It has been suggested that fracture and fault intersections promote enhanced transport of fluids in the brittle crust by forming zones of increased permeability. However, the underlying mechanisms that control the emplacement of magma at fault intersections remain poorly understood. To better understand the relation between magma emplacement, volcano development and fault zone intersections, we examine the Nevados de Chillan Volcanic Complex (NChVC, 36.8 degrees S) in the Southern Andean Volcanic Zone. The complex is thought to be located atop the intersection between two sets of NE-right lateral strike-slip faults and a seismically active regional scale NW- oriented inherited structure, also interpreted as a regional fault zone. We collected data on the orientation and frequency of tens of dykes and thousands of fractures, at the volcano scale, from representative outcrops using three-dimensional digital image correlation techniques, with images taken from Unmanned Aerial Vehicles (UAVs). We use these data to generate a conceptual model of the response of the different fracture sets to regional loads and the potential consequence in terms of magma emplacement. In our conceptual model, N-S to NW-SE striking fractures become reactivated by fault intersection-related local stress field rotations. This, in turn, favors NW-SE aligned magma emplacement, and the evolution of NW-SE aligned volcanoes. Our findings provide a mechanical explanation for rotated magma emplacement pathways, which do not necessarily require a transient stress state imposed by unlocking the megathrust.

A more comprehensive understanding of the progressive, time-dependent deformation and fracturing of brittle rock is crucial for assessing the long-term integrity of rock masses surrounding engineering structures. In this study, we propose a three-dimensional numerical model that integrates the microplane model and subcritical crack growth to investigate the progressive, time-dependent deformation and fracturing of brittle rock. The model incorporates subcritical crack growth and time-dependent damage evolution constitutive laws into the microplanes. By following the trend of subcritical crack growth observed in previous studies, the model accurately captures the time-dependent propagation of virtual cracks. The cooperative interaction between strain and damage evolution on the microplanes ultimately leads to localized material degeneration over extended time. Moreover, this model effectively characterizes the temporal and spatial distribution of damaged elements during time-dependent deformation and fracturing of brittle rock. The numerical simulations successfully replicate phenomena observed in laboratory experiments performed on brittle rock. Specifically, they demonstrate how different stress levels influence creep strain rate and time-to-failure. Additionally, the simulations reveal that the microscale interaction of potential cracks (microplanes) can effectively describe the complex macroscopic time-dependent behavior of brittle rock. As a result, it becomes possible to predict time-to-failure and rupture patterns using the calibrated model based on laboratory tests. The proposed numerical model holds the potential to be further extended for predicting the long-term stability of larger rock masses.

We have developed a new True Triaxial Apparatus (TTA) for rock deformation consisting of six servo-controlled loading rams that transmit maximum stresses of 220 MPa in the two horizontal axes and 400 MPa in the vertical axis to 50 mm side cubic rock samples. The sample and loading platens are introduced in a steel vessel where rock specimens can be subjected to up to 60 MPa of confining pressure, and pore fluids line connected to two pump intensifiers allow for highly accurate permeability measurements along the three loading axes. We present a suite of Finite Element Method (FEM) models implemented to determine the conditions and loading configuration that minimise the loading boundary effects during true triaxial loading. These observations are generic and we expect they will contribute to the development of true triaxial loading systems generally. Finally, we validate our experimental configuration by presenting results on permeability measurements along the three axes on cubic samples of three types of well studied rocks: Darley Dale sandstone, Crab Orchard sandstone, and Etna basalt.

3D printing technology offers the possibility of producing synthetic samples with accurately defined microstructures. As indicated by effective medium theory (EMT), the shapes, orientations, and sizes of voids significantly affect the overall elastic response of a solid body. By performing uniaxial compression tests on 20 types of 3D‐printed samples containing voids of different geometries, we examine whether the measured effective elasticities are accurately predicted by EMT. To manufacture the sample, we selected printers that use different technologies; fused deposition modelling (FDM), and stereolithography (SLA). We show how printer settings (FDM case) or sample cure time (SLA case) affect the measured properties. We also examine the reproducibility of elasticity tests on identically designed samples. To obtain the range of theoretical predictions, we assume either uniform strain or uniform stress. Our study of over two hundred samples shows that measured effective elastic moduli can fit EMT predictions with an error of less than 5% using both FDM and SLA methods if certain printing specifications and sample design considerations are taken into account. Notably, we find that the pore volume fraction of the designed samples should be above to induce a measurable softening effect, but below to produce accurate EMT estimations that fit the measured elastic properties of the samples. Our results highlight both the strengths of EMT for predicting the effective properties of solids with low pore fraction volume microstructural configurations, and the limitations for high porosity microstructures, particularly, those with interactive pores geometries.

We attempt to formalise the relationship between the poroelasticity theory and the effective medium theory of micromechanics. The assumptions of these two approaches vary, but both can be linked by considering the undrained response of a material; and that is the main focus of the paper. To analyse the linkage between poroelasticity and micromechanics, we do not limit ourselves to the original theory of Biot. Instead, we consider a multi-porous extension of anisotropic poroelasticity, where pore fluid pressure may vary within the bulk medium of interest. As a consequence, any inhomogeneities in the material are not necessarily interconnected; instead, they may form isolated pore sets that are described by different poroelastic parameters and fluid pressures. We attempt to incorporate the effective methods inside Biot-like theory and investigate the poroelastic response of various microstructures. We show the cases where such implementation is valid and the others that appear to be questionable. During micromechanical analysis, we derive a particular case of cylindrical transverse isotropy -- commonly assumed in conventional laboratory triaxial tests -- where the symmetry is induced by sets of aligned cracks.

Eruptive style transitions are common in silicic volcanoes and an improved understanding of transitional controls is necessary for hazard forecasting. Examples of hybrid eruptions where both explosive and effusive eruptive behaviours occur simultaneously have led to a re-examination of models used to understand these complex and poorly understood processes. Exposed fossilised conduits record evidence of magmatic processes and provide the opportunity to examine structures and textures related to these transitions. Here we present a conceptual model of the evolution of a narrow (2.5 m wide) conduit located on the SW flank of the Nevados de Chill ' an Volcanic Complex, Chile. This conduit records evidence of fragmentation and densification processes through intercalated and juxtaposed banded, porous and dense domains. To understand how the products of each eruptive style relate and evolve during conduit formation, we combined qualitative textural analyses at different scales (outcrop, optical microscope and electron microscope), pore size and shape measurements using ImageJ, connected porosity measurements made using a helium pycnometer and total water content measurements using Fourier transform infrared spectroscopy. The results allow us to identify five principal phases of the conduit evolution: (I) an explosive phase where the conduit is filled with pyroclastic material, evidenced in the pyroclastic deposit preserved at the conduit wall, (II) a cyclic process of fragmentation and densification within the conduit that generates intercalation of the porous and dense domains, and leads to a hybrid explosive -effusive phase, (III) the formation of a dense magma plug that eventually seals the conduit and deforms vesicles and bands, (IV) the compaction of the pyroclastic domain due to the ascent of the plug, driving porosity reduction (to as little as 3% in the densest bands), with micro -folds and glassy fiamme, and (V) a final phase of post -sintering vesicle relaxation, yielding regular, mainly rounded, shapes. We compare our results with other exposed and examined conduits to propose a model of conduit evolution during small -volume, short-lived silicic eruptions.

Semi-brittle and plastic deformation behaviors of mafic granulite are significant for evaluating characteristics of ductile zones in the lower crust region and the rheological strength of the lower crust. Axial compression experiments were carried out in this study with natural mafic granulite collected from the North China Craton, using a gas medium apparatus at 950-1,150 degrees C and 300 MPa with strain up to 17%. The samples are composed of 57 vol.% Plagioclase, 19 vol.% Clinopyroxene, 20 vol.% Orthopyroxene, and 4 vol.% magnetite and ilmentite. The mean grain size is 300-700 mu m. The bulk structural water content is 891 +/- 399 wt ppm. At 950-1,000 degrees C, the samples were brittly broken by scattered cracks and localized fault zones. At 1,050-1,075 degrees C, the samples were deformed by ductile shear zones that broadened with increasing temperature, the deformation behavior is characterized by a steady-state semi-brittle creep; mechanic data yield a flow law of epsilon(center dot)=106.0 +/- 0.3MPa-5.8s-1 sigma 5.8 +/- 0.1exp-651 +/- 68kJ/molRT $\dot{\varepsilon }={10}<^>{6.0\pm 0.3}{\text{MPa}}<^>{-5.8}{{\mathrm{s}}<^>{-1}\sigma }<^>{5.8\pm 0.1}\mathrm{exp}\left(-\frac{651\pm 68\text{kJ}/\text{mol}}{RT}\right)$. At 1,100-1,150 degrees C, the samples plastically deformed with dislocation creep, and the deformation strength is reduced by recrystallization and partial melting; mechanical data yield a flow law of epsilon(center dot)=102.7 +/- 0.8MPa-4.1s-1 sigma 4.1 +/- 0.2exp-442 +/- 13kJ/molRT $\dot{\varepsilon }={10}<^>{2.7\pm 0.8}{\text{MPa}}<^>{-4.1}{{\mathrm{s}}<^>{-1}\sigma }<^>{4.1\pm 0.2}\mathrm{exp}\left(-\frac{442\pm 13\text{kJ}/\text{mol}}{RT}\right)$. The strength profile based on our data implies that North China Craton has a wet and cold continental lower crust. Recrystallization and cataclastic flow involve grain size reduction that can lead to steady-state ductile behaviors of fault zones.

We propose the generalisation of the anisotropic poroelasticity theory. At a large scale, a medium is viewed as quasi-static, which is the original assumption of Biot. At a smaller scale, we distinguish different porosity clusters (sets of pores or fractures) that are characterized by various fluid pressures, which is the original poroelastic extension of Aifantis. In consequence, both instantaneous and time-dependent deformation lead to fluid content variations that are different in each cluster. We present the equations for such phenomena, where the anisotropic properties of both the solid matrix and pore sets are assumed. Novel poroelastic coefficients that relate solid and fluid phases in our extension are proposed, and their physical meaning is determined. To demonstrate the utility of our equations and emphasize the meaning of new coefficients, we perform numerical simulations of a triple-porosity consolidation. These simulations reveal positive pore pressure transients in the drained behaviour of weakly connected pore sets, and these may result in mechanical weakening of the material.

Several lunar samples collected during the Apollo missions were kept sealed and stored in controlled conditions in order to be studied decades later exploiting future, more advanced capabilities. Two of the preserved samples are Apollo 17 double drive tube 73002/73001. The double drive tube extracted a core sample of the Light Mantle deposit at Station 3 in the Taurus-Littrow Valley (Figure 1). As part of the NASA Apollo Next Generation Sample Analysis (ANGSA) program, samples 73002 and 73001 became available to study in 2019 and 2022, respectively [1][2]. The Apollo 17 double drive tube sampled the Light Mantle deposit material down to a depth of 70.6 cm; the effective material length of each tube is 21.3 cm for 73002 and 34.9 cm for 73001 (some material was lost during sampling). This represents an unprecedented opportunity to study the Light Mantle deposit to previously unsampled depths.The Light Mantle deposit represents the only extraterrestrial landslide to have ever been studied in-situ. The Light Mantle is a 5-km-long deposit that formed from debris mobilised from the South Massif, a 2.2-km-high mountain in Taurus-Littrow Valley [3][4]][5]. The origin and hypermobility of the Light Mantle remain debated. The recently opened Apollo 17 double drive tube 73002/73001 provides a new set of samples to investigate the origin and the emplacement mechanisms of the Light Mantle.Prior to dissection and opening of the sample containers, the double drive tube was scanned using X-ray computed tomography (XCT) [6] so that a digital, high-resolution 3D dataset of the whole core sample is available and represents one of the ‘next generation’ capabilities now available to researchers to interrogate the data using novel approaches and obtain new insights into lunar material and processes. Additionally, the 3D dataset preserves the 3D context of all the subsamples extracted from the original core sample.In this work, we used high-resolution X-ray computed tomography (XCT) scans and high-resolution scans of thin sections of the upper 20 cm of the core, sample 73002, and conduct 3D clast-size analysis and investigation of clast morphological fabric. The aims of this work are to:Present a 3D data processing workflow that can be used as a basis for future investigations of lunar core samples. Demonstrate potential scientific information that can be extracted from 3D analysis of lunar core samples. Within this framework, we conduct: (1) 3D grain size analysis and compare the results with grain size analyses conducted on the grains extracted during the dissection of the core sample; (2) 3D analysis of clast size distribution. Additionally, as part of our investigation of the emplacement mechanism of the Light Mantle, we use 2D continuous thin sections (backscattered electron maps) of sample 73002 to search for diagnostic clast fabric similar to those generated during the friction experiments conducted in simulated lunar landslides [7]. The clast fabric is called Clast Cortex Aggregate (CCA) and it’s constituted by a central clast surrounded by nano-scale fine material (Figure 2).The data analysis and visualization of the XCT dataset of core sample 73002 were performed using 3D visualization software Avizo 2022.2 by ThermoFisher. We customized our workflow and established a best-practice protocol so that they can be used as reference for future analysis of 73001. We used backscattered electron (BSE) maps of the sample’s thin sections (73002,6011; 73002,6012; 73002,6013; 73002,6014) [8] to search for (CCAs).The results of clast-size distribution show that the sample is characterised by lack of the largest clast-size fraction in the top 4-5 cm, which we attribute to the fragmentation of larger regolith-hosted clasts and bedrock by space weathering and meteoroid bombardment. The observation of an uppermost layer presenting characteristics of reworked regolith is consistent with results from previous studies of lunar regolith and from other works conducted on 73002 as part of the ANGSA program [8][9]. Moreover, we found extensive presence of CCAs. The formation of CCAs in natural and lab-simulated landslides is attributed to granular flow dynamics, presence of nanoparticles, and adhering forces between such particles. Therefore, we concluded that the presence of CCAs in sample 73002 represents the first evidence that the Light Mantle was emplaced as a granular flow. This work shows that valuable information can be extracted from the 3D analysis of lunar core samples and, more generally, it shows the potential of morphometric and morphological clast analysis using high resolution XCT dataset and thin sections combined.Our work represents the first study to conduct a 3D clast analysis of a lunar regolith core sample. As such, it constitutes an important step in showing the novel information that can be extracted, and presenting a potential workflow for studying lunar regolith core samples that will be collected during future missions to the Moon. REFERENCES. [1] Shearer et al. (2020). AGU Fall Meeting. Abstract V013-0001. [2] Shearer et al. (2022). 53rd LPSC. Abstract 2546. [3] Schmitt (1973). Science, 182(4113), 681–690. [4] Lucchitta (1977). Icarus, 30(1), 80–96. [5] Kokelaar et al. (2017). JGR:Planets, 122(9), 1893-925. [6] Gross et al. (2023). https://curator.jsc.nasa.gov/lunar/angsa_attachments/aapreliminary_20catalog/preliminary_73001-73002_catalog.pdf. [7] Magnarini et al. (2023). JGR:Planets, 128(6), e2022JE007520. [8] Bell et al. (2024). Submitted to JGR:Planets – In review. [9] Neuman et al. (2024). Submitted to Science – In review.Figure 1 – a) Oblique view of Taurus-Littrow Valley; the yellow dot shows the location of the Apollo 17 landing site (LROC/NAC image M1266925685L. Image credit: NASA/GSFC/ASU); b) A frame from the original footage recorded from the Lunar Rover Vehicle onboard camera the showing astronaut Gene Cernan extracting the double drive tube containing material from the Light Mantle deposit. c) Double drive tube in the ground prior extraction (AS17-137-20981. Image credit: NASA). The yellow star in the three panel shows the location where the double drive tube core sample 73002/73001 was collected. Figure 2 – Comparison of Clast Cortex Aggregates (CCAs). (a-b) CCAs generated during the friction experiments conducted on anorthosite-bearing gouges by [7]; (c-f) CCAs found in the Apollo 17 core sample 73002. The red dotted lines and the white dotted line in (d) show the corona of finer fragments found around clasts.

Abstract In this study we use micromagnetic modeling to show that the magnetizations of magnetically single‐vortex particles rotate toward the stress axis on the application of a differential compression stress. This is the exact opposite response to magnetically single‐domain particles, which previously provided the theoretical underpinning of the effect of stress on the magnetic signals of rocks. We show that the magnetization directions of single‐vortex and equant single‐domain particles are altered by much lower stresses than previously predicted, c.f., 100 versus 1,000 MPa; where a change in magnetization is defined as a rotation of >3° after the removal of stress. The magnetization intensity of assemblages also drops by ∼20%–30% on the application and removal of stress of ∼100 MPa. Given that single‐vortex particles are now thought to dominate the magnetization of most rocks, future studies should account for paleomagnetic directional uncertainties and potential underestimation of the ancient magnetic field intensity.

Understanding how fluids flow to form halo-bearing veins is essential to assess the fundamental processes involved in fracture propagation and the formation of hydrothermal ore deposits. Haloes may mimic damage zones during fracture propagation, contributing to the identification of scaling relations between halo width and fracture displacement. In this work, we examine geometry, kinematics and mineral composition of well-exposed halo-bearing fault-vein network field samples. We studied a total of 18 veins from Iron-Oxide Copper Gold (IOCG) deposits in the Chilean Atacama Desert and from the Chinese Cathaysia tectonic block. Vein length and width and halo width were measured directly at the outcrop and later under optical microscope. We established a scaling relation, over five orders of magnitude, between halo width (HW) and vein width (VW) of the form log 10 HW = 1.07 & lowast; log 10 VW + 1.04 which suggests that the majority of analyzed haloes were formed as a result of crack tip process zone damage. Such ratios and scaling relationships, apart from elucidating the physical mechanisms driving halo/damage zone formation, have potential implications for a more reliable estimation of the nature and size of ore grade variations away from high-grade mineralized veins to the relatively lower-grade surrounding wall rock volumes.

Anisotropy is an important property that is widely present in crustal rocks. Efforts have been devoted to providing a constitutive model that can describe both inherent and stress-induced anisotropy in rock. Different from classic models, that are based on stress invariants or strain tensors, we propose here an anisotropic damage microplane model to capture the characteristics of rock properties in different orientations (i.e., their anisotropy). The basic idea is to couple continuum damage mechanics with the classic microplane model. The stress tensor in the model is dependent on the integration of microplane stresses in all orientations. The damage state of any element in the model is determined by the microplane that satisfies the maximum tensile stress criterion or Mohr–Coulomb criterion. An ellipsoidal function was used to characterize the failure strength, where the orientation of the failure plane changes with the preferred orientation of defects in the rock. The proposed model is validated against laboratory experiments performed on brittle material with orientated cracks and granite under true triaxial compression. The fracture pattern and the effect of the intermediate principal stress are numerically predicted by our anisotropic damage model and we discuss relationships between the damage evolution and the anisotropy of the rock under true triaxial compression. The proposed numerical model, based on microplane theory, offers a new approach to analyzing the effect of crack orientation on the deformation and fracture of brittle rock.

We measured poroelastic properties of cracked granite under triaxial conditions, at elevated confining pressure and a range of differential stresses. Skempton's coefficients and undrained Young's modulus and Poisson's ratio were determined directly by recording in situ fluid pressure during rapid cycles of axial and radial stress. Drained properties were measured both statically and dynamically at ultrasonic frequencies. At a given confining pressure, increasing differential stress leads to the development of elastically transverse isotropy, with symmetry axis aligned with the compression axis. Skempton's coefficients are also anisotropic, with larger changes in pore pressure in response to radial stress (coefficient B-x) than to axial stress steps (B-z). The anisotropy in the Skempton coefficients increases with increasing differential stress, with B-z decreasing and B-x slightly increasing. The evolution of static moduli and the Skempton coefficients is well approximated by Gassmann's equation using dry moduli obtained from ultrasonic measurements. Simplified predictions of the Skempton coefficients based on crack density tensors inverted from dynamic data also shows acceptable agreement with direct observations. Perfect quantitative agreement is not reached, due to the imprecision of our dynamic measurements, model simplifications, and inherent differences between static moduli obtained using stress steps of several MPa stress and dynamic ultrasonic stress oscillations.

Earthquakes on normal faults in the continental setting are relatively uncommon. The scarcity of surface-rupturing events underpins an absence of surface displacement measurements. It is a common practice to use surface offset as a proxy to understand the fault structure at depth. Hence, the lack of comprehensive surface data impedes the subsurface reconstruction of seismogenic normal faults and prohibits the thorough assessment of earthquake hazards. To supplement the available surface displacement measurements and to make statistically significant inferences, we apply optical image correlation (OIC) methods to historical images from three large continental normal earthquakes in the western United States (1954 Dixie Valley (Mw 6.8) - Fairview Peak (Mw 7.1) earthquake sequence, the 1959 Mw 7.2 Hebgen Lake earthquake and the 1983 Mw 6.9 Borah Peak earthquake). The results of this study are displacement maps with three components of deformation from which we extract high-resolution 3-d measurements everywhere along the surface rupture. The high-resolution 3-d data are used to quantify the magnitude and direction of the earthquake-related offset, the percentage of off-fault damage as well as the width of the fault zone. These parameters represent the fault maturity, geometric complexity and subsurface structure of the fault. Our observations confirm behaviours previously observed along strike-slip faults (e.g. magnitude of off-fault deformation is proportional to the rupture complexity). In addition, a comparative assessment of the results from the three study areas demonstrates that features such as excess slip detected close to the fault scarp are not unique and can be found along multiple dip-slip faults. Consequently, this study documents the variation of the quantifiable parameters along the normal faults. It suggests that while some parameters are a universal reflection of the fault characteristics, others vary according to the geology or topography in the area and should not be accepted without further investigation.

Fluid flow through the brittle crust is primarily controlled by the capability of fracture networks to provide pathways for fluid transport. The dominant permeability orientation within fractured rock masses has been consistently correlated with the development of fracture intersections; an observation also made at the meso‐regional scale. Despite the importance attributed to fracture intersections in promoting fluid flow, the magnitude of their enhancement of fractured rock permeability has not yet been quantified. Here, we characterize the hydro‐mechanical properties of intersections in samples of Seljadalur Basalt by generating two orthogonal, tensile fractures produced by two separate loadings using a Brazilian test apparatus, and measuring their permeability as a function of hydrostatic pressure. We observe that intersecting fractures are significantly more permeable and less compliant than two independent macro‐fractures. We formulate a model for fracture intersection permeability as a function of pressure by adding the contributions of two independent fractures plus a tube‐like cavity with an effective elastic compressibility determined by its geometry. Permeability measurements during cyclic loading allowed determination of the effective stress coefficient ( α in p e = p c − αp p ) for fracture and intersection permeability. We observe a trend of lower α intersection values with respect to α fracture , which suggests that the channels controlling fluid flow have a higher aspect ratio (are more tubular) for the intersections relative to independent fractures. Our results suggest that fracture intersections play a critical role in maintaining permeability at depth, which has significant implications for the quantification and upscaling of fracture permeability toward reservoir‐scale simulations.

Data obtained from triaxial loading experiments conducted on thermally cracked Westerly granite which was initially dry and later saturated with water. Text files (.txt) are raw, unprocessed time series of mechanical data including load, shortening and radial and axial strain gauge measurements. Except noted, units are in Volts. Strain gauge voltages can be converted into strain using gauge factor of 2.11 and amplification factor of 40. External shortening can be converted to sample shortening using a machine stiffness of 480 kN/mm. Raw ultrasonic data are combined in folder named BSF*. Data format is binary, and can be read using ASC ltd. software "Insite". Files "sensors.txt" contain ultrasonic sensor positions and time offset corrections. Mechanical and Ultrasonic data are provided for when the sample was dry. Only mechanical data are provided for saturated conditions.

Time-dependent cracking and brittle creep of rock is fundamental to understanding the long-term evolution and dynamic failure in underground rock engineering. In the present paper, we present a systematic laboratory investigation into the control of single open macrofractures of differing orientations on time-dependent cracking and brittle creep in sandstone using digital image correlation (DIC). For a given macrofracture inclination angle β, we find that the failure of macrofractured sandstone under a constant stress is accompanied by the generation of more tensile fractures (wing cracks and secondary cracks) than in our constant strain rate experiments. This result differs from experiments performed on intact sandstones, for which macroscopic failure under a constant stress and constant strain rate were essentially identical. The nucleation site for the wing cracks is β-dependent. As β is increased, the crack nucleation position gradually moves from the center of the fracture towards the fracture tip with a decreasing speed. The kink angle of the secondary crack (k1) increases quasi-linearly with the increase of fracture angle γ. With the increase of the secondary crack angle θ, the kink angle of the tail crack (k2) shows different increasing trends for the left-lateral and right-lateral shear. The secondary crack could be inclined at a maximum of 26° (θ) to the maximum principal stress direction. Creep bursts—transient accelerations in deformation—are more easily triggered in macrofractured rock than in initially intact rock, and coincide in time with the coalescence of secondary cracks. The likelihood of occurrence of a creep burst was found to be higher for lower values of β. Finally, we present a secondary crack location map that defines the swing interval and identifies the fracture mechanism. The influence of a macrofracture, and its orientation, on damage evolution and the likelihood of creep bursts during interseismic periods provides crucial information for those tasked with monitoring hazards associated with the dynamic failure of crustal rocks.

The Light Mantle landslide is a hypermobile landslide on the Moon. Apollo 17 astronauts collected a core sample of the top 60 cm of the Light Mantle deposit, which is currently being analyzed as part of the NASA's Apollo Next Generation Sample Analysis program. The origin of its hypermobility remains undetermined, as the proposed mechanisms are difficult to prove because of the lack of theoretical and experimental support and the scarcity of field data related to the internal structures of its deposit. Regardless of the emplacement mechanisms, it has been proposed that localized dynamic frictional weakening is responsible for the early stage instability that leads to catastrophic failure. Here, we conduct friction experiments under vacuum to investigate the viability of dynamic friction weakening in lunar analog anorthosite‐bearing gouges (i.e., rock powders). Our results show that localized dynamic friction weakening does not occur in these gouges at loading conditions where, instead, weakening is observed in other materials on Earth. Therefore, possibly other fluidization‐related mechanisms contributed to the initiation of the hypermobile Light Mantle landslide. Finally, we describe the microstructures formed in the experiments, including the presence of clast cortex aggregates. Preliminary investigation of the Light Mantle core samples (73001/73002) shows the presence of similar microstructures. Therefore, our microstructural observations will help the analysis and interpretation of the Apollo 17 core samples, as keys to insights about internal processes occurring during the emplacement of the landslide.

The 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.