Recent  

A multi-scale analysis of aeromagnetic data combining tilt derivative, Euler deconvolution, upward continuation, and 2.75D modelling was applied over Cameroon between the latitudes 5°30'–6° N and the longitudes 13°30'–14°45' E. Major families of faults oriented ENE–WSW, E–W, NW–SE, and N–S with a NE–SW prevalence were mapped. Depths of interpreted faults range from 1000 to 3400 m, mylonitic veins were identified, and 2.75D modelling revealed fault depths greater than 1200 m.

Small earthquakes in Alberta and north-east British Columbia have been previously ascribed to industrial activities. The COVID-19 pandemic forced almost all these activities to stop for ~ 4 months. However, unexpectedly, earthquakes still occurred during this time. Some of these earthquakes may be natural and some the result of earthquakes > M6 occurring around the world. However, ~ 65 % of the earthquakes detected may be the remnants of previous fluid injection in the area (latent seismicity).

This work investigates the impact of commonly used seismic interpretation methods on the analysis of faults. Fault analysis refers to fault length, displacement, and the impact these factors have on geological modelling and hydrocarbon volume calculation workflows. This research was conducted to give geoscientists a better understanding of the importance of interpretation methods and the impact of unsuitable methology on geological analyses.

During the COVID-19 pandemic lockdown, the city of Barcelona was covered by a network of 19 seismometers. The results confirm that the quieting of human activity during lockdown has resulted in a reduction of seismic vibrations. The different lockdown phases in Barcelona are recognized consistently at most of the seismic stations. Our contribution demonstrates that seismic noise can be used as a free and reliable tool to monitor human activity in urban environments.

COVID-19 pandemic lockdowns in countries with a dominant informal economy have been a greater challenge than in other places. This motivated the monitoring of the mobility of populations with seismic noise throughout the various phases of lockdown and in the city of Querétaro (central Mexico). Our results emphasize the benefit of densifying urban seismic networks, even with low-cost instruments, to observe variations in mobility at the city scale over exclusively relying on mobile technology.

In this paper, we evaluate a multi-methodological approach for the comprehensive characterization of reservoir sandstones. The approach enables identification of links between rock permeability and textural and topological rock descriptors quantified at microscale. It is applied to study samples from three sandstone layers of Lower Cretaceous age in northern Israel, which differ in features observed at the outcrop, hand specimen and micro-CT scales, and leads to their accurate characterization.

This study estimates the gravitational contribution from subcrustal density heterogeneities interpreted as subducting lithosphere beneath the Alps to the gravity field. We showed that those heterogeneities contribute up to 40 mGal of gravitational signal. Such density variations are often not accounted for in Alpine lithospheric models. We demonstrate that future studies should account for subcrustal density variations to provide a meaningful representation of the complex geodynamic Alpine area.

The last lava dome eruption of Mount Unzen (Japan) ended in 1995, but ongoing instability means much of the area remains an exclusion zone. The rocks in the lava dome impact its stability; heterogeneity (contrasting properties) and anisotropy (orientation-specific properties) can channel fluids and localise deformation, enhancing the risk of lava dome collapse. We recommend using measured material properties to interpret geophysical signals and to model volcanic systems.

The study of intraplate volcanism can inform us about underlying mantle dynamic processes and thermal and/or compositional anomalies. Here, we investigated numerical models of mantle flow and melting of edge-driven convection (EDC), a potential origin for intraplate volcanism. Our most important conclusion is that EDC can only produce moderate amounts of mantle melting. By itself, EDC is insufficient to support the formation of voluminous island-building volcanism over several millions of years.

We performed shear experiments on calcite–dolomite gouge mixtures to better understand the behaviour of carbonates during sub-seismic to seismic deformation in the shallow crust. The development of a foliation in the gouge was only restricted to coseismic sliding, whereas fluidisation occurred over a wide range of slip velocities (sub-seismic to coseismic) in the presence of water. These observations will contribute to a better interpretation of the rock record.

The low-relief, mean-elevation Baima Xueshan massif experienced slow exhumation at a rate of 0.01 km/Myr since at least 22 Ma and then regional rock uplift at 0.25 km/Myr since ~10 Ma. The high-relief, high-elevation Kawagebo massif shows much stronger local rock uplift related to the motion along a west-dipping thrust fault, at a rate of 0.45 km/Myr since at least 10 Ma, accelerating to 1.86 km/Myr since 1.6 Ma. Mekong River incision plays a minor role in total exhumation in both massifs.

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.

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 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.

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.

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.

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.