Rheology of polymineralic rocks is crucial to unravel the strain and stress distribution in Earth’s middle crust, with implications for seismicity or geothermal systems. Our experimental study of the viscous rheology of natural, fine-grained granitoid rocks shows that dissolution–precipitation creep and pinning are active in extremely weak narrow zones. Due to the polymineralic character, strain localizes with and without a precursory fracture in zones weaker than monomineralic quartz.

To date, there remains a deficiency in rheological parameters for polymineralic rocks to be used in models, e.g., for strain localization in the Earth's continental middle crust. We provide a first estimate on grain size and stress sensitivity of experimentally deformed natural fine-grained granitoid rocks. Extrapolation of these parameters predicts a switch in the weakest material as a function of grain size and deformation mechanism from coarse monomineralic quartz to fine polymineralic rocks.

Induced earthquakes present a major obstacle for developing geoenergy resources. These occur during hydraulic stimulations that enhance fluid pathways in the rock. In the Bedretto Underground Laboratory, hydraulic stimulations are investigated in a downscaled manner. A workflow to analyze the hazard posed by induced earthquakes is applied at different stages of the test program. The hazard estimates illustrate the difficulty in reducing the uncertainty due to the variable seismogenic responses.

Two regional reflection seismic profiles were acquired to map the geometrical architecture of the Koillismaa Layered Igneous Complex (KLIC) in north-eastern Finland. Reflectivity up to a depth of ~5–6 km is delineated. The magma conduit associated with the KLIC was successfully revealed and the associated mineralization potential was established. A regional fault system associated with the magma emplacement was mapped for the first time.

We have studied the stress conditions at the Decatur CO₂ storage site that would induce the observed microseismicity. Initial estimates suggested that faults required higher pressure to slip than the injection pressure, but refining pressure and friction assumptions led to more realistic scenarios. Our study highlights the importance of accurate stress state measurements and high-quality data to better predict reservoir response to injection and improve the safety and reliability of CO₂ storage.

This study makes use of advanced seismic exploration techniques to look at the subsurface of South Africa's Kheis region. The results reveal hidden faults and folded rocks that help explain how ancient continents collided. The findings challenge older ideas about major geological boundaries and suggest a new model for how the crust formed and evolved. This work shows how old data, when re-analyzed with new methods and integrated with supporting data, can disclose important geological qualities.

This study presents a new geological model of the Fano-Pesaro offshore area, refining its tectonic framework. We identified multiple fault detachments at different depths, influencing thrust system dynamics and deformation. This work highlights the importance of integrating seismic and borehole data, even legacy, to build reliable subsurface models. These findings contribute to improved seismic hazard assessment and support offshore energy development and carbon storage projects.

The St. Paul Transform System on the equatorial Atlantic is a seismically oceanic transform fault system. This study re-examines the focal depths of 35 earthquakes (M_W 5.3–6.9) from Transforms A, B, and C. The data suggest that the seismogenic zone ranges from 5 to 18 km deep, with the deepest occurring in cooler lithosphere around the center of the transform segments. This challenges earlier hypotheses and indicates a global pattern of cooler mantle in center of oceanic transform faults.

In some situations where the crust plates collide into each other, they deform by creating folds and thrusts. Based on the development direction of the thrusts, they are categorized into fore- or back-thrusts. We use numerical simulation to investigate their development over geological timescales. We examine the importance of rock strength, friction, displacement type, and geometry on back-thrusting with regard to the final geometry of the deformation, along with the distribution of porosity and stresses.

This study analyzes geological faults using triangular surface data to model displaced horizons, considering scenarios with and without elevation uncertainties. Formal proofs and computational experiments show that, without elevation errors, identical dip directions occur. Even with uncertainties, the expected dip direction remains consistent. The findings offer insights for predicting fault geometry in data-sparse environments, improving fault modeling with imprecise elevation data.

Understanding the stress and strain conditions in the Earth's crust is crucial for various activities, such as oil and gas exploration and assessing seismic hazards. In this article, we have updated the database of moment tensor focal mechanisms for Greater Iberia. We conducted kinematic and dynamic analyses on the selected populations, determining the average focal mechanism, strain and stress orientations, and tectonic regime. The orientation for horizontal compression is primarily N154° E.

We propose a new method to map faults automatically in digital elevation models (DEMs) and measure long-term crustal deformation in rift contexts. By combining our data with rock ages, we reconstruct rift evolution in Afar during the last 4.5 Myr. We show that the rift axis is most active, with rifting propagating north-west over time. Here magma promotes crustal deformation and faulting caused by dike opening. In the southern sector Afar, two fault systems respond to different motions of diverging tectonic plates.

Among sedimentary rocks, evaporites (as salt) have a particular behavior when deformed under geological forces: they flow while the others break. Such behavior controls the evolution of mountain building events. By mapping the distribution of rocks and interpreting the subsurface architecture of geological structures we were able to reconstruct the mountain building processes of an area in the Southern Pyrenees and how those evaporites flowed and accumulated.

Carbonates can control how strong the Earth's crust is in places. They are often described in simple terms as calcite or dolomite, but they are more complicated. At the atomistic level different amounts of elements, like magnesium and calcium, are incorporated at different temperatures and at the microscopic level carbonates can have different internal structures which leads to differences in strength. We review 50 years of experimental data to provide new equations that describe this strength.

Geological storage of CO₂ has emerged again in recent years as a complement to reducing CO₂ emissions to the atmosphere. The Swedish government recently gave the task of further studying the potential for CO₂ storage within Swedish territory to the Geological Survey of Sweden. We report here on results from investigations on southern Gotland island. We find that we can map several geological formations of interest and that the rock is seismically anisotropic.

We used computer models to study how mountains formed by the collision of tectonic plates can later affect the breakup of these same plates. Our results show that in large, warm mountain belts, new faults form due to the orogen being  weak overall, while in smaller, colder belts, breakup follows old fault zones. Microcontinents that were accreted during collision can create new continental fragments during extension. These findings help explain how past geological events shape continent margins.

The Wufeng–Longmaxi (WF-LMX) Formation is the most important shale gas play in China. Here, we present a feasible approach using nanoindentation to characterize the mechanical properties of the WF-LMX Formation. Mechanical properties varied synchronously with mineral and organic content across the vertical drilling profile, reflecting changes in lithology and sedimentary facies. The effect of shale constituents on micromechanics is essentially controlled by the sedimentary environment.

The spatial correlation between the crustal magma reservoir and seismicity is crucial for investigating the dynamics of the Wudalianchi volcanic systems. A high-resolution 3-D shear-wave velocity crustal model reveals a distinct low-velocity body located at depths of ∼ 10–23 km below the Wudalianchi volcano. Together with the earthquake distribution, this provides new insights into the magmatic activity of the active Wudalianchi volcano.

Subsurface geometries of ancient faults mapped by high-resolution geophysical surveys use reflected seismic waves. Such surveys in southern Canada map faults which host significant gold or nickel deposits. Reflectors are considered to be brittle if upper-crustal, lava flows if folded or broken, and mid-crustal if mostly parallel. Steep fault zones possibly first formed in ocean settings when the lava erupted. Folding and horizontal shortening probably occurred during later mountain building.