Abstract: Globally, more people are impacted by extreme hydrologic events such as flooding than all other types of natural disasters combined, and the effects can be devastating. Two examples are the 2012 and 2022 floods along the Niger and Benue Rivers within the Lower Niger River Basin (LNRB) in Nigeria. Flooding within the LNRB typically occurs annually during the rainy season, however, the 2012 and 2022 flood events were of similar magnitude, had catastrophic socioenvironmental impacts, and occurred one decade apart. Limited historical gage data along the Niger and Benue Rivers precludes traditional flood frequency analysis in the LNRB. Hence, this study seeks to utilize globally available observations from satellite remote sensing to compute flood depths using the Floodwater Depth Estimation Tool (FwDETv2.1 version) implemented in Google Earth Engine. Other hydrological and physiographic characteristics of LNRB in 2012 and 2022 are also evaluated using remote sensing observations. Since the FwDET requires only globally available input data (flood inundation map and Digital Elevation Model) which favors data-sparse regions such as Nigeria, the potential for the FwDET tool to automatically quantify flood water depths, an important variable in flood frequency estimation and damage assessment, can be analyzed even when historical observations are lacking. The utility of the FwDETv2.1 for flood management and mitigation studies along global rivers with limited historical data is discussed. ReferenceIdowu, Dorcas, and Wendy Zhou. "Performance evaluation of a potential component of an early flood warning system—A case study of the 2012 flood, Lower Niger River Basin, Nigeria." Remote Sensing 11.17 (2019): 1970.Brakenridge, G. R., Kettner, A. J., Paris, S., Cohen, S., Nghiem, S. V. , River and Reservoir Watch Version 4.5, Satellite-based river discharge and reservoir area measurements, DFO Flood Observatory, University of Colorado, USA. http://floodobservatory.colorado.edu/ SiteDisplays/ 20.htm (Accessed 6 December 2023).Cohen, S.; Peter, B.G.; Haag, A.; Munasinghe, D.; Moragoda, N.; Narayanan, A.; May, S. Sensitivity of Remote Sensing Floodwater Depth Calculation to Boundary Filtering and Digital Elevation Model Selections. Remote Sens. 2022, 14, 5313. https://doi.org/10.3390/rs14215313.B. G. Peter, S. Cohen, R. Lucey, D. Munasinghe, A. Raney and G. R. Brakenridge, "Google Earth Engine Implementation of the Floodwater Depth Estimation Tool (FwDET-GEE) for Rapid and Large Scale Flood Analysis," in IEEE Geoscience and Remote Sensing Letters, vol. 19, pp. 1-5, 2022, Art no. 1501005, doi: 10.1109/LGRS.2020.3031190.Brakenridge, G. Robert, Son V. Nghiem, and Zsofia Kugler. "Passive microwave radiometry at different frequency bands for river discharge retrievals." Earth and Space Science 10.8 (2023): e2023EA002859.Idowu, Dorcas. Assessing the Utilization of Remote Sensing and GIS Techniques for Flood Studies and Land Use/Land Cover Analysis Through Case Studies in Nigeria and the USA. Diss. Colorado School of Mines, 2021.Idowu, Dorcas, and Wendy Zhou. "Global Megacities and Frequent Floods: Correlation between Urban Expansion Patterns and Urban Flood Hazards." Sustainability 15.3 (2023): 2514.

A document by Saman Aryana. Click on the document to view its contents.

Current and emerging approaches to subsurface storage suffer from geographical limitations and in some cases insufficient seal integrity or lateral containment. We propose an innovative containment strategy based on time-dependent yield stress materials, namely Smectite clay suspensions, to address these challenges and make subsurface storage reliable and geographically agnostic. We outline a containment strategy designed to reinforce natural subsurface seals and engineer flow barriers. As a high-risk, high-reward approach, suspension can be injected at its initial low viscosity and elasticity into a porous medium, allowing for easy pumping and targeted delivery, once inside the target zone, it matures into a soft solid with much higher viscosity and elasticity, acting as a flow barrier. We introduce and discuss the exceptional properties of this Smectite suspensions that we believe can revolutionize subsurface containment and storage to move in tandem with the energy transition. There are no adverse effects from higher temperatures on its long-term stability, unlike most polymer aqueous dispersions used in the industry. Moreover, its thixotropic microstructure offers many advantages in operations, such as handling sudden pump shutdowns.

CO2-foams show significant potential for improving mobility control in CO2 Enhanced Oil Recovery (EOR) processes and for the geological carbon sequestration. The addition of nanoparticles (NPs), such as Fe3O4, has been shown to enhance the stability of these foams, especially when used in conjunction with surfactants. Apart from their role in stabilization, Fe3O4 NPs possess distinctive magnetic properties, making them useful in various applications. In this study, we explore the novel application of these nanoparticles, initially intended for stabilizing CO2-foams, as tracers for monitoring the migration of subsurface CO2 plumes. This monitoring is envisioned through the detection of small quantities of these particles within subsurface fluid environments. To facilitate this, we use an Induction Heating (IH) technique, involving exposing a solution with small amounts of Fe3O4 NPs to a high-frequency alternating magnetic field, then measuring the resulting temperature changes using an infrared camera variations. The results indicate a direct correlation between the NP concentration and the observed temperature increase in the solution.

A document by John Louie. Click on the document to view its contents.

The early Paleogene is characterized by a “hothouse” environment with repetitive transient warming events known as “hyperthermals.” While these paleoenvironmental changes are well-documented in the Pacific and Atlantic Oceans, records of such changes in the Indian Ocean are limited. Here, we present a new dataset of bulk chemical composition and stable isotopic ratios of the late Paleocene–middle Eocene sediments on the Exmouth Plateau in the mid-latitude eastern Indian Ocean. The bulk δ13C and δ18O suggest a warming period called the Early Eocene Climate Optimum (EECO) and cooling towards the middle Eocene in a long-term perspective. From a short-term perspective, we identified at least five hyperthermals (PETM, H2, I1, J, and ETM3) in the studied sections. We identified six independent components (ICs) corresponding to sediment source materials and post-depositional processes by applying independent component analyses (ICA) to the bulk chemical composition data. The time-series behavior of IC3 indicates an increase in detrital material or a decrease in carbonate rain flux during both long-term (EECO) and short-term (hyperthermal) warming. Additionally, the rise in IC2 implies an increased population of high consumers in the oceanic ecosystem during warming events around the Exmouth Plateau. Other ICs (IC1, IC4, IC5, and IC6), indicators of diagenetic processes and post-depositional remobilization of elements, showed excursions across hyperthermal horizons. These observations indicate that changes in the redox state of pore or bottom water in the Exmouth Plateau are associated with hyperthermals.

The rheology of crystalline units controls the large-scale deformation geometry and dynamics of collisional orogens. Defining a time-constrained rheological evolution of such units may help unravel the details of collisional dynamics. Here, we integrate field analysis, pseudosection calculations and in-situ garnet U-Pb and mica Rb-Sr geochronology to define the structural and rheological evolution of the Rotondo granite (Gotthard nappe, Central Alps). We identify a sequence of four (D1-D4) deformation stages. Pre-collisional D1 brittle faults developed before Alpine peak metamorphism, which occurred at 34-20 Ma (U-Pb garnet ages) at 590 ± 25ºC and 0.95 ± 0.1 GPa. The reactivation of D1 structures controlled the rheological evolution, from D2 reverse mylonitic shearing at amphibolite facies (520 ± 40ºC and 0.85 ± 0.1 GPa) at 18-20 Ma (white mica Rb-Sr ages), to strike-slip, brittle-ductile shearing at greenschist-facies D3 (395 ± 25 ºC and 0.4 ± 0.1 GPa) at 14-15 Ma (white and dark mica Rb-Sr ages), and then to D4 strike-slip faulting at shallow conditions. Although highly misoriented for the Alpine collisional stress orientation, D1 brittle structures controlled the localization of D2 ductile mylonites accommodating fast (1-3 mm/yr) exhumation rates due to their weak shear strength (<10 MPa). This structural and rheological evolution is common across External Crystalline Massifs (e.g., Aar, Mont Blanc), suggesting that the entire European crust was extremely weak during Alpine collision, its strength controlled by weak ductile shear zones localized on pre-collisional deformation structures, that in turn controlled localized exhumation at the scale of the orogen.

A document by Emily Zawacki. Click on the document to view its contents.

A document by Emily Zawacki. Click on the document to view its contents.

Critical Zone (CZ) scientists study the coupled chemical, biological, physical, and geological processes operating across scales to support life at the Earth's surface. In 2020, the U.S. National Science Foundation funded a network of Thematic Cluster projects called “CZ Net” to work collaboratively in answering scientific questions related to effects of urbanization on CZ processes; CZ function in semi-arid landscapes and the role of dust in sustaining these ecosystems; deep bedrock processes and their relationship to CZ evolution; CZ recovery from disturbances such as fire and flooding; and changes in the coastal CZ related to rising sea level. Data collected by these projects are diverse, ranging from time series from in situ sensors to laboratory analysis of physical samples, geophysical measurements, and others. Thus, coordinating data collection, archival, discovery, and access for the network presents significant challenges. Given the diversity in scientific domains represented, data produced, and collaborations, no single repository fully meets the needs of CZ scientists, posing questions of which repositories to use, how to enable discovery of and access to data across different repositories, and how to develop and promote best practices for sharing research products. This presentation describes cyberinfrastructure (CI) development by the CZ Net Coordinating Hub that leverages existing, domain-specific repositories for managing, curating, disseminating, and preserving data and research products from the CZ Net projects. We have developed CI that links existing data facilities and services, including HydroShare, EarthChem, Zenodo, and other repositories via a CZ Hub that provides tools for data submission, resource registry, metadata cataloging, resource discovery/access, and links to computational resources for analysis and visualization. The CZ Hub’s goal is to make data, samples, software, and other research products created by CZ Net projects Findable, Accessible, Interoperable, and Reusable (FAIR), using existing domain-specific repositories. The repository interoperability we have demonstrated for delivering data services for an interdisciplinary science program may provide a template for future development of integrated, interdisciplinary data services.

A document by Mark Hall. Click on the document to view its contents.

The intermediate infrared region (IMIR, 4 – 8 µm) provides significant advantages over the visible-shortwave infrared and mid-infrared for quantitative determination of mafic mineral composition. In particular, olivine’s sharp spectral features in IMIR spectra exhibit systematic shifts in wavelength position with iron-magnesium content. Previous IMIR studies have used laboratory data, with signal-to-noise ratios (SNRs) and spectral resolutions greater than those expected of imaging spectrometers. Here we employ a feature fitting algorithm to quantitatively assess the influence of SNR and sampling rate on olivine detection and compositional interpretation from IMIR data. We demonstrate that olivine is easily distinguished from pyroxene and other lunar-relevant minerals across IMIR wavelengths, with the feature-fitting algorithm effectively determining olivine composition for various synthetic, terrestrial, Martian, and lunar samples with an average error of only 6.4 mol%. We then apply the feature-fitting routine to degraded spectra with reduced SNRs and sampling rates, establishing data-quality thresholds for accurate determination of olivine composition. Spectra for the sample most relevant to lunar exploration, an Apollo 74002 drive tube consisting of microcrystalline olivine and glass-rich pyroclastics, required SNRs ≥ 200 for sampling rates ≤ 25 nm to predict composition within ±11 Mg# (molar Mg/[Mg+Fe] * 100) of the sample’s true composition. Derived limits on SNRs and sampling rates will serve as valuable inputs for the development of IMIR imaging spectrometers, enabling comprehensive knowledge of olivine composition across the lunar surface and providing valuable insight into the Moon’s crustal history and thermal evolution.

Estimating the radiated energy of small-to-moderate (Mw < 5) events remains challenging because their waveforms are strongly distorted during wave propagation. Even when near-source records are available, seismic waves pass through the shallow crust with strong attenuation; consequently, high-frequency energy may be significantly dissipated. Here, we evaluated the degree of energy dissipation in the shallow crust by estimating the depth-dependent attenuation (Q-1) by modeling near-source (< 12 km) waveform data in northern Ibaraki Prefecture, Japan. High-quality waveforms recorded by a downhole sensor confined by granite with high seismic velocity helped to investigate this issue. We first estimated the moment tensors for M1–4 events and computed their synthetic waveforms, assuming a tentative one-dimensional -model. We then modified the -model in the 5–20 Hz range such that the frequency components of the synthetic and observed waveforms of small events (Mw < 1.7) matched. The results show that the Q-value is 55 at depths of < 4 km and shows no obvious frequency dependence. Using the derived -model, we estimated the moment-scaled energy (eR) of 3,884 events with Mw 2.0–4.5. The median eR is 3.6×10-5 , similar to the values reported for Mw >6 events, with no obvious Mw dependence. If we use an empirically derived Q-model (~350), the median eR becomes a one-order underestimation (3.1×10-6). These results indicate the importance of accurately assuming the Q-value in the shallow crust for energy estimation of small events, even when near-source high-quality waveforms are available.

Newly formed oceanic crust interacts with penetrating seawater, resulting in the formation of secondary minerals. Sediment cover can potentially change the redox conditions of underlying basaltic crusts, significantly affecting the types of secondary minerals and element transfer during alteration. However, previous studies have not revealed the quantitative regional variation and controlling factors of seafloor alteration using altered samples taken from different sites. We present a novel approach for the quantitative analyses of element mobility related to seafloor alteration based on a regional dataset of altered basalt bulk compositions and highlights the effects of the redox state and duration on alteration. The protolith reconstruction models (PRMs), machine learning-based element mobility analyses, were applied to the compositional data of the basaltic crusts from the South/Northwest Pacific region. The analyses revealed that altered basalts with older ages showed higher element mobility, particularly characterized by an enrichment of Rb and K, which were associated by up to 100 times with the formation of secondary minerals. In the oxidative settings of the South Pacific region, enrichment of Ba, U, and Pb and depletion of P were observed in samples with intense alteration. In contrast, under reductive conditions in the Northwest Pacific region, alterations associated with carbonate veins caused U enrichment. Our research suggests that sediment thickness is a key factor in the redox conditions during alteration, which changes the characteristics of element transfer and secondary minerals. Additionally, seafloor alteration likely persisted for at least 30 Myr, irrespective of whether the environment was oxidative or reductive.

A document by Hilary Chang. Click on the document to view its contents.

A good understanding of the rupture patterns of small earthquakes is essential to understand the differences between earthquakes of different sizes. However, resolving the source complexity of small events (Mw<5) is challenging, because their seismic waveforms are distorted during propagation. In this study, we used high-quality seismic waveforms recorded by an excellent downhole sensor in Japan to directly examine the source complexities of 64 Mw3.3-5.0 short-range earthquakes (< 8 km). We found that even the waveforms of microearthquakes (Mw < 2) were simple at the sensor, indicating that the waveforms were scarcely disturbed by structural inhomogeneities. We inferred the moment rate functions from the shapes of the direct P-waves, which showed diversity in their complexity. Even conservatively estimated, 30% of the events had multiple subevents. The results suggest that methods that account for complexity, rather than those that assume a simple source pattern, are required to characterize even small earthquakes.

Radio-echo sounding (RES) has shown that large-scale folds in the englacial stratigraphy is ubiquitous in Greenland’s ice sheet. However, there is no consensus yet on how these folds form. Here, we use the full-Stokes code Underworld2 to simulate ice movements in three-dimensional convergent flow, mainly investigating the effect of ice anisotropy due to a crystallographic preferred orientation, vertical viscosity and density contrasts in ice layers, and bedrock topography. Our simulated folds show complex patterns and are classified into three types: large-scale folds, small-scale folds and basal-shear folds. The amplitudes of large-scale folds tend to be at their maximum in middle ice layers and decrease towards the surface, in accordance with observations in RES data. We conclude that bedrock topography contributes to perturbations in ice layers, and that ice anisotropy amplifies these into large-scale folds, while vertical viscosity contrasts in ice layers are insufficient for large-scale fold amplification.

The central Andean Precordillera, between 30-31°S, has experienced active faulting and deformation from the early Miocene to present driven by a flat-slab segment of the down-going Pacific Plate. Basic models for fault propagation, in this region, involve progressive eastward stepping of deformation; however, out-of-sequence faulting has been postulated. Furthermore, deformation appears to have started earlier in the northern part of this region and later in the southern part. We use apatite (U-Th-Sm)/He (AHe) low-temperature thermochronology to quantify timing of fault exhumation and fault growth patterns to test hypotheses about out-of-sequence thrusting and the southward propagation of deformation in the region. Nine vertical transects were collected in the eastern-most part of the Precordillera. Preliminary AHe data indicate complete and partial age resetting in middle to late Miocene sedimentary units, that were deposited, buried, and subsequently exhumed. AHe ages range between 30 - 2Ma and trend younger to the south, supporting previous suggestions of north to south deformation migration. Additionally, we use cosmogenic radionuclides (CRN) to assess modern erosion rates across the landscape. Initial erosion rates range from 22 – 1330 m/my, with generally lower rates in the north and higher rates to the south. Ongoing analysis and modeling of both thermochronologic and CRN data will help to constrain the recent exhumation and erosion history in the central Andean Precordillera and determine if combining these two techniques can be used to identify out-of-sequence faulting and changes in spatial patterns of tectonically driven deformation. 

The crustal components in a magma plumbing system often contain mechanically heterogeneous layers and structural discontinuities such as pre-existing fracture (PEF) systems. Such layers and discontinuities, depending upon their mechanical properties, can either facilitate upward magma movement or inhibit it at some depths by acting as stress barriers. This study considers a visco-plastic crustal rheology to study the variation of yield strength around the two lateral tips of an elliptical magma chamber (MC), aided by the presence of a PEF, by employing a finite element modelling (FEM) approach. The orientation of the PEF is varied in the FE models and the patterns of localized tensile stress have been examined from these models. The model results find no difference between the yield strength at the two lateral tips of the MC, when there is no PEF in the crustal domain. On the other hand, the presence of a PEF significantly decreases the yield strength around the associated MC tip. We also observed that the yield strength around the MC is also dependent upon the vertical and horizontal separation between the MC and the PEF. When a heterogeneous layer above the MC is taken into consideration, the yield strength depends on whether the PEF terminates above, within, or below the heterogeneous layer. The model results show that the difference in the magnitude of yield strength between the two MC tips is least when the PEF is located above the heterogeneous layer, whereas, it is maximum when the PEF is located below the MC. These results provide finer interpretation in understanding the kinematic evolution of a magma plumbing system, with large structural discontinuities housed within shallow crustal depths.

A document by Raj Pandya. Click on the document to view its contents.

The humidity-dependent acoustic emission (AE) activity in a quartz gouge layer was investigated via sliding-rate step tests. Because AE events are generated by the brittle failure of the contact junction, their activity reflects the micromechanics of friction. AE activity was evaluated by the m-value (characterizing amplitude distribution), AE rate (number of events per unit sliding distance), and their sliding-rate dependences. The m-value decreased with increasing humidity, suggesting contact junction growth by the pressure solution. Increased humidity decreased the AE rate and enhanced the rate-weakening of friction, implying the role of water in suppressing the brittleness of contact junction and strengthening macroscopic instability. Notably, the relationship between the direct effect of friction and the sliding-rate dependence of AE rate under dry conditions was distinct from those under other conditions, suggesting these are sensitivity to areal fraction of the water film on the surface of the gouge particle.

The Superstition Hills Fault (SHF) exhibits a rich spectrum of slip modes, including M 6+ earthquakes, afterslip, quasi-steady creep, and both triggered and spontaneous slow slip events (SSEs). Following 13 years of quiescence, creepmeters recorded 25 mm of slip during 16-19 May 2023. Additional sub-events brought the total slip to 41 mm. The event nucleated on the northern SHF in early-May and propagated bi-laterally at rates on the order of kilometers per day. Surface offsets reveal a bi-modal slip distribution, with slip on the northern section of the fault being less localized and lower amplitude compared to the southern section. Kinematic slip models confirm systematic variations in the slip distribution along-strike and with depth and suggest that slip is largely confined to the shallow sedimentary layer. Observations and models of the 2023 SSE bear a strong similarity to previous slip episodes in 1999, 2006, and 2010, suggesting a characteristic behavior.

As a particularly common minerals in granites, the presence of feldspar and altered feldspar-chlorite gouges at hydrothermal conditions have important implications in fault strength and reactivation. We present laboratory observations of frictional strength and stability of feldspar (K-feldspar and albite) and altered feldspar-chlorite gouges under conditions representative of deep geothermal reservoirs to evaluate the impact on fault stability. Velocity‐ stepping experiments are performed at a confining stress of 95 MPa, pore pressures of 35-90 MPa and temperatures of 120-400°C representative of in situ conditions for such reservoirs. Our experiment results show that the feldspar gouge is frictionally strong (μ~0.71) at all experimental temperatures (~120-400℃) but transits from velocity-strengthening to velocity-weakening at T>120°C. Increasing the pore pressure increases the friction coefficient (~0.70-0.87) and the gouge remains velocity weakening, but this weakening decreases as pore pressures increase. The presence of alteration-sourced chlorite leads to a transition from velocity weakening to velocity strengthening in the mixed gouge at experimental temperatures and pore pressures. As a ubiquitous mineral in reservoir rocks, feldspar is shown to potentially contribute to unstable sliding over ranges in temperature and pressure typical in deep hydrothermal reservoirs. These findings emphasize that feldspar minerals may increase the potential for injection-induced seismicity on pre-existing faults if devoid of chlorite alteration.

Extreme weather events are reshaping hydrological cycles across the globe, yet our understanding of the groundwater response to these extremes remains limited. Here we analyze groundwater levels across the South Coast of British Columbia (BC) in the Pacific Northwest with the objective of determining groundwater responses to atmospheric rivers (ARs) and drought. An AR catalogue was derived and associated to local rainfall defining extreme precipitation. Droughts were quantified using dry day metrics, in conjunction with the standardized precipitation index (SPI). From September to January, approximately 40% of total precipitation is contributed by ARs. From April to September, more than 50% of days receive no precipitation, with typically 26 consecutive dry days. We used the autocorrelation structure of groundwater levels to quantify aquifer memory characteristics and identified two distinct clusters. Cluster 1 wells respond to recharge from local precipitation, primarily rainfall, and respond rapidly to both ARs during winter recharge and significant rainfall deficits during summer. Cluster 2 wells are also driven by local precipitation, and are additionally influenced by the Fraser River’s large summer freshet, briefly providing a secondary recharge mechanism to South Coast aquifers. Accordingly, groundwater recessions are offset to later in the summer, contingent on the Fraser River, mediating drought. The results suggest that groundwater memory encapsulates multiple hydrogeological factors, including boundary conditions, influencing the response outcome to extreme events.