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Passive seismic imaging methods use natural earthquakes as seismic sources, while in active seismic imaging methods, artificial sources (e.g. explosives) are used to generate seismic waves. We imaged some structures related to a major fault plane through a passive seismic imaging approach using microearthquakes with magnitudes smaller than 0.9 (M_w). These structures have not been illuminated by a previously conducted 3D active seismic survey due to their large dip angles.

The Alpine mountain belt was formed by the collision of the Eurasian and African plates in the geological past, during which parts of the colliding plates sank into the earth's mantle. Using seismological data from distant earthquakes recorded by the AlpArray Seismic Network, we have derived an image of the current location of these subducted parts in the earth's mantle. Their quantity and spatial distribution is key information needed to understand how the Alpine orogen was formed.

New images from the multi-national AlpArray experiment illuminate the Alps from below. They indicate thick European mantle descending beneath the Alps and forming blobs that are mostly detached from the Alps above. In contrast, the Adriatic mantle in the Alps is much thinner. This difference helps explain the rugged mountains and the abundance of subducted and exhumed units at the core of the Alps. The blobs are stretched remnants of old ocean and its margins that reach down to at least 410 km.

Here we present new surface elevation constraints for the middle Miocene Central Alps based on stable and clumped isotope geochemical analyses. Our reconstructed paleoelevation estimate is supported by isotope-enabled paleoclimate simulations and indicates that the Miocene Central Alps were characterized by a heterogeneous and spatially transient topography with high elevations locally exceeding 4000 m.

The Ligurian Sea opened ~30–15 Ma during SE migration of the Calabrian subduction zone. Using ambient seismic noise from stations on land and at the ocean bottom, we calculated a 3D shear-velocity model of the Ligurian Basin. In keeping with existing 2D studies, we find a shallow crust–mantle transition at the SW basin centre that deepens towards the northeast, Corsica, and the Liguro-Provençal coast. We observe a separation of SW and NE basins. We do not observe high crustal v_P/v_S ratios.

Past strong earthquakes can produce topographic deformations, often memorized in Quaternary sediments, which are typically studied by paleoseismologists through trenching. Using a ground-penetrating radar (GPR), we unveiled possible buried Quaternary faulting in the Mt. Pollino seismic gap region (southern Italy). We aim to contribute to seismic hazard assessment of an area potentially prone to destructive events as well as promote our workflow in similar contexts around the world.

We analyse broadband ocean bottom seismometer data of the AlpArray OBS network in the Ligurian Basin. Two earthquake clusters with thrust faulting focal mechanisms indicate compression of the rift basin. The locations of seismicity suggest reactivation of pre-existing rift structures and strengthening of crust and uppermost mantle during rifting-related extension. Slightly different striking directions of faults may mimic the anti-clockwise rotation of the Corsica–Sardinia block.

In this paper, we dated fault movements at geological timescales which uplifted the sedimentary successions of the Jura Mountains from below the sea level up to Earth's surface. To do so, we applied the novel technique of U–Pb geochronology on calcite mineralizations that precipitated on fault surfaces during times of tectonic activity. Our results document a time frame of the tectonic evolution of the Jura Mountains and provide new insight into the broad geological history of the Western Alps.

After an earthquake, the fault continues to slip for days to months. Yet, little is know about the very early part of this phase (i.e., minutes to hours). We have looked at what happens just after an earthquake in Chile from 2015. We find that the fault responds in two ways: south of the rupture zone it slips seismically in the form of aftershocks, while north of the rupture zone it slips slowly. Early inference of such bimodal behavior could prove to be useful for forecasting aftershocks.

A large amount of new seismic data from the greater Alpine area have been obtained within the AlpArray and SWATH-D projects. S-to-P converted seismic phases from the Moho and from the mantle lithosphere have been processed with a newly developed method. Examples of new observations are a rapid change in Moho depth at 13° E below the Tauern Window from 60 km in the west to 40 km in the east and a second Moho trough along the boundary of the Bohemian Massif towards the Western Carpathians.

As continental plates collide, mountain belts grow. This study investigated the provenance of rocks from the northwestern segment of the Zagros mountain belt to unravel the convergence history of the Arabian and Eurasian plates. Provenance data synthesis and field relationships suggest that the Zagros Mountains developed as a result of the oceanic crust emplacement on the Arabian continental plate, followed by the Arabia–Eurasia collision and later uplift of the broader region.

The 2 June 1994 Java tsunami earthquake ruptured in a seismically quiet subduction zone and generated a larger-than-expected tsunami. Here, we re-process a seismic line across the rupture area. We show that a subducting seamount is located up-dip of the mainshock in a region that did not rupture during the earthquake. Seamount subduction modulates the topography of the marine forearc and acts as a seismic barrier in the 1994 earthquake rupture.

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.

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.

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.

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.

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.

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.