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We use the seismic multichannel analysis of surface waves (MASW) method, which originally used active sources (i.e., controlled by users), to present a new alternative technique for surface-wave analysis of passive data (i.e., seismic sources not controlled by users). Our passive MASW technique uses two types of receiver arrays, 1D and 2D, for two different purposes. The 2D square array is used for assessing the number and directionality of passive seismic sources to help identify optimal time window(s) when such sources are of sufficient quality and aligned with the 1D receiver spread. Then, these time windows are used to selectively extract passive seismic data recorded by the 1D receiver spread for subsequent MASW analysis. In such a manner, this hybrid 1D–2D passive MASW approach can approximate the higher quality advantages of the active MASW method. This technique is successfully applied at a test site in southcentral Kansas taking advantage of train energy as the passive sources monitoring and assessing the potential development of vertically migrating voids that could endanger groundwater and infrastructure. The 1D–2D passive MASW method has proven beneficial for optimizing passive-data dispersion patterns and accurately assessing relative velocities for investigations with reduced labor costs and minimal added processing time and can be considered as a contribution to the surface-wave analysis tools.

The modern use of clandestine tunnels has antagonized military and law enforcement agencies alike over the past 50 years, not only in their simplicity and effectiveness, but also in the challenges of defending against them. Likewise, geophysicists have been confounded, finding what should be a straightforward target on paper — detecting an anomaly with often vastly different physical properties than its surroundings — a much more difficult task than models would suggest. We have evaluated half a century of applied seismic investigation, gaining a history of the use of active seismic methods to detect subterranean tunnels in war zones, along borders, and around facility perimeters. Previously published studies using a variety of seismic methods such as reflection, refraction, surface waves, diffraction, resonance, and full-waveform inversion were aggregated to serve as a reference for void and tunnel detection-related research and to show the progression of the methods used over time.

Seismic surface waves that were likely converted from incident body waves were used to detect a 3 m deep tunnel using two novel processing methods. In data acquired at a tunnel test site, a unique forward-propagating wave (traveling away from the tunnel and seismic source) was identified as an early-arriving surface wave converted at the tunnel from an incident body wave. To our knowledge, our research represents the first time converted surface waves have been observed originating from a tunnel. We have developed two novel processing methods targeting this unique wavefield component for detecting tunnels, cavities, or other shallow anomalies. The first is a time-domain imaging method that takes advantage of the unique kinematic characteristics of converted surface waves to produce a cross section with a coherent, high-amplitude signature originating from the horizontal location of the tunnel. The second method uses frequency-domain analysis of surface-wave amplitudes, which reveals increased amplitudes (primarily from converted surface waves) at locations expected for the tunnel. These proposed approaches for analysis of converted surface waves were successfully used to detect the tunnel and accurately interpret its horizontal location in real-world data. These novel methods could be the key for detecting shallow tunnels or other subsurface anomalies and complement existing seismic detection methods.

Azimuthal stress-field variations in Permian shale overlying voids in salt appear related to localized void roof failure based on interpretations of time-lapse recordings of passive seismic surface-wave data. Salt-dissolution voids in south-central Kansas exist within the Hutchinson Salt Member as a result of solution mining operations early in the 20th century. Since shear-wave velocity can be estimated from surface-wave analysis and is directly related to the shear modulus, or material rigidity, it can be used to indicate shale cap-rock competency. Temporal bulk-velocity variations in bedrock acquired over a known void from 2013 to 2018 are consistent with cyclic stress-field behavior expected with repetitive localized failure within the shale cap rock. It was determined that roof failure and associated subsidence began prior to the 2013 surveys along a north–south failure plane with consistent progression from southwest to northeast until 2017. A low-velocity anomaly observed in 2014–2015 on both profiles indicated a load redistribution in the shale cap rock. This low-velocity region was gradually replaced by an increasing velocity field in subsequent years. These bulk-velocity variations are interpreted as representations of stoping, which occurs when overlying roof layers or sidewall segments progressively fail. As of 2018, the velocity trend in the affected area remained lower than the recorded baseline conditions, with no low-velocity anomalies observed since 2015. Shear-wave velocities are not likely to return to 2013 conditions due to loss of roof material and redistribution of load. Annual surveys will monitor for conditions consistent with the beginning of a stress buildup and roof collapse unless monitoring indicates a change in the subsurface that warrants invasive analysis or other actions.

Clandestine tunnels, used for drug or human trafficking and tactical operations, pose a security threat worldwide and remain elusive targets for detection with geophysical methods. P-wave diffraction imaging is an increasingly common technique for detecting subsurface discontinuities that are smaller than the seismic wavelength (such as faults, pinch outs, and small voids) and has been successfully used to detect shallow tunnels. P-wave diffractions from tunnels typically have very low signal-to-noise ratios and are therefore challenging wavefield components for imaging. Mode-specific amplitude characteristics of theoretical diffractions from a shallow tunnel were evaluated using 9C seismic modeling. Results indicate that SH-wave diffraction has the largest amplitude and coherent phase characteristics along the traveltime hyperbola, making it ideal for diffraction imaging. In real data acquired over a 9.2 m deep tunnel, amplitudes of SH-wave diffractions are 20 dB greater than P-wave diffractions. The tunnel signature on the P-wave diffraction section is of low amplitude relative to the background. The SH-wave diffraction section has a high-amplitude signal focused at the horizontal location and a traveltime consistent with the tunnel location, indicating that the SH-wave may be optimal for diffraction imaging to detect shallow tunnels.

Technology transfer of a small volume continuous (SVC) process and Current Good Manufacturing Practices (cGMP) manufacturing of merestinib are described. A hybrid batch-SVC campaign was completed at a contract manufacturing organization under cGMP. The decision process by which unit operations were selected for implementation in flow for the cGMP campaign is discussed. The hybrid process comprised a Suzuki–Miyaura cross-coupling reaction, a nitro-group hydrogenolysis, a continuous amide bond formation, and a continuous deprotection. A continuous crystallization using two mixed suspension, mixed product removal (MSMPR) crystallizers and a filtration with in situ dissolution were employed for purification between the two SVC steps. Impurity levels were monitored using both online process analytical technology (PAT) and offline measurements. The continuous processing steps operated uninterrupted for 18 days to yield the drug substance in solution at a throughput of 12.5 kg/day. Crystallization in batch mode ...

Development of a small volume continuous process that used a combination of batch and flow unit operations to manufacture the small molecule oncolytic candidate merestinib is described. Continuous processing was enabled following the identification and development of suitable chemical transformations and unit operations. Aspects of the nascent process control strategy were evaluated in the context of a 20 kg laboratory demonstration campaign, executed in walk-in fume hoods at a throughput of 5–10 kg of active pharmaceutical ingredient per day. The process comprised an automated Suzuki–Miyaura cross-coupling reaction, a nitro-group hydrogenolysis, a continuous amide bond formation, and a continuous deprotection. Three of the four steps were purified using mixed-suspension, mixed-product removal crystallizations. Process analytical technology enabled real-time or nearly real-time process diagnostics. Findings from the demonstration campaign informed a second process development cycle as well as decision mak...

We have applied time domain 2D full-waveform inversion (FWI) to detect a known 10 m deep wood-framed tunnel at Yuma Proving Ground, Arizona. The acquired seismic data consist of a series of 2D survey lines that are perpendicular to the long axis of the tunnel. With the use of an initial model estimated from surface wave methods, a void-detection-oriented FWI workflow was applied. A straightforward [Formula: see text] quotient masking method was used to reduce the inversion artifacts and improve confidence in identifying anomalies that possess a high [Formula: see text] ratio. Using near-surface FWI, [Formula: see text] and [Formula: see text] velocity profiles were obtained with void anomalies that are easily interpreted. The inverted velocity profiles depict the tunnel as a low-velocity anomaly at the correct location and depth. A comparison of the observed and simulated waveforms demonstrates the reliability of inverted models. Because the known tunnel has a uniform shape and for our purposes an infinite length, we apply 1D interpolation to the inverted [Formula: see text] profiles to generate a pseudo 3D (2.5D) volume. Based on this research, we conclude the following: (1) FWI is effective in near-surface tunnel detection when high resolution is necessary. (2) Surface-wave methods can provide accurate initial S-wave velocity [Formula: see text] models for near-surface 2D FWI.

We have applied time-domain 3D elastic full-waveform inversion (FWI) to a known tunnel constructed 10 m below the surface with no distinguishing surface expressions. Multicomponent inversion experiments that use an initial model estimated from surface wave methods suggest that the vertical sources and the combination of vertical and longitudinal receivers result in the clearest image of the tunnel. We obtain an approximate 3D image of the tunnel using 24 vertical sources and 720 vertical and 720 longitudinal receivers. We find that increasing the number of vertical sources to 216 does not significantly improve the details of the tunnel. Further experimentation indicates that we can detect the tunnel using a reduced data set of 6–10 vertical sources and 216 vertical sensors. In addition, calculating the [Formula: see text] ratio helps remove artifacts from the inverted model and highlights the location of the tunnel. We compare the 3D inversion results with the 2D FWI results for the same tunnel that we previously evaluated. The variety of successful inversion experiments suggest that FWI is capable of imaging shallow tunnels in desert geologies.

Since 1930, SEG has been the world's leading promoter of applied geophysics and supporter of practicing geophysicists. Over that 90-plus-year period, the Society has adapted effectively to changing member needs and industry expectations. SEG and the majority of professionals it serves have been at the heart of exploring for and discovering the energy that has powered the economic revolution of the last three-quarters of a century.

Geophysical detection of clandestine tunnels is a complex problem that has been met with limited success. Multiple methods have been applied spanning several decades, but a reliable solution has yet to be found. This report presents shallow seismic data collected at a tunnel test site representative of geologic settings found along the southwestern U.S. border. Results demonstrate the capability of using compressional wave diffraction and surface-wave backscatter techniques to detect a purpose-built subterranean tunnel. Near-surface seismic data were also collected at multiple sites in Afghanistan to detect and locate subsurface anomalies (e.g., data collected over an escape tunnel discovered in 2011 at the Sarposa Prison in Kandahar, Afghanistan, which allowed more than 480 prisoners to escape, and data from another shallow tunnel recently discovered at an undisclosed location). The final example from Afghanistan is the first time surface-based seismic methods have detected a tunnel whose presence and location were not previously known. Seismic results directly led to the discovery of the tunnel. Interpreted tunnel locations for all examples were less than 2 m of the actual location. Seismic surface wave backscatter and body-wave diffraction methods show promise for efficient data acquisition and processing for locating purposefully hidden tunnels within unconsolidated sediments.

Shear-wave velocities were estimated at a levee site by inverting Love waves using the multichannel analysis of surface waves (MASW) method augmented with the high-resolution linear Radon transform (HRLRT). The selected site was one of five levee sites in southern Texas chosen for the evaluation of several seismic data-analysis techniques readily available in 2004. The methods included P- and S-wave refraction tomography, Rayleigh- and Love-wave surface-wave analysis using MASW, and P- and S-wave cross-levee tomography. The results from the 2004 analysis revealed that although the P-wave methods provided reasonable and stable results, the S-wave methods produced surprisingly inconsistent shear-wave velocity [Formula: see text] estimates and trends compared with previous studies and borehole investigations. In addition, the Rayleigh-wave MASW method was nearly useless within the levee due to the sparsity of high frequencies in fundamental-mode surface waves and complexities associated with inverting higher modes. This prevented any reliable [Formula: see text] estimates for the levee core. Recent advances in methodology, such as the HRLRT for obtaining higher resolution dispersion-curve images with the MASW method and the use of Love-wave inversion routines specific to Love waves as part of the MASW method, provided the motivation to extend the 2004 original study by using horizontal-component seismic data for characterizing the geologic properties of levees. Contributions from the above-mentioned techniques were instrumental in obtaining [Formula: see text] estimates from within these levees that were very comparable with the measured borehole samples. A Love-wave approach can be a viable alternative to Rayleigh-wave MASW surveys at sites where complications associated with material or levee geometries inhibit reliable [Formula: see text] results from Rayleigh waves.

Advances in drug potency and tailored therapeutics are promoting pharmaceutical manufacturing to transition from a traditional batch paradigm to more flexible continuous processing. Here we report the development of a multistep continuous-flow CGMP (current good manufacturing practices) process that produced 24 kilograms of prexasertib monolactate monohydrate suitable for use in human clinical trials. Eight continuous unit operations were conducted to produce the target at roughly 3 kilograms per day using small continuous reactors, extractors, evaporators, crystallizers, and filters in laboratory fume hoods. Success was enabled by advances in chemistry, engineering, analytical science, process modeling, and equipment design. Substantial technical and business drivers were identified, which merited the continuous process. The continuous process afforded improved performance and safety relative to batch processes and also improved containment of a highly potent compound.

We assessed the impact of density on the estimation of inverted shear-wave velocity ( V s ) using the multi-channel analysis of surface waves (MASW) method. We considered the forward modeling theory, evaluated model sensitivity, and tested the effect of density information on the inversion of seismic data acquired in the Arctic. Theoretical review, numerical modeling and inversion of modeled and real data indicated that the density ratios between layers, not the actual density values, impact the determination of surface-wave phase velocities. Application on real data compared surface-wave inversion results using: a) constant density, the most common approach in practice, b) indirect density estimates derived from refraction compressional-wave velocity observations, and c) from direct density measurements in a borehole. The use of indirect density estimates reduced the final shear-wave velocity ( V s ) results typically by 6–7% and the use of densities from a borehole reduced the final V s estimates by 10–11% compared to those from assumed constant density. In addition to the improved absolute V s accuracy, the resulting overall V s changes were unevenly distributed laterally when viewed on a 2-D section leading to an overall V s model structure that was more representative of the subsurface environment. It was observed that the use of constant density instead of increasing density with depth not only can lead to V s overestimation but it can also create inaccurate model structures, such as a low-velocity layer. Thus, optimal V s estimations can be best achieved using field estimates of subsurface density ratios.

A high-resolution seismic-reflection investigation mapped reflectors and identified characteristics influencing the hydrogeology underlying a portion of the Oxnard Plain in Ventura County, California. Design and implementation of this study was heavily influenced by high levels of cultural noise from vehicles, power lines, roads, manufacturing facilities, and underground utilities/vaults. An abundance of very high quality reflections within the optimum window on shot gathers allowed accurate velocity analysis and statics corrections, which resulted in consistent and coherent common-midpoint (CMP)-stacked reflections with minimal wavelet degradation. Acquisition and processing flows were tailored to this noisy environment and relatively shallow target interval. Layering within both upper and lower aquifer systems was delineated at a vertical resolution potential of about 2.5 m at 350 m depth. Discontinuities in bedding with significant impact on the groundwater flow, particularly related to saltwater intrusion from agricultural pumping near the coast, were delineated on CMP-stacked sections and correlated to widely separated boring data, thereby providing continuity and realism to hydrologic models.

Perimeter-defense operations, geohazard assessment, and engineering characterization require the detection and localization of subsurface anomalies. Seismic waves incident upon these discontinuities generate a scattered wavefield. We have developed various surface-wave techniques, currently being fielded, that have consistently delivered accurate and precise results across a wide range of survey parameters and geographical locations. We use the multichannel analysis of surface waves approach to study the multimode Rayleigh wave, the backscatter analysis of surface waves (BASW) method to detect anomalies, 3D visualization for efficient seismic interpretation, BASW correlation for attribute analysis, and instantaneous-amplitude integration in the complex BASW method. Discrete linear moveout functions and [Formula: see text]-[Formula: see text] filter designs are optimized for BASW considering the fundamental and higher mode dispersion trends of the Rayleigh wave. Synthetic and field data were used to demonstrate multimode BASW and mode separation, which accentuated individual scatter events, and ultimately increased confidence in points of interest. Simple correlation algorithms between fundamental and higher-mode BASW data offer attribute analysis that limits the subjective interpretation of BASW images. Domain sorting and Hilbert transforms allow for 3D visualization and rapid interpretation of an anomaly’s wavefield phenomena within an amplitude cube. Furthermore, instantaneous-amplitude analysis can be incorporated into a more robust complex BASW method that forgives velocity-estimation inaccuracies, while requiring less rigorous preprocessing. Our investigations have suggested that a multifaceted surface-wave analysis provides a valuable tool for today’s geophysicists to fulfill anomaly-detection survey requirements.

A fully automated fill/empty reactor system for liquid–liquid biphasic Suzuki couplings is described. The system was capable of charging reactant and catalyst solutions to a heated vessel, heating reagent solutions by flow heat exchanger on the way into the reactor, allowing the reaction to occur, monitoring reaction completion, discharge of the product solution, and initiation of another cycle in a repeating fashion. A unique noncontact colorimetric method was used to monitor reaction completion. The reactor system exhibits many of the characteristics of a fully continuous reactor such as (1) high productivity from a small process footprint, (2) a large number of volume turnovers each day, (3) higher heat transfer area per unit volume compared to batch because the reactor is 50× smaller, and (4) rapid heat up and cool down of process streams enabled by heat exchangers. Downstream unit operations that are intended for eventual integrated end-to-end continuous production included a batch metal removal step...

Without question, the last nine months have presented unprecedented challenges to humanity and delivered significant blows to portions of our profession. But if there is good that comes from previous bad, we can feel good that we have endured and even emerged stronger from previous economic cycles that have been driven by oil supply and demand.

High-volume fluid injection can cumulatively increase underground pore pressure and induce earthquakes in regions unexpectedly far from injection wells, recent Kansas studies show.

The 90th anniversary of the founding of our Society is coming up on 11 March 2020. In 1930, SEG was established at a time when the integration of geophysics — specifically, seismic and gravity — into oil exploration dramatically improved discovery successes. The amazing accomplishments and forethought of those groundbreaking pioneers in the early 20th century positioned our profession extremely well to be not only significant but vital to meeting the energy needs of the world over the last 100 years. Today, it is extremely rare that a production well is considered, much less drilled, without geophysics.

An NH4Cl-catalyzed ethoxy ethyl deprotection was developed for the synthesis of merestinib, a MET inhibitor. Alternative reactor technologies using temperatures above the solvent boiling point are combined with this mild catalyst to promote the deprotection reaction. The reaction is optimized for flow and has been used to synthesize over 100 kg of the target compound. The generality of the reaction conditions is also demonstrated with other compounds and protecting groups.

Geophysical detection of clandestine tunnels is a complex problem that has met with limited success. Multiple methods have been applied, spanning several decades, but a reliable solution has yet to be found. We evaluated shallow seismic data collected at a tunnel test site representative of geologic settings found along the southwestern U.S. border. Our results demonstrated the capability of using P-wave diffraction and surface-wave backscatter techniques to detect a purpose-built subterranean tunnel. Near-surface seismic data were also collected at multiple sites in Afghanistan to detect and locate subsurface anomalies, including data collected over the escape tunnel discovered in 2011 at the Sarposa Prison in Kandahar, Afghanistan, which allowed more than 480 prisoners to escape, and data from another shallow tunnel recently discovered at an undisclosed location. The final example from Afghanistan was the first time surface-based geophysical methods have detected a tunnel whose presence and location was not previously known. Seismic results directly led to the discovery of the tunnel. Interpreted tunnel locations for all examples were within less than 2 m of the actual location. Seismic surface-wave backscatter and body-wave diffraction methods showed promise for efficient data acquisition and processing for locating purposefully hidden tunnels within unconsolidated sediments.