The Southern African Magnetotelluric Experiment (SAMTEX) involved the collection of data at over 700 sites in Archean to Proterozoic southern Africa, spanning features including the Kalahari Craton, Bushveld Complex and voluminous kimberlites. Here, we present the first 3D inversions of the full SAMTEX dataset. In this paper, we focus on assessing the robustness of the 3D models by comparing two different inversion codes, jif3D and ModEM, and two different subsets of the data, one containing all acceptable data and the other containing a smaller selection of undistorted, high-quality data. Results show that the main conductive and resistive features are imaged by all inversions, including deep resistive features in the central Kaapvaal Craton and southern Congo Craton and a lithospheric-scale conductor beneath the Bushveld Complex. Despite this, differences exist between the jif3D and ModEM inverse models that derive mainly from the differences in regularization between the models, with jif3D producing models that are very smooth laterally and with depth, while ModEM produces models with more discrete conductive and resistive features. Analysis of the differences between these two inversions can provide a good indication of the model resolution. More minor differences are apparent between models run with different subsets of data, with the models containing all acceptable data featuring higher wavelength conductivity variations than those run with fewer stations but also demonstrating poorer data fit.

In the 2011 Tohoku-Oki earthquake, the rupture in the subduction megathrust reached the trench axis and triggered a large tsunami. The shallow portion of the subduction megathrust fault was regarded as an aseismic stable zone. The frictional properties along the shallow subduction plate boundary are an important foundation for understanding the cause of the dynamic fault rupture in the earthquake near the trench. The critical taper model of a sedimentary wedge best describes the first-order mechanics of a subduction zone wedge. The tapered wedge geometry (slope angle α and basal dip angle β) is responsible for the strength of a shallow megathrust. However, to apply the critical taper model for the investigation of spatial heterogeneity, we need to improve handling β, since β is derived from the subsurface structure and its value depends on the number of accurately depth-converted seismic profiles. Here, the effect of décollement dip angle β in the critical taper model of a sedimentary wedge is examined. The effect is negligible for a high pore fluid pressure ratio, allowing the frictional variation to be obtained with only bathymetry data. We applied the model to the Japan Trench. The frictional variation indicates that a smaller frictional area corresponds to an area with a larger coseismic shallow rupture during the 2011 earthquake than those of the southern and northern areas. The method can be applied to other trenches to predict seismic potential.

Studies attempting to gain new insights into the last stage of the subduction cycle are typically challenged by limited direct observations owing to a lack of recent post-subduction settings around the world. Central to unravelling how the subduction cycle ends is an understanding of crust and mantle processes that take place after subduction termination. Northern Borneo (Malaysia) represents a unique natural laboratory because it has been the site of two sequential subduction episodes of opposite polarity since the mid-Paleogene. The region exhibits several enigmatic post-subduction (after ~10 Ma) features, including: subsidence followed by rapid uplift, localised intraplate volcanism, possible orogen collapse, and a pluton that emerged to become the third highest peak in southeast Asia, Mt Kinabalu (4095 m). Arrival-time residuals from distant earthquake data recorded by the nBOSS seismic network have been used to investigate P- and S-wavespeed variations in the crust and underlying upper mantle beneath northern Borneo. Our 3-D tomographic images consistently show a high-velocity perturbation in western Sabah that we associate with an upper-mantle remnant of the Proto South-China Sea slab, thus providing important constraints for tectonic reconstructions of SE Asia. The tomographic models, combined with other seismological and geological information, reveal evidence for lithospheric removal in eastern Sabah via a drip instability. Our results suggest that lithospheric drips can be smaller than previously thought, yet their effects on the post-subduction evolution of continental lithosphere can be significant.

Ground-based Global Navigation Satellite System (GNSS) receivers have become an ubiquitous tool for monitoring the ionosphere. Total Electron Content (TEC) data from globally distributed networks of ground-based GNSS receivers are increasingly being used to characterize the ionosphere and its variability. The deployment of these GNSS receivers is currently limited to landmasses. This means that 7/10 of Earth’s surface, which is covered by the oceans, is left unexplored for persistent ionospheric measurements. In this paper, we describe a new low-power dual-frequency Global Positioning System (GPS) receiver, called Remote Ionospheric Observatory (RIO), which is capable of operating from locations in the air, space, and the oceans as well as on land. Two RIO receivers were deployed and operated from the Tropical Atmosphere Ocean buoys in the Pacific Ocean, and the results are described in this paper. This is the first time that GPS receivers have been operated in open waters for an extended period of time. Data collected between September 1, 2018 and December 31, 2019 are shown. The observed TEC exhibits a clear seasonal dependence characterized by equinoctial maxima in the data at both locations. Both RIO receivers, deployed near the geomagnetic equator, show an 18-35% increase in TEC during moderately disturbed geomagnetic periods. Comparisons with the International Reference Ionosphere model show good agreement. The new capability presented in this paper addresses a critical gap in our ability to monitor the ionosphere from the seventy percent of the Earth’s surface that is covered by water.

We use high-resolution earthquake locations to characterize the three-dimensional structure of active faults and how it evolves with fault structural maturity. We investigate the distribution of aftershocks of several recent large earthquakes that occurred on crustal strike slip faults of various structural maturity (i.e. various cumulative fault displacement, length, initiation age and slip rate). Aftershocks define a tabular zone of shear deformation surrounding the mainshock rupture plane. Comparing this to geological observations, we conclude that this results from the re-activation of secondary faults. We observe a rapid fall off of the number of aftershocks at a distance range of 0.06-0.25 km from the main fault surface of mature faults, and 0.7-1.5 km from the fault surface of immature faults. The total width of the active shear deformation zone surrounding the main fault plane reaches ~1.5 km and 2.5-6 km for mature and immature faults, respectively. We find that the width of the shear deformation zone decreases as a power law with cumulative fault displacement. Comparing with an existing dynamic rough fault model, we show that the narrowing of the shear deformation zone agrees quantitatively with earlier estimates of the smoothing of faults with displacement, both of which are aspects of fault wear. We compare this evolution of fault structure with several attributes of earthquakes, and find that earthquake stress drop decreases with fault displacement and hence with increased smoothness.

The GeoSciFramework project (GSF), funded by the NSF Office of Advanced Cyberinfrastructure and NSF EarthCube programs, aims to improve intermediate-to-short term forecasts of catastrophic natural hazard events, allowing researchers to instantly detect when an event has occurred and reveal more suppressed, long-term motions of Earth’s surface at unprecedented spatial and temporal scales. These goals will be accomplished by training machine learning algorithms to recognize patterns across various data signals during geophysical events and deliver scalable, real-time data processing proficiencies for time series generation. The algorithm will employ an advanced convolutional neural network method wherein spatio-temporal analyses are informed both by physics-based models and continuous datasets, including Interferometric Synthetic Aperture Radar (InSAR), seismic, GNSS, tide gauge, and gas-emission data. The project architecture accommodates increasingly large datasets by implementing similar software packages already proven to support internet searches and intelligence gathering. This talk will focus primarily on the Differential InSAR (DInSAR) time-series analysis component, which quantifies line-of-sight (LOS) ground deformation at mm-cm spatial resolution. Here, we compare time series products generated under three different processing techniques. The first, an automated version of InSAR processing using the small baseline subset (SBAS) method performed in parallel on systems such as Generic Mapping Tool SAR (GMT5SAR) and the Generic InSAR Analysis Toolbox (GIAnT). The second method will resemble the first but will implement different processing systems for performance comparison using the InSAR Scientific Computing Environment (ISCE) and the Miami InSAR Time Series Software in Python (MintPy). The final strategy, developed by Drs. Zheng and Zebker from Stanford University, concentrates on the topographic phase component of the SAR signal so that simple cross multiplication returns an observation sequence of interferograms in geographic coordinates [Zebker, 2017]. Our results provide high-resolution views of ground motions and measure LOS deformation over both short and long periods of time.

For the first time, we monitored continuous 2D tidal currents at a shallow tidal junction using the fluvial acoustic tomography (FAT) system during a period of ~ 34.4 days. The horizontal distribution and spatiotemporal variation of the tidal velocities were efficiently estimated by the inverse analysis method, and the reconstructed velocity patterns agreed well with the recorded acoustic Doppler current profiler series data. Additionally, the high frequency observation interval (1-min) used provided us with the opportunity to detect the rapid processes of the transformation of tidal current patterns during flood tide at the junction. These results further demonstrate that FAT is a potent tool for continuously mapping variable 2D tidal currents at shallow tidal junctions. Furthermore, tidal harmonic analyses of the reconstructed tidal currents were performed to clarify the nonlinear spatial evolution processes of the variations in tidal energy, when tides propagated from the estuary to the tidal junction. The sub-tide species (, ) caused significant fortnightly variations in the tidal range along the tidal branches. The variations in the tidal current were dominated by semidiurnal species (D2: , , , ), followed by diurnal species (D1: , , ) and quarter-diurnal species (D4: , ). The / amplitude ratios were higher during low river discharge periods, signifying that the nonlinear tidal distortion varies with river discharge. River-tide interactions strongly affected tidal asymmetry. It is believed that this study provides further understanding of hydrological research in shallow tidal systems.

The ICEBERG (Imagery Cyber-infrastructure and Extensible Building blocks to Enhance Research in the Geosciences) project (NSF 1740595) aims to (1) develop open source image classification tools tailored to high-resolution satellite imagery of the Arctic and Antarctic to be used on HPDC resources, (2) create easy-to-use interfaces to facilitate the development and testing of algorithms for application to specific geoscience requirements, (3) apply these tools through use cases that span the biological, hydrological, and geoscience needs of the polar community, and, (4) transfer these tools to the larger non-polar community.

The origin of Kiruna-type magnetite-apatite deposits, which are thought to form by magmatic and/or hydrothermal processes, has recently come under renewed scrutiny. Geological and geochemical studies of volcanic-hosted magnetite deposits that include magnetite lava flows and ash layers at El Laco, a volcano in the Central Volcanic Zone, northern Chile, suggest a formation by eruptive emplacement of an iron oxide-rich melt. The generation of such exotic high density, low viscosity melts by dissociation from an andesitic host magma contaminated by shallow crustal sediments has only recently been shown experimentally. The dynamics of volcanic emplacement have remained enigmatic because the high density of iron-rich melts seems to negate their eruption potential. Yet, observations of ubiquitous vesiculation, degassing structures, and steam-heated alteration provide important clues that volatiles had a pivotal role in the volcanic emplacement. Here, we posit a scenario in which an iron-rich immiscible liquid gravitationally separates from its andesitic parent magma in a shallow magma reservoir and subsequently rises as a bubbly suspension along volcano-tectonic faults extending to the flanks of the edifice. We test this hypothesis through numerical models that capture both the deformation of the volcanic edifice as well as the melt transport within. Preliminary results indicate that separation of a low-viscosity, iron- and volatile-rich melt from a silicic magma within a reasonable time is possible only if an interconnected melt drainage networks forms at the granular scale. Results further suggest that magma reservoir deflation and/or minor local extension combined with the topographic load of the edifice may explain normal faults connecting the magma reservoir with magnetite flow locations on the volcano flanks. Finally, our models show that hydrostatically driven flow of iron-rich melts into these faults at depth may trigger volatile exsolution and bubble expansion to provide sufficient driving force for an eruptive emplacement. Although the case for such magmatic ore formation is perhaps strongest at El Laco, evidence from other localities suggests that similar processes have been at work. The new insights derived from our models may, therefore, apply more generally to Kiruna-type deposits elsewhere.

Combing geochemical and seismological results constrains the composition of the middle and lower continental crust better than either field can achieve alone. The inaccessible nature of the deep crust (typically >15 km) forces reliance on analogue samples and modeling results to interpret its bulk composition, evolution, and physical properties. A common practice relates major oxide compositions of small- to medium-scale samples (e.g. medium to high metamorphic grade terrains and xenoliths) to large scale measurements of seismic velocities (Vp, Vs, Vp/Vs) to determine the composition of the deep crust. We provide a framework for building crustal models with multidisciplinary constraints on composition. We present a global deep crustal model that documents compositional changes with depth and accounts for uncertainties in Moho depth, temperature, and physical and chemical properties. Our 3D deep crust global compositional model uses the USGS global seismic database (Mooney, 2015) and a compilation of geochemical analyses on amphibolite and granulite facies lithologies (Sammon McDonough, 2021). We find a compositional gradient from 61.2 ± 7.3 to 53.8 ± 3.0 wt.% SiO2 from the middle to the base of the crust, with the equivalent lithological gradient ranging from quartz monzonite to gabbronorite. In addition, we calculate trace element abundances as a function of depth from their relationships to major oxides. From here, other lithospheric properties, such as Moho heat flux, are derived (18.8 ± 8.8 mW/m2). This study provides a global assessment of major element composition in the deep continental crust.

The 2022 Menyuan earthquake occurred in the Qilian-Haiyuan fault system in northeastern Tibet. To investigate the reason behind this earthquake and the seismic hazards of the Tianzhu Seismic Gap, we demonstrated the spatiotemporal stress variation on the fault system before and after 2022 through numerical modelling. We found that the 2022 earthquake was delayed due to a stress shadow caused by historical earthquakes. This stress shadow also covers the middle of the Tianzhu Seismic Gap and prohibits its seismic activities to some extent. Acting as a stress barrier to prevent the Tianzhu Seismic Gap rupturing in one event, this stress shadow may decrease the possibility of generating a future earthquake of magnitude more than Mw7.7 in this gap. The east portion of the Tianzhu Seismic Gap was stress loaded, indicating its increased seismic hazards. Attention should be paid to the hazards prevention in the eastern portion of the gap.

To improve our understanding of the Canoe Reach Geothermal Field in the Rocky Mountain Trench of western Canada, we examine the distribution of local earthquakes using a network of 10 broadband seismometers deployed over a 40 by 60 km area across the trench. The Canoe Reach area exhibits strong cultural noise from communities, roads and trains that makes detecting earthquake signals challenging. We propose detecting earthquakes in the area of the trench by measuring the kurtosis of the seismic signal, which is a statistical moment representing the distribution tail and is insensitive to emerging signals but more sensitive to impulsive earthquake onsets. Examining the kurtosis of the three-component seismograms for four months of data, we identified eight local earthquakes. An earthquake catalog produced by STA/LTA detections found 11 events for the same four-month period, four of which were detected through our kurtosis approach. By further exploring the kurtosis detections, we are refining our catalog to identify the source of discrepancies between it and the STA/LTA catalog. We then estimated locations of our detected events, and the uncertainties of those locations, through nonlinear Bayesian sampling. This method treats the origin times, half-space velocities, and the picking noise for P and S arrivals as unknowns. We employed this parameterization to test whether Bayesian sampling could account for the challenging noise environment. Locating our detected events found that five events occurred outside the seismic network and three events occurred inside. The average horizontal and vertical uncertainty is 28 and 19 km respectively for the outside events. These uncertainties are lower at 7 and 9 km for the inside events. While the inside events exhibit lower spatial uncertainties than the outside events, their uncertainties remain large. We then examined whether the uncertainties could be further improved by jointly locating multiple events. Jointly inverting two of the events from within the array decreased their average horizontal uncertainty from 6.5 to 2.5 km and the vertical from 14 to 7 km. Reducing uncertainties in the locations of the events in this manner will clarify their distribution and all for an improved understanding of the seismicity and structure of the Rocky Mountain Trench.

Gridded precipitation datasets have been used as alternatives to rain gauge observations, but their applicability for a specific region should be thoroughly evaluated. This paper aims at finding the most appropriate one for climatological and hydrological applications in Indonesia, by evaluating the statistics of the performance of eight different datasets (research products) having horizontal resolutions between 0.1◦ and 0.25◦ and with a time span of data availability from 2003 to 2015. The datasets are compared against the observed daily rainfall at 133 stations using 13 statistical metrics that can be classified into three groups with different characteristics of measurements, namely, distribution, time sequence, and extreme value representations. By applying Summation of Rank (SR), it is found that MSWEP and TMPA 3B42 are the top two datasets that outperformed based on distribution and time-sequence performance metric groups. The extreme performances for all datasets are still good in 75th percentiles, however the performance decreasing for more than 75th percentiles indicating still poorly representation of daily extreme rainfall for all gridded datasets. Results of this study suggest that MSWEP (v2) is presently the best gridded precipitation datasets available for climatological and hydrological applications in Indonesia.

Statistical studies of paleosecular variation (PSV) are used to infer the structure and behavior of the geomagnetic field. This study presents a new database, PSVM, of high-quality directional data from the Miocene era (5.3 – 23 Ma), compiled from 1,454 sites from 44 different localities. This database is used to model the latitude dependence of paleosecular variation with varying selection criteria using a quadratic form after Model G. Our fitted model parameter for latitude-invariant PSV (Model G a) is 15.7° and the latitude dependent PSV term (Model G b) is 0.23. The latitude invariant term is substantially higher than previously observed for the past 10 Myrs or any other studied era. We also present a new stochastic model of the time-average field, BB-M22, using a covariant giant Gaussian process (GGP) which is constrained using data from PSVM and Earth-like geodynamo numerical simulations. BB-M22 improves the fit to PSVM data relative to prior GGP models, as it reproduces the higher VGP dispersion observed during the Miocene. Our findings suggest a more variable magnetic field and more active geodynamo in the Miocene era than the past 10 Myrs, perhaps linked to stronger driving by elevated core-mantle heat flow. Although our results support that the average axial dipole dominance of the time-instantaneous field was lower than in more recent times, we note that based on inclination anomaly estimates cannot rule out that the Miocene time averaged field resembles a geocentric axial dipole.

The high energetic plasma and the embedded magnetic field of coronal mass ejections interact with planetary magnetospheres giving rise to transient perturbations such as geomagnetic storms. Predicting the geomagnetic impact of such interplanetary coronal mass ejections (ICME) is of utmost importance for the protection of our technological infrastructure that is affected by space weather. We use 3D compressible magnetohydrodynamic simulation of a star-planet system to model and study an ICME-Earth interaction event of 20th November 2003. In the modelled interaction, we observe a change in magnetopause shape and stand-off distance on ICME impact, day and night side reconnections and induction of high currents in the magnetosphere. We also notice the formation of a ring of strong equatorial current around the Earth, leading to a reduction of the geomagnetic field. We calculate the simulated reduction in the magnetic field and compare that to the observed geomagnetic indices in order to establish a predictive approach for geomagnetic storms. These simulations are expected to illuminate the physical processes that result in space weather impacts of stellar magnetic storms in planetary and exoplanetary systems.

Modeling studies have predicted that the acoustic resonance of the atmosphere during geophysical events such as earthquakes and volcanos can lead to an oscillation of the geomagnetic field with a frequency of about 4 mHz. However, observational evidence is still limited due to scarcity of suitable events. On January 15, 2022, the submarine volcano Hunga Tonga-Hunga Ha’apai (20.5˚S, 175.4˚W, Tonga) erupted in the Pacific Ocean and caused severe atmospheric disturbance, providing an opportunity to investigate geomagnetic effects associated with acoustic resonance. Following the eruption, geomagnetic oscillation is observed at Apia, approximately 835 km from Hunga Tonga, mainly in the Pc 5 band (150-600 s, or 1.7-6.7 mHz) lasting for about 2 hours. The dominant frequency of the oscillation is 3.8 mHz, which is consistent with the frequency of the atmospheric oscillation due to acoustic resonance. The oscillation is most prominent in the eastward (Y) component, with an amplitude of ~3 nT, which is much larger than those previously reported for other events (<1 nT). Comparably large oscillation is not found at other stations located further away (>2700 km). However, geomagnetic oscillation with a much smaller amplitude (~0.3 nT) is observed at Honolulu, which is located near the magnetic conjugate point of Hunga Tonga, in a similar wave form as at Apia, indicating interhemispheric coupling. This is the first time that geomagnetic oscillations due to the atmospheric acoustic resonance are simultaneously detected at magnetic conjugate points.

Explosive volcanic eruptions can loft ash, gases and water into the stratosphere, which affects both human activities and the climate. Using geostationary satellite images of the January 2022 Hunga-Tonga volcano eruption we find that the volcanic cloud produced by this volcano reached an altitude of 57km at its highest extent. This places the cloud in the lower mesosphere and provides the first observational evidence of a volcanic eruption injecting material through the stratosphere and directly into the mesosphere. We then discuss potential implications of this injection and suggest that the altitude reached by plumes from previous eruptions, such as Pinatubo in 1991, are very likely to be underestimated.

Understanding fluid flow in rough fractures is of high importance to large scale geologic processes and to most anthropogenic geo-energy activities. Here, we conducted fluid transport experiments on Carrara marble fractures with a novel customized surface topography. Transmissivity measurements were conducted under mechanical loading conditions representative of deep geothermal reservoirs (normal stresses from 20 to 70 MPa and shear stresses from 0 to 30 MPa). A numerical procedure simulating normal contact and fluid flow through fractures with complex geometries was validated towards experiments. Using it, we isolated the effects of roughness parameters on fracture fluid flow. Under normal loading, we find that i) the transmissivity decreases with normal loading and is strongly dependent on fault geometry ii) the standard deviation of heights (RMS) and macroscopic wavelength of the surface asperities control fracture transmissivity. Transmissivity evolution is non-monotonic, with more than 4 orders of magnitude difference for small variations of macroscopic wavelength and RMS roughness. Reversible shear loading has little effect on transmissivity, it can increase or decrease depending on the combined contact geometry and overall stress state on the fault. Finally, irreversible shear displacement (up to 1 mm offset) slightly decreases transmissivity contrary to common thinking. The transmissivity variation with irreversible shear displacements can be predicted geometrically at low normal stress only. Finally, irreversible changes in surface roughness (plasticity and wear) due to shear displacement result in a permanent decrease of transmissivity when decreasing differential stress. We discuss the implications for Enhanced Geothermal Systems stimulation.

Long-lasting Pc5 ultralow frequency (ULF) waves spanning the dayside and extending from L~5.5 into the polar cap region were observed by conjugate ground magnetometers. Observations from MMS satellites in the magnetosphere and magnetometers on the ground confirmed that the ULF waves on closed field lines were due to fundamental toroidal field line resonances (FLRs). Monochromatic waves at lower latitudes tended to maximize their power away from noon in both the morning and afternoon sectors, while more broadband waves at higher latitudes tended to have a wave power maximum near noon. The wave power distribution and anti-sunward wave propagation suggest surface waves on a Kelvin-Helmholtz (KH) unstable magnetopause coupled with FLRs. Based on satellite observations in the foreshock/magnetosheath, the more turbulent ion foreshock during an extended period of radial interplanetary magnetic field (IMF) likely plays an important role in providing seed perturbations for the growth of the KH waves.

Constraining the volatile budget of the lunar interior has important ramifications for models of Moon formation. While many early and previous measurements of samples acquired from the Luna and Apollo missions suggested the lunar interior is depleted in highly volatile elements like H, a number of high-precision analytical studies over the past decade have argued that it may be more enriched in water than previously thought. Here, we integrate recent remotely sensed near-infrared reflectance measurements of several Dark-Mantle-Deposits (DMDs), interpreted to represent pyroclastic deposits, and physics-based eruption models to better constrain the pre-eruptive water content of lunar volcanic glasses. We model the trajectory and water loss of pyroclasts from eruption to deposition, coupling eruption dynamics with a volatile diffusion model for each pyroclast. Modeled pyroclast sizes and final water contents are then used to predict spectral reflectance properties for comparison with the observed orbital near-infrared data. We develop an inversion scheme based on the Markov-Chain Monte-Carlo (MCMC) method to retrieve constraints between governing parameters such as the initial volatile content of the melt and the pyroclast size distribution (which influences the remotely measured water absorption strengths). The MCMC inversion allows us to estimate the primordial (pre-eruption) water content for different DMDs and test whether their source is volatile-rich. Our results suggest that the parts of the lunar interior sampled by the source material of the DMDs investigated in this study range in water content from 400 to 800 ppm.

In this study, by simulating the wave-particle interactions, we show that sub-relativistic/relativistic electron microbursts form the high-energy tail of pulsating aurora (PsA). Whistler-mode chorus waves that propagate along the magnetic field lines at high latitudes cause precipitation bursts of electrons with a wide energy range from a few keV (PsA) to several MeV (relativistic microbursts). The rising tone elements of chorus waves cause individual microbursts of sub-relativistic/relativistic electrons and the internal modulation of PsA with a frequency of a few Hz. The chorus bursts for a few seconds cause the microburst trains of sub-relativistic/relativistic electrons and the main pulsations of PsA. Our simulation studies demonstrate that both PsA and relativistic electron microbursts originate simultaneously from pitch angle scattering by chorus wave-particle interactions.

We performed laboratory-scale experiments on Barre granite specimen with a single pre-existing flaw to study the microscopic processes that occur during the deformation of a brittle material such as granite at different stress levels from crack initiation to the failure of the specimen. Here, we focus on the evolution of the tensile and shear cracks as a function of stress under unconfined compression. Acoustic emission technique (AET) in combination with the two dimensional (2-D) digital image correlation (DIC) technique have been used to track the changes in the source mechanisms of the registered AE events, along with the development of strains around the flaw tips of a uniaxially loaded prismatic Barre granite specimen. The parametric analysis along with the moment tensor inversion of the AE signals were used to discuss the cracking levels and the cracking mechanisms. In particular, the microcracks observed through AE monitoring prior to specimen failure were presented in terms of their spatio-temporal evolution and linked with the changes in the inelastic strain component measured through the 2D-DIC along the localized area. The mode of deformation computed from the image based strain profiles, enabled direct comparison of the nucleation, growth and interaction of the microcracks with the AE monitoring technique.

Ionospheric Total Electron Content (TEC) prediction has important reference significance for the accuracy of global navigation satellite systems (GNSS) based global positioning system, satellite communications and other space communications applications. In the study, an available prediction model of global IGS-TEC map is established based on testing several different LSTM-based algorithms. We find that Multi-step auxiliary algorithm based prediction model performs the best. It can precisely predict the global ionospheric IGS-TEC in the next 6 days (the MAD and RMSE are 2.485 and 3.511 TECU, respectively). Then, the autoencoder network algorithm is adopted to construct an assimilation model that transforming IGS-TEC map to MIT-TEC map. In order to judge the validity of the assimilation model, the outputs of the assimilation model are evaluated and compared with the IRI2016 model in four different geomagnetic storm events. It seems that the assimilation model can accurately forecast MIT-TEC by inputting the predicted IGS-TEC value. The performance of assimilation model for the predicting MIT-TEC is better than that of IRI2016.

The apparent end of the internally generated Martian magnetic field at 3.6-4.1 Ga has been linked to insufficient core cooling. While the dynamo cessation time is a key event in the Martian history, a large range of solutions exist to satisfy this observation, limiting the insight it provides on the Martian interior. We produce a suite of models improving our understanding of the evolution of Mars in three keys areas. Firstly, we account for thermal stratification in the core, producing improved estimates on the core thermal structure. Secondly, we match estimates for the present-day areotherm. Finally, we consider recent experimental data for the core thermal conductivity, kc, much lower than previously thought for Mars. In order to yield a consistent dynamo cessation time we require kc<18 Wm-1K-1. Furthermore, the majority of our models indicate the core is fully conductive at present and too hot to form any solid.