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 densely populated eastern Sicily, we observed a decrease in the seismic noise amplitude reaching 50 %. We found similarities between the temporal patterns of seismic noise and human mobility, as quantified by mobile-phone-derived data and ship traffic data.

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

This study shows the presence of two structural domains in the western border fault system of the Roer Valley graben. These domains, dominated by NW–SE-striking faults, displayed distinctly different strain distributions during both Late Cretaceous compression and Cenozoic extension. The southern domain is characterized by narrow, localized faulting, while the northern domain is characterized by wide, distributed faulting. The non-colinear WNW–ESE Grote Brogel fault links both domains.

The Auckland Volcanic Field is monitored by a seismic network. The lockdown measures to combat COVID-19 in New Zealand provided an opportunity to evaluate the performance of seismic stations in the network and to search for small(er) local earthquakes, potentially hidden in the noise during "normal" times. Cross-correlation of template events resulted in detection of 30 new events not detected by GeoNet, but there is no evidence of an increase in detections during the quiet period of lockdown.

The competing modes of fault network development, including nucleation, propagation, and coalescence, influence the localization and connectivity of fracture networks and are thus critical influences on permeability. We distinguish between these modes of fracture development using in situ X-ray tomography triaxial compression experiments on crystalline rocks. The results underscore the importance of confining stress (burial depth) and fluids on fault network development.

In this work, the formation of natural magnesium silicate hydrate cement has been studied. The cement forms through the extraordinarily fast dissolution of quartz under high-pH, Mg-rich conditions that occur in south-east Norway where an ultramafic body is exposed. We studied the cemented rocks and the processes that led to the formation of the cement from the field scale to the nanoscale. Magnesium silicate hydrate cement might be a low-CO₂ alternative to Portland cement.

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 it 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 never supposed to have this occur.

We use numerical models to investigate the thermo-chemical evolution of a solid mantle during a magma ocean stage. When applied to the Earth, our study shows that the solid mantle and a magma ocean tend toward chemical equilibration before crystallisation of this magma ocean. Our findings suggest that a very strong chemical stratification of the solid mantle is unlikely to occur (as predicted by previous studies), which may explain why the Earth’s mantle is rather homogeneous in composition.

We use seismic, electromagnetic, and geoelectrical methods to assess sediment thickness and lake-bottom geology of two karst lakes. An unexpected drainage event provided us with the unusual opportunity to compare water-borne measurements with measurements carried out on the dry lake floor. The resulting data set does not only provide insight into the specific lake-bottom geology of the studied lakes but also evidences the potential and limitations of the employed field methods.

In this study, ground motion caused by distant earthquakes recorded in southeast Australia is used to image the structure of the crust and underlying mantle. This part of the Australian continent was assembled over the last 500 million years, but it remains poorly understood. By studying variations in crustal properties and thickness, we find evidence for the presence of an old microcontinent that is embedded in the younger terrane and forms a connection between Victoria and Tasmania.

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 a 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 and a historical tailing in central Sweden.

Seismic and infrasound methods are techniques used to monitor natural events and explosions. At low frequencies, band signal can be dominated by microbaroms and microseisms. The noise observations in the Kazakh network are performed and compared with source and propagation modeling. The network is dense and well situated for studying very distant source regions of the ambient noise. The prospects are opening for the use of ocean noise in solid Earth and atmosphere tomography.

We performed a seismic survey in two 4.3 km deep geothermal research wells using the novel method of distributed acoustic sensing and wireline cables. The characteristics of the acquired data, methods for data processing and quality improvement, and interpretations on the geometry and structure of the sedimentary and volcanic reservoir rocks are presented. The method enables measurements at high temperatures and reduced cost compared to conventional sensors.

We present an innovative approach to estimate a lithosphere density distribution model based on seismic tomography and gravity data. In the studied area, the model shows that magmatic events have increased density in the middle to lower crust, which explains the observed positive gravity anomaly. We interpret the densification through crustal intrusion and magmatic underplating. The proposed method has been tested in the Alps but can be applied to other geological contexts.