We have developed improved seismic hazard maps with the effect of local geology for the Washington, DC area. The input ground motion prediction equations, source model, and logic tree for the analysis is taken from the 2014 U.S. Geological Survey national seismic hazard model (Petersen et al., 2014). We have added an improved local geology model based on the overburden thickness map of Froelich (1976). As in our preliminary effort (Cramer et al., 2016) we use three shear-wave velocity profiles for Piedmont, Fall Line, and Coastal Plain regions (Olgun et al, 2015). We developed reference profiles from the three Olgun et al. profiles that extend to hard rock for site amplification relative to the rock conditions for the ground motion prediction equations. Our seismic hazard maps include both probabilistic (2% in 50 years) and scenario (M6.0 at Mineral, VA) maps. The local geology in the Washington DC area strongly amplifies higher frequency ground motions (peak ground acceleration, 0.2 s spectral acceleration) in keeping with the three site-specific profiles of Olgun et al. (2015) and the observations of Pratt et al. (2017). The soil response is driven by the 10 to 20 m thick low shear-wave velocity (200–300 m/s) top layers of the reference profiles. These low velocity layers are composed of residual soil and/or alluvium. The thicker Cretaceous Potomac Formation sediments, up to 600 m thick in the SE corner of the study area, have an effect on seismic hazard at 1.0 s and longer periods. The greatest effect on 1.0 s spectral acceleration seismic hazard is from the ~200 m thick sediments near the SE edge of Washington DC. Our maps have a resolution of 0.005 degree (500 m) and have some of the sub-km scale detailed geology variation in the Washington, DC area. These maps can serve as a guide to improving the understanding of seismic hazard and risk in the area and stimulate further work on a more detailed local geology model with higher resolution.

One of the next giant leaps for humanity—inhabiting our neighbor planet Mars—requires enough water to support multi-year human survival and to create rocket fuel for the nearly 150-million-mile return trip to Earth. Water that is already on Mars, in the form of ice, is one of the leading in situ resources being considered in preparation for human exploration. Human missions will need to land in locations with relatively warm temperatures and consistent sunlight. But in these locations, ice (if present) is buried underground. Much of the ice known to exist in mid-latitude locations was likely emplaced under climate conditions (and orbital parameters) different from today. So in addition to providing an in-situ resource for human exploration, Martian ice also provides a crucial record of planetary climate change and the effects of orbital forcing.This presentation will highlight techniques and recent activities to characterize Mars’ underground ice, such as the Subsurface Water Ice Mapping (SWIM) Project (Morgan et al. 2021, Nature Astro.; Putzig et al. In Press, Handbook of Space Resources; Putzig et al. this AGU; Morgan et al. this AGU). We present outstanding questions that will be vital to address in the context of ISRU (in situ resource utilization) and connections between these questions and the climate in which the ice was emplaced and evolved (e.g., Bramson et al. 2020, Decadal White Paper). Lastly, we discuss how these science activities intersect with future exploration, particularly that enabled by collaborations between space agencies as well as industry partners (Heldmann et al. 2020, Decadal White Paper; Golombek et al. 2021, LPSC).High-priority future work includes better orbital characterization of shallow ice deposits, such as radar sounding at shallower scales (<~10m) than that of SHARAD, as proposed for the International Mars Ice Mapper. Also needed are detailed studies of the engineering required to build potential settlements at specific candidate locations; this includes characterization of the nature of the overburden above the ice, which will inform future resource extraction technology development efforts. Ideally, initial landing sites would be chosen with a long-term vision which includes preparation and development of the basic technologies and designs needed for human landing on Mars.

Rock slope failures often result from progressive rock mass damage which accumulates over long timescales, and is driven by changing environmental boundary conditions. In deglaciating environments, rock slopes are affected by stress perturbations driven by mechanical unloading due to ice downwasting and concurrent changes in thermal and hydraulic boundary conditions. Since in-situ data is rare, the different processes and their relative contribution to slope damage remain poorly understood. Here we present detailed analyses of subsurface pore pressures and micrometer scale strain time series recorded in three boreholes drilled in a rock slope aside the retreating Great Aletsch Glacier (Switzerland). Additionally, we use monitored englacial water levels, climatic data, and annually acquired ice surface measurements for our process analysis. Pore pressures in our glacial adjacent rock slope show a seasonal signal controlled by infiltration from snowmelt and rainfall as well as effects from the connectivity to the englacial hydrological system. We find that reversible and irreversible strains are driven by hydromechanical effects from diffusing englacial pressure fluctuations and pore pressure reactions on infiltration events, stress transfer related to changing mechanical glacial loads from short-term englacial water level fluctuations and longer-term ice downwasting, and thermomechanical effects from annual temperature cycles penetrating the shallow subsurface. We relate most observed irreversible strain (damage) to mechanical unloading from ice downwasting. Additionally, short-term stress changes related to mechanical loading from englacial water level fluctuations and hydromechanical effects from pore pressure variations due to infiltration events were identified to contribute to the observed irreversible strain.

The Crustal Fault Zones provides an interesting geological target for high temperature geothermal energy source in naturally deep-fractured basement areas. Field and laboratory studies have already shown the ability of these systems to let fluid flow down to Brittle-Ductile-Transition. However, several key questions about exploration still exist, in particular the fundamental effect of tectonic regimes on fluid flow in fractured basement domains. Based on poroelasticity assumption, we considered an idealized 3D geometry and realistic physical properties. We examined a model with no tectonic regime (benchmark experiment) and a model with different tectonic regimes applied. Compared to the benchmark experiment, the results suggest that different tectonic regimes cause pressure changes in the fault/basement system. The tectonic-induced pressure changes affect fluid patterns, onset of convection as well as the spatial extent of thermal plumes and the intensity of the temperature anomalies.

Knowledge of the contemporary in-situ stress orientations in the Earth’s crust can improve our understanding of active crustal deformation, geodynamic processes, and seismicity in tectonically active regions such as the Hikurangi Subduction Margin (HSM), New Zealand. The HSM subduction interface is characterized by varying slip behavior along strike, which may be a manifestation of variation in the stress state and the mechanical strength of faults and their hanging walls, or, alternatively, these variations in seismic behavior may generate variation in the stress state in space and time. In this study, we analyze borehole image and oriented four-arm caliper logs acquired from thirteen boreholes along the HSM to present the first comprehensive stress orientation dataset within the HSM upper plate. Our results reveal a NE-SW SHmax orientation (parallel to the Hikurangi margin) within the central HSM (Hawke’s Bay region) which rotates to a WNW- ESE SHmax orientation (roughly perpendicular to the Hikurangi margin) in the southern HSM. This rotation of SHmax orientation spatially correlates with along-strike variations in subduction interface slip behavior, characterized by creep and/or shallow episodic slip events in the central HSM and interseismic locking in the southern HSM. Observed borehole SHmax orientations are largely parallel to maximum contraction directions derived from geodetic surface deformation measurements, suggesting that modern stress orientations may reflect contemporary elastic strain accumulation processes related to subduction megathrust locking.

The western India-Eurasia collision zone (IECZ) has experienced devastating earthquakes in the past century and continues to be seismically active. However, the Stress regime and Seismotectonics of the region remains poorly understood. In view of this, we carried out iterative, joint stress inversions of 245 well-constrained earthquake focal mechanisms to constrain the stress regime and its spatial variability in the region and dwell upon their implications for earthquake generation. Salient new findings from the study are, (i) the Kangra-Chamba-Kishtwar region shows arc-oblique horizontal maximum compressive stress (sigma 1, WSW-ENE) in contrast to arc-normal (NNE-SSW) in other regions of the Himalaya, (ii) the Kashmir earthquake sequence (in 2005) and its epicentral region i.e. the Hazara Syntaxis show similar stress patterns with that of the Central Himalaya, (iii) Nanga Parbat Syntaxis experiences pure extension, and (iv) Kaurik Chango Rift, with N-S trending sigma 1, probably extends deep into the Karakoram fault. Based on these findings, we categorize the region into six state of stress fields consistent with geology and plate motion models. The magnitudes for these stress fields show a decreasing trend from 0.90 in the southeast (Garhwal-Kumaun-Shimla) to 0.46 in the northwest (Hazara Syntaxis) and 0.39 in the northeast (Karakoram) suggesting multiple tectonic forces in northwestern and northeastern regions. The study reveals heterogeneity in the stress field within the western IECZ, induced by tectonic forces and structural variability.

On the 22nd of May 2021, although no alarming precursory unrest had been reported, Nyiragongo volcano erupted and lava flows threatened about 1 million of inhabitants living in the cities of Goma (Democratic Republic of Congo) and Giseny (Rwanda). After January 1977 and January 2002, it was the beginning of the third historically known flank eruption of Nyiragongo volcano and the first ever to be recorded by dense measurements both on the ground and from space. In the following days, seismic and geodetic data as well as fracture mapping revealed the gradual southward propagation of a shallow dike from the Nyiragongo edifice underlying below Goma airport on May 23-24, then Goma and Gisenyi city centers on May 25-26 and finally below the northern part of Lake Kivu on May 27. Southward migration of the associated seismic swarm slowed down between May 27 and June 02. Micro seismicity became more diffuse, progressively activating transverse tectonic structures previously identified in the whole Lake Kivu basin. Here we exploit ground based and remote sensing data as well as inversion and physics-based models to fully characterize the dike sized, the dynamics of dike propagation and its arrest against a structural lineament known as the Nyabihu Fault. This work highlights the shallow origin of the dike, the segmented dike propagation controlled by the interaction with pre-existing fracture networks and the incremental crater collapse associated with drainage which led to the disappearance of the world’s largest long-living lava lake on top of Nyiragongo.

Oceanic basalts provide an invaluable window into evolutionary processes governing mantle spatial and temporal chemical heterogeneity. Ocean island basalts (OIBs) and enriched mid-ocean ridge basalts (E-MORBs) are powerful tracers of mantle melting and crust-mantle recycling processes. Whether the elemental and isotopic variations observed in both E-MORBs and OIBs are derived from similar mechanisms, however, remains under debate. Investigating compositional differences between E-MORBs and OIBs is a simple approach to constrain their origins, a technique for which machine learning classification algorithms are optimal. Here we implemented a novel machine learning approach complemented by mantle component mixing models to highlight compositional differences between E-MORBs and OIBs and further investigate their petrogenesis (data sourced from GEOROC database and Gale et al., 2013). Considering Random Forest-based Gini indexes, elements sensitive to pressure and degree of melting (FeO, TiO2, Lu, and Sr) were identified as the best discriminators between E-MORBs and OIBs. Our Gaussian process classification algorithm successfully classified OIBs and E-MORBs better than 97% of the time when considering 1) Sr & FeO and 2) TiO2 & Lu. The probabilistic nature of Gaussian process modeling permitted calculation of new quantitative discriminant diagrams rooted in probability (Sr vs. FeO and TiO2 vs. Lu). Complementary trace element modeling yielded compositionally similar E-MORB and OIB sources with moderately incompatible element enrichments in the OIB source due to the influence of recycled oceanic crust (Prytulak & Elliott, 2007). Our source compositions are consistent with a simple, joint model for E-MORB and OIB petrogenesis after Donnelley et al. (2014): low-degree partial melts of subducted slabs metasomatize the depleted mantle producing a re-fertilized mantle (RM). RM is randomly sampled at mid-ocean ridges to produce E-MORB, while upwelling plumes sample both RM and recycled oceanic crust, yielding OIB. References: Donnelly et al. (2004). Earth and Planet. Sci. Lett., 226(3–4), 347–366. Gale et al. (2013). Geochem., Geophys., Geosyst., 14(3), 489–518. Prytulak & Elliott (2007). Earth and Planet. Sci. Lett., 263(3–4), 388–403.

All material that is collected from Mars (gases, dust, rock, regolith) will need to be carefully handled, stored, and analyzed following Earth return to minimize the alteration or contamination that could occur, and to maximize the scientific information that can be extracted from the samples, now and into the future. A Sample Receiving Facility (SRF) would be where the Earth Entry System is opened, and the sample tubes opened and processed after they land on Earth. The Mars Sample Return (MSR) Science Planning Group Phase 2 (MSPG2) was tasked with identifying the steps that encompass the curation activities that would happen within an MSR SRF and any anticipated curation-related requirements. To make the samples accessible for scientific investigation, a series of observations and preliminary analytical measurements would need to be completed to produce a sample catalog for the scientific community. The sample catalog would provide data to make informed requests for samples for scientific investigations and for the approval of allocations of appropriate samples to satisfy these requests. The catalog would include data and information generated during all phases of activity, including data derived from the landed Mars 2020 mission, during sample retrieval and transport to Earth, and upon receipt within the SRF, as well as through the initial sample characterization process, sterilization- and time-sensitive and science investigations. The Initial sample characterization process can be divided into three phases, with increasing complexity and invasiveness: Pre-Basic Characterization (Pre-BC), Basic Characterization (BC), and Preliminary Examination (PE). A significant portion of the Curation Focus Group’s efforts was determining which analyzes and thus instrumentation would be required to produce the sample catalog and how and when certain instrumentation should be used. The goal is to provide enough information for the PIs to request material for their studies but to avoid doing targeted scientific research better left to peer-reviewed competitive processes. Disclaimer: The decision to implement Mars Sample Return will not be finalized until NASA’s completion of the National Environmental Policy Act (NEPA) process. This document is being made available for planning and information purposes only.

Estimating the melt fraction and volatile content of regions of partial melt beneath volcanoes has important implications for volcanic hazards since higher melt fraction, volatile-rich magmas are more buoyant and have a lower viscosity, and thus are more susceptible to mobilization and possibly eruption. Magnetotelluric (MT) data can be used to model subsurface bulk resistivity structures through inversion algorithms and can provide information on the distribution and amount of melt and volatiles contained in the residing magma by converting bulk resistivity to estimates of melt fraction, temperature, and water content. These are often treated as independent variables but, in reality, they are thermodynamically correlated. Thermodynamic models such as MELTS can be used to constrain the possible combinations of melt fraction, temperature, and water content such that MT interpretations are petrologically consistent. Probabilistic Bayesian inversion that incorporates these constraints can be used to find a distribution of models and interpretations which fit the MT data and provide a better understanding of the uncertainty in MT-derived estimates of melt fraction. In this study, we apply MELTS-coupled 1-D Bayesian inversions of MT data at Uturuncu Volcano to evaluate the constraints that MT data can provide on melt fraction estimates. Uturuncu Volcano is a large composite volcano in southern Bolivia at the center of the Altiplano Puna Volcanic Complex (APVC), the result of a large ignimbrite flare-up during the past 10 Ma. Previous geophysical studies have shown that the APVC is underlain by the voluminous, laterally-extensive Altiplano Puna Magma Body (APMB) at approximately 15-20 km depth below surface. The APMB has previously been interpreted to have a wide range of melt fractions anywhere from 4% to 45%, but MT results suggest anomalously high water contents of up to 10 wt%. Initial results from petrologically-consistent MT inversion modelling suggests that the resulting low resistivity of the APMB beneath Uturuncu requires high melt fractions (e.g. >90%) in near-saturated conditions. This suggests that either high melt fraction near-saturated magma reservoirs exist at depth or that a significant phase of saline fluids in over-saturated low melt fraction conditions is present.

Geohazards, including earthquakes, volcanic eruptions, floods, and landslides, cause billions of dollars in U.S. economic losses, loss of life, injuries, and significant disruption to lives and livelihoods on an annual basis. The ability of the geoscience community to respond rapidly after a hazardous event or at the signs of precursors to these events, provides critical data to understand the physical processes responsible for these destructive events. The Seismological Facility for the Advancement of Geoscience (SAGE) is an NSF-funded facility operated by the Incorporated Research Institutions for Seismology (IRIS). As a part of the SAGE award, IRIS will implement an expanded capability to facilitate rapidly responding to geohazards with geophysical instrumentation. After several years of gathering community input, IRIS is ready to begin procurement of a new suite of instrumentation for rapidly responding to geohazard events. During the past year, staff at the IRIS/PASSCAL Instrument Center have conducted instrument testing and evaluation to inform the preferred mix of instrumentation for the new rapid response equipment pool—which is expected to include broadband and nodal seismometers, digitizers, and infrasound sensors. This effort has been guided by recommendations from a recent Rapid Response Community Whitepaper, with ongoing oversight from the PASSCAL Standing Committee. A copy of the whitepaper, as well as recordings and presentations from hosted gatherings have been posted to IRIS’ Rapid Response to Geohazards webpage (www.iris.edu/rapid). With testing and evaluation complete, IRIS is looking ahead to procuring instruments and associated equipment over the next year, followed by acceptance testing and integration at the IRIS/PASSCAL Instrument Center. Concurrently, IRIS is working with community governance to formalize new policies and procedures that will outline how this new community resource can most effectively and efficiently be used for geohazard-related observations. Beginning in 2023, PIs will be able to schedule and use this equipment from the IRIS/PASSCAL Instrument Center. We look forward to presenting further details on the above-mentioned activities during the AGU Fall Meeting.

Urbanization alters the geomorphological attributes of rivers by increasing peak flows and reducing sediment inputs due to surface sealing and efficient stormwater systems. Attribution of geomorphological changes to urbanization has been mostly done using purely statistical tools under a regional analysis framework, which does not explicitly account for the hydrological processes by which urbanization controls river morphology. Using a process-based hourly hydrological model, we aimed to relate the observed geomorphological changes in three French rivers to the historical urbanization of their catchments over the period 1959-2018. Firstly, we applied the hydrological model to generate an hourly streamflow time series from climatic inputs by accounting for the changes in catchment imperviousness, which we estimated from historical land-cover databases. Secondly, we exploited the obtained streamflow time series to analyze the temporal evolution of the flow competence, i.e. its ability to transport sediments, with regard to the increased imperviousness of the catchments. Results show that urbanization significantly increased flow competence on the urbanized rivers, but the impact and its trend were variable from one catchment to another. This demonstrates the role of urbanization in increasing the channel instability that led to the general incision and widening observed on these rivers over the past three to four decades. Our approach shows promise in projecting the impact of changing land-use and climate on channel geomorphology.

The Magnetics Information Consortium (MagIC), hosted at http://earthref.org/MagIC is a database that serves as a Findable, Accessible, Interoperable, Reusable (FAIR) archive for paleomagnetic and rock magnetic data. It has a flexible, comprehensive data model that can accomodate most kinds of paleomagnetic data. The **PmagPy** software package is a cross-platform and open-source set of tools written in Python for the analysis of paleomagnetic data that serves as one interface to MagIC, accommodating various levels of user expertise. It is available through github.com/PmagPy. Because PmagPy requires installation of Python, several non-standard Python modules, and the PmagPy software package, there is a speed bump for many practitioners on beginning to use the software. In order to make the software and MagIC more accessible to the broad spectrum of scientists interested in paleo and rock magnetism, we have prepared a set of Jupyter notebooks, hosted on [jupyterhub.earthref.org](https://jupyterhub.earthref.org) which serve a set of purposes. 1) There is a complete course in Python for Earth Scientists, 2) a set of notebooks that introduce PmagPy (pulling the software package from the github repository) and illustrate how it can be used to create data products and figures for typical papers, and 3) show how to prepare data from the laboratory to upload into the MagIC database. The latter will satisfy expectations from NSF for data archiving and for example the AGU publication data archiving requirements.

Detrital zircon records of provenance are used to reconstruct paleogeography, sediment sources, and tectonic configuration. Recognition of the biases in detrital zircon records that result from hydraulic sorting of sediment and the initial characteristics of zircons in source regions (e.g., size and abundance) has added new complexity and caution in the interpretation of these records. In this study, we examine the role of transport process and sediment sorting in these records. We begin our analysis by investigating the influence of grain size and transport process in biasing detrital zircon provenance records in an idealized sedimentary system. Our modeling results show that settling and selective entrainment can leave distinct, process-dependent fingerprints in detrital zircon spectra if initial size variation between source zircon populations exists. We then consider a case study: a detrital zircon record from Ediacaran to Terreneuvian Death Valley. We focus on the Rainstorm Member, which is geochemically, mineralogically, and sedimentologically unusual. In addition to Earth’s largest negative carbon isotope excursion (the Shuram excursion), the Rainstorm Member also contains anachronistic carbonate structures and a detrital mineral suite enriched in heavy minerals. We evaluate the detrital zircon provenance record of the Rainstorm Member, and find that, despite its unusual character, the provenance of the unit is similar to other units in the succession, with substantial input from Yavapai-Matzatzal provinces. Size and density measurements of heavy and light density components of the deposit suggest that its enriched heavy mineral suite is best explained through concentration by selective entrainment and winnowing. We find that our detrital zircon dataset is susceptible to hydrodynamic fractionation, so that grain size exerts influence on its provenance record, in particular for large Grenville-aged (1.0-1.2 Ga) grains.

What tectonic regimes operated on the early Earth and how these differed from modern plate tectonics remain unresolved questions. We use numerical modelling of mantle convection, melting and melt-depletion to address how the regimes emerge under conditions spanning back from a modern to an early Earth, when internal radiogenic heat was higher. For Phanerozoic values of internal heat, the tectonic regime depends on the ability of the lithosphere to yield and form plate margins. For early Earth internal heat values, the mantle reaches higher temperatures, high-degree depletion and differentiated into a thicker and stiffer lithospheric mantle. This thermochemical differentiation stabilises the lithosphere over a large range of modelled strengths, narrowing the viable tectonic regimes of the early Earth. All the models develop in two stages: an early stage, when decreasing yield strength favours mobility and depletion, and a later stabilisation, when inherited features remain preserved in the rigid lid. The thick lithosphere reduces surface heat loss and its dependence on mantle temperature, reconciling with the thermal history of the early Earth. When compared to the models, the Archean record of large melting, episodic mobility and plate margin activity, subsequently fossilised in rigid cratons, is best explained by the two-stage evolution of a lithosphere prone to yielding, progressively differentiating and stabilising. Thermochemical differentiation holds the key for the evolution of Earth’s tectonics: dehydration stiffening resisted the operation of plate margins preserving lithospheric cores, until its waning, as radioactive heat decays, marks the emergence of stable features of modern plate tectonics.

The Butterknowle Fault is a major normal fault of Dinantian age in northern England, bounding the Stainmore Basin and the Alston Block. This fault zone has been proposed as a source of deep geothermal energy; to facilitate the design of a geothermal project in the town of Bishop Auckland further investigation of its geometry was necessary and led to the present study. We show using three-dimensional modelling of a dense local gravity survey, combined with structural inversion, that this fault has a ramp-flat-ramp geometry, ~250 m of latest Carboniferous / Early Permian downthrow having occurred on a fault surface that is not a planar updip continuation of that which had accommodated the many kilometres of Dinantian extension. The gravity survey also reveals relatively low-density sediments in the hanging-wall of the Dinantian fault, interpreted as porous alluvial fan deposits, indicating that a favourable geothermal target indeed exists in the area. This study demonstrates the value of gravity data for elucidating geological structure, even in a well-studied region such as Britain, and highlights the need to verify published structural interpretations as future deep geothermal projects are designed. Future work of this type might be undertaken more expeditiously using microelectromechanical gravimeters.

SE Asia is renowned as a region of complex plate tectonic interactions, both in the present day and throughout its Mesozoic and Cenozoic history. The study of subduction processes in SE Asia has been instrumental in our understanding of how complex subduction systems develop and evolve, including understanding double subduction zones, areas of subduction polarity reversal, and the interaction of subduction and strike-slip systems. This complexity in subduction style makes SE Asia an ideal natural laboratory for studying forearc development in a range of subduction styles across a relatively small area still exposed in the rock record. Here we present a recently studied example of forearc development in a Mesozoic double subduction zone exposed on Natuna Island in the South China Sea, as well as highlighting two other examples of forearc development in SE Asia. These include a Cenozoic subduction polarity reversal event and transform plate boundary in western New Guinea and forearc sedimentation along the Sunda Trench. All three scenarios chronicle histories of forearc accretion, either of deep-water cherts or continental-derived turbidites, whilst also recording the impacts of case-specific tectonic processes (such as ophiolite obduction, arc-continent collision, or strike-slip movement) that have fundamentally impacted their respective forearcs. Comparing these contrasting examples shows that studying forearc development of these complex subduction systems (including their structural styles, geochemistry and timing of associated magmatism, and sedimentation) in SE Asia can be a powerful tool for improving understanding of forearc evolution in other ancient and complex subduction systems.

We report palaeomagnetic and K-Ar geochronologic results of two volcanic sections from Ethiopia. One section, dated around 29-30 Ma and spanning ~1 km in thickness, is related to the Oligocene Afro-Arabian traps. The second ~700-m-thick section was emplaced during the Miocene in two pulses around 10-11 and 14-15 Ma. We sampled 67 flows (550 cores) of predominantly basaltic rocks at the Oligocene section and 59 rhyolitic to trachybasaltic flows (500 cores) at the Miocene section. The Oligocene section was correlated to subchrons C11r to C11n.1n, with an average emplacement rate of 1m/kyr and instantaneous rates increasing with time from ~0.5 m/kyr near the base to ~1.36 m/kyr towards the top. We combined our results to the available paleomagnetic studies for the Early Oligocene (N = 4; 167 sites), Middle Miocene (N = 2; 125 sites) and Plio-Pleistocene (N = 8; 249 sites) to better understand how geomagnetic secular variation changed through time in the Afro-Arabian region. Recentred directional distributions for all three periods are elongated in the meridian plane (e = 2.7 ± 0.4, 1.8 ± 0.6, 2.3 ± 0.4, respectively), in coherence with field models for a dipole-dominated field. The angular dispersion S of the virtual geomagnetic poles, representative of the vigour of the palaeosecular variation, was higher during the Early Oligocene (S=14.2°|13.2°15.4°) and the Middle Miocene (S=15.0°|13.8°16.5°) than during the Plio-Pleistocene (S=9.7°|9.0°10.5°). As the reversal frequency f during the Early Oligocene is half that for the Plio-Pleistocene, it appears that S and f are uncorrelated in this near-equatorial region.

The leading paradigm for rift initiation suggests “magma-assisted (wet)” rifting is required to weaken strong lithosphere such that only small tectonic stresses are needed for rupture to occur. However, there is no surface expression of magma along the 300 km long Albertine-Rhino Graben (except at its southernmost tip within the Tore Ankole Volcanic Field), which is the northernmost rift in the Western Branch of the East African Rift System. The two prevailing models explaining magma-poor rifting are: 1) Melt is present at depth weakening the lithosphere, but it has not reached the surface or 2) far-field forces driving extension are accommodated along weak pre-existing structures without melt at depth. The goal of this study is to test the hypothesis that melt is generated below the Albertine-Rhino Graben from Lithospheric Modulated Convection (LMC) using the 3D finite element code ASPECT. We develop a regional model of a rigid lithosphere and an underlying convecting sublithospheric mantle that has dimensions 1000 by 1000 by 660 km along latitude, longitude, and depth, respectively. We solve the Stokes equations using the extended Boussinesq approximation for an incompressible fluid which considers the effects of adiabatic heating and frictional heating. We include latent heating such that we can test for melt generation in the sublithospheric mantle from LMC. Using LITHO1.0 as the base of our lithosphere, our preliminary results suggest melt could be generated beneath the Albertine-Rhino graben given a mantle potential temperature of 1800 K. These early results indicate LMC can generate melt beneath the northernmost Western branch of the East African Rift System.

The coal fires that started over a century ago in Jharia Coal Fields constitute a significant threat to the coal reserves, infrastructure, and residents’ lives. The fires burn underground coal leaving the surface with no support, leading to land subsidence and roof collapse. This will have a multiplier effect as it creates cracks and crevices that pump in more oxygen to aggravate the coal fires further. Despite the various measures taken by authorities, coal fires and land subsidence still have an increasing presence. In this study, we investigated the two hazards and their impact on the coal mines and surrounding settlements. We observed the subsidence and coal fires in the study area with the help of Persistent Scatterer Interferometry analysis of Sentinel-1 images and Temperature anomaly mapping of Thermal Infrared Imagery from Landsat-8, respectively. The subsidence velocity results and the coal fire zones are analysed, and a significant spatial overlap of both hazards is noticed. A few key locations severely affected by both the hazards are identified and examined to understand the mutual effect of coal fires and land subsidence. The subsidence of up to 20 cm/yr is observed in the study area. The results show that nearly 80% of the subsiding area is also affected by coal fires. Kusunda, Bararee and Keshalpur collieries are critically affected by both the hazards and need immediate intervention. Subsidence and coal fires extending towards the residential zones in several collieries is a matter of concern. In conclusion, the study presents an efficient methodology for multi-hazard monitoring, and the findings assist the authorities in enforcing appropriate disaster management strategies.

Automatically extracting buildings from remotely sensed imagery has always been a challenging task, given the spectral homogeneity of buildings with the non-building features as well as the complex structural diversity within the image. Traditional machine learning (ML) based methods deeply rely on a huge number of samples and are best suited for medium resolution images. Unmanned aerial vehicle (UAV) imagery offers the distinct advantage of very high spatial resolution, which is helpful in improving building extraction by characterizing patterns and structures. However, with increased finer details, the number of images also increase many fold in a UAV dataset, which require robust processing algorithms. Deep learning algorithms, specifically Fully Convolutional Networks (FCNs) have greatly improved the results of building extraction from such high resolution remotely sensed imagery, as compared to traditional methods. This study proposes a deep learning based segmentation approach to extract buildings by transferring the learning of a deep Residual Network (ResNet) to the segmentation based FCN U-Net. This combined dense architecture of ResNet and U-Net (Res-U-Net) is trained and tested for building extraction on the open source Inria Aerial Image Labelling (IAIL) dataset. This dataset contains 360 orthorectified images with a tile size of 1500m2 each, at 30cm spatial resolution with red, green and blue bands; while covering total area of 805km2 in select US and Austrian cities. Quantitative assessments show that the proposed methodology outperforms the current deep learning based building extraction methods. When compared with a singular U-Net model for building extraction for the IAIL dataset, the proposed Res-U-Net model improves the overall accuracy from 92.85% to 96.5%, the mean F1-score from 0.83 to 0.88 and the mean IoU metric from 0.71 to 0.80. Results show that such a combination of two deep learning architectures greatly improves the building extraction accuracy as compared to a singular architecture.

The nature of deep earthquakes with depths greater than 70 km is enigmatic because brittle failure at this high-temperature and the high-pressure regime should be inhibited. Three main hypotheses have been proposed to explain what causes deep earthquakes within the subducting slabs, dehydration embrittlement, phase transformational faulting, and thermal runaway instability. However, the existing seismological constraints can’t yet definitively distinguish between these hypotheses because the fine 3D slab structures are not well constrained in terms of slab upper interface, thickness, and internal fine layering. To better image the slabs in the Western Pacific subduction zones, this study employs a full waveform inversion (FWI) that minimizes waveform shape misfit between the synthetics and the observed waveforms from a large dataset, with 142 earthquakes recorded by about 2,400 broadband stations in East Asia. A 3-D initial model that combines two previous FWI models in East Asia (i.e., FWEA18 and EARA2014) are iteratively updated by minimizing the misfit measured from both body waves (8–40 s) and surface waves (30–120 s). Compared to the previous models, the new FWI model (EARA2020) shows much stronger wave speed perturbations within the imaged slabs with respect to the ambient mantle, with maximum perturbation of 8% for Vp and 13% for Vs. Furthermore, the slab thickness derived from EARA2020 exhibits significant downdip and along-strike variations at depths greater than 100 km. The large intra-slab deep earthquakes (Mw>6.0) appear to occur where significant slab thinning happens. This observation suggests that the significant deformation (or strain accumulation) of the slab is likely the first-order factor that controls the distribution of large deep earthquakes within the slab regardless of their triggering mechanism.

Rapid progress in investigation of zircon records for U-Th-Pb ages and O and Hf isotopes in igneous rocks require understanding how magma bodies are formed and evolve in the crust. We here present a 2D model of magma bodies formation in granitic crust by injection of rhyolitic or andesitic dikes and sills. We combine this model with our zircon crystallization/dissolution software and compute zircon survival histories in individual batches of magma and country rocks. Simulations reproduces incremental accumulation of intruded magma into magma chambers generating eruptible and interconnected magma batches with melt fraction >50 vol% that form in clusters. The rate of melt production is highly variable in space and time. The volume of eruptible melt strongly depends on the input rates of magma Q and the width W of the dike injection region. For example, dikes injection with Q=0.25 m3/s with W=500 m during 4 ka generate 20 km3 of melt while no significant melt forms if W=4 km. Injection of andesitic dikes produces only slightly more melt than rhyolite to granite injection despite of much larger thermal input. Due to rock melting most of zircons loose significant portion of their old cores and, thus, average age. Magmatic zircons in the periphery of the intrusion form very quickly while in its central part crystals contain old cores and young rims and can grow during several hundreds of ka. We observe diverse proportions of crustal melt/newly intruded magma, which translates into diverse O and Hf isotope distribution in zircons.

The Department of Earth & Environmental Sciences at the University of Michigan formed an Unlearning Racism in GEosciences (URGE) pod composed of six graduate students, three postdocs and eight faculty in the beginning of 2021. The department’s Diversity, Equity and Inclusion (DEI) efforts have been building in the preceding years. Our first DEI committee was formed in 2017 and increased its activity since initiation, hosting DEI discussions and initiatives with participation from students, postdocs, staff and faculty. Existing DEI activities include a Fall Preview event for prospective graduate students, DEI office hours and book discussions, adding DEI resources to the public-facing Department website, student grants for DEI related activities, and hosting workshops. The formation of an URGE pod provided new, focused energy to our DEI efforts and bolstered ongoing work by creating a bigger, critical mass of people who met regularly and were focused on action. The scope of URGE, the NSF support for it, and the interactions with other institutions that came from it, helped give our pod momentum, legitimacy, and contributed to broader departmental support for the recommendations that it produced. It also helped our department identify our most critical deficits on a DEI front and concrete ways that we will respond to them, which parallel needs articulated in a recent report from our college’s anti-racism task force, a major focus of our Dean. Actions emerging from the URGE pod include, but are not limited to, hiring a Wellness and Inclusion Advocate staff member, creation of field safety training and guidance, and building a workshop series to address issues centered on creating a culture of wellness and inclusion (anti-bias training, ally training, etc). The formation of our pod coincided with and complemented the finalization of our department’s self-study as part of a decadal strategic planning process. Many recommendations related to hiring, inclusive teaching, reporting, and deliberate mentoring practices that our URGE pod discussed were incorporated into our department’s strategic plan that was finalized in July 2021. We are eager to translate these recommendations for anti-racism work into actions, building on and contributing to the momentum and resources of the URGE community.