Recent  

The lockdown imposed in Romania to prevent the spread of COVID-19 has significantly impacted human activity across the country. By analyzing the ground vibrations recorded at seismic stations, we were able to monitor the changes in human activity before and during the lockdown. The reduced human activity during the lockdown has also provided a good opportunity for stations sited in noisy urban areas to record earthquake signals that would not have been recorded under normal conditions.

This study uses seismic reflection data to interpret the geometric relationship and evolution of intra-basement and rift-related structures in the Enping sag in the northern South China Sea. Our observations suggest the primary control of pre-existing thrust faults is the formation of low-angle normal faults, with possible help from low-friction materials, and the significant role of pre-existing basement thrust faults in fault geometry, paleotopography, and syn-rift stratigraphy of rift basins.

We combine gravity anomaly and topographic data with observations from thermochronology, metamorphic grades, and the granite inventory to detect patterns of basement block segmentation and differential exhumation along the southwestern Bohemian Massif. Based on our analyses, we introduce a previously unknown tectonic structure termed Cham Fault, which, together with the Pfahl and Danube shear zones, is responsible for the exposure of different crustal levels during late to post-Variscan times.

Rocks in mountain belts have been deformed during continental collision causing a certain alignment of the minerals referred to as crystallographic preferred orientation (CPO). Minerals have anisotropic properties: the velocity of seismic waves travelling through them is direction dependent. This leads to anisotropy of the rocks. We measured the CPO of common rocks within the Alps. With this data and known anisotropic properties of the minerals we calculated the seismic anisotropy of the rocks.

We do not know when the ancient Tethys Ocean lithosphere began to founder, but one clue can be found in subduction accreted tectonic slices, including Gondwanan basement terranes on the island of Ios, Cyclades, Greece. We propose a 250–300 km southwards jump of the subduction megathrust with a period of flat-slab subduction followed by slab break-off. The initiation and its subsequent rollback of a new subduction zone would explain the onset of Oligo–Miocene extension and accompanying magmatism.

Upscaling fluid flow in fractured reservoirs is an important practice in subsurface resource utilization. In this study, we first conduct numerical simulations of direct fluid flow at locations where fractures intersect to analyze the arising hydraulic complexities. Next, we develop a model that integrates these effects into larger-scale continuum models of fracture networks to investigate their impact on the upscaling. For intensively fractured systems, these effects become important.

Several large strike-slip faults in western Slovenia are known to be active, but most of them have not produced strong earthquakes in historical times. In this study we use geomorphology, near-surface geophysics, and fault excavations to show that two of these faults had surface-rupturing earthquakes during the Holocene. Instrumental and historical seismicity data do not capture the strongest events in this area.

Rock fractures are organized as networks with spatially varying arrangements. Due to networks' influence on bulk rock behaviour, it is important to quantify network spatial variation. We utilize an approach where fracture networks are treated as spatial graphs. By combining graph similarity measures with clustering techniques, spatial clusters within large-scale fracture networks are identified and organized hierarchically. The method is validated on a dataset with nearly 300 000 fractures.

We present the first seismic noise variation levels during COVID-19 in Central America using 10 seismometers. We study the impact of the seismic noise reduction on the detectability of earthquakes and on the felt reports. Our results show maximum values (~50 % decrease) at seismic stations near airports and densely inhabited cities. The decrease in seismic noise improved earthquake locations and reports. Seismic noise could also be useful to verify compliance with lockdown measures.

This paper aims to illustrate how the timing and duration of contractional deformation associated with folding in orogenic forelands can be constrained by the dating of brittle mesostructures observed in folded strata. The study combines new and already published absolute ages of fractures to provide, for the first time, an educated discussion about the factors controlling the duration of the sequence of deformation encompassing layer-parallel shortening, fold growth, and late fold tightening.

An experimentally deformed sample of Opalinus Clay (OPA), which is being considered as host rock for nuclear waste in Switzerland, was studied by electron microscopy to image deformation microstructures. Deformation localised by forming micrometre-thick fractures. Deformation zones show dilatant micro-cracking, granular flow and bending grains, and pore collapse. Our model, with three different stages of damage accumulation, illustrates microstructural deformation in a compressed OPA sample.

The lower mantle extends from 660–2890 km depth, making up > 50 % of the Earth’s volume. Its composition and structure, however, remain poorly understood. In this study, we investigate several hypotheses with computer simulations of mantle convection that include different materials: recycled, dense rocks and ancient, strong rocks. We propose a new integrated style of mantle convection including piles, blobs, and streaks that agrees with various observations of the deep Earth.

Sediments accumulated in accretionary prisms are deformed by the compression imposed by plate subduction. Here we show that deformation of the sediments transforms some minerals in them. We suggest that these mineral transformations are due to the proliferation of microorganisms boosted by deformation. Deformation-enhanced microbial proliferation may change our view of sedimentary and tectonic processes in subduction zones.

We analyse folded multilayer sequences in the Ocnele Mari salt mine (Romania) to gain insight into the long-term rheological behaviour of rock salt. Our results indicate the large role of even a small number of impurities in the rock salt for its effective mechanical behaviour. We demonstrate how the development of folds that occur at various scales can be used to constrain the viscosity ratio in the deformed multilayer sequence.

In weakly seismic or poorly monitored areas, the uncritical use of earthquake catalogues can be misleading. This is the case for a central sector in the Po Valley, where the Northern Apennines and Southern Alps collide. We collect and reprocess the available instrumental data of about 300 earthquakes from 1951 to 2019. The seismicity is weak, deeper than expected, and far from some existing human activities carried out underground. The potential tectonic causative sources are still unknown.

A new analogue modelling approach was used to simulate the influence of tectonic extension and tilting of the basin floor on salt tectonics in rift basins. Our results show that downward salt flow and gravity gliding takes place if the flanks of the rift basin are tilted. Thus, extension occurs at the basin margins, which is compensated for by reduced extension and later by shortening in the graben centre. These outcomes improve the reconstruction of salt-related structures in rift basins.

The long-lived Schio-Vicenza Fault System is a major shear zone cross-cutting the foreland and the thrust belt of the eastern southern Alps. We review 150 years of scientific works and explain its activity and kinematics, characterized by sinistral and dextral transcurrent motion along its southern and northern sections, respectively, by a geodynamic model that has the Adria indenter as the main actor and coherently reconciles the available geological and geophysical evidence collected so far.

This study analyses recently acquired marine seismic data offshore of southeastern Mozambique. It aims to better constrain the early history and formation of southeastern African margins. The crustal structure and segmentation of the Limpopo margin provide evidence of strike-slip rifting along the eastern North Natal Valley. This has profound consequences on our understanding of the East Gondwana breakup, challenging kinematic models based on an overlap between the Antarctic and African plates.

The thermal evolution of the East European Platform is reconstructed by means of thermal maturity and low-temperature thermochronometry. Results showed that major heating occurred before the Permian, with maximum paleotemperatures in the earliest and latest Carboniferous for Baltic–Podlasie and Lublin basins, respectively. The Mesozoic thermal history was characterized by gradual cooling from peak temperatures at the transition from Triassic to Jurassic due to decreasing heat flow.

We performed a detailed study of the rocks surrounding a major Zn–Pb–Cu ore deposit in southwestern Spain in order to characterize the behaviour of chemical elements in the influence area of the hydrothermal system that produced the deposit. Based on this information we propose new ways of detecting the nearby presence of ore deposits of this kind during exploration, thus improving our ability to detect new resources and contributing to securing the future supply of metals for our society.

Frequency-dependent amplitude decays of seismic signals induced by wind turbines are determined from (up to) 6 months of continuous recordings measured along an 8 km profile located at a wind farm in Bavaria, Germany. The radiation pattern and amplitude decay of the induced signals are accounted for by an analytical approach that includes path and source effects. This approach is generalized to predict the characteristic seismic radiation patterns of arbitrary wind farm configurations.