Infill Thickness Research Articles

Effect of Optimised Infill Parameters on the Tensile Properties of MEX Co-polyester Models

To optimize the infill parameters and improve the tensile properties of 3D printed polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG) models, this study explored the effects of infill thickness, infill flow rate, and infill overlap length on the tensile properties of 3D printed PETG models via the one-way test combined with the Taguchi test. The results of the one-way test showed that the tensile strength and elastic modulus of the PETG models increased with the increase of infill thickness, infill flow rate, and infill overlap length. The results of Taguchi s test showed that the influence of infill parameters on the tensile properties of PETG models was as follows: infill thickness ] infill flow rate ] infill overlap length; the optimized infill parameters were: infill thickness of 1.2 mm, infill flow rate of 120%, and infill overlap length of 2.8 mm, and the tensile strength of the 3D printed PETG models with optimized parameters was 20.13 MPa, and elastic modulus was 1.32 GPa, which gave the best tensile properties.

Brittle rock mass failure in deep tunnels: The role of infilled structural plane with varying dip angles

Filled rock discontinuities are commonly encountered in underground engineering excavations, and their mechanical behavior has a significant impact on the stability of surrounding rocks. However, their performance under three-dimensional stress conditions has rarely been explored in the past. In this study, we summarized the typical failure characteristics of filled structural planes in deep-buried tunnels and conducted laboratory true triaxial tests on granite specimens to investigate the effect of dip angle and infill thickness on the failure characteristics of high-stress brittle surrounding rocks. The study monitored the characteristics of vertical stress-displacement, acoustic emission, acceleration, and failure process of granite specimens during the loading process and revealed the failure mechanism of brittle rock masses under the influence of infill thickness and structural plane dip angle. The results showed that the dip angle of structural planes has a significant influence on the failure mode of rock masses in deep tunnels. There exists a critical range of dip angles, within which the rock mass undergoes shear slip failure along the pre-existing structural plane, manifested by rock spalling near the structural plane. Beyond this critical range, the rock mass experiences strain-type brittle failure, characterized by violent rock ejection. Furthermore, the filling of structural planes can change the failure mode of rock masses and lead to more severe damage when the friction coefficient of the structural plane falls below a specific threshold. Additionally, it was revealed that a perpendicular ejection force exists on the free surface of the rock mass under loading, which is approximately vertical to the normal direction and is the primary factor responsible for the formation of vertical parallel cracks within the rock mass. The findings of this work are of paramount importance for comprehending the failure characteristics of deep-buried tunnels containing infilling joints.

Effect of fused deposition modeling process parameter in influence of mechanical property of acrylonitrile butadiene styrene polymer

The objective of this study is to investigate how the mechanical properties of components produced using acrylonitrile butadiene styrene (ABS) on a Creality Ender-3 3D printer are affected by various fused deposition modeling (FDM) printing parameters. The impact of various factors, including infill density, printing speed, platform temperature, extruder temperature, and so on, was assessed in terms of their influence on the ultimate tensile strength, yield strength, and elastic modulus of the manufactured components. The impact of each parameter was assessed using a Multi-criteria decision-making (MCDM) methodology. Finally, the second set of parameters, including a 35% infill thickness, 0.25 mm layer level, 40 mm/s printing speed, 75 °C platform temperature, 210 °C extruder temperature, and 75 mm/s travel speed, was discovered to be the most suitable for ABS filament used to make impellers.

Numerical Modelling of Secant Piles

This study presents numerical modeling of a secant pile wall and investigates the lateral displacements, as well as the pressure exerted on the secant pile wall due to the existing soil. The analysis was performed using a finite element method software package, which simulates the behavior of the soil-pile interaction system under various soil conditions. The numerical model considers the geometrical and material properties of the soil, pile, and concrete infill, as well as the effects of water pressure, soil swelling, and ground movement on the stability of the wall. The results of the analysis show that the secant pile wall is capable of resisting the expected lateral and vertical loads, and earth pressures, and the deflection of the wall is within the acceptable limits. Furthermore, the study investigates the effects of different design parameters on the performance of the secant pile wall, including the spacing and diameter of the piles, the thickness and strength of the concrete infill, and the soil properties. The findings of this research provide valuable insights into the behavior and performance of secant pile walls, which can help engineers and contractors to improve the safety and efficiency of deep excavation projects in urban environments.

Experimental investigation and strength model of rough ice-filled joints under tensile and shear loading

Warming softening of ice-filled joints has caused many rockfall disasters in cold regions. A series tensile and shear strength tests were conducted to investigate the thawing softening mechanism of ice-filled joints by considering the effect of the joint opening, temperature and roughness. The joint opening has little influence on the tensile strength of ice-filled joints, but the temperature is a remarkable influencing factor. When the temperature increases from −15 °C to −0.5 °C, the average tensile strength of ice-filled joint reduces from 0.64 MPa to 0.22 MPa, which displays a constant logarithmic decay function against the freezing temperature and it is similar to the change rule of pure ice. The shear strength of the ice-filled joint decreases with increasing the infill thickness, and tends to be the shear strength of pure ice beyond the critical infilling thickness. In addition, all the tensile failures are inside the joint ice, however, the shear failure is mainly caused by the debonding of ice-rock interface when the temperature increases to −0.5 °C. It implies that the tensile bonding strength of ice-rock interface also is larger than that of the solid ice itself even at a high freezing temperature. Based on the experimental results, a new shear strength model of the ice-filled joint is proposed for Barton's joint profiles by considering the effect of temperature and infill thickness. It has been validated that this model is accurate to predict the shear strength of ice-filled joint, which may be used to estimate the stability of freezing joint rock slope in cold regions.

Laboratory-Scale Investigation on Shear Behavior of Non-Persistent Joints and Joint Infill Using Lattice-Spring-Based Synthetic Rock Mass Model

Discontinuities mainly control the mechanical behavior of rock mass and cause a significant reduction in the rock mass strength. Joint persistency and joint infill conditions are considered the most significant joint parameters that control the mechanical response of rock mass. In this study, numerical and statistical analyses were performed on pre-cracked specimens with two flaws to investigate the effect of joint persistence parameters on shear strength. In addition, an extensive study was conducted to explore the effect of infilled mineral strength, infill thickness, and infill wall roughness on shear strength. The Lattice-Spring-Based Synthetic Rock Mass (LS-SRM) approach was utilized to perform the numerical models. The results showed that the tensile crack propagation is limited at higher normal stresses as tensile damage is largely suppressed. The increases in rock bridge angle slightly increased the shear strength and caused a change in the failure mechanisms of the rock bridge from tensile to shearing. The results of the models with infilled minerals revealed that infilled minerals mainly controlled the shear strength of specimens when the infill thickness was 4.0 mm or greater. The infill wall roughness had no apparent effect on the shear strength. In contrast, it governed the failure mechanisms; cracks initiated at the asperity of the rough filling wall and propagated through the hosted rock mass.

Seismic analysis of a G + 3 confined masonry building with AAC infill using SAP 2000

With increasing seismicity worldwide, there is a need for resilient structures that will withstand large earthquake forces. In this context, Autoclaved Aerated Concrete (AAC) blocks with Confined Masonry present an attractive option due to their light weightiness among other desirable qualities. Confined Masonry (CM) construction offers enhanced seismic resistance compared to unreinforced and non-engineered reinforced concrete frame construction and is preferred in high seismic zones. This study verifies the effectiveness of Confined Masonry construction with AAC blocks as infill material by modeling a 2D single-bay G + 3 frame in SAP2000. After the mesh convergence study and validation with existing results, the columns were checked as per IS 456 (2000) along with the stress and strain to ensure that they were within the linear limits of the AAC. The analysis is carried out for AAC infill thicknesses of 120 mm, 150 mm, and 200 mm for zones II, III, IV, and V as per IS 1893 (part 1) 2016. The result of the study is compared with 120 mm infill thickness in zone II as the base case.

Structure, seismostratigraphy, and tectonic evolution of Lago Roca (southern Patagonia, Argentina)

Lago Roca is a NE–SW elongated lacustrine body located to the south of Lago Argentino, the largest lake of the UNESCO ‘Los Glaciares’ National Park. An extensive high‐resolution seismic survey carried out within the Lago Roca, integrated with geological information gathered in the area, have allowed to produce: (a) a complete bathymetric map of the lake; (b) a basement topography map and a structural map; and (c) an analysis of the geometry, distribution, and thickness of the sedimentary infill. Two sub‐basins were recognized in Lago Roca, separated by a central basement high that shows a pop‐up structure. The northern and southern margins of the lake basement are bounded by NE–SW trending strike‐slip faults that constitute subsidiary faults strands of the regional structural lineament known as the ‘Lago Argentino transfer fault’. The shallow, low magnitude seismicity recorded in the area supports the interpretation that this fault segment is active at the present. The relative motion along the fault led to the deformation of the sedimentary infill of the lake, which was also affected by several subsidiary normal faults oriented parallel to the Lago Argentino transfer fault. Data show the peculiar asymmetry in the sedimentary filling of Lago Roca, typical of those of pull‐apart basins generated along transform margins. A simplified model for the evolution of Lago Roca is also here proposed, based on the analysed data and the regional tectonic background.

Flexural behaviour of circular reinforced concrete columns strengthened by glass fibre reinforced polymer wrapping system

The use of prefabricated glass fibre reinforced polymer (GFRP) wrapping systems in retrofitting reinforced concrete (RC) columns has emerged to enhance the overall axial performance. However, the effect of these systems on columns subjected to bending is still limited although the flexural loading on columns in real life is inevitable. This paper presents experimental, numerical, and theoretical investigations on the flexural behaviour of circular RC columns strengthened by a GFRP wrapping system. A total of eight columns were prepared and tested under three point bending to determine the contribution of the GFRP wrapping system to the overall flexural performance. The annulus between the RC columns and the GFRP wraps was filled with epoxy or cementitious grout to ensure transfer and distribution of stresses. The load-midspan deflection responses and failure modes were presented and evaluated. Furthermore, a nonlinear finite element modelling (FEM) was conducted using ABAQUS software to simulate the performance of unwrapped and GFRP-wrapped columns under flexural loading. A theoretical analysis was also developed using the basic beam theory to obtain the flexural capacity of the tested columns and compare it with experimental and FEM results. A parametric analysis was carried out to assess the effect of varying the thickness of GFRP and infill, as well as the loading mode, on the flexural behaviour of RC columns. The results of experimental tests demonstrated that GFRP-wrapped columns with epoxy infills significantly enhanced the flexural load capacity whereas columns with grout infills showed a prominent enhancement in ductility and energy absorption. The results of FEM and theoretical analyses were in good agreement with experimental results. The results of the developed theoretical model were found to have a good correlation with the results of the parametric investigation. Overall, the GFRP wrapping system implemented in this study is an effective repair technique for structural RC columns subjected to flexural loading. The proposed theoretical model can be used by the practising engineers to design a composite repair system for deteriorated reinforced concrete columns.

Effect of Joint Roughness and Infill Thickness on Shear Characteristics of Rock Mass

The joint planes in fractured rock mass will reduce the tensile strength and shear strength of rock mass, which has a decisive influence on the deformation and failure mode of engineering rock mass. Furthermore, infill also exists between the joint surfaces, which will also affect the shear characteristics of the joint. A method of importing standard joint profile into PFC2D was proposed, and a series of numerical simulation tests were carried out to study the effect of joint roughness and infill thickness on the shear characteristics of joints. The numerical results revealed that rock bolts profoundly improved the shear strength of the infilled rock joints, enhanced the toughness of the joint surface, increased the number of micro-cracks, and made the dilatation more obvious. The shear stress and the normal displacement of unbolted or bolted infilled rock joints increased with increasing the joint roughness and decreasing the infill thickness. The maximum horizontal compression stress in the middle of the bolt gradually increased with the increase of joint roughness coefficient. Different roughness has different effects on the number of micro-cracks in the sample. The number of total cracks and tensile cracks of the bolted and unbolted specimens increased with the increase of joint roughness coefficient, while the shear cracks remained almost the same. Through the study of the coupling effect of joint roughness and infill thickness on peak shear stress, results can be obtained as follows. The unbolted samples are highly sensitive to JRC changes. The greater the infill thickness, the greater the sensitivity of unbolted samples to JRC changes. The reinforcement effect of the bolt will strengthen the meshing strength between the joint surface and the filling material; that is, the meshing strength is positively correlated with joint roughness and negatively correlated with filling thickness.

Frictional Behavior of the Stressed Basalt Fracture

The frictional properties and sliding stability of rocks are critically important in several fields, e.g., earthquake dynamics, extraction of underground resources, and sequestration of carbon dioxide. Here a self-developed triaxial apparatus was employed to conduct sliding tests under the coupled hydro-mechanical (HM) conditions. We determined the evolution of frictional strength in the stressed basalt fracture. The relations were established through velocity-stepping (VS) experiments on split basalt core subject to various stress, infill, and hydraulic conditions. The basalt exhibited velocity-strengthening behavior under cyclic velocities of 1–30 μm/s. Moreover, the frictional property was observed to be stress- and infill-dependent, showing lower frictions at both larger effective normal stresses and larger infill thickness. Besides, the sliding stability of the basalt fracture is found to be velocity- and stress-dependent. In particular, an unstable slip of a stick-slip was observed at a small velocity of 1 μm/s, but stabilizes with increasing shearing velocities at about 6 μm/s. Meanwhile, there is a transition from stable slip to unstable slip with the increasing effective normal stress, which is 5 MPa. Whereas, the thickness of the gouge as large as 2 mm does not seem to influence the sliding stability, even though the gouge thickness will significantly weaken the frictional strength of basalt fracture. The results suggested that the evolution of basalt fracture friction is controlled considerably by hydro-mechanical conditions, the sliding velocity, and gouge thickness. The frictional strength tends to vary with specified hydraulic, mechanical, gouge-bearing conditions. Furthermore, the frictional behavior transits between stable- and unstable-slip based on the velocities, stress pore pressure, and gouge thickness. These conclusions are drawn from constrained conditions.

Delimiting morphological and volumetric elements of cave surveys as analogues for paleokarst reservoir modelling – A case study from the Maaras cave system, northern Greece

Active karst systems can offer good analogues for paleokarst reservoir modelling as they can provide links between present karst system geometries and the final reservoir architecture. Although clastic sediments are a characteristic and commonly conspicuous component of modern karst systems, their impact on the surveyed cave morphology has received limited attention. Here we address this topic by investigating the spatial and volumetric distribution of clastic sediments in a large karst cave hosting an active fluvial channel in northern Greece and discretize these in a geocellular framework. Mapping of cave floor sediment-types was supplemented by local stratigraphic logging of relict sediment terraces and electrical resistivity tomography in parts of the cave. Four resistivity groups were identified and interpreted as low- and high-porosity siliciclastic sediments, interbedded marble clasts, and host rock (marble). Sediment infill thickness ranges from 25 m to >45 m at the time of measurement; corresponding to a minimum of 64–95% of the cross-sectional area of the karst cavity in the surveyed part. These observations demonstrate that under certain circumstances, allochthonous siliciclastic sediments can form a significant volumetric component in karst systems and, by extension, in paleokarst reservoirs originating from similar karstic systems. This highlights the importance of understanding the context, organization and development of the initial karst system when characterizing paleokarst reservoirs. Mapping of sediment thickness is not usually carried out during cave surveys, which primarily focus on recording open cavities accessible to man. This implies that survey data concerning the shape and volume of cave systems and statistics compiled and derived from them should be handled with care when applied to paleokarst reservoir modelling.

Investigation of Diagonal Strut Actions in Masonry-Infilled Reinforced Concrete Frames

This study analytically investigated the behavior of reinforced concrete frames with masonry infills. For the analysis, VecTor2, a nonlinear finite element analysis program that implements the Modified Compression Field Theory and Disturbed Stress Field Model, was used. To account for the slip behavior at the mortar joints in the masonry element, the hyperbolic Mohr–Coulomb yield criterion, defined as a function of cohesion and friction angle, was used. The analysis results showed that the lateral resistance and failure mode of the infilled frames were significantly affected by the thickness of the masonry infill, cohesion on the mortar joint–brick interface, and poor mortar filling (or gap) on the masonry boundary under the beam. Diagonal strut actions developed along two or three load paths on the mortar infill, including the backstay actions near the tension column and push-down actions near the compression columns. Such backstay and push-down actions increased the axial and shear forces of columns, and ultimately affect the strength, ductility, and failure mode of the infilled frames.

2.5D Crustal Models Derived from Analytical Polynomial Separation Technique and Spectral Analysis of Gravity Data with Their Probable Gold Mineralization Migrations (Batouri, SE-Cameroon)

Geophysical surveying is crucial in the investigation of mineral resources in poorly exposed areas such as SE-Cameroon, a region known for its gold mineral potential. In this paper, gravity survey is carried out in the Batouri area, SE-Cameroon based on land gravity data from the Centre-south Cameroon. Therefore, an analytical polynomial separation program, based on least-square fitting of a third-degree polynomial surface to the Bouguer anomaly map, was used to separate the regional/residual components in gravity data. This technique permitted to better understand the disposition of the deep and near surface structures responsible of the observed anomalies in the Batouri area. Spectral analysis and 2.5D modelling of two profiles P1 (SW-NE) and P2 (N-S) selected from the residual anomaly map provided depths to basement. These depths constrain the gravity models along the profiles, indicating a variable thickness of the sedimentary infill with an approximate anomaly of -33 mGal. The 2.5D model of the basement shows a gravity body, with a signature suggesting two close and similar masses, which characterize the quartz-bearing formations associated here to granite and gneiss. Our work highlights a main heavy gravity: Gwe-Batouri anomaly, containing the major part of auriferous deposits located along the NE-SW direction. Further, three tectonic sub-basins bounded by normal faults have been highlighted at Guedal, Gwe, and Belimban, in the south of Guedal-Belimban depression. They are associated with the extension tectonics, more or less vertical tangential cuts and accidents that have affected the region. A correlation with previous results from tectonic, lithological and gold mineralization activities proves the relevance of the study and the need to intensify geophysical surveying in the area.

Effect of 3D printing process parameters on the impact strength of onyx – Glass fiber reinforced composites

Fused deposition modeling (FDM) is among the broadly used additive manufacturing methods to fabricate quality items with affordable advanced geometries with effective delivery and manufacturing logistics. Physical properties could be raised by checking out numerous FDM parameters as well as utilizing brand new substances through this method. Glass fiber is typical to support used in composites for applications needing effect resistance. This study examines the impact effect of onyx glass fiber 3D printed composites. In this analysis important methodological parameters were considered: layer layouts/ patterns (triangular, rectangular and hexagonal) and also infilled density (30, 40 and 50%) has thought about to check out right into their results on mechanical behaviors of 3D-printed onyx-glass fiber-reinforced composite samples, utilizing a premium 3D printing machine. The 3D printer used was a Mark forge's Mark X7 dual nozzle material extrusion machine. The impact test had carried out under ASTM guidelines. The obtained results showed that the impact strengths of onyx fiber composites were analyzed. From the outcomes gotten, it has observed that far better high qualities had accomplished with an enhanced infill thickness. Also, hexagonal-shaped style showed an optimum or maximum energy absorption when compared to various other equivalents. The findings had statistically evaluated to assess the relevant variables and their interactions.

Mechanical Behaviour of Polylactic Acid Parts Fabricated via Material Extrusion Process: A Taguchi-Grey Relational Analysis Approach

The acceptance and application of functional parts produced via additive manufacturing technologies is faced with challenges of poor surface finish, dimensional accuracy and mechanical properties among other which is mostly dependent on process parameters employed. In this study, the effect of infill density, layer thickness and extrusion temperature on mechanical properties of polylactic acid (PLA) part manufactured using fused deposition modelling process was investigated to obtain optimum process parameters to achieve the best properties. Solid cuboid bars were produced from which tensile, impact and hardness test specimens were obtained. A statistical approach based on Taguchi design of experiment was employed with process parameters varied and grey relational analysis coupled with principal component analysis was employed to obtain the unified optimum parameter. The single optimisation results showed that 50% infill density, 220°C extrusion temperature and 0.4 mm layer thickness resulted in best tensile strength; 30% density, 210°C temperature and 0.2 mm layer thickness is required to achieve the best impact strength, while 50% density, 215°C temperature and 0.3 mm thickness is required for highest hardness. The multi-response optimisation indicated that for the best of all the three properties to be achieved at once in a PLA built part, 50% infill density, 220°C extrusion temperature and 0.3 mm is required which yielded tensile strength of 30.02±2.15 MPa, impact strength 4.20±0.12 J and hardness of 76.80±0.38 BHN.

Geophysical methods for mapping Quaternary sediment thickness: Application to the Saint-Lary basin (French Pyrenees)

This study aims at mapping the sediment infill thickness in the Saint-Lary basin (Aure valley, French Pyrenees). For this purpose, we combine passive seismic and gravity surveys. The resonance frequencies of the sediment body are retrieved from seismic ambient measurements, while the gravimetric survey shows negative residual anomaly of about −3 mGal in the basin. Both methods reveal unexpected but consistent bedrock shape. The southern Saint-Lary basin appears deeper than its northern part, with maximal infill thickness of about 300 m and 150 m, respectively. Valley cross sections show regular and smooth “U”-shape in the southern Saint-Lary basin, in contrast to an irregular and asymmetric pattern in the northern basin. This basin shape may be related to Quaternary fluvio-glacial carving processes especially controlled by a regional fault (the Soulan fault), variations in bedrock hardness, and preferential ice flow paths.

Paraglacial adjustment of alluvial fans to the last deglaciation in the Snežnik Mountain, Dinaric karst (Slovenia)

Glaciokarst depressions are major glacigenic depocenters in the Dinaric mountain karst areas and often store important information about the timing and nature of glacial processes and paraglacial sediment reworking. This study focuses on Praprotna draga, which is one of the largest glaciokarst depressions in the Snežnik Mountain (Dinaric karst), with an area of ~3.4 km2 and a maximum depth of 140 m. The western slopes of the depression are characterized by undulated moraine morphology and alluvial fans are filling its entire floor. We present the results on the thickness, origin and age of the sediment infill using a complementary geomorphological, sedimentological, geophysical and dating approach. Distribution of moraines point to two glacial advances that were associated with two main alluvial fan aggradation phases recognized using the electrical resistivity tomography measurements. The youngest alluvial deposits were sampled for cosmogenic 36Cl analysis using amalgamated carbonate pebbles. The depth profile of 36Cl concentrations suggests an age of 12.3 ± 1.7 ka when assuming a likely denudation rate of 20 mm ka−1. Since the existence of the Younger Dryas glaciers in the study area is climatically difficult to explain, we tentatively propose that the youngest alluvial deposition in Praprotna draga took place after the glacier retreat during the paraglacial period. Our findings suggest that the time window of paraglacial adjustment in the Snežnik Mountain was brief and likely conditioned by quick recolonization with vegetation and inefficient surface runoff on deglaciated karst terrain.

Cyclic behaviour of infilled steel frames with different beam-to-column connection types

Although numerous researchers demonstrated the significant difference in performance between the various beam-to-column connection types, most of the previous studies in the area of infilled steel frames focused on the behaviour of frames with welded connections. Therefore, there is a need for conducting studies on infilled steel frames with other common connection types (extended endplate with and without rib stiffeners, flush endplate and shear connections). In this paper, firstly, a two-dimensional finite-element model simulating the cyclic response of infilled steel frames was presented. The infill-frame interaction, as well as the interactions between connections' components, were properly modelled. Using the previously-validated model, a parametric study on infilled steel frames with five different beam-to-column connection types, under cyclic loading, was carried out. Several parameters, including infill material, fracture energy of masonry and infill thickness, were investigated. The results showed that the infilled frames with welded connections had the highest initial stiffness and load-carrying capacity. However, the infilled frames with extended endplate connections (without rib stiffeners) showed the greatest energy dissipation capacity and about 96% of the load-carrying capacity of frames with welded connections which indicates that this type of connection could have the best performance among the studied connection types. Finally, a simplified analytical model for estimating the stiffness and strength of infilled steel frames (with different beam-to-column connection types) subjected to lateral cyclic loading, was suggested.

Geometry and Structure of a Fault‐Bounded Extensional Basin by Integrating Geophysical Surveys and Seismic Anisotropy Across the 30 October 2016 Mw 6.5 Earthquake Fault (Central Italy): The Pian Grande di Castelluccio Basin

AbstractThe Pian Grande di Castelluccio (PGC) basin is the main Quaternary depocenter of the Mt. Vettore‐Mt. Bove normal fault system (VBFS), responsible for the 30 October 2016 Mw 6.5 Norcia earthquake (central Italy). Coseismic surface faulting through the basin attests the occurrence of active splays of the seismogenic master fault; thus, we explore the subsurface basin structure to infer the long‐term behavior of the VBFS. We integrate electrical resistivity tomography (ERT), time domain electromagnetic soundings (TDEM), and horizontal‐to‐vertical spectral ratios of ambient seismic vibrations (HVSR) along a transect crossing the surface ruptures. The ERT models provide high‐resolution details of three shallow fault zones. One‐dimensional resistivity models from TDEM and HVSR frequency peaks suggest abrupt steps in the top bedrock caused by previously unknown faults and indicate an infill thickness of up to ~300 m. We also analyze shear wave splitting of S phases (fast direction φ and delay time δt) from local earthquakes recorded during our surveys to better constrain the fracture field and the properties of the inferred fault zones. We relate the retrieved pattern of fault‐parallel φ, and the associated larger δt, to the main and secondary faults in the upper crust and to the cracks or shear fabric in the damage zones of the active splays. The PGC basin is due to the interference of an older N30° striking fault system subsequently crosscut by the N150° striking VBFS, which is currently active, seismogenic, and capable of rupturing the surface during M > 6 earthquakes.