Douglas Ray Schmitt

The Kentland Impact Structure is a classic complex crater whose central peak is exposed in an active quarry in NW Indiana, USA. However, its diameter has remained poorly constrained due to the thick glacial sediment cover. Newly obtained seismic reflection profile images combined with refraction seismic tomography, earlier gravity surveying, and shallow drilling reveal the crater's rim faults to be at a radius of ∼4.3 km from the central peak. Evidence for the rim faults include a gravity low, dipping wedges of low velocity and reflective subcropping siliclastics underlain by a deeper highly scattering zone underneath. The rock mass on either side of the fault zone displays coherent horizontal reflections but is populated by numerous diffraction patterns indicative of damage with dimensions below the spatial resolution limits of the survey. The seismic wave speeds remain higher than expected in these strata, indicating a lack of microscopic damage in the rock matrix. The seismic profiles together with the significant positive Bouguer gravity anomaly may further suggest that zones with siliclastics deform differently than underlying carbonate formations with a potential for shock compaction. This rare structural information should be useful in constraining existing impact models.

Distributed acoustic sensing (DAS) records strain integrated over a finite gauge length depending on incidence angle, frequency, material velocities, fiber curvature, and gauge length. The DAS responses to a monofrequency plane wave of these are well understood. However, neither the full response of a DAS waveform to a source signature pulse over a band of frequencies nor this signature's evolution over the length of a single DAS channel due to attenuation have been examined. We use analytic expressions and numerical simulations to quantify how realistic source wavelets and in gauge attenuation reshape DAS strain/strain rate, including broadening, lobe splitting, and in some cases near, vanishing of the recorded signal. Full elastic wavefield modeling shows that fiber curvature and non‐planar wavefronts can further shift apparent transit times relative to co‐located point sensors. We illustrate these effects with a field example in which 1 m spaced downhole geophones are used to reconstruct a simultaneously acquired DAS record. The results delineate when DAS behaves like a scaled geophone and when it does not, and they motivate forward modeling for studies that demand high fidelity in timing and spectral content. A series of analytic and numerical tools are provided to assist with such evaluations.

The entire editorial board of the Journal of Geophysical Research‐Solid Earth would like to sincerely thank all our colleagues who reviewed manuscripts for us in 2025. The hours they spent reading in order to provide insightful comments on manuscripts not only help improve the quality of these manuscripts but also ensure the scientific rigor of our reviewing process and eventually, of the research published in the field of Solid Earth Geophysics by our journal. With the advent of open science and AGU's data policy, the reviewing process now also encompasses checking the accessibility and availability of data and developed software. This is a key objective of AGU's FAIR (Findable, Accessible, Interoperable and Reusable) policy, for which many reviewers have provided suggestions that helped to improve the data presentation and availability, and which also fed the editorial board's reflection on the matter. Of course, we particularly appreciate timely reviews, particularly in light of the growing demands imposed by the increase of manuscripts submitted to Journal of Geophysical Research‐Solid Earth . We received 2,090 submissions in 2025, and 1,789 reviewers contributed to their evaluation by providing 3,016 reviews in total. We are deeply thankful for all of their contributions.

My purpose in this commentary is to provide further context to Christensen (2026) in this issue of Seismica in order to fill some gaps so that readers better understand how the measurements are made, know what the analyses are based on, and know where the pitfalls in employing these results might lie. My experiences in reviewing and editing have revealed that many papers that focus on elastic or seismic anisotropy err as they are written often without understanding the basic principles. This problem is aggravated because some modern methods, such as Electron Backscatter Diffraction (EBSD), have made calculation of the anisotropy of metamorphic rocks readily accessible and production of figures perhaps too easy. I hope to both amplify and clarify the results archived in Christensen (2026) so they are not similarly misused and to provide readers with some tutorial background and more in-depth sources in order that they can avoid overinterpretation of anisotropy results more generally.

Our understanding of fault mechanics and earthquake processes remains limited, largely due to minimal direct observations near active faults at seismogenic depths. This lack of data restricts our ability to accurately assess and mitigate both natural and human-induced seismic hazards. However, recent advancements in drilling capabilities and downhole sensing technologies offer an opportunity: the ability to observe the physical conditions within a volume near active fault zones. In this contribution, we highlight how scientific drilling can provide access to the near-fault environment, enabling measurements of the stress, temperature, fluid pressure, and rock properties at depths where ruptures initiate, propagate, and arrest. These observations are essential to refine models of earthquake nucleation and dynamic rupture, bridging gaps between laboratory experiments, numerical simulations, and surface observations. These insights can advance fundamental understanding in earthquake science but also support the development of more effective seismic hazard assessments and risk mitigation strategies.

The entire editorial board of the Journal of Geophysical Research‐Solid Earth would like to sincerely thank all our colleagues who reviewed manuscripts for us in 2024. The hours they spent reading in order to provide insightful comments on manuscripts not only help improve the quality of these manuscripts but also ensure the scientific rigor of our reviewing process and eventually, of the research published in the field of Solid Earth Geophysics by our journal. With the advent of open science and AGU's data policy, the reviewing process now also encompasses checking the accessibility and availability of data and developed software. This is a key objective of AGU's FAIR (Findable, Accessible, Interoperable and Reusable) (FAIR) policy, for which many reviewers have provided suggestions that helped to improve the data presentation and availability, and which also fed the editorial board's reflection on the matter. Of course, we particularly appreciate timely reviews, particularly in light of the growing demands imposed by the increase of manuscripts submitted to Journal of Geophysical Research‐Solid Earth. We received 1,999 submissions in 2024, and 1,628 reviewers contributed to their evaluation by providing 2,534 reviews in total. We are deeply thankful for all of their contributions.

The third‐order elastic (TOE) model has been used to describe the widely observed nonlinear mechanical behaviors of earth materials. In addition to linear elastic constants (λ, μ), three nonlinear elastic moduli (A, B, C) are required for isotropic rocks. Contrary to previous research on dynamic TOE moduli, this study followed the protocol to measure strain and stress under uniaxial and hydrostatic compressive tests statically, which were later used to invert for the full set of TOE moduli for four standard rock types with differing pore structures of a porous oolitic limestone, quartz‐rich sandstones, and a dense crystalline basalt. The applicability of the TOE model to characterize nonlinearity depends on the fulfillment of path‐independence and small‐strain assumptions. Using the measured static TOE moduli, the finite element model demonstrates that the stress in the vicinity of the wellbore is more amplified than the stress in the linear elastic case, which leads to a wider zone of rock failure around the wellbore. Due to the long‐standing discrepancy between static and dynamic moduli, the rarely reported full set of static TOE moduli is necessary and will benefit future research in understanding the effect of rock nonlinearity on geophysical and geomechanical applications, such as long‐term safe storage of CO₂ and generating process of geohazards.

The entire editorial board of the Journal of Geophysical Research‐Solid Earth would like to sincerely thank all our colleagues who reviewed manuscripts for us in 2023. The hours they spent reading in order to provide insightful comments on manuscripts not only help improve the quality of these manuscripts but also ensure the scientific rigor of our reviewing process and eventually, of the research published in the field of Solid Earth Geophysics by our journal. With the advent of open science and AGU's data policy, the reviewing process now also encompasses checking the accessibility and availability of data and developed software. This is a key objective of AGU's FAIR (Findable, Accessible, Interoperable and Reusable) policy, for which many reviewers have provided suggestions that helped to improve the data presentation and availability, and which also fed the editorial board's reflection on the matter. Of course, we particularly appreciate timely reviews, particularly in light of the growing demands imposed by the increase of manuscripts submitted to Journal of Geophysical Research‐Solid Earth. We received 1,869 submissions in 2023, and 1,472 reviewers contributed to their evaluation by providing 2,237 reviews in total. We are deeply thankful for all of their contributions. The editorial board of Journal of Geophysical Research‐Solid Earth: Rachel Abercrombie, Yves Bernabé, Michael Bostock (former editor), Mark Dekkers, Anke Friedrich, Shin‐Chan Han, Satoshi Ide, Isabelle Manighetti (former EIC), Fenglin Niu, Douglas R. Schmitt, Alexandre Schubnel (EIC), Jun Tsuchiya, and all the associate editors of JGR‐SE.

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