Why is plane-bed topography unstable under certain flow conditions? We investigate the grain-scale mechanisms responsible for topographic instability at the onset of bedform development. Measurements of fluorescent tracer particle motion were used to estimate the ensemble mean particle activity, entrainment rate, hop distance, travel time, and particle velocity characteristic of flow conditions straddling the threshold stress for bedform development. Based on these data, we propose two hypotheses to explain the destabilization of planar topography with rising transport conditions. Hypothesis 1: plane-bed topography is unstable above a theory-predicted entrainment rate threshold that varies primarily as a function of particle diameter. Hypothesis 2: plane-bed topography is unstable above a threshold particle collision frequency that is proportional to bedload flux.The threshold particle collision frequency is predicted analogously to the propensity for congestion shockwaves in vehicular traffic flow theory.

This paper focuses on the study of the temporal evolution of seismicity and the role of fluids during major earthquake sequences that occurred in the central Apennines and Eastern California Shear Zone-Walker Lane belt over the last two decades: The 1997 Colfiorito sequence, the 2009 L’Aquila sequence, the 2016 Amatrice-Norcia sequence, and the 2019 Ridgecrest sequence. The availability of different high-quality seismic catalogs offers the opportunity to evaluate in detail the temporal evolution of the earthquake’s size distribution (or b-value) and propose a physical explanation based on the effect of the fluid flow process in triggering seismicity. For all seismic sequences, the b value time series show a gradual decrease from a few months to one year before mainshocks. The gradual decrease in the b value is interpreted in terms of coupled fluid-stress intensity as a gradual increase in earthquake activity due essentially to the short-term to intermediate-term pore-fluid fluctuations. For the 2016 Amatrice-Norcia sequence and the 2019 Ridgecrest sequence, the temporal variation of b value during the foreshock sequence is characterized by a double b value minimum separated by a short-lived b value increase as observed in laboratory experiments on water-saturated rocks. Based on laboratory experiments results, the observed short–term fluctuation of b value is presented here as an accelerating cracks growth due essentially to the fluid flow instability. Despite that the occurrence of seismic precursors could have been predictable in areas with high dense seismic networks, the different b value time series show difficulty to establish a correspondence between the duration of the foreshock activity and the magnitude of the next largest expected earthquake. This may suggest that the spatial and temporal evolution of fluid migration controls the size of the ruptures.

Seamounts are isolated elevations in the seafloor with circular or elliptical plan, comparatively steep slopes, and relatively small summit area (Menard, 1964). The vertical gravity gradient (VGG), which is the curvature of the ocean surface topography derived from satellite altimeter measurements, has been used to map the global distribution of seamounts (Kim & Wessel, 2011). We used the latest grid of VGG to update and refine the global seamount catalog; we identified 10,796 new seamounts, expanding the catalog by 1/3. 739 well-surveyed seamounts, having heights ranging from 421 m to 2500 m, were then used to estimate the typical radially-symmetric seamount morphology. First, an Empirical Orthogonal Function (EOF) analysis was used to demonstrate that these small seamounts have a basal radius that is linearly related to their height – their shapes are scale invariant. Two methods were then used to compute this characteristic base to height ratio: an average Gaussian fit to the stack of all profiles and an individual Gaussian fit for each seamount in the sample. The first method combined the radial normalized height data from all 739 seamounts to form median and median-absolute deviation. These data were fit by a 3-parameter Gaussian model that explained 99.82% of the variance. The second method used the Gaussian function to individually model each seamount in the sample and further establish the Gaussian model. Using this characteristic Gaussian shape we show that VGG can be used to estimate the height of small seamounts to an accuracy of ~270 m.

For more than 150 years, geological features claimed to be evidence for pre-Pleistocene glaciations have been debated. Advancements in recent decades, in understanding features generated by glacial and mass flow processes, are here reviewed. It is timely to make renewed comparisons and to re-visit the interpretations of data used to support pre-Pleistocene glaciations. Similarities and differences of Quaternary glaciogenic and sediment gravity flow features, which are most often referred to as proxies and evidence of ancient glaciations, are documented, discussed and closely examined, in order to uncover the origin of more ancient deposits. It is necessary to use multiple proxies to develop a correct interpretation of ancient strata. Analyses and evaluation of data are from a) Quaternary glaciations and glaciers, b) formations which have been assigned to pre-Pleistocene glaciations, and c) formations with comparable features associated with mass-flow deposition (and occasionally tectonics). The aim is not to reinterpret specific formations and past climate changes, but to enable data to be evaluated using a broader and more inclusive conceptual framework. To achieve this goal, detailed descriptions of field evidences are documented from papers that may suggest different interpretations of these data. This is not in an intention to present revised interpretations of these papers, but to collect data and develop a foundation for enhanced analysis of geologic processes and features. Regularly occurring features interpreted to be glaciogenic and are contemporaneous with pre-Pleistocene diamictites which have been interpreted to be tillites, have often been shown to have few or no Quaternary glaciogenic equivalents. These same features commonly form by sediment gravity flows or other non-glacial processes, which may have led to misinterpretations of ancient deposits. These features include, for example, appearances and documented data from the extent and thickness of diamictite deposits, environmental and depositional affinity of fossils in close connection to diamictites, grading and bedding of diamictites, fabrics, size of erratics, polished and striated clasts and surfaces (“pavements”), boulder pavements, lineations, valleys, glaciofluvial deposits, dropstones, laminated sediments, glaciomarine sediments, periglacial structures, soft sediment tectonics, and surface microtextures. The analysis of these features provide detailed documentation that may be used to help identify the origin for many pre-Pleistocene diamictites. Recent decades of progress in research relating to glacial and sediment gravity flow processes has resulted in proposals by geologists, based on more detailed field data, more often of an origin by mass movements and tectonism than glaciation. The most coherent data of this review, i.e. appearances of features produced by glaciation, sediment gravity flows and a few other geological processes, are summarized in a Diamict Origin

Subtle elastic rock deformation during aquifer testing may bear hydraulic parameter (permeability and compressibility) information owing to the poroelastic hydromechanical coupling effect. Here we report that such in situ rock deformations (~50 µε) during an aquifer pumping test are successfully measured along a vertical well by a high-resolution fiber optic distributed strain sensing (DSS) tool with an accuracy of 0.5 µε. We investigate the feasibility of hydraulic parameter estimation at meter scale using DSS data through a coupled hydromechanical model. Both synthetic and field cases are tested with sensitivity analysis. The results indicate that the simultaneous estimation of permeability and compressibility using DSS data is possible at low noise levels. However, only non-global near-optimal solutions can be obtained using the applied gradient-based inversion algorithm, because of parameter crosstalk and sensitivity problems when the data contain large noise. In particular, estimation is difficult for zones with relatively low permeability due to the low sensitivity to the strain changes. The estimated permeability/compressibility structures for the field test are largely consistent with other geological information from well logs. Our study suggests that DSS data can be quite useful in aquifer characterization and fluid flow profiling in addition to geomechanical monitoring. The obtained hydraulic information is beneficial for the optimized reservoir management of water and oil/gas storage.

High-resolution space-based spectral imaging of the Earth’s surface delivers critical information for monitoring changes in the Earth system as well as resource management and utilization. Orbiting spectrometers are built according to multiple design parameters, including ground sampling distance (GSD), spectral resolution, temporal resolution, and signal-to-noise. The different applications drive divergent instrument designs, so optimization for wide-reaching missions is complex. The Surface Biology and Geology component of NASA’s Earth System Observatory addresses science questions and meets applications needs across diverse fields, including terrestrial and aquatic ecosystems, natural disasters, and the cryosphere. The algorithms required to generate the geophysical variables from the observed spectral imagery each have their own inherent dependencies and sensitivities, and weighting these objectively is challenging. Here, we introduce intrinsic dimensionality (ID), a measure of information content, as an applications-agnostic, data-driven metric to quantify performance sensitivity to various design parameters. ID is computed through the analysis of the eigenvalues of the image covariance matrix, and can be thought of as the number of significant principal components. This metric is extremely powerful for quantifying the information content in high-dimensional data, such as spectrally resolved radiances and their changes over space and time. We find that the intrinsic dimensionality decreases for coarser GSD, decreased spectral resolution and range, less frequent acquisitions, and lower signal-to-noise levels. This decrease in information content has implications for all derived products. Intrinsic dimensionality is simple to compute, providing a single quantitative standard to evaluate combinations of design parameters, irrespective of higher-level algorithms, products, applications, or disciplines.

The India-Asia continental collision, starting at ~50 Ma, has resulted in about 2000 km crustal shortening to build the Himalaya-Tibetan plateau, which is one of the landmark terrestrial features on the Earth. In this study, using a thin viscous sheet approximation we performed scaled laboratory model experiments to investigate the spatiotemporal variation in the Himalaya-Tibetan tectonics. The experiments allow us to constrain the Tibetan plateau topography as a function of the varying India-Asia convergence rates. Our results suggest two rigid crustal blocks: Tarim and Sichuan basins steered the growth pattern in the Tibetan plateau. Because of the resistance from the rigid Tarim block western Tibet uplifted first relative to eastern part, creating a topographic elevation difference, which directed the crustal flows grossly to NE. We show from experiments the elevated plateau topography underwent gravitational collapse when the indentation velocity dropped to present average of ~3.5 cm/yr at around 18 Ma. This event eventually led to a transition from contraction to extensional tectonics, dominated by east-directed crustal flows in response to the eastward topographic gradient developed during the early stage of fast collision. We compare the present day crustal flow velocity field, strain rates, and topographic variations in the model Tibet with the actual observations in the Himalaya-Tibet Mountain System.

Global tomographic models have revealed the existence of two large low shear-wave velocity provinces (LLSVPs) underlying Africa and the Pacific, which are regarded as sources of most typical mantle plumes. Plume-induced basalts have the potential to imply the formation mechanisms and evolutional histories of the LLSVPs. In this study, we measured H2O contents in clinopyroxene and olivine phenocrysts from Cenozoic basalts produced by the Kerguelen and Crozet mantle plumes, which are deeply rooted in the African LLSVP. The results were used to constrain the H2O content in the source of basalts, yielding 1805 ± 579 ppm for the Kerguelen plume and 2144 ± 690 ppm for the Crozet plume. H2O contents in the mantle sources of basalts fed by other plumes rooted in these two LLSVPs were calculated from literature data. Combining these results together, we show that the African LLSVP seems to have higher H2O content and H2O/Ce (620-2144 ppm and 184-592, respectively) than the Pacific LLSVP (262-671 ppm and 89-306, respectively). These features could be ascribed to incorporation of subducted material, which had experienced variable degrees of dehydration during its downwelling, into the LLSVPs. Our results imply that the continuous incorporation of subducted oceanic crust modifies the compositions of LLSVPs and induces heterogeneous distribution of H2O within individual LLSVPs and distinct H2O contents between the African and Pacific LLSVPs. This suggests that the African and Pacific LLSVPs might have different formation and evolution histories.

Recent developments in space-based surveying methods of Earth’s topography, including the differential synthetic aperture radar interferometry (DInSAR), increased the availability of options for monitoring of land subsidence. However, DInSAR methods require expert knowledge, specialized software, and are time-consuming. Here, we demonstrate that a land subsidence signal in the difference of freely available global digital elevation models (DEMs), e.g., SRTM and TanDEM-X, is identifiable using a simple statistical method. This finding opens up a venue to develop a dedicated computer application to identify land subsidence or uplift of the order > 20 mm yr. Such an application would allow for the monitoring of the impacts of underground mining, earthquakes, landslides, volcanic activities, and similar effects on the Earth’s topography. This software will provide a useful and cost-effective approach to scan the global DEMs for the benefit of many land planning and management agencies around the world.

Unsaturated fractured aquifer systems offer a domain for complex gravity-driven flow dynamics leading to the development of preferential flow along fracture networks that often strongly contributes to rapid mass fluxes. This behaviour is difficult to recover by volume-effective modeling approaches (e.g. Richards equation) due to the non-linear nature of free-surface flows and mass partitioning processes at unsaturated fracture intersections. The application of well-controlled laboratory experiments enables to isolate single aspects of the mass redistribution process that ultimately affects travel time distributions across scales. We use custom-made acrylic cubes (20 cm x 20 cm x 20 cm) in analogue percolation experiments to create simple fracture networks with single or multiple horizontal fractures. A high precision multichannel dispenser produces gravity-driven free surface flow (droplets; rivulets) at flow rates ranging from 1 ml/min to 5 ml/min. Hereby, total inflow rates are kept constant while the fluid is injected via 15 (droplet flow) or 3 inlets (rivulet flow) to reduce the impact of erratic flow dynamics. Normalized fracture inflow rates (Q_f/Q_0) are calculated and compared for aperture widths d_f of 1 mm and 2.5 mm. A higher efficiency in filling an unsaturated fracture by rivulet flow observed in former studies can be confirmed. The onset of a capillary driven Washburn-type flow is determined and recovered by an analytical solution. In order to upscale the dynamics and enable the prediction of mass partitioning for arbitrary-sized fracture cascades a Gaussian transfer function is derived that reproduces the repetitive filling of fractures, where rivulet flow is the prevailing regime. Results show good agreement with experimental data for all tested aperture widths.

Experimental study of the phase and amplitude observations of sub-ionospheric very low and low frequency signals is performed to analyze the response of the lower ionosphere during the August 21, 2017 total solar eclipse in the United States of America. Three subionospheric wave paths have been investigated. The length of the paths varied from 2200 to 6500 km, signal frequencies were 21.4 kHz, 25.2 kHz and 40.8 kHz. Two paths crossed the region of total eclipse and the third path was in the region of 40-60% of obscuration. None of the signals revealed any noticeable amplitude changes during the eclipse while negative phase anomalies (from -35° to -95°) were detected for all three paths. It was shown that the effective reflection height of the ionosphere in low and middle latitudes has been increased by 3.5-5 km during the eclipse.

High concentration of fluoride in the groundwater is observed to be associated with granitic aquifers as well as near phosphate mines around the globe. The present work is a hydrogeological study of the ground water of Beldih phosphate mines in India. Being located in the Singhbhum shear zone the area has a complex tectonic history and is dominated by phosphate, alkali granites, amphibolites, and granitic gneiss with higer abundance of fluoride bearing minerals like apatite and biotite. Total of 12 water samples were collected for a preliminary study to assess the spatial variation of fluoride in ground water and surface water with an aim to understand the effect of phosphate mines in elevating fluorosis in adjoining areas. The groundwater chemistry shows a trend that the concentration of fluoride and nitrate gets elevated as we approach towards the open cast phosphate mines. From the spatial observation combined with the water chemistry and geology it is evident that the apatite dissolution is the prime cause of the elevation in fluoride concentration. However presence of iron in the lithology controls the fluoride level to some extent. Since the area is effected with high fluorosis its can be concluded that the groundwater geochemistry along with the air borne fluoride present in the phosphate dust are the major cause of the fluorosis. The exploration of phosphate must be carried out with out most environmental care and the mitigation of post mining effect should be planned before mining operation. Fluorosis is an irreparable health hazard and a major geohealth concern that has already affected a large amount of population.

Transmission muography is an expanding technique based on the attenuation of the natural-occurring cosmic muons flux due to the opacity of the medium to obtain the distribution of density around the detector. The current work introduces the technology developed by the Temporal Tomography of the Densitometry by the Measurement of Muons (T2DM2) collaboration. The MUST2 camera leans on a thin time projection chamber read by a resistive Micromegas. This new tool presents interesting distinctive features, allowing a wide angular acceptance of the detector with a low weight and volume, well adapted for confined spaces or underground operation. The results obtained from field measurement campaign carried out at the dam overlooking the village of Saint-Saturnin-les-Apt (South-East of France) are presented. The influences of (i) the host rock body of the barrage and dam’s structure, (ii) the temporal water level variations of the reservoir and (iii) the effect of the temperature on the muons flux measurements are discussed The main challenge that faces the project is that the muon trajectory reconstruction algorithm cannot infer the arrival angles for a non-negligible number of detected events, with the subsequent loss of information. The data collected during the campaign of measurements, should help improving the algorithm’s robustness and reconstruction efficiency. Field transportability and the capability to perform long-term out-of-lab measurements have been demonstrated. The successful proof-of-concept trial makes the MUST2 camera a valuable candidate for transmission muography purposes, particularly in challenging available volume scenarios. The next phase of the T2DM2 project aims at imaging and monitoring the hydrodynamics across the unsaturated zone of the Fontaine-de Vaucluse aquifer. To do so, a network of 20 autonomous detectors will be constructed and deployed within the facilities of the Low Background Noise Laboratory of Rustrel (LSBB), France. The privileged emplacement of the LSBB allows the access to both the surface and to a network of 4 km of underground galleries with depths ranging from 0 to 518 m.

River deltas are under external stress from sea-level rise, subsidence, and decreases in sediment and water discharges caused by anthropogenic activity. Naturally, delta channels respond to these stressors by avulsing and bifurcating. Avulsion involves an abrupt change of channel course that changes the locus of sediment deposition. Bifurcation occurs in the most seaward parts of river deltas where channels divide due to mouth bar deposition. However, how avulsion (top-down) and bifurcation (bottom-up) processes interact in river deltas is poorly understood. We conducted a suite of morphodynamic numerical model experiments using six scenarios with different slopes, selected within the range observed in natural deltas, upstream from the delta apex. The experiments allow us to understand the internal (autogenic) interaction of avulsion and bifurcation in the absence of external (allogenic) forcing. We find that topset slope (Stopset) primarily controls the avulsion timescale (Ta) with Ta = 0.3Stopset-1.18 (R2 = 69%; p < 0.05). Avulsion and bifurcation are shown to occur simultaneously based on the non-unimodal distribution of dimensionless island sizes created in our model, even though these are mechanistically different processes. Comparing our findings to natural deltas, we find consistent avulsion timescale-topset slope (Ta-Stopset) relationships. Our findings show how the delta topset slope serves as the first order control of the avulsion timescale, and how avulsion and bifurcation interact throughout delta building processes. This interaction is significant due to their direct impact on coastal and inland hazards that arise from rapid geomorphic change and flooding on densely populated deltas.

Researcher Ridge (RR) is a 400km long, WNW-ESE oriented chain of volcanic seamounts, located on ~20 to 40 Ma old oceanic crust on the western flank of the Mid-Atlantic Ridge (MAR) at ~15°N. RR remained nearly unstudied, and thus its age and origin are currently unclear. At roughly the same latitude, the MAR axis is bathymetrically elevated and produces geochemically enriched lavas (the well-known 14°N MAR anomaly). This study presents 40Ar/39Ar age data, major and trace elements, and Sr-Nd-Pb-Hf isotopic compositions of volcanic rocks dredged from several seamounts of the RR and along the MAR between 13-14°N. The results reveal that RR lavas have geochemically enriched ocean island basalt (OIB) compositions ([La/Sm]N=1.7-5.0, [Ce/Yb]N=1.58-11.3) with isotopic signatures (143Nd/144Nd = 0.51294-0.51316, 206Pb/204Pb = 19.14-19.93, 176Hf/177Hf = 0.28307-0.28312) trending to or overlapping the ubiquitous FOZO (Focal Zone, e.g., Hart et al., 1992, Science 256) mantle composition. Major and trace element characteristics denote that RR lavas formed by small degrees of melting from a deep source in the garnet stability field and experienced high pressure fractionation beneath a lithospheric lid. Although the sparseness of samples suitable for 40Ar/39Ar dating prevents establishing a clear age progression for the seamount chain, one well constrained basalt groundmass age of 28.75 ± 0.14 Ma (2σ) for one seamount near the western end of RR indicates that this volcano formed ~11 Ma later than the underlying lithosphere. Taken together, RR is interpreted as a hotspot track, albeit formed by a relatively weak melting anomaly. Compared to RR, the lavas from the 14° N MAR anomaly have slightly less enriched compositions, exhibiting enriched (E)-MORB compositions ([La/Sm]N=1.81-2.29). Their isotopic ratios largely overlap with the RR compositions, thus suggesting a genetic relationship. We therefore propose that the enigmatic 14°N MAR anomaly is caused by deflection of upwelling RR plume material towards the approaching (westward migrating) MAR, causing the production of E-MORBs with nearly similar isotopic compositions to the RR lavas. Once the plume was captured by the spreading ridge, off-axis hotspot track volcanism ceased, resulting in a 300 km wide gap of seamount formation between the eastern end of RR and the MAR.

Study of solid and fluid inclusions in carbonatite is vital for understanding the nature of primary carbonatitic magma. In this study, biphase fluid inclusions were observed in calcites and solid mineral inclusions were observed in accessory magnetite in Sung Valley carbonatite of NE India. Thi carbonatite is part of an Ultramafic-Alkaline-Carbonatite Complex (UACC), related to the Kargue-len Plume activity. All of the studied inclusions are primary in nature. Raman spectroscopy of these inclusions suggested that the biphase inclusions hosted by calcite are essentially composed of water whereas, the solid mineral inclusions hosted by magnetite in the Sung Valley carbonatite are manasseite, ferrohog-bomite and amesite. The extremely hydrous minerals inclusions occurring in the magnetite are not a product of hydrothermal alteration but represent the primary magmatic characteristics of the parental magma. Our observations suggest that the parental magma of the Sung Valley carbonatite was ultra-hydrous in nature, which can be attributed to metasomatism of the source carbonated peridotite. Our study also suggests that there is a strong possibility for more hydrous carbonatite melts to occur on a global scale. Plain Language Summary Primary solid inclusions of manasseite, ferrohogbomite and amesite and biphase fluid inclusions of H 2 O were observed in magnetite and calcite respectively in Sung Valley carbonatite of northeast India. These carbonatite are related to Kerguelen mantle plume. Solid and fluid inclusions, identified with the help of Raman spectroscopy, are all of hydrous nature and provide detailed information about the magma these carbonatite have crystallized from. Inclusion data suggests that the parental magma of these carbonatite had a significant amount of dissolved water. Such ultra-hydrous character of the parental magma could be acquired due to the exhaustion of hydrous minerals during low degree of partial melting of the source carbonated peridotite.

The transition from active to passive continental margin of the South China Sea (SCS) is usually inferred to occur in the Late Mesozoic to Early Cenozoic. However, it is less known about the tectonic characteristics of active continental margins before the Late Mesozoic, which hampers the recognition of integral evolution of the SCS. The International Ocean Discovery Program (IODP) site U1504 has sampled greenschist facies mylonite from the basement in the Outer Margin High of the northern SCS continental margin, which potentially record the Mesozoic and Cenozoic tectonic evolution of the SCS region. The microstructure has identified two episodes of deformation in the mylonite, namely early ductile and late brittle deformation, but without age constraints. Here, we further identify three episodes of carbonate veins (pre-mylonite, syn-mylonite and post-mylonite) in the greenschist facies mylonite according to the intersecting relationship between the veins and the mylonite foliation. Then we select 10 carbonate samples for in situ U-Pb dating, and obtain three accurate ages. The pre-mylonite carbonate veins are dated to 210 ± 20 Ma and 195 ± 32 Ma, respectively, which might denote the age of the protolith clast. The age of the syn-mylonite carbonate vein is 135 ± 12 Ma. But for the post-mylonite carbonate veins, no effective age was obtained using U-Pb dating method. Post-mylonite carbonate veins and late brittle fractures were formed at the same time, and the formation environment is similar to the overlying Late Eocene bioclastic limestone. Therefore, combining the microstructure, geochemistry and seismic profile, we speculate that the post-mylonite carbonate veins and brittle fractures may be formed during the Early Cenozoic rifting. These dating ages of the three episodes of carbonate veins suggest that the mylonite records at least two main periods of continental extension in the SCS region since the Early Cretaceous. In reference to the Mesozoic tectonic settings, we infer that, due to the slab rollback of the subducting paleo-Pacific, the SCS continental margin started significant extension during the Early Cretaceous as shown by the ductile deformation of the mylonite. In the Early Cenozoic, the mylonite was exhumated to the seafloor along with further continental extension, and weak brittle deformation occurred in the mylonite. Therefore, the Early Cretaceous extension of the SCS active continental margin may have a certain promotion effect on the rupture of the passive continental margin in the Cenozoic. Keywords: Greenschist facies mylonite; Carbonate U-Pb dating; Continental margin of the SCS; Early Cretaceous; IODP 368

Seismic rupture in strong, anhydrous lithologies of the lower continental crust requires high failure stress, in the absence of high pore fluid pressure. Several mechanisms proposed to generate high stresses at depth imply transient loading driven by a spectrum of stress changes, ranging from highly localised stress amplifications to crustal-scale stress transfers. High transient stresses up to GPa magnitude are proposed by field and modelling studies, but the evidence for transient pre-seismic stress loading is often difficult to extract from the geological record due to overprinting by coseismic damage and slip. However, the local preservation of deformation microstructures indicative of crystal-plastic and brittle deformation associated with the seismic cycle in the lower crust offers the opportunity to constrain the progression of deformation before, during and after rupture, including stress and temperature evolution. Here, detailed study of pyroxene microstructures characterises the short-term evolution of high stress deformation and temperature changes experienced prior to, and during, lower crustal earthquake rupture. Pyroxenes are sampled from pseudotachylyte-bearing faults and damage zones of lower crustal earthquakes recorded in the exhumed granulite facies terrane of Lofoten, northern Norway. The progressive sequence of microstructures indicates localised high-stress (at the GPa level) preseismic loading accommodated by low temperature plasticity, followed by coseismic pulverisation-style fragmentation and subsequent grain growth triggered by the short-term heat pulse associated with frictional sliding. Thus, up to GPa-level transient high stress leading to earthquake nucleation in the dry lower crust can occur in nature, and can be preserved in the fault rock microstructure.

Information on the elemental abundances and distribution is essential for understanding the petrological characteristics and geological evolution of the Moon. In this paper, the thermal infrared data acquired by Lunar Reconnaissance Orbiter (LRO) Diviner are processed to investigate lunar elemental abundances on a global scale (60°N/S) for the first time. The Diviner Level 3 Standard Christiansen feature (CF) product with the resolution of 128 pixels/degree and the coverage of 99.86% is first analyzed and used. The Diviner global models are then established by the univariate regression methods based on the relationships between Diviner CF and ground truths of elemental abundances at 48 lunar sampling sites and the limitations of 1 RMSE of 48 datasets. Finally, the best maps of SiO, TiO, AlO, FeO, MgO and CaO abundances considering both resolution and coverage simultaneously are presented and analyzed from global, geologic units, crater and ejecta surfaces. The comparisons indicate that a satisfactory consistency is observed between Diviner results and Clementine or Chang’E (CE)-1 results, while Diviner results exhibit better practicability in presenting detailed information for elemental abundances on lunar surfaces and higher accuracy on the surface with high latitudes or poor light conditions. Meanwhile, it is also demonstrated that Diviner results is the reliable data sources for the applications in classifications of mare basalt, inhomogeneity of highland crust and Mg#.

An outstanding question for induced seismicity is whether the volume of injected fluid and/or the spatial extent of the resulting pore pressure and stress perturbations limit rupture size. We simulate ruptures with and without injection-induced pore pressure perturbations, using 2-D dynamic rupture simulations on rough faults. Ruptures are not necessarily limited by pressure perturbations when 1) background shear stress is above a critical value, or 2) pore pressure is high. Both conditions depend on fault roughness. Stress heterogeneity from fault roughness primarily determines where ruptures stop; pore pressure has a secondary effect. Ruptures may be limited by fluid volume or pressure extent when background stress and fault roughness are low, and the maximum pore pressure perturbation is less than 10% of the background effective normal stress. Future work should combine our methodology with simulation of the loading, injection, and nucleation phases to improve understanding of injection-induced ruptures.

The demise and closure of the Neotethyan Ocean gave way to the collision and finally amalgamation of various continental fragments in Turkey along the Izmir-Ankara-Erzincan and Intra-Tauride suture zones. These continental fragments include Pontides in the north and Menderes-Tauride , and Kırşehir Block in the south. This study aims to the restoration of these suture zones in central Anatolia using paleomagnetic tools during Neogene. Most of the paleomagnetic studies carried out in the region consider the deformation of Anatolian Block as a monolithic block rotated counter-clockwise due to escape tectonics since the Miocene. We introduce new paleomagnetic evidence obtained from Neogene sedimentary successions and few volcanic suits. Our results point out five distinct tectonic domains with distinct rotation patterns that indicate the rotational deformation of Central Anatolia is far more complex than generally presumed. Among these, 1) Kırıkkale-Bala Domain (KB) is rotated ~18° clockwise, 2) the Tuz Gölü Domain (TG) underwent ~15° counter-clockwise rotation, 3) the Alcı-Orhaniye Domain (AO) rotated ~25° counter-clockwise sense, 4) the Haymana Basin is divided into two different domains, (4) the Northern Haymana Domain (NHY) underwent ~17° counter-clockwise rotation while (5) the Southern Haymana Domain (SHY) underwent barely no net rotation (~5° clockwise) since the early Miocene. The Kırşehir Block was proposed to be an NNE-SSW striking tectonic block that broken into three fragments. These fragments underwent clockwise, in the north, and counterclockwise rotations in the south, respectively, during early Tertiary due to collision and N-S shortening of the Kırşehir Block between Taurides and the Pontides.

The tectonic development of the Southeast Anatolian Orogenic Belt (SAOB) is closely related to the demise of the NeoTethys Ocean, which was located between the Arabian and Eurasian plates from the late Cretaceous to Late Miocene. The ocean contained several continental slivers and intra-oceanic magmatic arcs. The continental slivers represent narrow tectonic belts rifted off and drifted away from the Arabian Plate while the NeoTethyan Ocean and the back-arc basins were opened. Later they collided with one another during the branches of the oceans were eliminated. In these periods, the continental slivers were involved in the subduction zone and turned into metamorphic massifs. During the Late Cretaceous, the first collision occurred when an accretionary complex was thrust over the Arabian Plate’s leading edge. Despite the collision, the ocean survived in the North and Its northward subduction generated a new intra oceanic arc, which collided later with the northerly located continental slivers. In this period, the metamorphic massifs and the intra-oceanic arc front migrated to the South. The new magmatic arc collided with the southerly transported nappe package during the Late Eocene. The amalgamated nappe pile eventually obducted onto the Arabian Plate during the Late Miocene. The collision produced escape structures during the Neotectonic period.

The East Anatolian High Plateau, part of the Alpine-Himalayan orogen, is a 200 km wide, approximately E-W trending belt surrounded by two peripheral mountains of the Anatolian Peninsula. The plateau is covered by a thick, interbedded Neogene volcanic and sedimentary rocks. Outcrops of the underlying rocks are rare. Therefore, contrasting views were proposed on the nature of the basement rocks. New geological and geophysical data suggest the presence of an ophiolitic mélange-accretionary complex under cover rocks of Eastern Anatolia. The cover units began to be deposited during the closure of the NeoTethyan Ocean that was located between the Pontide arc to the north, and the continental slivers drifted away from the Arabian Plate to the south. The surrounding orogenic belts experienced different orogenic evolution. The Eastern Anatolian orogen was formed during the later stages of the development of the surrounding orogenic belts. In this period, the melange-accretionary prism that occupied a large terrain behaved like a wide and thick cushion, which did not allow a head-on collision of the bordering continents. NeoTethyan oceanic lithosphere was eliminated from entire eastern Turkey by the Late Eocene. The eastern Anatolia began to rise when the northern advance of the Arabian Plate continued after the total demise of the oceanic lithosphere. The present stage of the elevation of the East Anatolian Plateau as a coherent block started during the Late Miocene.

The Rochester and Adna 7.5 minute quadrangles in the Washington forearc of the Cascadia subduction zone encompass the Doty fault, a large forearc fault crossing the I-5 corridor south of Centralia. We have begun a cooperative geological and geophysical study of the area to assess the seismic hazard to a water retention facility that has been proposed to mitigate flooding along the Chehalis River and the I-5 corridor. This region between Olympia and Portland is undergoing north-south compression, clockwise rotation, and regional uplift associated with both subduction processes and the northward migration of the forearc block. Past studies identified multiple faults that strike NW-SE and E-W in the northern and southern parts of the study area, respectively. The Kopiah, Scammon Creek, Salzer Creek and Doty faults all interact within our study area, in ways that are poorly understood. An integrated geophysical investigation will assist the State-Federal cooperative mapping program called STATEMAP efforts to produce detailed 1:24,000 scale geologic maps of the area. Geophysical field work in the summer of 2018 includes a roughly 15 x 32 km gravity grid with ~2 km station spacing. Station spacing along known geologic structures is ~1 km to provide greater resolution. Results from our coarse gravity grid will provide targets for additional high resolution profiles. A high resolution ground magnetic grid also extends across both quadrangles, and preliminary results demonstrate its efficacy at elucidating structure. Seismic profiles acquired by the USGS across the Doty fault will constrain our geophysical modeling, which will combine the high resolution gravity and magnetic profiles in a geologic model of the subsurface to support the mapping efforts of the STATEMAP program. The data and models will provide insight about total offset across these faults, precisely identify locations of faults that are not exposed at the surface, and allow us to better understand the structure of these faults. These interpretations will allow us to more accurately understand the potential seismic risk these faults pose to nearby population centers and infrastructure.