Subsurface Geometry Research Articles

Direct Waveform Inversion for Irregularly Layered Media

Abstract Full waveform inversion is based on iterative perturbation approaches and often encounters convergence problems when the global initial model is far from the true model. As an alternative solution, our direct waveform inversion (DWI) can accurately invert for the acoustic properties of layered media without requiring a global initial model and furthermore DWI convergence is unconditional. However, previous studies of DWI focused only on inverting 1D horizontally layered media using incident plane waves. Its performance in higher dimensions is yet to be evaluated. Now, we have developed a new DWI scheme designed to invert for 2D irregularly multilayered acoustic media using point-source data. Leveraging the advantages of boundary integral equations in handling irregular layer boundaries, we derived a new wavefield representation and implemented it in our 2D DWI. We incorporated a localized imaging and inversion process for determining the geometries of the irregular interfaces. Similar to our previous 1D DWI, our new 2D DWI explicitly enforces the time–space causality property of the wavefields, retaining the key advantage of not requiring a global initial model and avoiding local minimum and cycle-skipping pitfalls. We tested our 2D DWI on two irregular layered models using explosive point sources. The results confirm that our 2D DWI can effectively and accurately invert for P-wave velocities as well as irregular subsurface geometries.

Geo-electrical investigation for groundwater reserves in the Boranakanive Reservoir Catchment in Tumkur district, Karnataka, India

The groundwater resources have been under significant constraints due to excessive exploitation and climate change. It is imperative to comprehend these dwindling resources' characteristics, given their distribution and occurrence variability across the space and time. A semi-arid climate characterizes the study area and agriculture is the primary occupation, their reliance on groundwater is indispensable due to the lack of surface water sources and erratic rainfall patterns. Consequently, the study employed the Schlumberger array of 200 m-spaced half-current electrodes Vertical Electrical Sounding (VES) survey was conducted at 100 VES locations to identify groundwater potential zones. Further, curve-matching and correlation of lithologies have been carried out from various VES-soundings, and also generated pseudo-cross sections of the subsurface geometry. The results revealed the existence of five geoelectrical resistivity layers as follows layer 1–6 to 422 Ωm, layer 2–8 to 7708 Ωm, layer 3–4 to 37117 Ωm, layer 4–37 to 95059 Ωm, and layer 5–205 to 83142 Ωm. The iso-apparent resistivity maps of the study area reveal values ranging for the first layer 11Ωm - 333 Ωm, the second layer 23Ωm - 5347Ωm, the third layer 11Ωm - 26734Ωm and 10Ωm - 67250Ωm for the fourth layer. The present research determined that the third and fourth layer constitute the principal aquifers due to their fractured structures. As a result, these layers produce a significant quantity of groundwater in the north-eastern (NE) and southern (S) regions of the study region. As a consequence of these findings, further exploration and management of groundwater resources in the study areas can be carried out with valuable insight.

A non-contact quantitative risk assessment framework for translational highway landslides: Integration of InSAR, geophysical inversion, and numerical simulation

Landslides frequently disrupt highway networks in mountainous regions globally, presenting a grave threat to the safety of vehicles and pedestrians. A quantitative assessment of landslide risk within the highway network is crucial for the implementation of targeted monitoring, early warning, and engineering interventions. In this study, a non-contact quantitative risk assessment framework for translational landslides is proposed, which integrates Interferometric Synthetic Aperture Radar (InSAR), geophysical inversion, and numerical simulation techniques. The framework can reliably estimate the surface velocity, subsurface geometry, volume, and potential spatial consequences of landslides, and assess the potential damages and losses resulting from the landslide failure. Taking Lashagou L6 landslide in Linxia City, China as a case study, the results demonstrate a robust agreement between the InSAR-derived two-dimensional (2D) displacements and Global Navigation Satellite System (GNSS) observations, which are suitable for the inversion of active landslide thickness. The minimum mean error between the inverted landslide thickness and the observed borehole thickness is 0.8 m. The maximum thickness of the inverted basal sliding surface is 4.1 m, corresponding to a landslide volume of 1.25 × 104 m3. Fully considering the uncertainties within the technical framework, an estimated 1.2–1.7 vehicles are projected to be impacted, resulting in 5.3–7.7 casualties. The proposed non-contact framework demonstrates high reliability and considerable application versatility, particularly beneficial in inaccessible mountainous regions.

Morphological and Structural Characterization of Shortening Landforms on Mars

AbstractThe lithosphere of Mars accommodates horizontal shortening through folding and faulting, producing landforms described as wrinkle ridges or lobate scarps. Despite this nomenclature, we lack a deep understanding of the drivers of morphological differences observed between landform types. This study aims to develop a quantitative model for shortening landform classification based on surface morphology, subsurface architecture, and strain accommodation, facilitating interpretations of where and how lithospheric stresses are recorded. We developed this model by mapping 100 shortening landforms in a Geographic Information System, recording 12 unique geomorphic parameters such as length and asymmetry, and estimating the strain of each landform. We conducted a Discriminant Function Analysis (DFA) using surface morphometrics. This DFA produced a predictive linear function for categorizing wrinkle ridges and lobate scarps and for quantifying which landforms were exemplars within those categories. The three most influential variables on the surface morphometry DFA were the maximum width, forelimb slope, and back limb length. We then modeled the subsurface structural geology of 50 landforms using MOVE Structural Geology Modeling Software and conducted a second DFA based on subsurface metrics. DFA was most influenced by the dip and depth of the lower ramp base. When both surface morphology and subsurface geometry are input into single DFA, wrinkle ridges and lobate scarps can be distinguished quantitatively 96% of the time. Our results also show that lobate scarps accommodate more strain and imply that studies should consider landform type when interpreting local, regional, and global geological stress histories.

Magnetic surface geometry inversion of Kimberlites in Botswana

AbstractSurface geometry inversion of geophysical data has recently been introduced as an effective approach for generating surface‐based geological models. The models obtained through surface geometry inversion clearly delineate the contacts between distinct rock units, making them easily interpretable by geologists. Surface geometry inversion has shown promising preliminary results in other works, but the practical application of surface geometry inversion on real geophysical data has not been thoroughly investigated. To move towards a better understanding of the practicalities involved, we applied surface geometry inversion to a real magnetic dataset acquired over two kimberlite pipes located in north‐central Botswana. The objective was to assess the effectiveness and limitations of the surface geometry inversion approach in accurately characterizing the subsurface geometry and identifying the boundaries of the kimberlite pipes. We first perform an anomaly separation approach to isolate the magnetic anomalies associated with the kimberlite pipes. A surface geometry inversion algorithm was applied to the original and separated datasets using various initial models and other control parameters. Several tests were performed to investigate the effects that data processing, initial models, and other parameter choices have on the surface geometry inversion results. We successfully recover the geometry, extension and dip of the two kimberlite pipes. We discuss the results of our various tests and provide advice for practitioners interested in applying surface geometry inversion methods to their data. Our work indicates that surface geometry inversion can be used as a complementary approach to voxel inversion, and we propose an iterative surface geometry inversion algorithm as a possible alternative approach to voxel inversion for simple geological scenarios. This work provides valuable insights into the appropriate application of surface geometry inversion on real geophysical datasets.

Assessing the relative activity of faulting along both flanks of the Ou Backbone Range, Tohoku Region, Japan, from fluvial geomorphic analyses

The Ou Backbone Range in the Tohoku Region of Japan is bounded on its both sides by two major active fault systems: the Western Fault Zone of Kitakami Lowland in the east and the Eastern Fault Zone of Yokote Basin in the west. Although these two systems are primary active fault systems in the region, information on their long-term activity characteristics is still quite limited. Therefore, we analyzed the normalized channel steepness indexes of river valleys trending perpendicular to the range front along both flanks of the Ou Backbone Range. Our results show that the eastern flank has gentler river valleys, whereas rivers along the northwestern flank are steeper. Our field investigation shows that knickpoints in this area are mostly related to local lithologic boundaries or are check dams along the valleys, thus the river systems are likely under steady-state conditions. Hence, the steeper river valleys in northwestern Ou Backbone Range indicate a higher uplift rate of the area. Because both fault systems are primarily dip-slip reverse faults and do not have significant variations in their subsurface geometry, the faster uplift suggests that the northern segment of the Eastern Fault Zone of Yokote Basin has a higher slip rate. This is consistent with results of previous studies, and the fact that the rupture of the 1896 Rikuu earthquake, the only historical surface-rupturing event in this region, was only limited along the northern segment of this fault system.

Reconstruction of High-Resolution 3D GPR Data from 2D Profiles: A Multiple-Point Statistical Approach

Ground-penetrating radar (GPR) is a popular geophysical tool for mapping the underground. High-resolution 3D GPR data carry a large amount of information and can greatly help to interpret complex subsurface geometries. However, such data require a dense collection along closely spaced parallel survey lines, which is time consuming and costly. In many cases, for the sake of efficiency, a choice is made during 3D acquisitions to use a larger spacing between the profile lines, resulting in a dense measurement spacing along the lines but a much coarser one in the across-line direction. Simple interpolation methods are then commonly used to increase the sampling before interpretation, which can work well when the subsurface structures are already well sampled in the across-line direction but can distort such structures when this is not the case. In this work, we address the latter problem using a novel multiple-point geostatistical (MPS) simulation methodology. For a considered 3D GPR dataset with reduced sampling in the across-line direction, we attempt to reconstruct a more densely spaced, high-resolution dataset using a series of 2D conditional stochastic simulations in both the along-line and across-line directions. For these simulations, the existing profile data serve as training images from which complex spatial patterns are quantified and reproduced. To reduce discontinuities in the generated 3D spatial structures caused by independent 2D simulations, the target profile being simulated is chosen randomly, and simulations in the along-line and across-line directions are performed alternately. We show the successful application of our approach to 100 MHz synthetic and 200 MHz field GPR data under multiple decimation scenarios where survey lines are regularly deleted from a dense 3D reference dataset, and the corresponding reconstructions are compared with the original data.

Study on the Seismic Response of a Water-Conveyance Tunnel Considering Non-Uniform Longitudinal Subsurface Geometry and Obliquely Incident SV-Waves

The longitudinal seismic response characteristics of a shallow-buried water-conveyance tunnel under non-uniform longitudinal subsurface geometry and obliquely incident SV-waves was studied using the numerical method, where the effect of the non-uniform longitudinal subsurface geometry due to the existence of a local one-sided rock mountain on the seismic response of the tunnel was focused on. Correspondingly, a large-scale three-dimensional (3D) finite-element model was established, where different incidence angles and incidence directions of the SV-wave were taken into consideration. Also, the non-linearity of soil and rock and the damage plastic of the concrete lining were incorporated. In addition, the wave field of the site and the acceleration response as well as damage of the tunnel were observed. The results revealed the following: (i) a local inclined subsurface geometry may focus an obliquely incident wave due to refraction or total reflection; (ii) a tunnel in a site adjacent to a rock mountain may exhibit a higher acceleration response than a tunnel in a homogeneous plain site; and (iii) damage in the tunnel in the site adjacent to a rock mountain may appear in multiple positions, and the effect of the incidence angle on the mode of compressive deformation and damage of the lining is of significance.

Contribution to advancing aquifer geometric mapping using machine learning and deep learning techniques: a case study of the AL Haouz-Mejjate aquifer, Marrakech, Morocco

Groundwater resources in Morocco often face sustainability challenges due to increased exploitation and climate change. Specifically, the Al-Haouz-Mejjate groundwater in the Marrakesh region is faced with overexploitation and insufficient recharge. However, the complex subsurface geometries hamper hydrogeological modeling, characterization, and effective management. Reliably estimating aquifer substrate topography is critical for groundwater models but is challenged by limited direct measurements. This study develops nonlinear machine learning models to infer substrate depths by fusing sparse borehole logs with regional geospatial data. A Gaussian process regression approach provided robust holistic mapping, leveraging flexibility, and uncertainty quantification. Supplementary neural network architectures focus on isolating specific variable relationships, like surface elevation–substrate. Model accuracy exceeded 0.8 R-squared against validation boreholes. Spatial visualizations confirmed consistency across landscape transects. Elevation and piezometric data proved most predictive, though multivariate inputs were required for the lowest errors. The results highlight the power of statistical learning to extract meaningful patterns from disparate hydrological data. However, model opacity and the need for broader training datasets remain barriers. Overall, the work demonstrates advanced machine learning as a promising avenue for illuminating complex aquifer geometries essential for sustainability. Hybrid approaches that use both data-driven and physics-based methods can help solve long-standing problems with hydrogeological characterization.

Carbonnet: How Computer Vision Plays a Role in Climate Change? Application: Learning Geomechanics from Subsurface Geometry of CCS to Mitigate Global Warming

We introduce a new approach using computer vision to predict the land surface displacement from subsurface geometry images for Carbon Capture and Seques- tration (CCS). CCS has been proved to be a key component for a carbon neutral society. However, scientists see there are challenges along the way including the high computational cost due to the large model scale and limitations to generalize a pre-trained model with complex physics. We tackle those challenges by training models directly from the subsurface geometry images. The goal is to understand the respons of land surface displacement due to carbon injection and utilize our trained models to inform decision making in CCS projects. We implement multiple models (CNN, ResNet, and ResNetUNet) for static me- chanics problem, which is a image prediction problem. Next, we use the LSTM and transformer for transient mechanics scenario, which is a video prediction problem. It shows ResNetUNet outperforms the others thanks to its architecture in static mechanics problem, and LSTM shows comparable performance to transformer in transient problem. This report proceeds by outlining our dataset in detail followed by model descriptions in method section. Result and discussion state the key learning, observations, and conclusion with future work rounds out the paper.

Geophysical modelling of the Bjerkreim–Lobe, southern Norway

SUMMARY The Bjerkreim–Sokndal (BKS) intrusion in southern Norway has been studied for decades due to the presence of magnetic remanence creating anomalies 12 000 nT below background as measured by airborne magnetic surveys. The strong magnetic remanence also makes the BKS intrusion a good Earth analogue for remote studies of planets that have prominent magnetic signatures, such as Martian geological environments. Although numerous geophysical surveys and samples have been collected in the area, there are limited 3-D geological interpretations of the subsurface. Here, we used existing geophysical data to conduct forward and inversion modelling of the Bjerkreim lobe to investigate the subsurface geometry of the BKS intrusion. An extensive petrophysical property compilation was used as input data for the models, in combination with airborne magnetics and digital elevation models. This petrophysical compilation was initially analysed using principal component analysis to understand which variables would have the greatest impact on the models. Forward and inversion modelling show that cross-cutting jotunite bodies, and small anorthosite blocks within the Bjerkreim lobe have a limited depth extent of 1 km. Massive and foliated anorthosites to the west of the Bjerkreim lobe extend to depths greater than 4 km indicating that the BKS intruded into these anorthosites. Complications in magnetic field fitting during the forward modelling of megacyclic units with strong magnetic remanence and the results from a new ground magnetic survey support the need to revisit mapped contacts of the cyclical units.

Trial-and-error modeling of ground-airborne electromagnetic data in the Yishu Faulting Basin, China

Although trial-and-error modeling may give some level of interpretation about the subsurface while sacrificing certainty, it is a viable alternative for precise 3D interpretation of real ground-airborne frequency-domain electromagnetic (GAFEM) data. In this sense, a semiautomatic trial-and-error modeling approach is developed. Specifically, we first develop the 3D GAFEM forward-modeling code. Its accuracy is demonstrated using a 3D synthetic model with topography and a tilted anomalous body. Second, an initial model is established based on known geologic constraints. Then, the code is conducted repeatedly, and the parameters of the model are renewed semiautomatically based on a predefined geometry-resistivity combination list. Finally, the model that can achieve the minimum error between the computed response and the collected GAFEM data is selected as the final model. Furthermore, we apply the presented semiautomatic trial-and-error modeling approach to the geothermal resources survey at the Yishu Faulting Basin, China. The purpose of the survey is to interpret the resistivity structure of the subsurface and evaluate the potential development of the geothermal resources in the survey area. As a result, the final model obtained by the trial-and-error modeling, which is constrained by the known geologic information and subsurface geoelectric structures inferred from 2D models inverted by the magnetotelluric and controlled-source audio-frequency magnetotelluric data measured at the same location, indicates the existence of the geothermal resources. This indication is proven by the drilling result of a well site located on the survey line. To further verify the reliability, a comparative analysis is conducted between the model obtained by the trial-and-error modeling and the models obtained by 3D inversion of a GAFEM data set and apparent resistivity calculation using the same data. The results indicate that different approaches can achieve similar subsurface geometry and resistivity distribution of the faulting basin structure.

Integrating Seismic Methods for Characterizing and Monitoring Landslides: A Case Study of the Heinzenberg Deep-Seated Gravitational Slope Deformation (Switzerland)

While geodetic measurements have long been used to assess landslides, seismic methods are increasingly recognized as valuable tools for providing additional insights into subsurface structures and mechanisms. This work aims to characterize the subsurface structures of the deep-seated gravitational slope deformation (DSGSD) at Heinzenberg through the integration of active and passive seismic measurements. Seismic techniques can hereby deliver additional information on the subsurface structure and mechanisms involved, e.g., the degree of rock mass degradation, the resonant frequencies of the potentially unstable compartments, and the local fracture network orientations that are influenced by wavefield polarization. By employing advanced methods such as H/V analysis, site-to-reference spectral ratios, polarization analysis, surface wave analysis, and the joint multizonal transdimensional Bayesian inversion of velocity structures, we establish a comprehensive baseline model of the landslide at five selected sites. This baseline model shall help identify potential changes after the refilling of Lake Lüsch, which started in 2021. Our results reveal the rupture surface of the DSGSD at various depths ranging from 30 m at the top to over 90 m in the middle of the slope. Additionally, we estimate key parameters including the shear wave velocities of the different rock masses. The 2D geophysical profiles and rock mass properties contribute to the understanding of the subsurface geometry, geomechanical properties, and potential water pathways. This study demonstrates the significance of integrating seismic methods with traditional geodetic measurements and geomorphologic analysis techniques for a comprehensive assessment of landslides, enhancing our ability to monitor and mitigate hazardous events.

Fault Coalescence, Slip Distribution, and Stress Drop of the February 2023 Southeast Türkiye Earthquakes from Joint Inversion of SAR, GNSS, and Burst Overlap Interferometry

Abstract Two devastating earthquakes struck southeastern Türkiye and northwestern Syria on 6 February 2023: an Mw 7.8 mainshock, followed 9 hr later by an Mw 7.6 aftershock. To recover and separate the subsurface geometry and slip distributions along the two earthquake faults, we jointly invert Interferometric Synthetic Aperture Radar, Synthetic Aperture Radar pixel offset tracking, burst overlap interferometry (BOI), Global Navigation Satellite System, and aftershock datasets. We introduce a new Kalman filter-based approach for merging spatially dense azimuth offset (AZO) data with the more precise yet spatially sparse BOI data. This procedure yields improved measurements of the displacements parallel to the near north-south satellite tracks, which are critical for resolving slip along most of the Mw 7.8 fault segments. We optimize the inversion using a new metric for assessing the degree of spatial correlation between the coseismic slip gradients and early aftershocks, resulting in a stable solution honoring the complementarity between the geodetic and aftershock datasets. The analysis suggests that the Mw 7.8 rupture consisted of three large segments and two short fault branches, covering about 300 km along the East Anatolian fault (EAF), whereas the Mw 7.6 rupture consisted of three segments extending for about 160 km along the nearby Sürgü fault (SF). On the basis of moment-to-stress-drop scaling relations, we show that the Mw 7.6 stress drop is four times larger than the Mw 7.8 stress drop, consistent with the larger recurrence intervals for Mw > 7 earthquakes on the SF than on the EAF. The moment released during the 2023 Mw 7.8 earthquake is 2–4 times larger than the sum of the moments released during individual historical Mw > 7 earthquakes along the three segments of the 2023 Mw 7.8 earthquake. Thus, when considering moment release for multisegment earthquakes, one should note that the final moment of fault coalescence is likely larger than the arithmetic sum of individual segment ruptures.

Quaternary-Active Faults and the Role of Inherited Structures in the Sacramento-San Joaquin Delta, Western Central Valley, Northern California

Seismic sources and their associated hazards within the Sacramento-San Joaquin Delta region of north-central California are relatively poorly characterized as compared to other, more heavily studied regions of northern California, such as the San Francisco Bay Area. Here we present a synthesis of subsurface, bedrock geology, and geodetic datasets from the Delta and from the Coast Ranges and Diablo Range to the northwest and southwest, respectively. We integrate these data and our own surface geologic and geomorphic observations to present a comprehensive review of faults in the Delta that exhibit Quaternary activity. Structural geologic data from the surrounding region highlight the significant influence that Late Cretaceous-to-Paleogene forearc structures exert on the geometry and kinematics of major Quaternary-active structures within the Delta. These inherited structures — including the Pittsburg-Kirby Hills Fault, Midland Fault, and Great Valley Fault System — exhibit a range of geometries and kinematics. Analysis of geomorphology along these structures suggests that these structures combine to accommodate Quaternary strain across the Delta region. A clearer understanding of subsurface geometries and structural relationships, built upon the regional tectonic history, provides insight into modern deformation accommodated on older structures and helps inform interpretations of seismic hazard within the Delta.

3‐D geophysical modeling of a buried, simple impact crater: Holleford impact structure, Ontario, Canada

AbstractHolleford Crater is a deeply buried, 2.35 km diameter late Proterozoic‐early Cambrian (550 ± 50 Ma) simple impact crater located in southeastern Ontario, Canada. Exploration drilling in the 1950–60s indicated a >450 m deep, simple impact structure with an infill stratigraphy of Cambro‐Ordovician clastic and carbonate sediments and a −2.2 mGal gravity anomaly. We conducted new ground‐based geophysical surveys (magnetics, gravity) and potential field modeling to better resolve the buried impact structure depth, subsurface geometry, and postimpact modification. Geophysical surveys reveal a well‐defined ~3 mGal Bouguer gravity low and <20 nT residual magnetic anomaly over the crater basin. The lack of a well‐defined magnetic anomaly is due to the low magnetic contrast between Mesoproterozoic metasedimentary target rocks and Paleozoic infill sediments. The modeled basement surface shows a deeply buried (>400 m), eroded simple impact structure with a rim‐to‐rim diameter (D) of 1.8–2 km, a residual rim height of about 30 m and a true depth (dt) >400 m. The modeled diameter is smaller than the previous estimate (2.35 km) based on the surface outcrop pattern of Paleozoic strata, which overestimates the buried impact structure dimensions. The modeled basement surface identifies a rim breach and a possible fluvial outflow channel in the southeast impact structure rim. The channel is up to 150 m deep and 400 m in width and has morphology similar to outlet channels produced by fluvial rim dissection of terrestrial impact structures and “tadpole craters” on Mars.

Multisensor and Multiscale Data Integration Method of TLS and GPR for Three-Dimensional Detailed Virtual Reconstruction.

Integrated TLS and GPR data can provide multisensor and multiscale spatial data for the comprehensive identification and analysis of surficial and subsurface information, but a reliable systematic methodology associated with data integration of TLS and GPR is still scarce. The aim of this research is to develop a methodology for the data integration of TLS and GPR for detailed, three-dimensional (3D) virtual reconstruction. GPR data and high-precision geographical coordinates at the centimeter level were simultaneously gathered using the GPR system and the Global Navigation Satellite System (GNSS) signal receiver. A time synchronization algorithm was proposed to combine each trace of the GPR data with its position information. In view of the improved propagation model of electromagnetic waves, the GPR data were transformed into dense point clouds in the geodetic coordinate system. Finally, the TLS-based and GPR-derived point clouds were merged into a single point cloud dataset using coordinate transformation. In addition, TLS and GPR (250 MHz and 500 MHz antenna) surveys were conducted in the Litang fault to assess the feasibility and overall accuracy of the proposed methodology. The 3D realistic surface and subsurface geometry of the fault scarp were displayed using the integration data of TLS and GPR. A total of 40 common points between the TLS-based and GPR-derived point clouds were implemented to assess the data fusion accuracy. The difference values in the x and y directions were relatively stable within 2 cm, while the difference values in the z direction had an abrupt fluctuation and the maximum values could be up to 5 cm. The standard deviations (STD) of the common points between the TLS-based and GPR-derived point clouds were 0.9 cm, 0.8 cm, and 2.9 cm. Based on the difference values and the STD in the x, y, and z directions, the field experimental results demonstrate that the GPR-derived point clouds exhibit good consistency with the TLS-based point clouds. Furthermore, this study offers a good future prospect for the integration method of TLS and GPR for comprehensive interpretation and analysis of the surficial and subsurface information in many fields, such as archaeology, urban infrastructure detection, geological investigation, and other fields.

Modeling and Simulation of Robotic Palpation to Detect Subsurface Soft Tissue Anomaly for Presurgical Assessment

Abstract Surgical Haptics is an emergent field of research to integrate and advance the sense of robotic touch in laparoscopic tools in robot-assisted minimally invasive surgery. Haptic feedback from the tooltip and soft tissue surface interaction during robotic palpation can be leveraged to detect the texture and contour of subsurface geometry. However, precise force modulation of the robotic palpating probe is necessary to determine stiff inclusions of the anatomy and maneuver successive manipulation tasks during surgery. This paper focuses on investigating the layered deformations associated with different force profiles involved in manipulating the superficial anatomy of soft tissues during dynamic robotic palpation to determine the underlying anomaly. A realistic three-dimensional (3D) cross-sectional soft tissue phantom with anatomical layers and tumor, as an anomaly, is designed, modeled, and analyzed to examine the effects of oriented palpating forces (0–5 N) of a 7 DOF robot arm equipped with a contoured palpation probe. Finite element static structural analysis of oriented robotic palpation on the developed 3D soft tissue phantoms (with and without anomaly) reveals the soft tissue layer deformations and associated strains needed to identify presence of stiffer inclusions or anomaly during Robotic palpation. The finite element analysis study shows that the difference in deformations of soft tissue layers (e.g., underlying myofascial layers) under stiffer inclusions at different force levels can facilitate haptic feedback to acquire information about subsurface tumors. The deformation variations are further compared to assess better palpation orientations for subsurface anomaly detection.

How thick is the Strathbogie Complex?

The Strathbogie Complex is a large granitic body in north central Victoria. Previous detailed mapping of part of its western and southern boundary suggested that the body was relatively thin, probably less than 1 km. However, forward modelling its gravity response suggests the complex is thicker, perhaps more than 6 km in its deepest parts. The only way the measured gravity response could be modelled to fit a maximum thickness of 1.5 km is with an unrealistically low density. While not definitive, the modelling provides a warning that, where available, even excellent surface mapping should be combined with other data to obtain the most realistic subsurface geometries.

Slope Deformation Associated With Recent Tectonism and the Lasting Effect of Local Subsurface Geometry in the Taurus‐Littrow Valley, Apollo 17 Landing Site

AbstractThe South Massif and Taurus‐Littrow valley represent a unique area for understanding recent geological processes on the Moon. The presence of two recent overlapping landslide deposits, and boulder falls, suggests that repetitive instability has affected the north‐east facing slope of the South Massif. The presence of the young Lee‐Lincoln lobate scarp associated with a thrust fault suggests that seismic shaking may have been an important factor in triggering surface changes and mass‐wasting events in the area. In this work, we use the younger landslide deposit as a geomorphological marker. The age of the deposit, 70–110 Ma, is known due to the returned samples of the Apollo 17 mission, therefore allowing to set a time constraint to surface changes that have occurred since its emplacement. Here, we extend the body of evidence of slope deformation of the north‐east slope of the South Massif post‐dating the emplacement of the younger landslide deposit. We map boulder tracks, zones of disturbed regolith, summit and slope structures. We described their mutual relationships and their relationships with the topography and local tectonic structures. We identified features directly related to the local stress field, as well as features derived from gravitational adjustment following basal slope support removal due to reactivation of the ancient valley‐bounding fault in reverse mode associated with the Lee‐Lincoln thrust fault. Our interpretation favors a scenario in which recent tectonism, coupled with long‐lasting influence of the subsurface geometry, has caused continuous slope deformation of the South Massif.