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.

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.

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.

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.

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.

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.

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.

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.

In the first part of this article, we present a new methodology that we have developed to model the deformation and the microstructural evolutions of olivine rocks, which make up the main part of the Earth upper mantle. In a second part, using this methodology we show that microstructural features such as small grain sizes and preferential grain orientations can localize strain at the same intensity and can act together to produce an even stronger strain localization.

One motivation for this study is to develop a workflow that enables the integration of geophysical datasets with different coverages that are quite common in exploration geophysics. We have utilized a level set approach to achieve this goal. The utilized technique parameterizes the subsurface in the same fashion as geological models. Our results indicate that the approach is capable of integrating information from seismic data in 2D to guide the 3D inversion results of the gravity data.

We use numerical simulations and laboratory experiments on rock samples to investigate how stress conditions influence the geometry and roughness of fracture surfaces. The roughness of the surfaces was analyzed in terms of absolute roughness and scaling properties. The results show that the surfaces are self-affine but with different scaling properties between the numerical models and the real rock samples. Results suggest that stress conditions have little influence on the surface roughness.

Central western Europe underwent a strange episode of lithospheric deformation, resulting in a chain of small mountains that run almost west–east across the continent and that formed in the middle of a tectonic plate, not at its edges as is usually expected. Associated with these mountains, in particular the Harz in central Germany, are marine basins contemporaneous with the mountain growth. We explain how those basins came to be as a result of the mountains bending the adjacent plate.

Biochemical reactions related to hydrocarbon seepage are known to induce carbonates in marine sediments. Seep carbonates may act as seals and force lateral deviations of rising hydrocarbons. However, crustacean burrows may act as efficient vertical fluid channels allowing hydrocarbons to pass through upward, thereby allowing the vertical growth of carbonate stacks over time. This mechanism may explain the origin of carbonate columns in marine sediments throughout hydrocarbon provinces worldwide.