The spatial separation of macroscopic rheological behaviours has led to independent conceptual treatments of frictional failure, often referred to as brittle, and viscous deformation. Detailed microstructural investigations of naturally deformed carbonate rocks indicate that both, frictional failure, and viscous mechanisms might operate during seismic deformation of carbonates. Here, we investigate the deformation mechanisms that were active in two carbonate fault zones in Greece by performing detailed slip-system analyses on data from automated crystal-orientation mapping transmission electron microscopy and electron backscatter diffraction. We combine the slip system analyses with interpretations of nanostructures and predictions from deformation mechanism maps for calcite. The nanometric grains at the principal slip surface should deform by diffusion creep but the activation of the (0001)<-12-10> slip system is evidence for a contribution of crystal plasticity. A similar crystallographic preferred orientation appears in the cataclastic parts of the fault rocks despite exhibiting a larger grain size and a different fractal dimension, compared to the principal slip surface. The cataclastic region exhibits microstructures consistent with activation of the (0001)<-12-10> and {10-14}<-2021> slip systems. Post-deformational, static recrystallisation and annealing produces an equilibrium microstructure with triple junctions and equant grain size. We propose that repeated introduction of plastic strain and recrystallisation reduces the grain size and offers a mechanism to form a cohesive nanogranular material. This formation mechanism leads to a grain-boundary strengthening effect resulting in slip delocalisation which is observed over six orders of magnitude (μm–m) and is expressed by multiple faults planes, suggesting cyclic repetition of deformation and annealing.

Controls on the deformation pattern (shortening mode and tectonic style) of orogenic forelands during lithospheric shortening remain poorly understood. Here, we use high-resolution 2D thermomechanical models to demonstrate that orogenic crustal thickness and foreland lithospheric thickness significantly control the shortening mode in the foreland. Pure-shear shortening occurs when the orogenic crust is not thicker than the foreland crust or thick, but the foreland lithosphere is thin (< 70-80 km, as in the Puna foreland case). Conversely, simple-shear shortening, characterized by foreland underthrusting beneath the orogen, arises when the orogenic crust is much thicker. This thickened crust results in high gravitational potential energy in the orogen, which triggers the migration of deformation to the foreland under further shortening. Our models present fully thick-skinned, fully thin-skinned, and intermediate tectonic styles in the foreland. The first tectonics forms in a pure-shear shortening mode whereas the others require a simple-shear mode and the presence of thick (> ~4 km) sediments that are mechanically weak (friction coefficient < ~0.05) or weakened rapidly during deformation. The formation of fully thin-skinned tectonics in thick and weak foreland sediments, as in the Subandean Ranges, requires the strength of the orogenic upper lithosphere to be less than one-third as strong as that of the foreland upper lithosphere. Our models successfully reproduce foreland deformation patterns in the Central and Southern Andes and the Laramide province.

Tight oil and gas reservoirs have attracted an increasing amount of attentions and have become one of the focus of research field in recent years. Tight sandstones have complex pore structures and narrow pores and throats with pore sizes varying from nanometers to micrometers, and studying flow mechanisms in tight sandstones is of great importance to tight oil/gas reservoir development. Reconstructing digital rock, which can comprehensively represent the petrophysical properties of tight sandstone, is key to simulating the fluid flow in micro/nanopores. This paper proposes a new method of reconstructing 3D digital rock from CT images of tight sandstones based on a deep convolutional generative adversative network (DCGAN), and 3D convolution in the generator and discriminator are adopted to realize reconstruction from 1D data to a 3D digital rock model. The model adopts pore area, volume, spatial distribution and connectivity, Fréchet inception distance score to evaluate the proposed model. Studies show that when the training effect is slightly poor, the generated digital rock model will exhibit noise, which can be reduced by postprocessing; when the training effect is good, DCGAN can accurately reconstruct the 3D digital rock model of tight sandstones, and the reconstructed digital rock is very consistent with the pore size, geometric structure, and connectivity of natural tight sandstones. When multiple 3D tight sandstone CT images are used for training, the DCGAN can learn the pore structure characteristics of entire tight sandstone bodies, which have strong heterogeneous, and the porosity distribution obtained from the generated digital rock is similar to that of the original tight sandstone.

Alkalinity, the excess of proton acceptors over donors, plays a major role in ocean chemistry, in buffering and in calcium carbonate precipitation and dissolution. Understanding alkalinity dynamics is pivotal to quantify ocean carbon dioxide uptake during times of global change. Here we review ocean alkalinity and its role in ocean buffering as well as the biogeochemical processes governing alkalinity and pH in the ocean. We show that it is important to distinguish between measurable titration alkalinity and charge-balance alkalinity that is used to quantify calcification and carbonate dissolution and needed to understand the impact of biogeochemical processes on components of the carbon dioxide system. A general treatment of ocean buffering and quantification via sensitivity factors is presented and used to link existing buffer and sensitivity factors. The impact of individual biogeochemical processes on ocean alkalinity and pH is discussed and quantified using these sensitivity factors. Processes governing ocean alkalinity on longer time scales such as carbonate compensation, (reversed) silicate weathering and anaerobic mineralization are discussed and used to derive a close-to-balance ocean alkalinity budget for the modern ocean.

The stability, structure, and elastic properties of pyrite-type (FeS2 structured) FeO2H were determined using density functional theory-based computations with a self-consistent Coulombic self-interaction term (Ueff). The properties of pyrite-type FeO2H are compared to that of pyrite-type AlO2H with which it likely forms a solid solution at high temperature, as well as the respective lower pressure CaCl2-type polymorphs of both endmembers: e-FeOOH and d-AlOOH. Due to substantial differences in the CaCl2-type to pyrite-type structural transition pressures of these endmembers, the stabilities of the (Al,Fe)O2H solid solution polymorphs are anticipated to be compositionally driven at lower mantle pressures. As the geophysical properties of (Al,Fe)OOH are structurally dependant, interpretations regarding the contribution of pyrite-type FeO2H to seismically observed features must take into account the importance of this broad phase loop. With this in mind, Fe-rich pyrite-type (Al,Fe)OOH may coexist with Al-dominant CaCl2-type d-(Al,Fe)OOH in the deep Earth. Furthermore, pyrite-type (Al0.5-0.6,Fe0.4-0.5)O2H can reproduce the reduced compressional and shear velocities characteristic of seismically observed Ultra Low Velocity Zones (ULVZs) in the Earth’s lowermost mantle while Al-dominant but Fe-bearing CaCl2-type d-(Al,Fe)OOH may contribute to Large Low Shear Velocity Provinces (LLSPs).

We investigate if the commonly neglected riverine detrital carbonate fluxes might balance several chemical mass balances of the global ocean. Particulate inorganic carbon (PIC) concentrations in riverine suspended sediments, i.e., carbon contained by these detrital carbonate minerals, was quantified at the basin and global scale. Our approach is based on globally representative datasets of riverine suspended sediment composition, catchment properties and a two-step regression procedure. The present day global riverine PIC flux is estimated at 3.1 ± 0.3 Tmol C/y (13% of total inorganic carbon export and 4 % of total carbon export), with a flux-weighted mean concentration of 0.26 ± 0.03 wt%. The flux prior to damming was 4.1 ± 0.5 Tmol C/y. PIC fluxes are concentrated in limestone-rich, rather dry and mountainous catchments of large rivers in Arabia, South East Asia and Europe with 2.2 Tmol C/y (67.6 %) discharged between 15 °N and 45 °N. Greenlandic and Antarctic meltwater discharge and ice-rafting additionally contribute 0.8 ± 0.3 Tmol C/y. This amount of detrital carbonate minerals annually discharged into the ocean implies a significant contribution of calcium (~ 4.75 Tmol Ca/y) and alkalinity fluxes (~ 10 Tmol(eq)/y) to marine mass balances and moderate inputs of strontium (~ 5 Gmol Sr/y), based on undisturbed riverine and cryospheric inputs and a dolomite/calcite ratio of 0.1. Magnesium fluxes (~ 0.25 Tmol Mg/y), mostly hosted by less-soluble dolomite, are rather negligible. These unaccounted fluxes help elucidating respective marine mass balances and potentially alter conclusions based on these budgets.

Debate abounds regarding the composition of the deep (middle + lower) continental crust. Studies of medium and high grade metamorphic lithologies guide us but encompass mafic (< 52 wt.%) to felsic (> 68 wt.%) compositions. This study presents a global compilation of geochemical data on amphibolite (n = 6500), granulite (n = 4000), and eclogite (n = 200) facies lithologies and quantifies systematic trends, uncertainties, and sources of bias in the deep crust sampling. The continental crust’s Daly Gap is well documented in amphibolite and most granulite facies lithologies, with eclogite facies lithologies and granulite facies xenoliths having mostly mafic compositions. Al2O3, Lu, and Yb vary little from the top to bottom of the crust. In contrast, SiO2 and incompatible elements show a wider range of abundances. Because of oversampling of mafic lithologies, our predictions are a lower bound on middle crustal composition. The distinction between granulite facies terrains (intermediate SiO2, high heat production, high incompatibles) or granulite facies xenoliths (low SiO2, low heat production, low incompatibles) as being the best analogs of the deep crust remains disputable. We incorporated both, along with amphibolite facies lithologies, to define a deep crustal composition that approaches 57.6 wt.% SiO2. This number, however, represents a compositional middle ground, as seismological studies indicate a general increase in density and seismic velocity with increasing depth. Future studies should analyze more closely the depth dependent trends in deep crustal composition so that we may develop compositional models that are not limited to a three-layer crust.

Using E-W and vertical deformation-rate maps derived from radar interferometric time-series, we analyze the deformation field of an entire orogenic segment, i.e., the Tajik depression and its adjoining mountain belts, Tian Shan, Pamir, and Hindu Kush. The data-base consists of 900+ radar scenes acquired over 2.0–4.5 years and global navigation satellite system measurements. The recent, supra-regional kinematics is visualized in an unprecedented spatio-temporal resolution. We confirm the westward collapse of the Pamir-Plateau crust, inverting the Tajik basin into a fold-thrust belt with shortening rates decaying westward from ~15 to 2 mm/yr. Vertical rates in the Hindu Kush likely record slab-dynamic effects, i.e., the progressive break-off of the Hindu Kush slab. At least 10 mm/yr of each, uplift and westward motion occur along the western edge of the Pamir Plateau, outlining the crustal-scale ramp along which the Pamir Plateau overrides the Tajik depression. The latter shows a combination of basin-scale tectonics, halokinesis, and seasonal/weather-driven near-surface effects. Abrupt ~6 mm/yr horizontal-rate changes occur across the kinematically-linked dextral Ilyak strike-slip fault, bounding the Tajik fold-thrust belt to the north, and the Babatag backthrust, the major thrust of the fold-thrust belt, located far west in the belt. The sharp rate decay across the Ilyak fault indicates a locking depth of ≤1 km. The Hoja Mumin salt fountain is spreading laterally at ≤350 mm/yr. On the first-order, the modern 20–5 and fossil (since ~12 Ma) 12–8 mm/yr shortening rates across the fold-thrust belt correspond.

Crystal zonations provide valuable snapshot of the dynamic changes within a magma reservoir. However, crystal zonations are often heterogeneous down to the hand-sample scale, such that deciphering their signatures becomes convoluted. Crystals are reactively precipitated and dissolving as a function of temperature, pressure, and composition. In this manuscript, we investigate what temperature histories crystals experience in a magma lens after its injection into a cooler magma reservoir. We simulate the cooling interface in either hot basaltic or dacitic magmas after their injection into a cooler magma reservoir. We couple fluid dynamics to thermodynamics by resolving flow at the crystalline-scale and allowing crystals with constant density and size to precipitate and dissolve based on ambient melt properties. We infer zonations in our simulated crystals by tracking the magma temperatures they sample over time. Our results show that when thermodynamics and fluid dynamics are coupled, a reactive, crystal-driven instability arises, because the negative buoyancy of crystals pulls along the cooler-than-ambient melt in which they precipitated. As crystals continue to precipitate along the cooling boundary, the instability develops into a sustained convective flow. Our results show that crystals record complex and unique zonations in this crystalline-scale domain, suggesting that zonations and their heterogeneity can be indicative of local instead of system scale processes. Also, our results show that many of the crystals in the instability dissolve and lose their thermal record of the instability. These results highlight the challenges of deciphering system-scale process from crystalline data.

The δ34S of seawater sulfate reflects processes operating at the nexus of sulfur, carbon, and oxygen cycles. However, knowledge of past seawater sulfate δ34S values must be derived from proxy materials that are impacted differently by depositional and post-depositional processes. We produced new timeseries estimates for the δ34S value of seawater sulfate by combining 6710 published data from three sedimentary archives—marine barite, evaporites, and carbonate-associated sulfate—with updated age constraints on the deposits. Robust features in multiple records capture temporal trends in the δ34S value of seawater and its interplay with other Phanerozoic geochemical and stratigraphic trends. However, high-frequency discordances indicate that each record is differentially prone to depositional biases and diagenetic overprints. The amount of noise, quantified from the variograms of each record, increases with age for all δ34S proxies, indicating that post-depositional processes obscure detailed knowledge of seawater sulfate’s δ34S value deeper in time.

Bauville and Yamato (2021, G-cubed, https://doi.org/10.1029/2020GC009280) propose model-based methods to convert metamorphic pressures to depths based on the claim that pressure data from global (ultra)high-pressure rocks challenge the lithostatic assumption and support their model which invokes excessive overpressures. It is argued here that the opposite is true: Natural pressure data are fully consistent with the lithostatic assumption. They reflect selection of (ultra)high-pressure rocks by accessibility and preservation. The data are however inconsistent with the model predictions of Yamato and Brun (2017, Nature Geoscience 10, 46-50) and Bauville and Yamato (2021). Furthermore, their model requires critical assumptions that are not justified by the principles of rock mechanics and unsupported by microstructures from (U)HP rocks.

Many physical processes in the field of rock physics are influenced by the presence of fractures and microcracks. Therefore, intact rock samples are often used for reproducible experimental studies, and cracks are artificially created by various methods. For this, one possibility is the use of thermal treatments. In this work, twelve thermal treatments, differing in the applied maximum temperature and the applied cooling condition (slow versus fast cooling) are experimentally studied for dry Bianco Carrara marble under ambient conditions. Two sizes of cylindrical core samples are investigated to identify a potential size effect. As effective quantities on the core-scale, the bulk volume, the bulk density, and the P- and S-wave velocities, including shear wave splitting, are examined. To obtain a three-dimensional insight into the mechanisms occurring on the micro-scale level, micro X-Ray Computed Tomography (micro-XRCT) imaging is employed. For both cooling conditions, with increasing maximum temperature, the bulk volume increases, and the propagation velocities significantly drop. This behavior is amplified for fast cooling. The bulk volume increase is related to the initiated crack volume as micro-XRCT shows. Based on comprehensive measurements, a logarithmic relationship between the relative bulk volume change and the relative change of the ultrasound velocities can be observed. Although there is a size effect for fast cooling, the relationship found is independent of the sample size. Also the cooling protocol has almost no influence. A model is derived which predicts the relative change of the ultrasound velocities depending on the initiated relative bulk volume change.

Volcanic crises are often associated with magmatic intrusions or pressurization of magma chambers of various shapes. These volumetric sources deform the country rocks, changing their density, and cause uplift. Both the net mass of intruding magmatic fluids and these deformation effects contribute to surface gravity changes. Thus, to estimate the intrusion mass from gravity changes the deformation effects must be accounted for. We develop analytical solutions and computer codes for the gravity changes caused by triaxial sources of expansion. This establishes coupled solutions for joint inversions of deformation and gravity changes. Such inversions can constrain both the intrusion mass and the deformation source parameters more accurately.

Pore-pressure depletion in sandstone reservoirs is well known to cause both elastic and inelastic compaction, often resulting in notable surface subsidence and induced seismicity. Recent studies indicate that in such cases inelastic strain, which is often neglected in geomechanical models, represents a significant proportion of the total strain throughout reservoir production. While there has been considerable effort to quantify the proportion of continuous inelastic deformation from the mechanical response of laboratory samples, there has been little focus to date on the associated acoustic response throughout compaction. With this in mind, we employ three coda-wave based processing methods for the active source monitoring of ultrasonic velocity, scattering power, and intrinsic/scattering attenuation during the pore-pressure depletion of core samples from the Slochteren sandstone reservoir in the Groningen gas field (the Netherlands). Our results corroborate previous studies suggesting that initially, inelastic deformation occurs primarily along intergranular boundaries, with intergranular cracking developing towards the end of depletion and particularly for the highest porosity samples. Furthermore, analysis of Biot type intrinsic attenuation indicates that this compaction occurs in several stages of predominately intergranular closure, transitioning into predominantly intergranular slip/cracking, and eventually porosity-dependent intragranular cracking. We demonstrate how this segmentation of pore-pressure driven compaction can be used to characterise differences in sample properties, and monitor the evolution of microstructural inelastic deformation throughout depletion. We further discuss the feasibility of in/cross-borehole monitoring of reservoir compaction, for both improved geo-mechanical modelling and early warning detection of induced seismicity.

Barrier islands are especially vulnerable to hurricanes and other large storms, owing to their mobile composition, low elevations, and detachment from the mainland. Conceptual models of barrier-island evolution emphasize ocean-side processes that drive landward migration through overwash, inlet migration, and aeolian transport. In contrast, we found that the impact of Hurricane Dorian (2019) on North Core Banks, a 36-km barrier island on the Outer Banks of North Carolina, was primarily driven by inundation of the island from Pamlico Sound, as evidenced by storm-surge model results and observations of high-water marks and wrack lines. Analysis of photogrammetry products from aerial imagery collected before and after the storm indicate the loss of about 18% of the subaerial volume of the island through the formation of over 80 erosional washout channels extending from the marsh and washover platform, through gaps in the foredunes, to the shoreline. The washout channels were largely co-located with washover fans deposited by earlier events. Net seaward export of sediment resulted in the formation of deltaic bars offshore of the channels, which became part of the post-storm berm recovery by onshore bar migration and partial filling of the washouts with washover deposits within two months. The partially filled features have created new ponds and lowland habitats that will likely persist for years. We conclude that this event represents a setback in the overwash/rollover behavior required for barrier transgression.

A document by Alfred McEwen. Click on the document to view its contents.

Exposed sections of accretionary orogens allow reconstruction of their tectonic evolution. Most commonly, orogens are characterised by two-dimensional shortening perpendicular to the orogenic front. We describe the mid-crustal section of the back-arc of the early Paleozoic Famatinian accretionary orogen, exposed in the Sierra de Quilmes. Here crustal deformation evolved from a typical two-dimensional shortening with tectonic transport towards the west, to a non-coaxial constrictional strain with a southward tectonic transport parallel to the orogen. During the early phase of deformation, HT-LP metamorphic complexes were juxtaposed by west-directed thrusting on remarkably thick shear zones forming a thrust duplex. Deformation of the buried footwall complex continued after the exhumed hanging wall ceased to deform. We suggest that the thermally-weakened footwall complex responded by initiating a phase of south-verging thrusting, parallel to the orogen, associated with strong constriction, associated with L-tectonites, and sheath folds. This late phase of deformation defines a non-coaxial constrictional regime characterized by simultaneous east-west and vertical shortening and strong north-south, orogen-parallel stretching. Titanite ages and Zr-in-titanite thermometry demonstrate that this back-arc remained above 700 °C for 120 Ma between 500 and 380 Ma. Combined with regional geology, the new data suggest that west-verging thrusting interrupted an early, back-arc extensional phase, and lasted from ~ 470 to 440 Ma, and that footwall constriction and south-verging thrusting continued for another 40 to 60 Ma. The Famatinian back-arc exposed in Sierra de Quilmes thus is an example of how shortening and orogenic growth in a hot orogen was counterbalanced by lateral flow.

In the first several hours following an earthquake, municipalities are often forced to rely upon reports from first responders, reconnaissance along disrupted roadways by emergency personnel, or wait for aerial surveillance and remote sensing. The latter is expected to take at least 12 hours, a crucial period following a major earthquake in which situational awareness can be greatly improved using existing seismic risk modelling tools. This work presents a new initiative to develop a rapid disaster modelling protocol for earthquakes in British Columbia (BC). We explore best practices and the feasibility of using immediately available seismic data in the existing OpenQuake Canada framework to model the impacts to people, the built environment, and the economy from an earthquake in near real-time. The current prototype integrates observed ground motion data from regional strong motion seismometers, like the BC Smart Infrastructure Monitoring System, with physical exposure data from Natural Resources Canada’s Human Settlement Layer to report on key metrics for early response: collapsed buildings, entrapment injuries, hospital demand surge, roadway debris which may block response, and immediate mass care needs like shelter requirements. These indicators will be ported to the British Columbia Common Operating Picture Portal, the online situational awareness and mapping platform for authoritative, collaborative and coordinated distribution of emergency management information in the province. These outputs could be made available within tens of minutes of the earthquake occurring, potentially affording emergency managers the opportunity to best direct resources to save lives and reduce suffering.

Earthquake monitoring and many seismological studies depend on earthquake locations from phase arrival-times. We present an extended, arrival-time earthquake location procedure (NLL-SSST- coherence) which approaches the precision of differential-timing based, relative location methods and is applicable with few seismic stations. NLL-SSST-coherence is based on the probabilistic, global-search NonLinLoc (NLL) location algorithm which defines a probability density function (PDF) in 3D space for hypocenter location and is highly robust to outlier data. NLL-SSST-coherence location first reduces velocity model error through iteratively generated, smooth, source-specific, station travel-time corrections (SSST). Next, arrival-time error is reduced by consolidating location information across events based on inter-event waveform coherency. If the waveforms at a station for multiple events are very similar (have high coherency) up to a given frequency, then the distance separating these “multiplet” events is small relative to the seismic wavelength at that frequency. NLL-coherence relocation for a target event is a stack over 3D space of the NLL-SSST location PDF for the event and the PDF’s for other multiplet events, each weighted by its waveform coherency with the target. NLL-coherence relocation requires waveforms from only one or a few seismic stations, enabling precise relocation with sparse networks, for foreshocks and early aftershocks of significant events before installation of temporary stations, and for older data sets with few waveform data. We show the behavior and performance of NLL-SSST-coherence with synthetic and ground-truth tests, and through application and comparison to relative locations for California earthquake sequences with dense and sparse station coverage.

The Alto Tiberina normal fault (ATF) in Central Italy is a 50 km long crustal structure that dips at a low angle (15-20◦). Events on the fault plane are about ten times less frequent than those located in its shallower syn- and antithetic hanging-wall splays. To enhance ATF catalogue and achieve a better understanding of the degree of coupling in the fault system, we apply a template matching technique in the 2010-2014 time window. We augment by a factor 5 the detections and decrease the completeness magnitude to negative values. Contrary to what previously observed on ATF, we highlight intermittent seismic activity and long-lasting clusters interacting with sequences on the shallower splays. One of these episodes of prolonged seismic activity, detected at the end of 2013 on a 30 km long ATF segment, suggest the ATF active role during an aseismic transient unravelled by geodetic data.

Factors influencing data reproducibility of fission-track (FT) thermochronology can be summarized into three main categories associated with data acquisition steps. (1) Sample preparation involves mineral separation, mounting, polishing and etching; (2) data revelation relates to instrumentation (microscope, LAICPMS, etc.) and software settings; and (3) execution depends on feature selection by the analyst. Previous committee reports and studies (Hurford A.J. 1990; Ketcham et al. 2009; Ketcham et al. 2015; Ketcham et al. 2018) have contributed significant insights into the reproducibility of fission-track data by comparing length and age measurements produced by several laboratories using their own preparation and revelation procedures. A recent attempt to isolate analyst-specific factors in length measurement using an image-based approach (Tamer et al. 2019) found that when two analysts observe the same feature and agree it is a valid track, measurement reproducibility was very good, though impacted by etching. Dispersion of individual length measurements was 0.7-1.0 µm (2 for weaker etching and 0.5-0.8 µm for stronger etching, but mean lengths were always within 0.1 µm of each other. Where the analysts disagreed more significantly, however, was in finding tracks and evaluating whether they were valid, sufficiently clear, and sufficiently etched for measurement, which led to differences of up to ~0.8 µm in mean track length. This study builds on the image-based approach to encompass more aspects of the measurement process and increase the number of analysts being compared. We will look at confined track selection in greater detail, and also study analyst decisions behind age determination, including the selection of the region of interest for counting, and identification of grain-surface features as tracks appropriate for counting. Reflected and transmitted light image stacks for 41 grains and graticules are available on a cloud platform Participants will carry out analyses of these images using their preferred approach, e.g. suitable analytical software, manual measurements or AI-based analysis. A limited license for FastTracks (v3.2) will be available for those who would like to participate but do not have measurement software. Analysts are asked to fill out a questionnaire about their fission track experience, conduct track density estimations, confined track length and Dpar measurements, and especially provide comments on all grains being analyzed or skipped. FastTracks users are asked to send the .xml files produced by the software, while other participants are asked to submit the results using a template. The results will be entirely anonymous unless the analyst states otherwise. The deadline for the submission of the results is June 1st, 2022. The results will be shared on 18th International Conference on Thermochronology.

Based on manually analyzed waveforms recorded by the permanent Ecuadorian network and our large aftershock deployment installed after the Pedernales earthquake, we derive three-dimensional Vp and Vp/Vs structures and earthquake locations for central coastal Ecuador using local earthquake tomography. Images highlight the features in the subducting and overriding plates down to 35 km depth. Vp anomalies (~4.5 – 7.5 km/s) show the roughness of the incoming oceanic crust (OC). Vp/Vs varies from ~1.75 to ~1.94, averaging a value of 1.82 consistent with terranes of oceanic nature. We identify a low Vp (~5.5 km/s) region extending along strike, in the marine forearc. To the North, we relate this low Vp and Vp/Vs (<1.80) region to a subducted seamount that might be part of the Carnegie Ridge (CR). To the South, the low Vp region is associated with high Vp/Vs (>1.85) which we interpret as deeply fractured, probably hydrated OC caused by the CR being subducted. These features play an important role in controlling the seismic behavior of the margin. While subducted seamounts might contribute to the nucleation of intermediate megathrust earthquakes in the northern segment, the CR seems to be the main feature controlling the seismicity in the region by promoting creeping and slow slip events (SSE) offshore that can be linked to the updip limit of large megathrust earthquakes in the northern segment and the absence of them in the southern region over the instrumental period.

Constraining the subsurface thermal regime is of importance not just to the offshore hydrocarbon exploration industry but also for understanding the geothermal regime in context of microbiological activity. This regime is tested through the use of seismic data to noninvasively estimate subsurface temperatures through the identification of bottom simulating reflectors (BSRs) at the base gas hydrate stability zone (GHSZ) to mark out an isotherm. This reflection seismic thermometry methodology is applied to the Blake Ridge, offshore east coast USA, where ODP Leg 164 boreholes provide temperature data required for thermal model constraints. 3D thermal modelling using reflection seismic data is used to examine the lateral variability of the shallow thermal regime while 1D thermal modelling is applied to ODP Sites 994, 995 and 997. The resulting estimated subsurface temperature profiles had a margin of error of 13.9% compared to in situ temperature measurements recorded from the boreholes. This method of thermal modelling could significantly expand the application of thermal data from ODP sites to areas covered by seismic data, which would considerably benefit researchers worldwide in industry and academia.

The mixing and mingling of magmas of different compositions are important geological processes. They produce various distinctive textures and geochemical signals in both plutonic and volcanic rocks and have implications for eruption triggering. Both processes are widely studied, with prior work focusing on field and textural observations, geochemical analysis of samples, theoretical and numerical modelling, and experiments. However, despite the vast amount of existing literature, there remain numerous unresolved questions. In particular, how does the presence of crystals and exsolved volatiles control the dynamics of mixing and mingling? Furthermore, to what extent can this dependence be parameterised through the effect of crystallinity and vesicularity on bulk magma properties such as viscosity and density? In this contribution, we review the state of the art for models of mixing and mingling processes and how they have been informed by field, analytical, experimental and numerical investigations. We then show how analytical observations of mixed and mingled lavas from four volcanoes (Chaos Crags, Lassen Peak, Mt. Unzen and Soufrière Hills) have been used to infer a conceptual model for mixing and mingling dynamics in magma storage regions. Finally, we review recent advances in incorporating multi-phase effects in numerical modelling of mixing and mingling, and highlight the challenges associated with bringing together empirical conceptual models and theoretically-based numerical simulations.