The conditions controlling the formation of sedimentary dolomite are still poorly understood despite decades of research. Reconstructing formation temperatures and δ18O of fluids from which dolomite has precipitated is fundamental to constrain dolomitization models. Carbonate clumped isotopes are a very reliable technique to acquire such information if the original composition at the time of precipitation is preserved. Sedimentary dolomite first mostly forms as a poorly-ordered metastable phase (protodolomite) and subsequently transform to the more stable ordered phase. Due to this conversion its important to determine if the original clumped isotope composition of the disordered phase is preserved during diagenetic conversion to ordered dolomite, and how resistant clumped isotope signatures are against bond reordering at elevated temperatures during burial diagenesis. Here, we present a series of heating experiments at temperatures between 360 and 480 °C with durations between 0.125 and 426 hours. We uses fine-grained sedimentary dolomites to test the influence of grains size, and cation ordering on bond reordering kinetics. We analyzed a lacustrine dolomite with poor cation ordering and well ordered a replacement dolomite, both being almost stoichiometric. The poorly ordered dolomite shows a very rapid alteration of its bulk isotope composition and higher susceptibility to solid state bond reordering, whereas the well-ordered dolomite behaves like a previously studied coarse-grained hydrothermal dolomite. We derive dolomite-specific reordering kinetic parameters for ordered dolomitea and show that ∆47 reordering in dolomite is material specific. Our results call for further temperature-time series experiments to constrain dolomite ∆47 reordering over geologic timescales.

Relic coastal landforms (fossil corals, cemented intertidal deposits, or erosive features carved onto rock coasts) serve as sea-level index points (SLIPs) widely used to reconstruct past sea-level changes. Traditional SLIP-based sea-level reconstructions face challenges in capturing continuous sea-level variability and dating erosional outcrops, such as ubiquitous tidal notches, carved around tidal level on carbonate cliffs. We propose a novel approach to such challenges by using a numerical cliff erosion model embedded within a Monte-Carlo simulation to investigate the most likely sea-level scenarios responsible for shaping one of the best-preserved tidal notches of the Last Interglacial age in Sardinia, Italy. Results align with Glacial Isostatic Adjustment model predictions, indicating that synchronized or out-of-sync ice-volume shifts in Antarctic and Greenland ice sheets can reproduce the notch morphology, with sea level confidently peaking at 6m. This new approach yields continuous sea-level insights, bridging gaps in traditional methods and illuminating past Interglacial sea-level dynamics.

The Carrascoy and Palomares faults are two major active faults of the Eastern Betic Shear Zone (SE Iberia), both controlling conspicuous mountain fronts. However, the area in between both faults, corresponding to the Mazarron Graben (MG), is a nearly flat plain bounded by a relief of smooth hills whose tectonic origin and evolution remains uncertain. By means of a morphotectonic analysis, geophysical survey and paleoseismological trenching we point out that this is area of distributed deformation controlled by folds of variable amplitude nucleated in high angle reverse faults with sinistral component without a well-defined deformation front. The MG developed a marine basin during the Upper Miocene evolving into an alluvial environment with calcrete pedogenic development through the Pleistocene, which formed a tableland landscape that favors the identification of tectonic structures. In this study we demonstrate how some of the ancient normal faults controlling the graben were reactivated as reverse during the late Middle Pleistocene within a regional frame of positive tectonic inversion. Such inversion is evidenced by several emblematic structures: (i) presence of harpoon folding, and (ii) newly formed high angle reverse faults, which dips increase and ruptures become younger backwards on the hanging wall. Based on the timing of the observed deformation, we also suggest that the onset of the regional tectonic inversion might be related to the tectonic evolution of the neighboring Carrascoy and Palomares faults, producing a local stress tensor varying dramatically from extension to compression within the neotectonic period in a regional convergence tectonic frame.

Detachment faulting related to oceanic core complexes (OCCs) has been suggested to be a manifestation of slow seafloor spreading. Although numerical models suggest OCCs form under low magma supply, the specific interaction between magmatism and tectonic faulting remains elusive. This paper examines seismic observations detailing the spatiotemporal interactions between magmatism, high-angle faulting, and detachment faulting at a slow-spreading mid-ocean ridge in the West Philippine Basin. We identified a magma-rich spreading phase at 36 Ma, indicated by a magmatic top basement and normal oceanic crust with shallow-penetrating high-angle faults. An axial valley reveals an along-strike transition from normal to highly tectonized oceanic crust over a distance of 70 km. Two older OCCs with concave-down fault geometries and a younger OCC with steep-dipping faulting suggest sequential detachments with the same polarity. Our findings suggest: (1) slow seafloor spreading is cyclical, alternating between high-angle faulting with a relatively high magma supply and detachment faulting with limited magma supply; (2) sequential development of younger detachments in the footwall of its predecessor leads to an asymmetric split in the newly accreted crust; and (3) the life cycle of OCC ends with high-angle faults that overprint the detachment and act as magma pathways, sealing the OCC. Our study captures the dynamic interaction between high-angle and detachment faults and their concurrent and subsequent relationship to magmatic systems. This reveals that strain distribution along strike is critical to OCC formation, thus enriching our understanding beyond conventional considerations such as spreading rates and melt budgets at mid-ocean ridges.

Porous materials, such as carbonate rocks, frequently have pore sizes which span many orders of magnitude. This is a challenge for models that rely on an image of the pore space, since much of the pore space may be unresolved. There is a trade off between image size and resolution. For most carbonates, to have an image sufficiently large to be representative of the pore structure, many fine details cannot be captured. In this work, sub-resolution porosity in X-ray images is characterized using differential imaging which quantifies the difference between a dry scan and 30 wt\% KI brine saturated rock images. Once characterized, we develop a robust workflow to incorporate the sub-resolution pore space into network model using Darcy-type elements called micro-links. Each grain voxel with sub-resolution porosity is assigned to the two nearest resolved pores using an automatic dilation algorithm. By including these micro-links with empirical models in flow modeling, we simulate single-phase and multiphase flow. By fine-tuning the micro-link empirical models, we achieve effective permeability, formation factor, and drainage capillary pressure predictions that align with experimental results. We then show that our model can successfully predict steady-state relative permeability measurements on a water-wet Estaillades carbonate sample within the uncertainty of the experiments and modeling. Our approach of incorporating sub-resolution porosity in two-phase flow modeling using image-based multiscale pore network techniques can capture complex pore structures and accurately predict flow behavior in porous materials with a wide range of pore size.

We explored the geological history of the Taurus-Littrow Valley at the Apollo 17 landing site through the induced thermoluminescence (TL) properties of regolith samples collected from the foothills of the Northern and Southern Massifs, near the landing site, and the deep drill core taken in proximity to the landing site. The samples were recently made available by NASA through the Apollo Next Generation Sample Analysis program, in anticipation of the forthcoming Artemis missions. We found that the two samples from the foothills of the massifs exhibit induced TL values approximately four times higher than those of the valley samples. This observation is consistent with their elevated plagioclase content, indicating their predominantly highland material composition. Conversely, the valley samples display induced TL values characteristic of lunar mare material. The samples from the deep drill core demonstrate uniform induced TL properties, despite originating from depths of up to 3 meters. Notably, one of the samples from the lower section of the deep drill core presents anomalous induced TL readings. This anomaly coincides with elevated levels of low-potassium KREEP, along with reduced quantities of anorthositic gabbro and orange glass, and could be due to the traces of phosphate minerals. Alternatively, this observation raises the possibility that this sample contains Tycho impact material. The induced TL data is consistent with the regolith, extending to a depth of at least 3 meters, having been deposited by a singular event approximately 100 million years ago. This timing aligns with the hypothesized formation of the Tycho crater.

We deformed samples with varied proportions of olivine and orthopyroxene in a deformation-DIA apparatus to test the applicability of subgrain-size piezometry to polymineralic rocks. We measured the stress within each phase in situ via X-ray diffraction during deformation at a synchrotron beamline. Subgrain-size piezometry was subsequently applied to the recovered samples to estimate the stress that each phase supported during deformation. For olivine, the final in-situ stresses are consistent with the stresses estimated via subgrain-size piezometry, both in monomineralic and polymineralic samples, despite non-steady state conditions. However, stress estimates from subgrain-size piezometry do not reliably record the in-situ stress in samples with grain sizes that are too small for extensive subgrain-boundary formation. For orthopyroxene, subgrain boundaries are typically sparse due to the low strains attained by orthopyroxene in olivine-orthopyroxene mixtures. Where sufficient substructure does exist, our data supports the use of the subgrain-size piezometer on orthopyroxene. These results do, however, suggest that care should be taken when applying subgrain-size piezometry to strong minerals that may have experienced little strain. Stresses estimated by X-ray diffraction also offer insight into stress partitioning between phases. In mixtures deformed at mean stresses > 5 GPa, orthopyroxene supports stresses greater than those supported by olivine. This stress partitioning is consistent with established theory that predicts a slightly higher stress within a ‘strong’ phase contained in a material consisting of interconnected weak layers. Overall, these results demonstrate that subgrain-size piezometry is a valuable tool for quantifying the stress state of polymineralic rocks.

Oceanic plates experience extensive normal faulting as they bend and subduct, enabling fracturing of the crust and upper mantle. Debate remains about the relative importance of pre-existing faults, plate curvature and other factors in controlling the extent and style of bending-related faulting. The subduction zone off the Alaska Peninsula is an ideal place to investigate controls on bending-related faulting as the orientation of abyssal-hill fabric with respect to the trench and plate curvature vary along the margin. Here we characterize bending faulting between longitudes 161°W and 155ºW using newly collected multibeam bathymetry data. We also use a compilation of seismic reflection data to constrain patterns of sediment thickness on the incoming plate. Although sediment thickness increases by over 1 km from 156°W to 160°W, most sediments were deposited prior to the onset of bending faulting and thus have limited impact on the expression of bend-related fault strikes and throws in bathymetry data. Where magnetic anomalies trend subparallel to the trench (<30°) west of ~156ºW, bending faulting parallels magnetic anomalies, implying bending faulting reactivates pre-existing structures. Where magnetic anomalies are highly oblique (>30°) to the trench east of 156ºW, no bending faulting is observed. Summed fault throws increase to the west, including where pre-existing structure orientations do not vary between 157-161ºW, suggesting that the increase in slab curvature directly influences fault throws. However, the westward increase in summed fault throws is more abrupt than expected for changes in slab bending alone, suggesting potential feedbacks between pre-existing structures, slab dip, and faulting.

The bidispersity observed in the grain-size distribution of rock avalanches and volcanic debris avalanches (rock/debris avalanches) has been proposed as a property contributing to their long runout. This has been supported by small-scale analogue experimental studies which propose that a small proportions of fine particles, mixed with coarser, enhances granular avalanche runout. However, the mechanisms enabling this phenomenon and their resemblance to rock/debris avalanches have not been directly evaluated. Here, binary mixture granular avalanche experiments are employed to evaluate the potential of bidispersity in enhancing runout. Structure-from-motion photogrammetry is used to assess centre of mass mobility. The findings suggest that the processes generating increased runout in small-scale avalanches are scale-dependent and not representative of rock/debris avalanche dynamics. In small-scale experiments, the granular mass is size-segregated with fine particles migrating to the base through kinetic sieving. At the base, they reduce frictional areas between coarse particles and the substrate, and encourage rolling. The reduced frictional energy dissipation increases kinetic energy conversion, and avalanche mobility. However, kinetic sieving does not occur in rock/debris avalanches due to a dissimilar granular flow regime. The proposition of this hypothesis overlooks that scale-dependent behaviours of natural events are omitted in small-scale experiments. At the small scale, a collisional regime enables the necessary agitation for kinetic sieving. However, rock/debris avalanches are unlikely to acquire a purely collisional regime, and rather propagate under a frictional regime, lacking widespread agitation. Therefore, bidispersity is unlikely to enhance the mobility of rock/debris avalanches by enabling more efficient shearing at their base.

Fractures are frequently encountered in reservoirs used for geothermal heat extraction, CO2 storage, and other subsurface applications. Their significant impact on flow and transport requires accurate characterisation for performance estimation and risk assessment. However, fractures, and particularly their apertures, are usually associated with large uncertainties. Data assimilation (or history matching) is a well-established tool for reducing uncertainty and improving simulation results. In recent years, ensemble-based methods like the ensemble smoother with multiple data assimilation (ESMDA) have gained popularity. A key aspect of those methods is a well-constructed prior ensemble that accurately reflects available knowledge. Here, we consider a geological scenario where fracture opening is primarily created by shearing and assume a known fracture geometry. Generating prior realisations of aperture with geomechanical simulators might become computationally prohibitive, while purely stochastic approaches might not incorporate all available geological knowledge. We therefore introduce the far-field stress approximation (FFSA), a proxy model in which this stress is projected onto the fracture planes and shear displacement is approximated with linear elastic theory. We thereby compensate for modelling errors by introducing additional uncertainty in the underlying model parameters. The FFSA efficiently generates reasonable prior realisations at low computational costs. The resulting posterior ensemble obtained from our ESMDA framework matches the flow and transport behaviour of the synthetic reference at measurement locations and improves the estimation of the fracture apertures. These results markedly outperform those obtained from prior ensembles based on two naïve stochastic approaches, thus underlining the importance of accurate prior modelling.

A fundamental assumption in thermochronology is extrapolation of kinetic parameters over geologic timescales, temperatures, and mineral compositions that often differ significantly from the laboratory conditions used to quantify them. In this study, we aim to test and intercalibrate kinetic parametersof multiple thermochronometric systems using a tractable, natural thermal perturbation associated with the emplacement of a small, young basalt intrusion into granite in the Sierra Nevada, the site of the classic study of Calk and Naeser (1973). We collected a suite of samples along a linear transect orthogonal to the contact, from which the minerals apatite, zircon, titanite, epidote, magnetite, biotite, horneblende, K-feldspar, and plagioclase were separated. Our results to date reveal that the (U-Th)/He system in apatite was completely reset within ~7 m of the contact during basalt emplacement ~8 Ma. At distances >16 m from the contact, the apatite He ages are uniformly ~58 Ma, which likely represents the background (i.e., unperturbed) cooling ages of the granite. Apatite 4 He/ 3 He thermochronometry and an observed transition from background-to rest-ages of these samples are quantitatively consistent with a higher degree of thermal perturbation nearer to the contact. As predicted by our current quantification of radiation damage accumulation influence on He diffusion kinetics (Flowers et al, 2009), we observe correlation between the "effective uranium" concentration and He ages of individual apatite crystals, particularly within this transition zone. In contrast, the (U-Th)/He system in zircon is only partially reset ~7 m from the contact, and the background cooling ages at distances >10 m are ~78 Ma, consistent with a 40 Ar/ 39 Ar age-spectrum from a distal K-feldspar that rises from ~70 to ~80 Ma; both observations are consistent with the relative, experimentally determined temperature sensitivities of these minerals. We present ongoing numerical modeling that provides a framework with which to quantitatively compare and assess these results with forthcoming 40 Ar/ 39 Ar and fission track results in various mineral systems. Inversion of data using these multi-material conductive models will be used to assess the sensitivity of results to assumptions about geometry (1D, 2D, 3D), duration of basalt emplacement, and pre-intrusion cooling rate.

Accurately determining the seismic structure of the deep crust of continents is crucial for understanding the geological record and continental dynamics. However, traditional surface wave methods often face challenges in solving the trade-offs between elastic parameters and discontinuities. In this work, we present a new approach that combines two established inversion techniques, receiver function H-ᵰ5; stacking and joint inversion of surface wave dispersion and receiver function waveforms, within a Bayesian Monte Carlo (MC) framework to address these challenges. As demonstrated by the synthetic test, the new method greatly reduces trade-offs between critical parameters, such as the deep crustal Vs, Moho depth, and crustal Vp/Vs ratio. This eliminates the need for assumptions regarding crustal Vp/Vs ratios in joint inversion, leading to a more accurate outcome. Furthermore, it improves the precision of the upper mantle velocity structure by reducing its trade-off with Moho depth. Additional notes on the sources of bias in the results are also included. Application of the new approach to USArray stations in the Northwestern US reveals consistency with previous studies and also identifies new features. Notably, we find elevated Vp/Vs ratios in the crystalline crust of regions such as coastal Oregon, suggesting potential mafic composition or fluid presence. Shallower Moho depth in the Basin and Range indicates reduced crustal support to the topography. The uppermost mantle Vs, averaging 5 km below Moho, aligns well with the Pn-derived Moho temperature map, offering the potential of using Vs as an additional constraint to Moho temperature and crustal thermal properties.

We use seismic ambient noise recorded by dense ocean bottom nodes (OBNs) in the Gorgon gas field, Western Australia, to compute time-lapse seafloor models of shear-wave velocity. The extracted hourly cross-correlation (CC) functions in the frequency band 0.1 – 1 Hz contain mainly Scholte waves with very high signal to noise ratio. We observe temporal velocity variations (dv/v) at the order of 0.1% with a peak velocity change of 0.8% averaged from all station pairs, from the conventional time-lapse analysis with the assumption of a spatially homogeneous dv/v. With a high-resolution reference (baseline) model from full waveform inversion of Scholte waves, we present an elastic wave equation based double-difference inversion (EW-DD) method, using arrival time differences between the reference and time-lapsed Scholte waves, for mapping temporally varying dv/v in the heterogeneous subsurface. The time-lapse velocity models reveal increasing/decreasing patterns of shear-wave velocity in agreement with those from the conventional analysis. The velocity variation exhibits a ~24-hour cycling pattern, which appears to be inversely correlated with sea level height, possibly associated with dilatant effects for porous, low-velocity shallow seafloor and rising pore pressure with higher sea level. This study demonstrates the feasibility of using dense passive seismic surveys for quantitative monitoring of subsurface property changes in the horizontal and depth domain.

The Paleocene-Eocene Thermal Maximum (PETM) was a transient global warming event recognised in the geologic record by a prolonged negative carbon isotope excursion (CIE). The onset of the CIE was the result of a rapid influx of 13C-depleted carbon into the ocean-atmosphere system. However, the mechanisms required to sustain the negative CIE remains unclear. Previous studies have identified enhanced mobilisation of petrogenic organic carbon (OCpetro) and argued that this was likely oxidised, increasing atmospheric carbon dioxide (CO2) concentrations after the onset of the CIE. With existing evidence limited to the mid-latitudes and subtropics, we determine whether: (i) enhanced mobilisation and subsequent burial of OCpetro in marine sediments was a global phenomenon; and (ii) whether it occurred throughout the PETM. To achieve this, we utilised a lipid biomarker approach to trace and quantify OCpetro burial in a global compilation of PETM-aged shallow marine sites (n = 7, including five new sites). Our results confirm that OCpetro mass accumulation rates (MARs) increased within the subtropics and mid-latitudes during the PETM, consistent with evidence of higher physical erosion rates and intense episodic rainfall events. The high-latitude sites do not exhibit distinct changes in the organic carbon source during the PETM. This may be due to the more stable hydrological regime and/or additional controls. Crucially, we also demonstrate that OCpetro MARs remained elevated during the recovery phase of the PETM. Although OCpetro oxidation was likely an important positive feedback mechanism throughout the PETM, we show that this feedback was both spatially and temporally variable.

The heavily faulted Martian terrains of Ceraunius Fossae and Tractus Fossae, south of the Alba Mons volcano, have previously only been considered as parts of larger tectonic studies of Alba Mons, and the complexity of the faulting remains consequently unclear. As these terrains are in midst of the large Tharsis’ volcanoes, the study of their surface deformation has the potential to help unravel the volcano-tectonic deformation history associated with the growth of Tharsis, as well as decipher details of the responsible magma-tectonic processes. In this study, we distinguish between faults and collapse structures based on image and topographic evidence of pit-crater chains. We mapped ~12,000 faults, which we grouped into 3 distinct fault groups based on orientation, morphology, and relative ages. These show a temporal evolution in the mapped fault orientations from NE to NS to NW, with associated perpendicular stress orientations. Collapse features were also mapped and categorized into 4 different groups: pit-crater chains, catenae, u-shaped troughs and chasma. Examining the 4 collapse structures reveals that they are likely 4 different steps in the erosional evolution of pit-crater chains. Together this revealed a structural history heavily influenced by both local (radial to Alba Mons, Pavonis Mons and Ascraeus Mons) and regional (Tharsis radial) lateral diking, and vertical diking from a proposed Ceraunius Fossae centred magma source. This, along with an updated crater size-frequency distribution analysis of the unit ages, reveals a highly active tectonic and magmatic environment south of Alba Mons, in the Late Amazonian.

The tempo of subduction-related magmatic activity over geological time is episodic. Despite intense study and their importance in crustal addition, the fundamental driver of these episodes remains unclear. We demonstrate quantitatively a first order relationship between arc magmatic activity and subduction flux. The volume of oceanic lithosphere entering the mantle is the key parameter that regulates the proportion of H2O entering the sub-arc. New estimates of subduction zone H2O budgets over the last 150 million-years indicate a three- to five-fold increase in the proportion of H2O entering the sub-arc during the most recent global pulse of magmatism. Step changes in H2O flux enable proportionally greater partial melting in the sub-arc. Similar magmatic pulses in the ancient Earth could be related to variability in subduction flux associated with supercontinent cycles.

To effectively reduce CO2 emissions, it’s vital to identify and quantify their sources. While the focus has been on CO2 from fossil fuel combustion, especially coal, the CO2 produced from coal’s other elements, such as sulfur, through chemical reaction, remains an ‘invisible’ carbon source. We analyzed the invisible carbon flux due to coal burning in the Xijiang River Basin, a highly industrialized region in China, using river sulfate fluxes. Dissolved sulfate concentration in the Xijiang River rose by over 300% from 1985 to 2011, largely due to coal combustion. In 2011, this resulted in 3.14 Mt of invisible carbon dioxide. We evaluated the impact of two flue gas desulfurization (FGD) methods on carbon emissions using a predictive model. By enhancing SO2 removal efficiency through these methods, China could cut invisible carbon emissions by 27.8 Mt CO2 annually, paving the way for a sustainable future.

The Klamath Mountains in northern California and southern Oregon are thought to record 200+ m.y. of subduction and terrane accretion, whereas the outboard Franciscan Complex records classic ocean-continent subduction along the North American margin. Unraveling the Klamaths’ late history could help constrain this transition in subduction style. Key is the Mesozoic Condrey Mountain Schist (CMS), comprising, in part, a subduction complex that occupies a structural window through older, overlying central Klamath thrust sheets but with otherwise uncertain relationships to other, more outboard Klamath or Franciscan terranes. The CMS consists of two units (upper and lower), which could be correlated with 1) other Klamath terranes, 2) the Franciscan, or 3) neither based on regional structures and limited extant age data. Upper CMS protolith and metamorphic dates overlap with other Klamath terranes, but the lower CMS remains enigmatic. We used multiple geochronometers to constrain the timing of lower CMS deposition and metamorphism. Maximum depositional ages (MDAs) derived from detrital zircon geochronology of metasedimentary rocks are 153-135 Ma. Metamorphic ages from white mica K-Ar and Rb-Sr multi-mineral isochrons from intercalated and coherently deformed metamafic lenses are 133-116 Ma. Lower CMS MDAs (<153 Ma) predominantly postdate the age of other Klamath terranes, but subduction metamorphism appears to predate the earliest coherent Franciscan underplating (ca. 123 Ma). The lower CMS thus occupies a spatial and temporal position between the Klamaths and Franciscan and preserves a non-retrogressed record of the Franciscan Complex’s early history (>123 Ma), otherwise only partially preserved in retrogressed Franciscan high grade blocks.

The magnitude (MW) 6.6 earthquake that struck Masbate Island on 18 August 2020 offers a unique opportunity to investigate the slip and seismic behavior of the Philippine Fault in the Masbate region. In this study, we employ InSAR, seismicity analysis, and field investigations to comprehensively characterize the coseismic and postseismic slip associated with the event. Our findings reveal a 50-km-long fault rupture along the Masbate segment of the Philippine Fault, with ~23 km surface rupture mapped onshore, despite the occurrence of interseismic creep. The slip distribution demonstrates decreasing displacements northwestward towards the creeping section, with a maximum left-lateral displacement of 0.97 m near the epicenter. Toward the southeast offshore, the rupture terminates at a fault left stepover. While the surface rupture appears relatively straight and narrowly concentrated, the secondary ruptures and mapped offshore faults reveal a more complex transtensional fault structure in the vicinity of Cataingan Bay. This fault complexity represents an asperity that facilitates high-stress accumulation and rupture initiation. Postseismic slip persists for several months along the onshore creeping segment. We derived a slip rate of 2.8 to 4.3 cm/year from long-term and short-term slip measurements. Furthermore, we calculated a recurrence interval of 16 to 41 years for earthquakes similar to the 2020 Masbate earthquake.  Our study highlights how heterogeneity in fault properties, including geometry and coupling state, influences the distribution of slip and magnitude of earthquakes. The 2020 Masbate earthquake provides valuable insights into the rupture dynamics and fault behavior of the Philippine Fault in the Masbate region.

In sparsely fractured crystalline rock, aperture variability exhibits significant control of the flow field through the fracture network. However, its inclusion in models is hampered due to a lack of field measurements and adequate numerical representation. A model for aperture generation is developed based on self-affine methods which includes two key parameters, the Hurst exponent and a scaling parameter, and which accounts for relative anisotropy and correlation between the adjacent surfaces forming the fracture. A methodology for analysing and extracting the necessary parameters from 3D surface scans of natural rock fractures is also developed. Analysis of the Hurst exponent and scaling parameter space shows that input combinations following a linear upper bound can be used to generate aperture fields which accurately reproduce measurements. It is also shown that the Hurst and scaling parameters are more sensitive than the correlation between the upper and lower fracture surfaces. The new model can produce an aperture ensemble that closely corresponds with the aperture obtained from the surface scans, and is an improvement on previous methods. The model is also successfully used to up-scale fracture apertures based on measurements restricted to a small sub-section of the sample. Thereby, the aperture fields generated using the model are representative of natural fracture apertures and can be implemented in larger scale fracture network models, allowing for numerical simulations to included representation of aperture internal heterogeneity.

A document by Sergio León-Ríos. Click on the document to view its contents.

Deltas and fluvial fans are two fan-shaped landforms with complex channel networks. Deltas always occur where rivers enter a standing body of water, such as lakes or oceans. Fluvial fans are inland terrestrial landforms that may form thousands of kilometers from shorelines. Fluvial fans may however also reach lakes and oceans. The current state of knowledge lacks understanding of their morphometric differences or recognition criteria, despite their socioeconomic significance, vulnerability to natural hazards, and important differences in how these landforms respond to global climate change. Moreover, numerous fan-shaped landforms with channel networks have been identified on other planetary bodies, such as Mars and the Saturn's moon Titan, where deltas are important indicators of paleo-shorelines and offer attractive targets for mission sites due to their habitability and high biosignature preservation potential. Here we review the known morphometrics of delta and fluvial fan channel networks, and the differences in their formative processes, and develop morphometric criteria for distinguishing deltas and fluvial fans. We present an ensemble of quantitative metrics that distinguish deltas and fluvial fans and test these criteria on 80 modern channel networks on Earth. Our results improve mechanistic understanding of the fluvial record and delta evolution, provide criteria for accurate recognition of these landforms on planetary bodies and in the sedimentary record, and explain differences in their vulnerabilities to global change.

North of the Denali Fault, the collision between the Yakutat block with North America is accommodated by a fold-thrust belt that gives rise to the northern Alaska Range foothills. At the western end of the belt, the Kantishna Hills anticline hosts prominent microseismicity and surface deformation, together interpreted as active folding of the Kantishna Hills anticline above a midcrustal detachment. Here, we test for such a detachment by using anisotropy-aware receiver functions to image fabric contrasts within the crust and comparing the depths of such contrasts to seismicity statistics. Seismic stations near the crest of the Kantishna Hills anticline and near its southern flank show a single strong contrast in dipping fabric at depths of 12 and 13 km, near where the microseismicity clusters at depth and consistent with a detachment plane beneath the fold. A minimum in b-value at 10-13 km depth is consistent with seismicity on the detachment, compatible with the imaged anisotropic contrast, while off-fault seismicity is shallower, deeper, and limited to smaller magnitudes. South-dipping imbricate thrusts in schist characterize the northern Alaska Range foothills structure and support our interpretation of the observed anisotropy as reflecting SSW-SSE-dipping foliation above a detachment at ~10-13 km depth that may exploit existing crustal weaknesses along more subtle fabric contrasts observed in the seismically quiescent region north of the actively deforming belt.

In the central Tibetan Plateau, an east-west trending band of basins is developed. How such topography formed and the underlying geodynamic processes are still in debate. Magnetotelluric data were collected across the Lunpola basin to study the crustal structure beneath central Tibet. Phase tensors and 3-D inversion are employed to obtain the electrical resistivity model. Our model clearly portrays conductive sedimentary layers beneath the basins with average resistivity of 2.0 Ω·m. The low-resistivity mid-to-lower crust is revealed beneath the Lunpola basin with bulk resistivity of 20 Ω·m and fluid fraction of 1.3-3.0%, which would be attributed to partial melting. Compared to the significant conductive crust in southern Tibet, the crustal rheology is less well developed beneath central Tibet. We propose that the asthenospheric flow beneath central Tibet is responsible for the crustal partial melting and drives the eastward escape of the continental lithosphere in a rigid block fashion.