval. Constructing a database of time-varying co-seismic and post-seismic gravity change and a detectability assessment strategy
No full textAdvancements in mission concepts and instrumentation, such as those investigated under the Mass change And Geosciences International Constellation (MAGIC), could enable significant enhancements in the spatial and temporal resolution of gravity field products. Closed-loop simulations of these new constellations of instruments estimate radical improvements in the error budget in the retrieval of geophysical signals, including those arising from mass movement in the solid Earth – earthquakes included. The displacements caused by co-seismic dislocation and post-seismic relaxation are sensed by a broad array of seismological and geodetic techniques. Gravity has the potential of providing additional information, especially when the mass movement is a-seismic and when its surface expression occurs mostly in areas that are difficult or impossible to sense with other remote-sensing techniques (GNSS, dInSAR), such as off shore.
In order to assess by how much the improvements in MAGIC would lower the detectability threshold, we modelled a database of synthetic earthquake gravity signal, including the effect of post-seismic viscoelastic relaxation. We computed the gravity change in time using the QSSPSTATIC [1] code, set up in a way to obtain the spherical harmonics (SH) coefficients of the geopotential change through time. This data, which we then used in a detectability assessment, also allow comparing different modelling strategies and signal retrieval methods. We devised its data structure, by design, to be easily included as part of time-varying signals used in simulations, enhancing the solid-Earth component of models such as AOHIS [2].
We test detectability in terms of the SH-domain SNR between the earthquake signal and the gravity model errors. The SH coefficients of both quantities undergo a spatio-spectral localization procedure [3] and are compared in terms of their localized degree variances. We show how a spatial-scale dependent analysis, such as the one that a spectral-domain method allows, is needed to fully exploit the signal in the optimal range of spatial wavelengths owing to the coloured spectra of signal and noise. We perform a parametric study of the effect on detectability of moment magnitude, source parameters (focal mechanism, depth), and rheological profiles – with magnitude being the first-order predictor of detectability in co- and post-seismic signals. As a methodological test, we also present an experiment on the signal omission arising from approximating an earthquake dislocation as a point-source, comparing its signal to the one we can obtain using a finite fault solution of a real event instead. We assess and discuss the impact of a simpler model on the trade-space between the precision of a detectability assessment and the added computational effort.
References
[1] Wang et al., 2017 DOI:10.1093/gji/ggx259
[3] Dobslaw et al., 2015 DOI:10.1007/s00190-014-0787-8
[2] Wieczorek and Simons, 2005 DOI:10.1111/j.1365-246X.2005.02687.
Detecting the co-seismic and post-seismic gravity signal of large thrust earthquakes with Quantum Space Gravimetry mission concepts
No full textCo-seismic dislocation and post-seismic relaxation are mass transport processes that can be sensed by a broad array of seismological and/or geodetic techniques. Gravity observations through time have the potential of improving the amount of available information on these processes, especially when the dislocation is a-seismic and when its surface expression occurs mostly in areas that are difficult or impossible to sense with space geodesy (such as GNSS, DInSAR), as is the case for off shore areas. New mission concepts, such as those proposed for the Mass change And Geosciences International Constellation (MAGIC), have been recently assessed as capable of providing significant enhancements in the spatial and temporal resolution of gravity field products, resulting in turn in unprecedented impact on the scientific applications, including earthquake gravimetry [1]. The evolution of sensors beyond classic electrostatic accelerometers, such as future applications of Cold Atom Interferometry (CAI) on space borne platforms, has the potential to allow further steps forward in sensing the mass transport in the Earth’s system.
In this context, we aim at assessing the impact of Quantum Space Gravimetry (QSG) to earthquake detectability, by modelling a database of synthetic earthquake gravity signal, including the effect of post-seismic viscoelastic relaxation, and setting up a strategy do assess their detectability in simulated time-varying gravity field products. We compute the gravity change in time using the QSSPSTATIC [2] code and a workflow we developed to obtain the spherical harmonics (SH) expansion of the geopotential change through time. We designed the structure of this synthetic earthquake data to be easily included as part of time-varying signals used in simulations, improving the solid-Earth component of models such as AOHIS [3]. In this contribution we present the detection threshold of different events, real earthquakes ranging from Mw 9.2 to 7.6 with an assortment of depths, locations and focal mechanisms, using an SNR assessment in the spectral domain, between the modelled signal and retrieval errors (residuals) obtained from mission simulations.
This work is supported by the ESA QSG4EMT study, a collaboration between Technical University of Munich, Politecnico di Milano, Delft University of Technology, HafenCity University Hamburg, University of Bonn and University of Trieste.
[1] Daras I., March G., Pail R., Hughes C. W., Braitenberg C., Güntner A., Eicker A., Wouters B., Heller-Kaikov B., Pivetta T., & Pastorutti, A. (2023). Mass-change And Geosciences International Constellation (MAGIC) expected impact on science and applications. Geophysical Journal International, 1288–1308. https://doi.org/10.1093/gji/ggad472
[2] Wang, R., Heimann, S., Zhang, Y., Wang, H., & Dahm, T. (2017). Complete synthetic seismograms based on a spherical self-gravitating Earth model with an atmosphere-ocean-mantle-core structure. Geophysical Journal International, 210(3), 1739–1764. https://doi.org/10.1093/gji/ggx259
[3] Dobslaw, H., Bergmann-Wolf, I., Dill, R., Forootan, E., Klemann, V., Kusche, J., & Sasgen, I. (2015). The updated ESA Earth System Model for future gravity mission simulation studies. Journal of Geodesy, 89(5), 505–513. https://doi.org/10.1007/s00190-014-0787-
Geothermal estimates from GOCE data alone: assessment of feasibility and first results
No full textThe characteristics of the available global gravity models derived from satellite gravity suggest that they could be
applied in modelling the downward continuation of the temperature field at a continental scale.
To obtain this, we quantified how and to which extent the mass distribution that we can obtain from inverse modelling
of gravity can be linked to the factors affecting the temperature field, such as the radiogenic heat production
and the thermal conductivity of rocks.
Since there is no direct physical law linking the two fields, we resort to a reference lithosphere, built up on a set of
lithological parameters –including their associated uncertainties.
A central and most critical assumption is that the crustal heat production can be tied to crustal thickness, a relationship
which strength shows extreme variability in different geodynamic domains. We take this into account,
including it as a parameter uncertainty and propagating it to the results.
Pursuing the search for a reliable method to isolate the component of the heat flow due to the crustal heat production
from the available measurements, we test this framework on the go_cons_gcf_2_tim_r5 release of the
GOCE-derived field.
We so obtain a satisfactory distinction between different heat transport domains (dominated by heat production,
conduction from the mantle, or shallow plays), which proved helpful in interpolating regional heat flow maps at
the resolution of the gravity data (about 140 km)
Parameter sensitivity in satellite-gravity-constrained geothermal modelling
No full textThe use of satellite gravity data in thermal structure estimates require identifying the factors that affect the gravity
field and are related to the thermal characteristics of the lithosphere.
We propose a set of forward-modelled synthetics, investigating the model response in terms of heat flow, temperature,
and gravity effect at satellite altitude. The sensitivity analysis concerns the parameters involved, as heat
production, thermal conductivity, density and their temperature dependence.
We discuss the effect of the horizontal smoothing due to heat conduction, the superposition of the bulk thermal
effect of near-surface processes (e.g. advection in ground-water and permeable faults, paleoclimatic effects,
blanketing by sediments), and the out-of equilibrium conditions due to tectonic transients. All of them have the
potential to distort the gravity-derived estimates.We find that the temperature-conductivity relationship has a small
effect with respect to other parameter uncertainties on the modelled temperature depth variation, surface heat flow,
thermal lithosphere thickness.
We conclude that the global gravity is useful for geothermal studies
La gravimetria da satellite come vincolo nelle stime di flusso di calore : primi risultati
No full textUn confronto tra modelli globali di gravità (quali quelli ottenuti dai dati del satellite GOCE) e mappe di flusso di calore in superficie -due osservabili geofisiche non legate da semplici leggi- suggerisce un legame tra anomalia di Bouguer e diversi regimi di trasporto del calore.
In un quadro finalizzato a valutare quanto sia possibile quantificare in maniera rigorosa tale relazione, abbiamo verificato come un semplice modello in cui valga una relazione diretta spessore crostale - produzione radiogenica di calore in crosta continentale possa essere utilizzato per stimare la componente di flusso sub-continentale.
A causa dei vincoli logistici ed economici associati alle misure dirette del flusso di calore, la distribuzione di queste non è omogenea: in particolare è presente un bias verso i flussi elevati, associato all'interesse per lo sfruttamento della risorsa geotermica ad alta entalpia. Persistono aree prive di misure anche in zone non remote dell'Europa centro-occidentale. Compensare questi vuoti d'informazione tramite interpolazione può comportare la sovrastima dell'estensione delle zone ad alto flusso.
Una possibile strategia per ovviare a ciò è la separazione tra componenti di flusso a diverse profondità, con l'obiettivo di isolare le componenti più profonde (rappresentate dal flusso attraverso la base della crosta), alla quale sono associate lunghezze caratteristiche delle anomalie termiche misurate in superficie maggiori rispetto a quelle dovute a strutture più localizzate.
Otteniamo questo tramite una strategia di backstripping, stimando la componente crostale del flusso con la profondità di due interfacce crostali, usate come fattore di scala, ottenute tramite inversione del dato di gravità. Il risultato è una mappa di flusso a scala regionale (risoluzione di circa 100 km), che presentiamo in un area studio (includente Alpi e bacini adiacenti, massiccio renano, Graben del Reno), confrontandola col risultato di un'interpolazione non vincolata. Questo prodotto, meno suscettibile all'influenza di fenomeni locali, ha permesso di isolare i fattori e le criticità su cui andrà indirizzata una più sofisticata modellazione
Innovative solid Earth applications of future gravity field missions
No full textThe upcoming gravity missions anticipated in the next decade are expected to significantly reduce noise levels compared to current data acquisitions from GRACE and GRACE Follow On. Our objective is to proactively prepare for these future datasets and develop scientific processing tools that can yield innovative applications in solid earth research. These applications have the potential to evolve into community-relevant ser-vices for earth monitoring and exploration.
We specifically focus on key categories such as earthquakes, crustal uplift and subsidence, seamounts, and lithospheric structure. Accurately estimating the gravity field necessitates the formulation of realistic 3D models of density and their temporal changes.
Uplift and subsidence is considered for the Alpine mountain arc, where a lithosphere density model has been formulated (Tadiello & Braitenberg, 2021) imposing vertical movements from measured GNSS rates. The exploration of the lithosphere is tested on a recent 3D density model of Iran (Maurizio et al., 2023) which was inverted from the presently available gravity field integrated with a seismic tomography model. We distinguish crustal and mantle signals and evaluate prospective improvements to detect structures in crust and mantle.
In the context of earthquakes, our focus lies in improving the minimum detectable magnitude, depending on fault plane mechanisms, and detecting post-seismic relaxation. Seamounts pose a unique challenge with limited alternatives for detection, placing gravity detection in a primary role, provided the associated mass changes are sufficiently significant. Therefore, we conduct a review of documented seamount eruptions, estimating the associated mass changes. Particularly intriguing are 'silent' seamounts that grow several hundred meters high without breaking the ocean surface, remaining invisible.
We compare the signals against noise levels of the future gravity missions, including the polar and inclined satellite couples with inter satellite distance measurement, the MAGIC proposal (Daras et al., 2024) and proposals with the payload of quantum technology gradiometers presently under discussion at ESA and NASA.
References
Daras, I., March, G., Pail, R., Hughes, C. W., Braitenberg, C., Güntner, A., Eicker, A., Wouters, B., Heller-Kaikov, B., Pivetta, T., & Pastorutti, A. (2024). Mass-change And Geosciences International Constellation (MAGIC) expected impact on science and applications. Geophysical Journal International, 236(3), 1288–1308. https://doi.org/10.1093/gji/ggad472
Maurizio, G., Braitenberg, C., Sampietro, D., & Capponi, M. (2023). A New Lithospheric Density and Magnetic Susceptibility Model of Iran, Starting From High‐Resolution Seismic Tomography. Journal of Geophysical Research: Solid Earth, 128(12), e2023JB027383. https://doi.org/10.1029/2023JB027383
Tadiello, D., & Braitenberg, C. (2021). Gravity modeling of the Alpine lithosphere affected by magmatism based on seismic tomography. Solid Earth, 12(2), 539–561. https://doi.org/10.5194/se-12-539-202
Detection limit to Earthquakes and seamounts of Quantum gravimeter payload combined with satellite-satellite tracking from single GRACE type to multiple couples constellations
No full textAdvancements in space-based gravity observation are poised to undergo a significant
transformation in the coming years, propelled by innovations such as the MAGIC constellation,
featuring a single polar pair GRACE-C, and the enhanced ESA’s NGGM inclined
pair, boasting lower orbit altitudes and drag compensation capabilities. This trajectory is
further bolstered by the potential integration of augmented satellite constellations equipped
with absolute accelerometers utilizing Cold Atom Interferometer technologies. These developments
promise lower spectral noise curves, thereby enabling higher time resolution and a
superior spatial resolution compared to current standards set by GRACE-FO.
Our exploration extends to pioneering applications within the domain of solid earth sciences,
encompassing seismic events, seamount formations, vertical topographic shifts, and
fluid reservoir dynamics, all of which stand to benefit from the forthcoming advancements
in gravity observation from space. While phenomena linked to the earthquake cycle and
postseismic fault movements are effectively monitored on land through SAR and GPS, their
observation in remote oceanic regions remains challenging due to the absence of seismic
waves generated by slow fault movements. We delineate the observable magnitude limits
contingent upon fault mechanisms, depths, and satellite constellations.
Similarly, the detection of seamounts, particularly in remote areas where they may silently
grow, altering underwater bathymetry in uncharted ways, presents a formidable task that
could potentially be addressed through future spaceborne gravity observations (Braitenberg
and Pastorutti, 2024). The vertical topographic movement is documented by GPS and SAR,
leading to a mass change which we compare to competing mass changes as the hydrologic
and glacial mass loss in the Alps and to the detectability levels of the future satellite constellations.
We finally show that in future the isolated gravity signals for the tectonic movements are
complementary to data used in the Copernicus Services of a) Disaster Management and b)
Climate Change Monitoring and are prone to improve the completeness of these Services
GOCE and future gravity missions for geothermal energy exploitation
No full textGeothermal energy is a valuable renewable energy source the exploitation of which contributes to the worldwide reduction of consumption of fossil fuels oil and gas. The exploitation of geothermal energy is facilitated where the thermal gradient is higher than average leading to increased surface heat flow. Apart from the hydrologic circulation properties which depend on rock fractures and are important due to the heat transportation from the hotter layers to the surface, essential properties that increase the thermal gradient are crustal thinning and radiogenic heat producing rocks. Crustal thickness and rock composition form the link to the exploration with the satellite derived gravity field, because both induce subsurface mass changes that generate observable gravity anomalies. The recognition of gravity as a useful investigation tool for geothermal energy lead to a cooperation with ESA and the International Renewable Energy Agency (IRENA) that included the GOCE derived gravity field in the online geothermal energy investigation tool of the IRENA database. The relation between the gravity field products as the free air gravity anomaly, the Bouguer and isostatic anomalies and the heat flow values is though not straightforward and has not a unique relationship. It is complicated by the fact that it depends on the geodynamical context, on the geologic context and the age of the crustal rocks. Globally the geological context and geodynamical history of an area is known close to everywhere, so that a specific known relationship between gravity and geothermal potential can be applied. In this study we show the results of a systematic analysis of the problem, including some simulations of the key factors. The study relies on the data of GOCE and the resolution and accuracy of this satellite. We also give conclusions on the improved exploration power of a gravity mission with higher spatial resolution and reduced data error, as could be achieved in principle by flying an atom interferometer sensor on board a satellite
The Ross Sea formation: enquiring the sensitivity of basin architecture to prior conditions, with numerical models and a parameter search
No full textThe basins composing the 1000-km wide West Antarctica Rift System (WARS), derived from extensional dynamics lasting from the Cretaceous to the Middle Neogene, bear evidence of a peculiar evolution through time: a transition from a diffuse to a localized thinning style and a migration of the focus of deformation, which likely progressed towards the cratonic domains of West Antarctica. Using the current observations, we aim at identifying which inherited starting conditions [1] result in outcomes compatible with the present-time structures and which do not allow so, unless other factors are accounted for.
To this aim, we turn to an extensive grid search in the parameter space, running a large number of forward numerical models to cover the possible permutations of parameters under test. We use the open source Underworld2 code [2] with a simplified scheme of starting conditions and kinematics boundaries, for lithospheric-scale 2-D thermomechanical models. We analyse the results obtained by changing a great number of parameters, including initial geometries of the crust and lithosphere, different rheologies, inherited structures, such as strain-weakening scars and thermal remnants of slabs.
We identify that a high crustal thickness (more than 45 km) is required to accommodate the first rifting phase (170 km ca. of cumulated extension, [3]) without producing crustal necking and eventual ocean formation. Parameters that favour a weaker strength profile, chiefly temperature (due to a thicker crust and/or a shallow lithosphere-asthenosphere boundary), are also required to avoid an early transition to localized deformation, in agreement with previous studies [4]. Smaller scale features, such as partition in multiple sub-basins, require additional factors, such as inherited weak-zone seeds (“scars”) in the crust and mantle, which are likely remnants of previous compressive phases [5].
[1] Perron, P., Le Pourhiet, L., Guiraud, M., Vennin, E., Moretti, I., Portier, É., & Konaté, M. (2021). Control of inherited accreted lithospheric heterogeneity on the architecture and the low, long-term subsidence rate of intracratonic basins. BSGF - Earth Sciences Bulletin, 192. https://doi.org/10.1051/bsgf/2020038
[2] Mansour, J., Giordani, J., Moresi, L., Beucher, R., Kaluza, O., Velic, M., Farrington, R., Quenette, S., & Beall, A. (2020). Underworld2: Python Geodynamics Modelling for Desktop, HPC and Cloud. Journal of Open Source Software, 5(47), 1797. https://doi.org/10.21105/joss.01797
[3] Brancolini, G., Busetti, M., Coren, F., De Cillia, C., Marchetti, M., De Santis, L., Zanolla, C., Cooper, A.K., Cochrane, G.R., Zayatz, I., Belyaev, V., Knyazev, M., Vinnikovskaya, O., Davey, F.J., Hinz, K., 1995. ANTOSTRAT Project, seismic stratigraphic atlas of the Ross Sea, Antarctica. In: Cooper, A.K., Barker, P.F., Brancolini, G., (Eds.), Geology and Seismic Stratigraphy of the Antarctic Margin. Antarctic Research Series, vol. 68, https://doi.org/10.1029/AR068
[4] Huerta, A. D., & Harry, D. L. (2007). The transition from diffuse to focused extension: Modeled evolution of the West Antarctic Rift system. Earth and Planetary Science Letters, 255(1–2), 133–147. https://doi.org/10.1016/j.epsl.2006.12.011
[5] Talarico, F., Ghezzo, C., & Kleinschmidt, G. (2022). The Antarctic Continent in Gondwana: a perspective from the Ross Embayment and Potential Research Targets for Future Investigations. In Antarctic Climate Evolution (pp. 219–296). Elsevier. https://doi.org/10.1016/B978-0-12-819109-5.00004-
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