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Large-scale wastewater disposal has led to a fast-paced reawakening of faults in the Oklahoma/Kansas region. High-resolution earthquake relocations show that the inventory of ancient basement faults in the study region differs from results of seismic surveys and geologic mapping focused on the sedimentary cover. We analyze the evolution of seismic activity in the Guthrie-Langston sequence in central Oklahoma in greater detail. Here, seismic activity has reactivated a network of at least 12 subvertical faults in an area less than 10 km across. Recorded activity began in late 2013, peaked about six months later, and includes two M 4 earthquakes. These earthquakes characteristically occur at about 4 km depth below the top of the basement and do not reach the sedimentary cover. The sequence shows a radial growth pattern despite being no closer than 10 km to significant wastewater disposal activity. Hydrologic modeling suggests that activity initiated with a time lag of several years relative to early injection activity. Once initiated, earthquake interactions contribute to the propagation of seismicity along the reactivated faults. As a result, the spatiotemporal evolution of the seismicity mimics a diffusive pattern that is typically thought to be associated with injection activity. Analysis of the fault slip potential shows that most faults are critically stressed in the contemporary stress field. Activity on some faults, for which we find low slip probability, suggests a significant contribution of geomechanical heterogeneities to the reawakening of these ancient basement faults.

Documentation and analysis of groundwater responses to induced earthquakes are important to better understand their influence on shallow groundwater systems and hydrogeological properties and processes. Here we show that induced seismicity in Oklahoma can cause changes of groundwater level over distances >150 km from the epicenter. We test existing models for the cause of the observed responses and find that the model most consistent with observations is enhanced crustal permeability produced by seismic waves, changing aquifer recharge. Simulation suggests that the sources of this recharge are close to the responding wells and have lateral dimensions of ∼100 m. Continuous monitoring of pressure and temperature in wells, installing clustered wells to monitor multiple water levels near injection sites, and isotopic and chemical analysis of groundwater near injection sites are required to better understand and quantify the recharging sources.

In areas of induced seismicity, earthquakes can be triggered by stress changes due to fluid injection and static deformation from fault slip. Here we present a method to distinguish between injection‐driven and earthquake‐driven triggering of induced seismicity by combining a calibrated, fully coupled, poroelastic stress model of wastewater injection with interpretation of a machine learning algorithm trained on both earthquake catalog and modeled stress features. We investigate seismicity from Paradox Valley, Colorado as an ideal test case: a single, high‐pressure injector that has induced thousands of earthquakes since 1991. Using feature importance analysis, we find that injection‐driven earthquakes are approximately 22± $\pm $5% of the total catalog but act as background events that can trigger subsequent aftershocks. Injection‐driven events also have distinct spatiotemporal clustering properties with a larger b‐value, closer proximity to the well, and earlier occurrence in the injection history. Generalization of our technique can help characterize triggering processes in other regions where induced seismicity occurs. Plain Language Summary: The Paradox Valley Unit, Colorado in the central United States has had a remarkable increase in seismicity coincident with over 8 million cubic meters of brine fluid injection since 1991, inducing thousands of earthquakes within an aquifer 4.5 km below the surface. We use a physics‐based model of the Earth combined with statistical and machine learning techniques to help discern which earthquakes are triggered by other earthquakes and which earthquakes are directly triggered by the stress changes from the well as well as their comparative characteristics. Discerning which earthquakes are directly caused from pressure changes due to the fluid injected by the well can inform our understanding of earthquake physics and provide useful information to operators of energy production sites. Key Points: Physics‐based models with interpretable machine learning can identify likely triggering mechanism of earthquakes within an induced sequenceWith this technique, we show that only 22土5% of earthquakes in Paradox Valley are primarily injection‐drivenInjection‐driven events have a larger b‐value, are closer to the well, and occur earlier in the injection history [ABSTRACT FROM AUTHOR]

A practical synthesis of benzisoxazole and its conversion to alpha-aryloxyisobutyric acid using 1,1,1-trichloro-2-methyl-2-propanol is developed. A highly reactive, short-lived intermediate derived from chloretone is detected by ReacIR and its half-life determined to be ~5 min.

A variety of indenones and substituted butenolides can be synthesized using the rhodium(II)-catalyzed reaction of type II alpha-diazo carbonyl compounds. Data show that the tandem cyclization-rearrangement exhibits high chemoselectivity facilitating transformations along the synthetic pathway.

The rhodium(II)-catalyzed reaction of diazoamido ester was analyzed to determine the origin of cyclo-addition push-pull stabilized ylides during intramolecular cycloadditions. The formation of tetracycles during the rhodium-catalyzed formation of carbonyl intermediates from cyclic diazo amides was dependent on the presence of the carbonyl group in the tether that was engaged in ring formation. The presence of a carbonyl group in the dipolarophile tether also relieved steric congestion. Furthermore, severe cross-ring 1,3-diaxial crossing promoted a twist-boat conformation.

Transition metal-based tandem reactions are finding wide application in organic chemistry because of their potential to provide a new synthetic pathway for the construction of complex organic molecules. This review focuses on the use of intermediate rhodium carbenoids to the selective formations of polycyclic structures with high levels of stereoselectivity and high reactivity.

The apparent 6-endo-dig addition when several (phenylethynyl)aryl-substituted alcohols and ketones with neighboring oxygen atom that readily add to the unactivated triple bond undergo base-induced cyclization is actually a rearrangement of the initial benzofuran derivative. A novel acid-catalyzed rearrangement causes the 5-exo-dig produced to changes to a 6-endo-dig product. of the initially formed benzofuran derivative supported the apparent 6-endo-dig addition. The o-formyl- and o-carbomethoxy-substituted alkynyl alcohols prefer the 6-endo-dig pathway.

Synthesis of benzo-substituted cyclopentenones involves an intramolecular tandem ylide-cycloaddition sequence, catalyzed by Rh(II) carboxylates. The method uses O-alkynyl-substituted alpha-diazoacetophenones having tethered heteroatoms as starting materials, and substituents on the alkyne side chain influence the tandem annulation reaction. X-ray crystallography helps determine the structure of the rearranged cycloadduct. Mechanistic study suggests that ring-opening of a transient intermediate oxabicyclo(2.2. 1)heptane precedes a Wagner-Meerwein rearrangement.

In this work, we report on the thermal oxidation of AlInN/AlN/GaN heterostructures. A 'nearly native' Al2O3 oxide was formed during this oxidation procedure, which can be used as a gate oxide and thus enables the fabrication of metal insulator semiconductor hetero field effect transistors. A constant barrier height of [uppercase_phi_synonym]B ≈ 2.34 eV was obtained for all oxidized samples, independent of the oxidation time and temperature, indicating a stable AlInN-oxide interface. The interface state density was approximated to be as low as Nint = 2.5 × 1012 cm-2. Oxide thicknesses were estimated to be in the range of 0.6 nm and 3.2 nm, resulting in a suppression of reverse leakage currents oflarge area metal insulator semiconductor diodes by up to three orders of magnitude. Two-dimensional electron gas density and, in particular, carrier mobility are strongly affected by the thermal oxidation in the O2 atmosphere. A narrow processing window for successful thermal oxidation was identified, covering temperatures between 700 °C and 800 °C and durations of few minutes. The resulting oxide thickness scales well with the square root of oxidation time, indicating diffusion of oxygen atoms into the barrier. [ABSTRACT FROM AUTHOR]

A new approach involving the parallel synthesis and screening of a combinatorial library of potential chiral selectors on polystyrene beads is described. The approach enables the selection of the most enantioselective library member beads through visual inspection under a low-power microscope. The study shows that simple manual methods of parallel (split) synthesis and parallel (visual) screening can be used to find innovative enantioselective binding compounds.