Tectonic Scale Research Articles

Some genera and species of dissepimented solitary Rugosa (Anthozoa) from the Pennsylvanian (Carboniferous) and Cisuralian (Permian) of North America. Part 1. Yuanophylloides Fomichev, 1953

Several specimens derived from the Missourian (Pennsylvanian) deposits of the Glass Mountains (SW Texas, USA) are identified as Yuanophylloides Fomichev, 1953. Some species that earlier authors included in the genera Campophyllum Milne-Edwards and Haime, 1852, Bothrophyllum Trautschold, 1879, and Neokoninckophyllum Fomichev, 1939 are re-identified as belonging to Yuanophylloides. In addition to the type genus, a new subgenus Patulaxis of Yuanophylloides with the type species Y. (P.) molestus sp. nov. and the new species Y. (P.) parcus and Y. (P.) laxus are introduced. Re-identification of the upper Serpukhovian Campophyllum kansasense Miller and Gurley, 1893 as Yuanophylloides renders untenable the origin of that genus in the Donets Basin. The circum- Laurussia warm current is suggested as having carried Yuanophylloides larvae from the North American superprovince to the Paleotethyan superprovince. This genus supplements the group of genera suggested by Fedorowski (2023) as having originated in the North American superprovince and migrating to the Paleotethyan superprovince. Together, these genera demonstrate the importance of taxonomic investigation to establish paleobiogeography as a constrain on global (i.e., tectonic scale) environmental reconstructions.

Shuttle radar topography-based analysis reveals the active Borneo Island Fault in Borneo, SE Asia

This study presents the results of shuttle radar topography-based analysis providing new insights into the geological and structural architecture of the island of Borneo. The aim is to examine whether Borneo is tectonically active and to better understand the origin of prominent topographic features such as the Dulit Plateau and the large oroclinal bend of Sarawak. The results show that the Tinjar and the Lupar lines are tectonically active fault zones. The Lupar fault zone is broadly distributed along the spine of the island, representing a major suture featured by ophiolites and extensive volcanism. The development of the Dulit Triangle and the large oroclinal bend are related to fault interactions. The seismological, geodetic and geomorphological evidence suggests that Borneo is tectonically active. The Borneo Island Fault is the major active fault piercing through the island’s mountainous backbone. On a tectonic scale, the oblique northeastward active convergence of the Australian plate with the Sunda plate drives the deformation on the island of Borneo, some of which is also associated with the northward motion of the Philippine Sea plate. Recent GPS data indicate that the Sunda plate is moving slowly to the southwest, and our results suggest this motion is consistent with the interaction between the Sunda and the Australian plates.

Intelligent assessment of building damage of 2023 Turkey-Syria Earthquake by multiple remote sensing approaches

A catastrophic Mw7.8 earthquake hit southeast Turkey and northwest Syria on February 6th, 2023, leading to more than 44 k deaths and 160 k building collapses. The interpretation of earthquake-triggered building damage is usually subjective, labor intensive, and limited by accessibility to the sites and the availability of instant, high-resolution images. Here we propose a multi-class damage detection (MCDD) model enlightened by artificial intelligence to synergize four variables, i.e., amplitude dispersion index (ADI) and damage proxy (DP) map derived from Synthetic Aperture Radar (SAR) images, the change of the normalized difference built-up index (NDBI) derived from optical remote sensing images, as well as peak ground acceleration (PGA). This approach allows us to characterize damage on a large, tectonic scale and a small, individual-building scale. The integration of multiple variables in classifying damage levels into no damage, slight damage, and serious damage (including partial or complete collapses) excels the traditional practice of solely use of DP by 11.25% in performance. Our proposed approach can quantitatively and automatically sort out different building damage levels from publicly available satellite observations, which helps prioritize the rescue mission in response to emergent disasters.

Resolving Multi-Asperity Contacts at the Nanoscale through Super-Resolution Fluorescence Imaging.

Contact mechanics, spanning nanometer to tectonic scales, faces long-standing challenges arising from multiscale random roughness, which hinders experimental validation of theories. Understanding multi-asperity rough contacts is vital for addressing catastrophic consequences of these contacts failing such as earthquakes and for diverse technological applications. To visualize such contacts, we introduce a super-resolution microscopy method utilizing spontaneous millisecond ON/OFF fluorescence blinking of contact-sensitive molecular rotor molecules immobilized on a glass coverslip. This technique achieves ∼55 nm lateral imaging resolution for rough poly(methyl methacrylate) and glass spheres on glass contacts. For soft polymer spheres due to large plastic deformation, the resolution improvement does not significantly affect the area of real contact. However, for hard glass spheres, the real contact area is found to be 2.4 times smaller than that found by diffraction-limited imaging. This study highlights, through direct visualization, the impact of material stiffness on the nanoscale structure within the area of real contact.

Dynamically triggered seismicity on a tectonic scale: A review

AbstractEarthquakes triggered by dynamic disturbances have been confirmed by numerous observations and experiments. In the past several decades, earthquake triggering has attracted increasing attention of scholars in relation to exploring the mechanism of earthquake triggering, earthquake prediction, and the desire to use the mechanism of earthquake triggering to reduce, prevent, or trigger earthquakes. Natural earthquakes and large‐scale explosions are the most common sources of dynamic disturbances that trigger earthquakes. In the past several decades, some models have been developed, including static, dynamic, quasi‐static, and other models. Some reviews have been published, but explosion‐triggered seismicity was not included. In recent years, some new results on earthquake triggering have emerged. Therefore, this paper presents a new review to reflect the new results and include the content of explosion‐triggered earthquakes for the reference of scholars in this area. Instead of a complete review of the relevant literature, this paper primarily focuses on the main aspects of dynamic earthquake triggering on a tectonic scale and makes some suggestions on issues that need to be resolved in this area in the future.

Statistical analogies between earthquakes, micro-quakes in metals and avalanches in the 1D Burridge-Knopoff model

Universalities and intriguing analogies in the statistics of avalanches are revealed for three physical systems defined on largely different length and energy scales. Earthquakes induced by tectonic scale dynamics, micro-scale level quakes observed from slipping crystallographic planes in metals and a one-dimensional, room-scale spring-block type Burridge-Knopoff model is studied from similar statistical viewpoints. The validity of the Gutenberg-Richter law for the probability density of the energies dissipated in the avalanches is proven for all three systems. By analysing data for three different seismic zones and performing acoustic detection for different Zn samples under deformation, universality for the involved scaling exponent is revealed. With proper parameter choices the 1D Burridge-Knopoff model is able to reproduce the same scaling law. The recurrence times of earthquakes and micro-quakes with magnitudes above a given threshold present again similar distributions and striking quantitative similarities. However, the 1D Burridge-Knopoff model cannot account for the correlations observed in such statistics.

Control mechanisms of Os isotope anomalies of Co-rich crusts from the Line and Marcus–Wake seamounts areas

The evolution curve of the Os isotopic composition (187Os/188Os) of Co-rich ferromanganese crusts reflects the correlation between the supply of continental and mantle-derived materials to seawater in different growth periods of the crusts. In general, a certain ratio of the supply of these materials to the ocean is maintained based on the input–output law. This means that the evolution curves of the Os isotopic composition of crusts in different growth periods can be compared with that of seawater in the Central and Western Pacific Ocean. However, the Os isotopic composition of crusts from the Line and Marcus–Wake seamounts areas is anomalous before 40 Ma and after 7 Ma, respectively, with the ratio being higher than that of seawater, respectively. Throughout the long growth history of the crusts, continental denudation materials entering the marine system through monsoons and atmospheric circulation have been important sources of terrigenous materials in the metallogenetic process. Variations in the contents of indicator elements, such as Si and Al, reflect the input flux of terrigenous materials. During growth periods of the crusts, seamounts they located successively entered the influencing range of the southeast trade wind and westerlies owing to plate tectonics. Depending on the evolution of the atmospheric circulation system, the supply of terrigenous materials to the crusts changes in different seamount areas. The supply of aeolian dust from the Americas and Eurasia may be the dominant factor causing the Os isotope anomalies of the crusts. However, further paleoceanographic studies at the tectonic scale are required to understand the anomalies and enrichment of elements during the metallogenetic process of the crusts. Overall, increased supply of terrigenous materials, along with the evolution of the paleoceanographic environment, may promote the growth rate of the crusts.

THE RIPPLE EFFECT: ANALYZING THE INFLUENCE OF CURRENT GEOPOLITICAL CHALENGES ON NATIONAL ECONOMY (THE CASE OF RUSSIA)

<p>Current geopolitical shifts of tectonic scale generate a set of new challenges for global economic leaders all around the world testing their abilities to adjust fast enough to radically changing environment and finding the appropriate commercial solutions. Country’s global leadership refers to its ability to influence the global economy through its policies, trade agreements, and military power. Rising economic powers are challenging the dominance of traditional ones. Taking under consideration the fact that Russia nowadays is in the center of geopolitical tension with enormous number of various sanctions imposed on it and being actually forced to take a set of retaliatory measures, the authors focus on future prospects of the country’s commercial interaction with international counterparts on the basis of “BANI framework”, introduced by Jamais. The Russian case fits into it well. It is brittle in terms of existing economic links; anxious regarding the future prospects of country’s involvement into international economic transactions; nonlinear as there is a disconnection between cause and effect of all measures recently taken by the government and its opponents; and incomprehensible in terms of the future impact of existing situation to the world. The authors argue that current geopolitical tensions will inevitably change the entire sphere of international business in general, its geographical composition in particular. Active interaction with these or that international partners for the companies and their leaders all around the globe gradually seems to be more of strategic imperative, rather than an issue of willingness and choice.</p>

Earthquake Risk Probability Evaluation for Najin Lhasa in Southern Tibet

The probabilistic seismic hazard analysis (PSHA) method is effectively used in an earthquake risk probability evaluation in seismogenic regions with active faults. In this study, by focusing on the potential seismic source area in Najin Lhasa, southern Tibet, and by incorporating the PSHA method, we determined the seismic activity parameters and discussed the relationship of ground motion attenuation, the seismic hazard probability, and the horizontal bedrock ground motion acceleration peak value under different transcendence probabilities in this area. The calculation results show that the PSHA method divides the potential source area via specific tectonic scales and detailed tectonic markers, which reduces the scale of the potential source area and better reflects the uneven spatial distribution of seismic activity in the vicinity of Najin. The corrected attenuation relationship is also in line with the actual work requirements and is suitable for earthquake risk analysis. In addition, the major influences on the peak acceleration of ground motion in the study area are mainly in the potential source areas of Qushui (M7.5), Dangxiong (M8.5), and Kangma (M7.5). The peak horizontal ground motion acceleration (PGA) with a transcendence probability of 10% in 50 years is 185.9 cm/s2, and that with a transcendence probability of 2% in 50 years is 265.9 cm/s2.

How do tectonics influence the initiation and evolution of submarine canyons? A case study from the Otway Basin, SE Australia

The architecture of canyon-fills can provide a valuable record of the link between tectonics, sedimentation and depositional processes in submarine settings. We investigated the role of plate tectonics in the initiation and evolution of submarine canyons. We demonstrate that events at the plate tectonic scale (i.e. continental break-up and shortening) have a first-order influence on the initiation and development of submarine canyons. The Late Cretaceous ( c. 65 Ma) separation of Australia and Antarctica initially resulted in extensional fault systems, which then formed a steep stair-shaped palaeoseabed. Subsequently, the Late Miocene ( c. 5 Ma) collision of Australia and Eurasia resulted in substantial uplift and exhumation on the SE Australian continental margin. These tectonic events led to elevated seismicity, which ultimately gave rise to gravity-driven processes (i.e. turbidity currents and mass wasting processes) and formed the base of the canyon. The inherited stair-shaped topography then facilitated further gravity-driven processes that established a mature sediment conduit extending from the shallow marine shelf to the abyssal plain. We suggest that the stratigraphic architecture of canyons can be used as an archive to record tectonic movements. Moreover, the factors that precondition and trigger gravity-driven processes can induce canyon initiation and facilitate canyon development. Supplementary material: A PDF file containing all the clean, uninterpreted seismic sections is available at https://doi.org/10.6084/m9.figshare.c.5937760

Correlations between morphoneotectonic parameters and Precambrian tectonic structures in the Nyong Group greenstone belts: Example of the Kopongo area (NW of the Congo Craton, Southwestern Cameroon)

The satellite image processing techniques used (filtering, enhancements, slope and elevation analysis) and morphoneotectonic analysis were applied to the topography and hydrographic network draining the Paleoproterozoic iron formations of Kopongo in SW Cameroon. Morphostructural investigations have shown that this domain is marked by an elongated relief of NNE-SSW direction, composed of asymmetric hills, plateaus and plains. The typology of the relief, slopes and hydrographic network, in addition to the structural axes, reflect well the lithostructural characteristics of these iron formations. The analysis and interpretation of morphometric data, coupled with literature review, field and drill-core mapping investigations, have resulted in logical morphoneotectonic and geological maps illustrating the correlations between the iron formations and buried structures. The information obtained relates in part to the tectonic relationship between geological structures, morphological units and iron formations. In addition, the spatial distribution of drain lengths and elevation appear to indicate the presence of buried geological basement megastructures. The waviness of the Sn foliation, Sn+1 foliations and the concordance of the Sn+1 and Sn/Sn+1 foliations in this area at the megascopic scale are marked respectively by Fn, Fn+1 and Fn+2 map folds corresponding to tectonic scales from the multiple compressive tectonics that affected these iron formations. These observations also show that the Kopongo iron formations are controlled by polyharmonic Fn+1 and Fn+2 map folds whose surface traces of their respective axial planes are oriented NE-SW to NNE-SSW and NE-SW, NW-SE to NNW-SSE. On the other hand, Digital Terrain Model data and geographical information system (GIS) were used in the evaluation of morphometric parameters such as linear, aerial and relief features. Besides, swath profiles helped in the interpretation of the regional topographic patterns and topographic stream profiles allowed to recognise vertical deformations affecting the drainage network. It appears that, the investigated terrain has been rejuvenated due to the interaction between climatic, lithological and tectonic factors. The lithopackage from the top to the base stratigraphy comprises three units in this study area. The upper unit consists of a mixture of colluvium and pisolitic laterite material, while, the middle unit is represented by alternating magnetite, magnetite-pyroxene and enriched magnetite-pyroxene gneisses, and the lower unit is made up of amphibolites and hypersthene-bearing gneisses.

Numerical modeling of post-collisional carbonated alkaline magmatism: Variscan style Orogeny (the Ivrea Zone as natural laboratory)

The Ivrea Zone of northwest Italy exposes a section of the lower crust and lithospheric mantle deformed during the Variscan Orogeny, where a series of carbonated alkaline pipes was emplaced over a time span of ca. 40 Ma, following a crustal underplating event at ca. 288 Ma. We use a coupled 2D petrological-thermomechanical approach to geodynamically model the processes that led to the Variscan continental collision and subsequent emplacement of the alkaline pipes with application to craton margin metasomatic events. The following criteria are assessed to develop a generic model: 1) closure of Rheic Ocean through subduction of oceanic crust and subduction-related metasomatism of the lithospheric mantle, 2) high-temperature metamorphism of the lower crust associated with continental collision, preceding the 3) emplacement of a crustal underplating event, and 4) partial melting of metasomatized lithospheric mantle domains during gravitational collapse of the orogen to source the alkaline pipes. Our model investigates the collision process by varying thermal ages of the intervening oceanic crust (40, 60, and 80 Ma) and by changing the rheological strength of the lower crust. We employ two ideal end-member cases, wet quartzite and plagioclase An75, an intermediate dry quartz case to represent a migmatized lower crust, and two polymineralic cases of felsic granulite and mafic granulite as possible representations to the Ivrea Zone specifically. We discuss the results through three scenarios controlled by the age of the oceanic crust and rheology of the lower crust that can reproduce tectonic scale features that are observed in the Ivrea Zone. Scenario 1: the wet quartzite 40 Ma model features widespread H2O and CO2 fluxes within the continental lithospheric mantle. The model displays little melt productivity due to the presence of an overthickened crust and the continental lithospheric mantle decouples and peels off beneath the lower crust of the colliding terrane. Scenario 2: the plagioclase An75 60 Ma model shows high-temperature metamorphism in the lower crust and reproduces the metasomatism of the continental lithospheric mantle that is a precursor to the genesis of the alkaline pipes. The model is permissive for the emplacement of the crustal underplating event, but the relative timings are misplaced. Scenario 3: the mafic granulite 80 Ma model recreates the tectonic relationships between lower crustal high-temperature metamorphism followed by initiation of the magmatic underplating event, and lastly by localized melting of metasomatized domains of the lithospheric mantle. This model can potentially explain two of the prevailing hypotheses for the formation of the alkaline pipes. Whereas all models reproduced different stages of the tectono-magmatic evolution of continental collision, only scenario 3 could sufficiently recreate the relative sequence of events observed in the Ivrea Zone. Scenarios 1 and 2 may provide precious information about the nature and timing of metasomatic processes in the lithospheric mantle, with implications for the enhanced prospectivity for a wide range of ore systems in specific domains along the margins of lithospheric blocks.

Subduction, mantle metasomatism, and gold: A dynamic and genetic conjunction

Abstract Global gold deposit classes are enigmatic in relation to first-order tectonic scale, leading to controversial genetic models and exploration strategies. Traditionally, hydrothermal gold deposits that formed through transport and deposition from auriferous ore fluids are grouped into specific deposit types such as porphyry, skarn, high- and low-sulfidation–type epithermal, gold-rich volcanogenic massive sulfide (VMS), Carlin-type, orogenic, and iron-oxide copper-gold (IOCG), and intrusion-related gold deposits (IRGDs). District-scale mineral system approaches propose interrelated groups such as porphyry Cu-Au, skarn Cu-Au-Ag, and high-sulfidation Au-Ag. In this study, the temporal evolution of subduction-related processes in convergent margins was evaluated to propose a continuum of genetic models that unify the various types of gold deposits. At the tectonic scale of mineral systems, all hydrothermal gold deposits are interrelated in that they formed progressively during the evolution of direct or indirect subduction-related processes along convergent margins. Porphyry-related systems formed initially from magmatic-hydrothermal fluids related to melting of fertile mantle to initiate calc-alkaline to high-K felsic magmatism in volcanic arcs directly related to subduction. Formation of gold-rich VMS systems was related to hydrothermal circulation driven by magmatic activity during rifting of oceanic arcs. Orogenic gold deposits formed largely through fluids derived from devolatilization of the downgoing slab and overlying sediment wedge during late transpression in the orogenic cycle. Carlin-type deposits, IRGDs, and some continental-arc porphyry systems formed during the early stages of orogenic collapse via fluids directly or indirectly related to hybrid magmatism from melting of lithosphere that was metasomatized and gold-fertilized by earlier fluid release from subduction zones near margins of continental blocks. The IOCGs were formed during postorogenic asthenosphere upwelling beneath such subduction-related metasomatized and fertilized lithospheric blocks via fluid release and explosive emplacement of volatile-rich melts. Thus, importantly, subduction is clearly recognized as the key unifying dynamic factor in gold metallogenesis, with subduction-related fluids or melts providing the critical ore components for a wide variety of gold-rich deposit types.

Importance of permeability and deep channel network on the distribution of melt, fractionation of REE in abyssal peridotites, and U-series disequilibria in basalts beneath mid-ocean ridges: A numerical study using a 2D double-porosity model

A plethora of observations have been made at mid-ocean ridges and mantle sections of ophiolites: presence of tabular replacive dunites, highly depleted LREE in residual abyssal peridotites, U-series disequilibria in fresh basalts, crustal thickness, and highly attenuated seismic and magnetotelluric structures beneath spreading centers. These independent observations can become more powerful if they are jointly analyzed in a self-consistent model. The difficulty for such a model is to resolve and evaluate the effect of fine scale petrologic feature such as dunite channels in a tectonic scale geodynamic model. Here we present a two-dimensional double-porosity ridge model that consists of low-porosity residual lherzolite and harzburgite matrix and high-porosity interconnected channel network. The geodynamic simulation features a spatially distributed channel network and anisotropic permeability that gradually develops as the upwelling mantle is deformed. We compute the porosity, melt and solid flow fields for several choices of channel distribution and permeability model. We use the calculated porosity distribution and velocity fields to model the variations of REE in residual mantle and U-series disequilibria in melts.The present study underscores the importance of deep channel networks and permeability model to the interpretation of first order geophysical and geochemical observations at mid-ocean ridge spreading centers. The anisotropic permeability of channels can enhance melt focusing by 60%, resulting in thicker crust. The attenuated seismic and magnetotelluric structures require a channel network starting from 60 km depth beneath the ridge axis. The depleted REE patterns in clinopyroxenes in residual abyssal peridotites are also consistent with melt extraction into channels starting from 60 km depth. Although deep channels are conducive to producing U-series disequilibria in eruptible melts, the present model still cannot explain the full ranges of the observed U series disequilibria data in MORB samples. Additional factors, processes, and models are discussed. And finally, we found that, within the uncertainty of the permeability, the porosity varies by three folds and the excess of 230Th varies by up to two folds.

Effects of regional and local stresses on fault slip tendency in the southern Taranaki Basin, New Zealand

© 2019 Elsevier Ltd Determining the potential for faults to slip is widely employed for evaluating fault slip potential and associated earthquake hazards, and characterising hydrocarbon seal integrity and reservoir properties. Here we use borehole and 3D seismic reflection data to estimate stress orientations and magnitudes, fault geometries and slip tendency in the southern Taranaki Basin, New Zealand. Late Cenozoic normal faults in the basin range in strike from E-W to NE-SW and are associated with stress changes from basin to borehole scales. The Maui and Maari-Manaia regions, part of the eastern mobile belt, show a strike-slip/normal stress regime (SHmax ≥ Sv > Shmin). The Tui region, part of the western stable platform, shows a normal stress regime (Sv > SHmax > Shmin). Both regions have a mean SHmax azimuth of ENE-WSW. Although the southern Taranaki basin is undergoing active deformation at plate tectonic scales, the stress magnitudes appear insufficiently high to reactivate the faults assuming a classic coefficient of friction. SHmax azimuths and SHmax:Sv magnitude ratios vary locally between boreholes and with depth. A borehole that intersects an inactive seismic-scale fault and borehole-scale faults over a 150-m interval shows SHmax to rotate by up to 30° proximal to the faults, which are favourably orientated for slip in both strike-slip and normal regimes. The small borehole-scale faults may, however, be active within the inactive seismic scale fault's damage zone. We highlight changes of slip tendency along faults resulting from local variations in the stress field and non-planar fault geometries that could not be resolved using only seismic reflection data and regional stress tensor. In the Taranaki Basin additional sub-seismic fault mapping, stress information and mechanical rock property testing are required to realise the potential of stress-based prediction of along-fault permeability and fluid migration.

Active-couple indentation in geodynamics of NNW Iran: Evidence from synchronous left- and right-lateral co-linear seismogenic faults in western Alborz and Iranian Azerbaijan domains

Situated within the central portion of the Arabia-Eurasia collision zone, NNW Iran exhibits an interesting active tectonic context characterized by synchronous left- and right-lateral co-linear seismogenic faults along the adjacent WNW-striking West-Central Alborz (e.g. the Rudbar earthquake fault) and Iranian Azerbaijan (e.g. the North Tabriz seismogenic fault). These structural domains are deforming as a single deformable geomechanical territory between the nearly rigid Central Iran and South Caspian domains to the SSW and NNE, respectively. In this paper, we analyze tectonic interactions of these active structural domains and their influence on the geodynamics of NNW Iran based on morphotectonic and seismological investigations. Indentation tectonics is suggested to play an important role in the geodynamics of this territory. At a plate tectonic scale, the rigid Arabian plate acts as the main indenter which bulldozes the less rigid crustal domains ahead into folded belts (within Zagros and Caucasus to the north) and pushes other blocks aside. In this deformation system, the South Caspian domain acts as a backstop against southern and western deformation zones. The structural domains of Alborz (to the east) and Iranian Azerbaijan Caucasus (to the west) are separated by the NNW-striking Astara-Talesh dextral transpressional zone. Analysis of morphotectonic features and focal mechanisms conducted in this central portion of NNW Iran confirms dextral faulting localized along the NNW-striking deformation zone, which is in agreement with the observed reverse earthquake faulting on west-dipping planes. We also discuss the contraction trajectories derived from kinematics and geometry of active folding and faulting features observed within NNW Iran. Our study highlights two prominent sets of fan-shaped trajectories dominating in the west and east sides of the N–S zone in the Astara-Zanjan direction. We propose a couple-indentation geodynamic model to explain the fan-shaped pattern of these two laterally convergent sets of trajectories within the Talesh-Azerbaijan and Alborz domains.

A Method for Multiscale Interpretation of Fracture Processes in Carrara Marble Specimen Containing a Single Flaw Under Uniaxial Compression

AbstractThis paper presents a method for continuous multiscale observation of uniaxial compressive tests of Carrara marble specimens containing a single preexisting artificially created flaw. The experiments aim at analyzing the associated mesoscale‐macroscale phenomena in the fracture process of the specimens. In the macroscale, the crack types are observed and characterized by optical observation using a camcorder and a high‐speed camera. In the mesoscale, the crack types are analyzed and characterized by the moment tensor inversion of acoustic emission. For the experimental investigation on the fracture process on specimens containing a single preexisting flaw, it is the first time quantitative and continuous interpretation and comparison of the mesoscale‐macroscale fracture process have become available. The present findings provide substantial improvement on our understanding of the mesoscale‐macroscale fracture process in rock specimens containing a single preexisting flaw. In addition, the experimental results provide insightful information about the laboratory scale fault extension and propagation and laboratory scale acoustic emission moment‐frequency distribution. The findings are helpful for establishing the link between the laboratory scale tests and the tectonic scale seismic activities.

Crystallographic preferred orientations in eclogites – A review

During the last decades, processes taking place in subduction zones have been a topic of extensive debate. There are many models on a tectonic scale, but knowledge of deformation at microscopic levels is essential for an understanding of the processes involved. Crystallographic preferred orientation (CPO) investigations of minerals in eclogites yield the possibility to study deformation in the crustal part of subducted oceanic lithosphere, as well as subducted continental units containing basic intrusions, which are frequently exhumed during continental collision. From CPO data of omphacite and garnet, as well as other constituent minerals in eclogites, conclusions on stress and strain at depth in currently active subduction zones can be drawn, as the pressure-temperature and strain path of the now exhumed rocks can be unraveled. This contribution provides an overview of CPO studies of eclogites concerning slip systems, deformation, strain and other possible CPO forming mechanisms in all major constituent mineral phases in eclogites and the implications of these microstructural data on subduction zone processes are discussed. Nevertheless, there are still many open questions and future research is essential.

Fracto-emissions as seismic precursors

Three different forms of energy might be used as earthquake precursors for environmental protection against seismicity. At the tectonic scale, Acoustic Emission (AE) prevails, as well as Electro-Magnetic Emission (EME) at the intermediate scales, and Neutron Emission (NE) at the nano-scale. TeraHertz pressure waves are in fact produced at the last extremely small scale, and fracture experiments on natural rocks have recently demonstrated that these high-frequency waves are able to induce nuclear fission reactions with neutron and/or alpha particle emissions. Very important applications to earthquake precursors can be proposed. The authors present the results they are obtaining at a gypsum mine located in Northern Italy. In this mine, to avoid interference with human activities, the instrumental control units have been located at one hundred metres underground. The experimental results obtained from July 1st, 2013 to December 31, 2015 (five semesters) are analysed by means of a suitable multi-modal statistics. The experimental observations reveal a strong correlation between the three fracto-emission peaks (acoustic, electromagnetic, and neutron emissions) and the major earthquakes occurred in the surrounding areas.

Rock deformation goes magnetic

Geophysics The topography in regions such as the western United States depends on the strength of the crust and lithosphere. To better understand regional tectonic–scale topographic evolution, Liu et al. incorporated magnetotelluric imaging, which relies on electromagnetic fields to investigate