Abstracted/indexed

The city of Barcelona has been covered during the COVID-19 pandemic lockdown 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 in most of the seismic stations. Our contribution demonstrates that seismic noise can be used as a free and reliable tool to monitor the human activity in urban environments.

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 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 which are contemporaneous with the mountain's growth. We explain how those basins came to be, as a result of the mountains bending the adjacent plate.

The achieved high precision hypocenter locations of 344 earthquakes (with magnitudes in the range of 1–4.2 ML) have average uncertainties of ~500 m in epicenter and ~1.7 km in depth. The general pattern of seismicity in the Southern and Eastern Alps reflects head-on convergence of the Adriatic Indenter with the Alpine orogenic crust. The relatively deeper seismicity clusters in the eastern Southern Alps and Giudicarie Belt indicate southward propagation of the Southern Alpine deformation front.

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, hence 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.

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 250-300km 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.

Basin Inversion in Central Europe is believed to start during Late Cretaceous (MIddle Turonian) and to proceed probbaly until the Paleogene. Data from different marginal troughs in Central Europe point to an earlier start already in the Cenomanian. The end of inversion is overprinted by general uplift, but probably occurred already in the Late Campanian to Maastrichtian. Both start and end occurred with low rates of uplift and subsidence.

What is the effect of shearing, holding and effective normal stress on fault gouge permeability, parallel and perpendicular to fault boundaries, as well as on frictional behaviour? Experiments show a pre-shear permeability anisotropy, as well as a decrease in permeability with shear and eff. normal stress, for both fluid flow directions. The results have important implications for pre-existing faults in calcite-rich claystones that seal hydrocarbon reservoirs or potential CO₂ storage reservoirs.

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.

The European Alps formed during collision between the European and Adriatic plates, and are one of the most studied orogens for understanding the dynamics of mountain building. In Eastern Alps, the contact between the colliding plates is still a matter of debate. We have used the records from distant earthquakes to highlight the geometries of the crust-mantle boundary in the Eastern Alpine area; our results suggest a complex and faulted internal crustal structure beneath the higher crests.

The high-resolution 3-D shear velocity model of the BM crust imaged from high-density data and enhanced depth sensitivity of tomographic inversion. The dominant features of the model are relatively higher v_S in the upper crust than in its surrounding, distinct intra crustal interface and a velocity decrease in the lower part of the crust. The low v_S in the lower part of the crust is explained by an anisotropic fabric of the lower crust.

Elastic thermobarometry is an useful tool to recover the paleo-pressure and temperature. Here, we provide an analytical model based on the Eshelby solution to calculate the residual stress/strain preserved in a mineral inclusion exhumed from depth. The method applies to ellipsoidal, anisotropic inclusion in infinite isotropic host. Finite element method is also used for facet effect. It is found that the volumetrically avereged stress is a good proxy for the overall heterogeneous stress stage.

In this article, we investigate the potential of reverse time migration (RTM) for deep targeting iron-oxide deposits and possible AVO effect that is potentially seen in the common image gathers from this migration algorithm. The results are promising and help to delineate the deposits and host rock structures using a 2D dataset from Ludvika Mines of central Sweden.

This contribution shows that soft and coal-rich sedimentary rocks in central Spitsbergen absorbed most of the (Eurekan) contractional deformation that occurred in the early Cenozoic using seismic data and fieldwork, thus suggesting that no contractional deformation event is needed in the Late Devonian to explain the deformation differences among late Paleozoic sedimentary rocks. It also shows that the Billefjorden Fault Zone, a major crack in the Earth crust in Svalbard, is probably segmented.

In NW Iberia a low grade unit separates the unrooted accretionary prism from the autochthon. It was divided in Upper (pre-orogenic) and Lower (syn-orogenic) around the Morais Complex. A review on the sedimentary sequences characteristics, supported by U-Pb ages in 17 new samples of syn-orogenic sediments and volcanic olistoliths, allows to propose this model is general for the Galicia – Trás-os-Montes Zone forming a tectonic carpet exposed in most of the Parautochthon-Autochthon limit.

The low-relief, mean-elevation BaimaXueshan massif experienced slow exhumation at a rate of 0.01 km/Myr since at least 22 Ma, then regional rock uplift at a rate of 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 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.

The Albstadt Shear Zone, SW Germany, is an active rupture zone with sometimes damaging earthquakes but no visible surface structure. To identify its segmentations, geometry, faulting pattern and extension, we analyze the continuous earthquake activity 2011–2018. We find a segmented N-S oriented fault zone with mainly horizontal and minor vertical movement along preferably NNE and some NNW oriented rupture planes. The main horizontal stress is oriented NW and due to Alpine-related loading.

In this paper we test a simplified numerical model for pyroclastic density currents or PDCs (mixtures of hot gas, lapilli and ash moving across the landscape under the effect of gravity). The aim is quantifying the differences between real and modelled deposits of some PDCs of the AD 79 eruption of Vesuvius, Italy. This step is important because in the paper it is demostrated that this simplified model is useful for constraining input parameters for more computationally expensive models.

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.

Using plate tectonic reconstructions and geodynamic modelling, we show that the former Piemont-Liguria Ocean, which separated Europe from Africa-Adria in the Jurassic, opened as an arm of the Central Atlantic and reached only 250 km width between Europe and Adria. Moreover, at least 65 % of the lithosphere subducted into the mantle and/or incorporated into the Alpine mountain belt during convergence in Cretaceous and Cenozoic times was highly thinned continental, while only 35 % was truly oceanic.

Vertical incidence seismic profiling on the Iberian Massif images a mid-crustal scale discontinuity at the top of the reflective lower crust. This feature shows that upper and lower crustal reflections merge into it, thus suggesting that it has often behaved as a detachment. The orogen scale extension of this discontinuity, present in Gondwanan and Avalonian affinity terranes into the Iberian Massif demonstrates its relevance, leading us to interprete it as the Conrad Discontinuity.

We identified several problems in the Urbani et al. (2020) study, showing that their model does not conform to the age and location of faulting, identification and delimitation of uplifted areas and apical depressions, temperature and lithological wells log, and stratigraphic and radiometric data. Published data indicate that the pressurization of the LHVC magmatic/hydrothermal system driving resurgence faulting occurs at greater depth.

The Auckland Volcanic Field is monitored by a seismic network. The lockdown measures to combat COVID-19 in New Zealand proved an opportunity to evaluate the performance of the seismic stations in the network, and to search for small(er) local earthquakes, potentially hidden in the noise during normal times.