The Xianshuihe fault in eastern Tibet is one of the most active faults in China, with the next large earthquake most likely to occur along its SE part near Kangding. Quantifying its slip rate along the three parallel branches (Yalahe, Selaha and Zheduotang) as well as along the Moxi fault is essential to evaluate regional earthquake hazard, necessary to the construction of the Chengdu-Lhasa railroad. Here, we expand our previous work on the Selaha fault to the Zheduotang and Moxi faults, with observations on the Yalahe fault and the newly discovered Mugecuo South fault zone. Using tectonic-geomorphology approaches (LiDAR, UAV and 10Be dating), we had determined late Quaternary slip rates of 9.75±0.15 and 4.4±0.5 mm/yr along the NW and SE Selaha fault, respectively, hence had inferred a ~5 mm/yr rate along the parallel Zheduotang fault. Here, using the same methods, we confirm such rate (4.5[+0.9/-0.8] mm/yr, ZDT moraine site) thus suggest a total slip rate of >8.9±1.4 mm/yr in the SE Xianshuihe fault. Our rate along the Moxi fault (12.5[+2.3/-2.1] mm/yr, MX moraine site) is higher than those along the Ganzi (6-8 mm/yr) and Xianshuihe (~10 mm/yr) faults farther NW, which reinforces our earlier finding of a southeastward slip rate increase, in agreement with the eastward decrease of GPS vector values (with respect to Eurasia) located north of the fault. Our study reveals a high regional earthquake hazard (Mw6.5 to 7.3) in the near future, which adds to the challenge of building the new railroad in such mountainous area.

It has been long known that the preferred crack alignments and fractures in rock cause seismic anisotropy and corresponding S-wave birefringence. Here the S-wave birefringence caused by the preferred alignment of cracks due to subcritical stress in the granitic basement of north central Oklahoma is examined. The data used for this study was collected during the IRIS Community Wavefields Experiment (CWE) in June and July of 2016, where more than 300 3-component (3-C) short-period seismographs were deployed in dense arrays with station spacings of 100m or less. These arrays were also in an area where many small earthquakes were occurring on a monthly basis, so that many were recorded by these arrays. The seismic data were cut from the original 30-day field records to produce short 3-C SEG-Y records of local earthquakes and explosions at a variety of back azimuths from the CWE array. Each 3-C record was rotated to the back azimuth of the source, such that the components become vertical, radial, and transverse with respect to the source. Vertical components are dominated by P arrivals, while radial components are dominated by SV arrivals and transverse components are dominated by SH arrivals. Seismic sections of the radial components of the array are then plotted in one color and overlain by the corresponding transverse components from the same array in another color. S-wave birefringence can then be directly observed as the time difference between arrivals, particularly first arrivals. S-wave birefringence is proof of seismic anisotropy and some characteristics of that anisotropy can be observed in record sections. For instance, birefringence is high along some azimuths and absent along other azimuths. Where birefringence is absent arrivals coincide, this could be either due to arrivals crossing or arrivals meeting but do not crossing. The latter case is important because it is the direction of an axis of symmetry for the anisotropic medium where the arrivals are propagating. This is also the case is observed in the record sections. The axis of symmetry observed in the record sections has an azimuth of 335 +/- 5 degrees. The fact that an axis of symmetry with no birefringence exists in the horizontal plane indicates that the anisotropic medium exhibits hexagonal symmetry, also known as horizontal transverse isotropy (HTI). It indicates that cracks and fractures are open perpendicular to the axis of symmetry and closed in other directions. Because of the large number of earthquakes occurring in this area a number of studies have been conducted on the in-situ stress orientations. In the sedimentary section overlaying the basement close to the CWE seismic array, borehole image logs indicate that the azimuth of drilling induced tensile fractures is 59 +/- 12 degrees. This is interpreted as the orientation of the maximum horizontal stress in the borehole. The axis of seismic anisotropy, which indicates the direction of minimum horizontal stress.

Partial melting of the asthenospheric mantle generates the magma that supplies volcanic systems. The timescale of melt extraction from the mantle has been hotly debated. Microstructural measurements of the permeability of partially molten rocks typically suggest relatively slow melt extraction (1 m/yr) [e.g. 1]. By contrast, inferences from geochemical measurements of Uranium series and geophysical observations typically point to much faster melt extraction (100 m/yr) [e.g. 2]. The most recent deglaciation of Iceland caused the mantle below to depressurise, triggering additional mantle melting and magma flux at the surface, which has been extensively mapped. The rapid response of magmatic activity to deglaciation has been used to argue for relatively rapid melt extraction [3,4]. Perhaps, however, this unusual period when magma fluxes increased several-fold is not representative of steady-state melt velocities under Iceland, let alone the mid-ocean ridge system more generally. We develop a one-dimensional, but time-dependent and fully nonlinear, model of the generation and transport of mantle melts force by time-dependent ice unloading. We show that these models are sensitive to the nonlinear nature of the system, namely that the melt velocities are faster during and following a deglaciation event. For a given nonlinear model, we show that an equivalent linear estimate of the steady-state melt velocity is too fast. We calculate an overestimation factor as a function of the factor of mantle melting caused by deglaciation. For the most recent, and best mapped, deglaciation, we show that about 30 m/yr is the best estimate of melt velocity. This is a factor of 3 smaller than previously claimed [4], but still relatively fast. Finally, we discuss the applicability of these results to the mid-ocean ridge system by considering the role of spreading rate and the plume-influence on Iceland. [1] Wark, D. et al. (2003). JGR. doi:10.1029/2001JB001575 [2] Stracke, A., Bourdon, B., & McKenzie, D. (2006). EPSL. doi:10.1016/j.epsl.2006.01.057 [3] Maclennan, J. et al. (2002). Geochem. Geophys. Geosyst. doi:10.1029/2001GC000282 [4] Eksinchol I., Rudge J.F., Maclennan J. (2019) Geochem. Geophys. Geosyst. doi:10.1029/2019GC008222

Groundwater extraction at rates exceeding recharge is occurring throughout Iran for agricultural and industrial activities, resulting in land subsidence in many areas, particularly the Yazd-Ardakan Plain (YAP) in the dry and desert regions of central Iran. In this study, Interferometric Synthetic Aperture Radar (InSAR) time series analysis and statistical models are used to characterize the controls on land subsidence in the YAP, from 2003 to 2020. Our results reveal the existence of a northwest-southeast elongated area of 363 experiencing subsidence at rates up to 15 cm/yr. In the YAP, the international Airport, railway, transit road, and several industrial and historical sites are threatened by the differential subsidence. Well data confirm that groundwater levels have decreased by 18 meters between 1974 and 2018, driving the compaction of sediments within the underlying aquifer system. Our statistical analysis shows that the thickness of a shallow, clay-rich aquitard layer controls the extent of the observed subsidence and an Independent Component Analysis of the InSAR time series shows that inelastic compaction dominates. This work reveals that in central Iran, current groundwater extraction practices are not sustainable and result in permanent subsidence, ground fractures with impact on infrastructures, and a permanent decrease in water storage capacity.

A document by Alessio Testa. Click on the document to view its contents.

The Earth's Imbalanced Heat Budget and its Relationship to Past, Present and Future Climate Change Michel Vert IBMM, UMR CNRS 5247, University of Montpellier, France Corresponding author: [email protected] Abstract: Climate changes predicted by the International Panel on Climate Change are currently linked to the growth of an excess of carbon dioxide in the atmosphere, as successive reports have asserted. The forecasts are based on an unusual exploitation of greenhouse physics that results in ocean warming due to radiative forcing. In the absence of experimental support, the mechanism and predictions are universally adopted but only by consensus. Many scientists have opposed the consensus on the grounds that the bases do not respect the fundamentals of hard sciences. Recently, we proposed an alternative mechanism in which the radiative forcing due to carbon dioxide is replaced by heat, a fundamental phenomenon in physics and thermodynamics. According to this new mechanism briefly recalled, heat is managed on Earth by water and its interphase equilibria, whatever the sources. Previously developed for the present, it is used here to show that the Earth's heat balance, hitherto said to be balanced in terms of radiative flux inputs and outputs, has never been balanced in terms of heat. The thermal imbalance in the distant past was estimated from the energy necessary for the melting of the ice during the last deglaciation, during the current Holocene interglacial plateau, and between 1994 and 2017. The melting of the ice progressed almost linearly during the first 80% of the deglaciation period with a slow decline towards near-steady-state during the Holocene. Estimates of ice loss over the period 1994-2017 showed that the imbalance is increasing again, a feature that should lead to a proliferation of sun-obscuring clouds followed by the inversion of the imbalance required to initiate the next ice age. The confirmation of the disqualification of carbon dioxide as a source of global warming could put back in the saddle certain applications currently penalized due to the production of this gas. In any case, it is the fight against anthropogenic heat sources that should be promoted in the future. Keywords: global warming, paleoclimatology, heat management, thermal infrared radiations, glacial cycles,  Key Points•          The Earth budget is said to be balanced in terms of radiative input and output, but it is not balanced when thermal infrared waves present in solar irradiation are converted to heat.•          The thermal imbalance on Earth, significant during past glaciation periods, was almost stable during the Holocene interglacial plateau but is currently increasing again en route to the reversal necessary to cause the next glaciation•          Thermal imbalance provides credible justifications of glacial cycles and Holocene climate changes but leaves open the question of the responsibility for increased anthropogenic heat.  I Introduction Climate change is a source of concern, as it is currently linked to an increase of atmospheric carbon dioxide (CO2) attributed to human activities. Excessive carbon dioxide in the atmosphere is believed to be the cause of global warming at the origin of dramatic climate forecasts for coming decades. Both the mechanism and the forecasts result from successive reports issued by the Intergovernmental Panel on Climate Change (IPCC), an organization created in 1988 with the mission of assessing and exploiting the climatology publications fund [1]. In the absence of experimental support, the forecasts come solely from hypothesis and models in which a greenhouse effect, different from that well known in physics, and the resulting radiative forcing stored in oceans play essential roles. There are many reasons to contest this mechanism [2], not least because it lacks scientific consistency and does not respect the fundamentals of hard sciences [2]. This may be due to the fact that climatology is a field where state of the art and advances are not discussed in a multidisciplinary and contradictory manner in national or international congresses and conferences, unlike what is usually done in science. Until now, protest arguments, generally considered to be signs of climate skepticism, were mainly limited to the “state of the art” in the absence of alternative mechanism. To fill this gap, an alternative mechanism has recently been proposed [3] in which heat is the physical phenomenon that warms the planet, while water and its interphase equilibria are the means by which heat is managed until radiative removal in space is possible. Water exists in solid, liquid and vapor physical forms in the environment and in the atmosphere, unlike CO2 and other greenhouse gases (GHGs), which are only gaseous. In the hard sciences, melting of ice and evaporation of liquid water are recognized as highly efficient heat absorbers and transmitters. Based on these undisputable facts, it has been demonstrated that the role of water in heat management on Earth is comparable to that of the volatile refrigerant operating in a refrigerator to absorb internal heat and release it to the outside through evaporation-condensation cycles [4]. This new vision had several important consequences.  First, on Earth, the melting of ice in combination with evaporation and condensation phenomena absorb and manage the natural heat inputs (solar, volcanic, and from forest fires) since water and life exit on Earth. Today, the anthropogenic heat inputs are added that must be managed by the same mechanism.  Second, while solar irradiance passes through space unchanged, some waves are more or less absorbed specifically as soon as they encounter molecules and matters present on Earth, including GHGs present in the air. Despite this undisputable fact, it is common strategy to consider the solar irradiance in its entirety when discussing the Earth’s Heat Budget. This means that visible light is capable of heating atmosphere and land, which is obviously not observed in the environment. Reflection and diffraction are taken into account, but the selection of waves by absorption and the conversion of thermal infrared ones in heat are not. Physics teaches us that a thermal infrared radiation with a wavelength in the range of about 4 to 30 µm is absorbed (its intensity decreases proportionally to the concentration in absorber and to the path length) to generate heat. The process reflects an energetic harmony between the radiative energy of such a wave and the discrete interatomic vibrational energy of an asymmetric transition forming an electric dipole. Therefore, water vapor that absorbs strongly thermal infrared waves is an absorber (greenhouse gas) in reality much more efficient to generate heat than CO2. Despite this essential property, water vapor is neglected in climatology [1] and by NASA as well [5] because its residence time in the atmosphere is too small, particularly relative to the long-lived CO2. This is not correct because in chemistry and physics, it is the concentration that must be considered when it comes to interaction with and absorption by electromagnetic waves moving at the speed of light. Therefore, in addition to ice that cools the environment on melting, we have attributed to water vapor a major role in the water-based mechanism because when the temperature of the liquid water at the surface increases, evaporation tends to absorb the heat by generating warm vapor rising to a cooler zone to form clouds when local conditions are favorable. The result is a transfer of the heat from the surface to a cool zone from where it can be directly eliminated to space, notably through the 8-14 µm spectral transparency window specific of the atmospheric water vapor [6], or indirectly from clouds above which the concentration in water vapor is very small and favorable to radiative elimination of heat, as well schematized in a video [7]. Transparency above clouds or when the humidity is low has an unexpected advantage in the case of aircrafts flying high in the sky. Indeed, the heat due to hot CO2 and hot water vapor ejected by the engines can be easily removed in space radiatively, a property that can mitigate the negative role attributed to aircraft in terms of radiative forcing of CO2 and of carbon footprint. In other words, in terms of anthropogenic heat releases, an airplane at altitude could be more acceptable than a car on the surface, which remains to be proven quantitatively. Third, whatever its origin, if the heat input into the environment increases, the ice stock decreases and gradually evaporation increases, as does cloud formation. In addition to being a source of heavier rainfall, or even flooding, a dense cloud layer can block thermal infrared radiation on the way in and out, a process that must first lead to a rise in temperature under the clouds followed by a rapid inversion towards cooling, as is easily felt in cloudy weather. If the cooling is severe, as in winter when solar heat gain is minimized by longer nights and a longer Sun-Earth distance, or when the night-time atmosphere is dry, icing occurs. The process is well illustrated by a dark, stormy sky under which a fairly high temperature suddenly drops, while ice stones form and eventually fall to the surface. Environmental events such as winds, hurricanes, tornadoes, air and ocean streams are the means by which heat is distributed and tend to average out local temperatures and meteorological differences. In reality, the average is largely limited by the size of the planet, the heterogeneity of its components and the involvement of chaotic phenomena affecting the air, seas and oceans. It remains to be seen whether the various recently identified anthropogenic heat sources are sufficiently large to worsen natural climate change [8]. The balance between the input and output of radiative fluxes is a fundamental basis of climatology. This is no longer the case when thermal infrared radiation is converted into heat. A good reason for this is kinetic. In space and in a transparent medium, electromagnetic waves travel at and near light speed, respectively. Conversely, heat exchanges and balancing occur through slow convection and conduction phenomena. Currently, the small variations in global temperature and sea level occurring during the Holocene are in favor of balance, but if we consider ice loss and glacial ups and downs in distant past, they point to time-dependence of thermal imbalance. Indeed, glacial cycles are characterized by changes in temperature and sea level of up to around 10°C and 120 m, respectively [9]. A complete cycle lasts between 120 and 150 thousand years (kyrs), according to the last four glaciations reported by paleoclimatologists [9]. A cycle is made up of a period of fairly rapid deglaciation lasting 10 to 20 kyrs, followed by an interglacial plateau lasting 10 to 20 kyrs and a period of very slow glaciation lasting at least 100 kyrs. The case of the pre-Holocene deglaciation that covered the period from -20 to -10 kyrs before the present (BP) is schematized in Figure 1. The preceding glaciation period was about 10 times longer, a difference attributed in part to the involvement of several interphase transitions not involved in the deglaciation process [2]. Monitoring climate change is difficult, if not impossible, because it depends on many factors, most of which are time- and location-dependent, such as solar heating, temperature, evaporation and cloud formation. The corresponding data vary from one source to another and, unlike in many other scientific fields, the extent of errors and uncertainties is difficult to quantify. Although far from perfect, solid ice is a better indicator of change. Although rare, in situ glacier mass balance surveys date back to the 1890s [11].  It was not until the 1970s that substantial records of changes in the cryosphere became available through satellite observations. The extent of ice shelves has been monitored by satellite imagery since the 1940s [12]. The extent of sea ice has been monitored by satellite since the late 1970s [13]. Changes in ice cap, ice shelf, sea ice and glacier thickness have been systematically recorded by satellite altimetry since the 1990s [14].

NASA’s Capacity Building Program (CBP) works to empower communities around the globe to use Earth observation data and products in their decision making. Working through program and element activities, CBP developed a theoretical framework for engagement focused around user needs which identifies the appropriate path for engagement based on geography, discipline, data needs and availability, depth of support required, partnerships involved, length of engagement, and desired outcomes. These decision factors would determine which CBP element would take on the effort – ARSET, DEVELOP, or SERVIR, and which approach would be implemented – trainings or co-development. Each approach offers participants different benefits and leads to outcomes that fall on a spectrum from increased awareness to sustained use of Earth observations. However, implementation of this framework across multiple programs with differing constraints has been challenging. This presentation will highlight the CBP framework and its user-centric approach, capacity building methods and incentives, metrics and tracking indicators, challenges, and lessons learned.

In this study we identify a global seasonal bias in ocean color remote sensing reflectances (R rs , λ) using data from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instrument aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder) satellite, in addition to Argo floats and in-water reflectance from the Marine Optical BuoY (MOBY) site. The seasonal bias in R rs is present in the VIIRS (Visible Infrared Imaging Radiometer Suite), SeaWIFS (Sea-viewing Wide Field-of-view sensor), and MODIS (Moderate resolution imaging spectrometer) satellites at all visible wavelengths and is larger at longer wavelengths. Products derived from Rrs are affected by the bias to varying degrees, with particulate backscattering varying up to 50% over a year, chlorophyll varying up to 25% over a year, and absorption from phytoplankton or dissolved material varying by up to 15%. The seasonal bias is prominent in areas of low biomass (i.e., gyres) and is not easily discernable in areas of high biomass. We found that the seasonal bias in Rrs is not caused by Raman scattering choice or implementation, nor is it due to differences with satellite viewing angle. Biases in particulate backscattering are not affected by specific assumptions used within Rrs inversion models. Changing the specific space/time averaging window in different processing levels of remote sensing data and matchups were not the cause either. While we have eliminated several candidates which could cause the bias, there are still outstanding questions about the role atmospheric correction plays. We provide evidence that the Bidirectional Reflectance Distribution Function correction factor may control the observed seasonal bias to some extent, but does not preclude the effect of the aerosol correction. We provide recommendations for work to be conducted in the near-future. In particular, the use of CALIOP aerosol data may help improve the aerosol model used in atmospheric correction and the execution of more simulations to discern the relative influence of atmospheric correction parameters. Community efforts are needed to find the root cause of the seasonal bias because all past, present, and future data will be affected until a solution is implemented.

Mechanisms that control marsh edge erosion include wind-generated waves, vegetation, mudflats, anthropogenic factors, and geotechnical properties of sediments. However, existing models for predicting marsh edge evolution focus primarily on edge retreat rates as a function of wave energy while accounting for other controlling factors as empirical constants. This simplification rises from a lack of high frequency monitoring of marsh evolutions. In particular, marsh erosion is time-scale dependent and conducting field observations on short time and spatial scales could elucidate the progression of erosion, which may improve marsh erosion predictive models. This study developed and validated a near continuous camera monitoring system to document marsh edge erosion at a high frequency in Terrebonne Bay, Louisiana. Erosion pins were monitored with the cameras and daily erosion rates were estimated. This was supplemented with daily wave power to explore the relationships between daily erosion and wave power. The largest magnitude erosion events are driven by a buildup in wave energy over a seven-day time period coupled with a strong one-day wave event, indicating a gradual reduction in marsh edge resistance with continued wave attack. Long-term erosion monitoring methods, including monthly field visits, smooths over the large magnitude short-term erosion events. For example, satellite and aerial imagery provide a long period of record, but they seem to underestimate the average annual erosion rate in the region, the effect of which may become exasperated over the varying temporal scales considered in the planning efforts of projects meant to protect the Louisiana coastline.

Magnetic hysteresis measurements are routinely made in the Earth and planetary sciences to identify geologically meaningful  magnetic recorders, and to study variations in present and past environments. Interpreting magnetic hysteresis data in terms of domain state (particle size)  and paleomagnetic stability are major motivations behind undertaking these measurements, but the interpretations remain  fraught with challenges and ambiguities.To shed new light on these ambiguities, we have undertaken a systematic micromagnetic study to quantify the magnetic hysteresis behavior of room-temperature magnetite as a function of particle size (50-195 nm; equivalent spherical volume diameter) and shape (oblate, prolate and equant);our models span uniformly magnetized single domain (SD) to non-uniformly magnetized single vortex (SV) states.Within our models the reduced magnetization  marks a clear boundary between SD (≥0.5) and SV (<0.5) magnetite.We further identify particle sizes and shapes with unexpectedly low coercivity and coercivity of remanence. These low coercivity regions correspond to magnetite particles that typically have multiple possible magnetic domain states, which has been previously linked to a zone of unstable magnetic recorders.Of all hysteresis parameters investigated, transient hysteresis is most sensitive to particles that exhibit such domain state multiplicity, leading us to suggest that transient behavior be more routinely measured during rock magnetic investigations.

Previous laboratory experiments with KIS tracers have shown promising results with respect to the quantification of fluid-fluid interfacial area (IFA) for dynamic, two-phase flow conditions. However, pore-scale effects relevant for two-phase flow (e.g. the formation of hydrodynamically stagnant/ immobile zones) are not yet fully understood, and quantitative information in how far these effects influence the transport of the tracer reaction products is not yet available. Therefore, a pore-scale numerical model that includes two-phase, reactive flow and transport of the KIS tracer at the fluid-fluid interface is developed. We propose a new method to quantitatively analyze how the concentration of the KIS-tracer reaction product in the effluent is affected by the presence of immobile zones. The model employs the phase field method (PFM) and a new continuous mass transfer formulation, consistent with the PFM. We verify the model with the analytical solution of a reaction-diffusion process for two-phase flow conditions in a conceptual capillary tube. The applicability of the model is demonstrated in NAPL/water drainage scenarios in a conceptual porous domain, comparing the results in terms of the spatial distribution of the phases and the quantified macro-scale parameters (saturation, capillary pressure, IFA and solute concentration). Furthermore, we distinguish the mobile and immobile zones based on the local Péclet number, and the corresponding solute mass in these two zones is quantified. Finally, we show that the outflow concentration can be employed to selectively determine the mobile part of the IFA.

We re-examine data from a deep earthquake beneath NE Taiwan as recorded by the Formosa Array to explain mechanisms of a significant later P phase. For 2D simulations, we set up an initial velocity structure with (A) a high Vp anomaly in the mantle wedge above Ryukyu subduction, and (B) a slightly high Vp Eurasian lithosphere to the west with a sub-vertical boundary – based on results of tomographic studies. We conclude that (1) the small-amplitude first P phase is attributed to the energies radiated near the nodal point of the focal mechanism and propagated through (A), (2) those of the significant later P phase are analogous to a head wave that propagates and generates spherical waves along (B) that are received at the surface. Accordingly, stations of zero delay time between the first and second P provide a first-ever portrayal of the Eurasian lithosphere boundary by waveform constraints.

A current along a sloping bottom gives rise to upwelling, or downwelling Ekman transport within the stratified bottom boundary layer (BBL), also known as the bottom Ekman layer. In 1D models of slope currents, geostrophic vertical shear resulting from horizontal buoyancy gradients within the BBL is predicted to eventually bring the bottom stress to zero, leading to a shutdown, or \change{\lq arrest \rq \,,}{\lq arrest \rq,} of the BBL. Using 3D ROMS simulations, we explore how the dynamics of buoyancy adjustment in a current-ridge encounter problem differs from 1D and 2D temporal spin up problems. We show that in a downwelling BBL, the destruction of the ageostrophic BBL shear, and hence the bottom stress, is accomplished primarily by nonlinear straining effects during the initial topographic \change{counter}{encounter}. As the current advects along the ridge slopes, the BBL deepens and evolves toward thermal wind balance. The onset of negative potential vorticity (NPV) modes of instability and their subsequent dissipation partially offsets the reduction of the BBL dissipation during the ridge-current interaction. On the upwelling side, although the bottom stress weakens substantially during the encounter, the BBL experiences a horizontal inflectional point instability and separates from the slopes before sustained along-slope stress reduction can \change{occured}{occur}. In all our solutions, both the upwelling and downwelling BBLs are in a partially arrested state when the current separates from the ridge slope, characterized by a reduced, but non-zero bottom stress on the slopes.

Aseismic slip may occur during a long preparatory phase preceding earthquakes, and what controls it remains poorly understood. In this study, we explored the potential dependencies of the slow slip during the preparatory stage prior to stick-slip instabilities on two main factors, namely the loading rate and surface roughness. To that end, we conducted shear stress-driven friction experiments by imposing varying loading rates on sawcut granite samples with different surface roughness at confining pressure of 35 MPa. We measured the average slip along the fault using far-field displacements and strain changes, while using acoustic emission sensors and local strain gages to capture local slip variations. We found that the average aseismic slip during preparatory stage increases with roughness, whereas its duration decreases with increased loading rate. These results also evidence a complex slip pattern on rough faults which leads to dynamic ruptures at high loading rates.

The auroral acceleration region plays an important role in the magnetosphere-ionosphere coupling system. In this study, signatures of an auroral U-shaped potential structure were found for the first time in the near-equatorial inner magnetosphere by the Arase satellite at ~6.0 RE geocentric distance and 11˚ magnetic latitude. The observed magnetic and electric field variations corresponded to the equatorward motion of the upward field-aligned current and converging perpendicular electric field. Examining the three-dimensional velocity distribution function of H+ and O+ ions, we demonstrate that upflowing ion beams were significantly deflected in an east-west direction with a perpendicular velocity up to ~80 km/s, which is consistent with the ExB drift velocity. A simple particle drift model with the inferred auroral perpendicular potential presents a new kink-like drift path of ions from the magnetotail, implying that the auroral potential structure has a great impact on particle dynamics in the near-earth plasma sheet.

Urban water utilities, facing rising demands and limited supply expansion options, increasingly partner with neighboring utilities to develop and operate shared infrastructure. Inter-utility agreements can reduce costs via economies of scale and help limit environmental impacts, as substitutes for independent investments in large capital projects. However, unexpected shifts in demand growth or water availability, deviating from projections underpinning cooperative agreements, can introduce both supply and financial risk to utility partners. Risks may also be compounded by asymmetric growth in demand across partners or inflexibility of the agreement structure itself to adapt to changing conditions of supply and demand. This work explores the viability of both fixed and adjustable capacity inter-utility cooperative agreements to mitigate regional water supply and financial risk for utilities that vary in size, growth expectations, and independent infrastructure expansion options. Agreements formalized for a shared regional water treatment plant with fixed or adjustable treatment capacities, coupled with structured financing for partner utilities, are found to significantly improve regional supply reliability and financial outcomes. Regional improvements in performance, however, mask tradeoffs among individual agreement partners. Adjustable treatment capacity allocations add flexibility to inter-utility agreements but can compound the financial risk of each utility as a function of the decision-making of the other partners. Often the sensitivity to partners' decision-making under an adjustable agreement degrades financial performance, relative to agreements with fixed capacities allocated to each partner. Our results demonstrate the significant benefits cooperative agreements offer, providing a template to aid decision-makers in development of water supply partnerships.

A simple and efficient method was developed to improve soil moisture representation in an operational water balance model through satellite data assimilation. The proposed method exploits temporal covariance statistics between modelled and satellite-derived soil moisture to produce analysed estimates, as a weighted combination of all data sources. We demonstrate the application of the method to the Australian Water Resources Assessment (AWRA) model and evaluate the accuracy of the approach against in-situ observations across the water balance. The correlation between simulated surface soil moisture and in-situ observation is increased from 0.54 (open-loop) to 0.77 (data assimilation). We suggest an approach to use analysed surface moisture estimates to impart mass conservation constraints on related states and fluxes of the AWRA model in a post-analysis adjustment. The improvements gained from data assimilation can persist for more than one week in surface soil moisture estimates and one month in root-zone soil moisture estimates.

Electrical Resistivity Tomography (ERT) experiments are widely used for characterizing the natural environment because they easily provide a large number of data on a large extent and at various depths. These experiments are usually interpreted with forward models and inversion strategies that are well suited for equivalent porous medium representations. Dealing with fractured rocks requires using specific forward models, which are able to simulate the propagation of electric current flow in fracture networks that are embedded in conductive matrix-rock. Although such models have been recently developed, their integration into inversion strategies, and the definition of the inversion framework are still challenging. Here, we will start by showing how simple cases such as a single horizontal and vertical fracture can be handled by assuming the fracture position as known and inverting the fracture connectivity. We will then extend this to a regular network of fracture segments and will analyze various metrics of the inversion procedure, such as the convergence rate, resolution and depth of investigation. We will also discuss how defining prior information to improve the stochastic inversion strategy and future coupling with other characterization methods.