Abstracted/indexed

During the COVID-19 pandemic, most countries put in place social interventions, aimed at restricting human mobility, which caused a decrease in the seismic noise, generated by human activities and called anthropogenic seismic noise. In particular, in the densely populated Eastern Sicily, we observed a decrease in the seismic amplitude reaching 50 %. We also found an impressive similarity between the patterns of this seismic noise and human mobility, as quantified by the mobile phone-derived data.

Constraining the conditions at which rocks form is crucial for understanding geologic processes. For years, the conditions under which rocks from Syros, Greece formed, have remained enigmatic; yet, these rocks are fundamental for understanding processes occurring at the interface between colliding tectonic plates (subduction zones). Here, we constrain conditions under which these rocks formed, and show they were transported to the surface adjacent to the down-going (subducting) tectonic plate.

In the Pitoa-Figuil area (Northern Cameroon), an interpretation of aeromagnetic data was conducted with an aim of investigating lineaments hidden under geological formations and proposing subsurface structures through a 2.75D modelling. A multiscale analysis combines with the 2.75D modelling has lead to put in evidence 18 faults and some intrusive bodies. According to Euler's solutions, anomaly sources go up to a depth of 5.3 km.

As a result of the collision between the European and Apulian plates, the Alps have experienced several evolutionary stages. The Penninic Frontal Thrust (PFT) (major thrust) was associated to compression and now seismic studies show ongoing extensional activity. Calcite mineralisations associated to extension and compresionnal strucures were sampled. Last deformation stage is dated by U-Pb at 4.9–2.3 Ma and isotopes analysis evidence deep crustal fluid's mobilisation.

Dynamic change of aeolian landforms and desertification under global warming is a typical problem of climate change and landscape response. In the past half century, the warming and humidification of local climate caused a potential trend of anti-desertification in the Hexi Corridor, indicating a control of climate change but not human activities. However, restriction of the decline of groundwater is the only key to preventing desertification in oasis areas of arid environment, but not climate.

We have analysed the role of deep salt layers during tectonic shortening of a group of sedimentary basins buried below the North Sea. Due to the ability of salt to flow over geological timescales, the salt layers are much weaker than the surrounding rocks during tectonic deformation. Therefore, complex structures formed mainly where salt was present in our study area. Our results align with findings from other basins and experiments, underlining the importance of salt tectonics.

Serpentinite, generated by the hydration of ultramafic rocks, is thought to be related to slow earthquakes in the mantle wedge, although its mechanism is not fully understood yet. We conducted friction experiments on brucite, one of the main minerals of serpentinite, and found that brucite exhibits low and unstable friction under the low effective normal stress condition. This result suggests that brucite can be a key for slow earthquakes in the hydrated mantle wedge.

A smooth transition toward decarbonization demands access to more minerals of critical importance. Europe has a good geology for many of these mineral deposits but at depth requiring sensitive, environmentally-friendly and cost-effective methods for their exploration. In this context, we present a sparse 3D seismic dataset that allowed identification of potential iron-oxide resources at depth and helped to characterise key geological structures as well as a historical tailing in central Sweden.

Many orogenic belts exhibit arcuate form in map view. We deal with the different models proposed to explain the formation of the Ibero-Armorican Arc in the western European Variscan Belt. We suggest this arc is primary slightly modified by superposed contraction during late Carboniferous and/or Alpine times. We discuss the role of late-Variscan regional strike-slip faults in the Iberian and in the Armorican massifs that probably acted consecutively before and during the contraction of the arc.

A proper recognition of deep, long-lived fault systems is very important for society. They can produce potentially dangerous earthquakes. They can also act as pathways for magmas and hydrothermal fluids, leading to the formation of volcanoes, geothermal systems and mineral deposits. However, the manifestations of these very old faults in the present-day surface can be very subtle. Here we present a detailed, multi-disciplinary study of a fault system of this type in the Andes of central Chile.

A mean to better understand the evolution of the South American subduction zone, the building of the Andes and the forces that control them is through numerical modelling. Here we compare results of buoyancy-driven numerical subduction models with natural observations on slab geometry and surficial velocities. The model-nature comparison provides a way to constrain model parameters, namely upper mantle rheology, subduction interface strength and slab thermal weakening, for use in future models.

Using experiments that simulate deep tectonic interfaces, known as viscous shear zones, we found that these zones spontaneously develop periodic sheets of small pores. The presence of porous layers in deep rocks undergoing tectonic deformation is significant because requires a change to the current model of how the Earth deforms. Emergent porous layers in viscous rocks will focus mineralising fluids and could lead to the seismic failure of rocks that are supposed to never have this occur.

To assess the role smaller graben structures near the southern edge of the Central European Basin System play for the basin’s overall deformational history, we take advantage of a feature found on some of these structures, where slivers from older rock units appear along the graben's main fault, surrounded on both sides by younger strata. The implications for the geometry of the fault provide a substantially improved estimate for the magnitude of normal and thrust motion along the fault system.

The success of geological storage of carbon dioxide is linked to the availability at depth of a capable reservoir and of an impermeable caprock. The sealing capacity of the caprock is a key parameter for the long-term CO₂ containment. Faults crosscutting the caprock might represent preferential pathways for CO₂ to escape. A decameter scale experiment of injection in a fault, monitored by an integrated network of multi-paramerter sensors shed light to the mobility of fluids within the fault.

In this paper we expand on a recent discovery of slow cross-diffusion hydromechanical waves cast into a new concise reaction-diffusion equation for thermo-, hydro-, mechano-, chemical coupling (THMC). We introduce the new concept of acceleration waves linking multiphysics phenomena across scales. They are also encountered in systems where quantum particles interact, such as in quantum optics.

The influence and interaction of elastic material properties (Young's modulus, Poisson's ratio), density and low frictional faults on the resulting far-field stress pattern in the Earth's crust is tested with generic models. A Young's modulus contrast can lead to a significant stress rotation. Discontinuities with low friction in homogeneous models change the stress pattern only slightly, away from the fault. In addition, active discontinuities are able to compensate stress rotation.

In partially molten regions within the earth the melt is able to move separately to the surrounding rocks. This allows for the emergence of so called solitary porosity waves, driven by compaction and decompaction due to the melt with higher buoyancy. Our numerical models can predict whether a partially molten region will ascend using this mechanism or by diapirism, depending on the size of the initial perturbation. Between these endmembers we observe porosity wave induced focusing.

The 2008 Wenchuan Earthquake (Mw 7.9) in China had never occurred since the beginning of the recorded history of the world. The continuous variation of mineral assemblages and major element contents in the fault zone was observed. Significant fuild-rock interaction occurred in the fault zone and leaded to variation of mechanism of material loss in the fault zone with time and space. This study has important significance and provides an example for investigation of coseismic fluid action.

We use 2D numerical models to highlight the role of basal drag in subduction force balance. We show that basal drag can significantly affect velocities and evolution in our simulations, and suggest an explanation to why there are no trends in plate velocities with age in the Cenozoic subduction record (which we extracted from recent reconstruction using GPlates). The insights into the role of basal drag will help setting up global models of plates dynamics or specific regional subduction models.

A multi-scale analysis of aeromagnetic data combining tilt derivative, Euler deconvolution, upward continuation and the 2.75D modelling is applied over Cameroon territory between the latitudes 5°30′–6° N and the longitudes 13°30′–14°45′ E. It emerges that: major families of faults oriented ENE-WSW, E-W, NW-SE, N-S with a NE-SW prevalence are mapped.Depths of Interpreted faults ranges from 1000 to 3400 m; mylonitic veins were identified; 2.75D modelling revealed faults depth greater than 1200 m.