Slip Variation Research Articles

Digital Image Correlation-Based Investigation of the Shear Performance of Connection Systems of Assembled Bamboo Scrimber-Lightweight Concrete Composite Beams.

To investigate the shear performance of assembled bamboo scrimber (BS)-lightweight concrete (LC) connection systems, three groups of nine BS-LC shear connections were fabricated in this work using BS, LC, dowels, and grout. The experimental parameters included the dowel diameter and fabrication process (cast-in-place vs. assembly). Push-out tests were conducted on the specimens, and traditional linear variable displacement transducer (LVDT) measurements and the advanced digital image correlation (DIC) technique were employed to determine performance indicators such as the cross-section slip of composite members. Subsequently, the method for calculating the shear capacity of assembled BS-LC connection systems was theoretically analyzed. The research results showed that the load-slip curves measured by DIC were highly correlated with those measured by LVDT, thus, validating the reliability of the DIC data. According to the DIC data, the variations in slip of the shear connection over the interface height were further analyzed. An equation for calculating the shear capacity of dowel shear connectors was proposed based on theoretical analysis with comprehensive consideration of the experimental indicators such as the failure mode, load-slip curve, shear stiffness, and shear capacity of the specimens. The theoretical calculation values were in good agreement with the experimental results.

Acoustic Emission Monitoring of Bond Deterioration in GFRP-Reinforced Concrete Members: An Entropy-Based Approach

The primary objective of acoustic emission (AE) monitoring is to accurately detect imminent critical damage, preventing premature failure by analysing the dynamic evolution of AE parameters. This study introduces AE entropy, a distinctive parameter derived from Shannon's entropy, employed to monitor the bond degradation between glass fibre-reinforced polymer (GFRP) rebars and the concrete interface in GFRP-reinforced concrete elements. Characteristic AE parameters have been synchronously collected during flexural bond tests, and information entropy and weighted information entropy, composed of typical AE characteristic parameters based on Shannon’s information entropy theory in the time domain, have been defined. Findings indicate that, with increasing bond stress, the specimens exhibit a trend characterized by "decreasing, stabilizing, and then increasing" in both AE characteristic parameters and weighted information entropy. The information entropy value shows fluctuations during any damage associated with GFRP-concrete bond deterioration. At peak bond stress values, information entropy values experience a rapid surge, indicating significant deterioration. The evolution process of debonding between GFRP rebar and concrete, switching between a chaotic state that develops randomly and an organized state that produces in order, follows specific laws (disordered–ordered–disordered), corresponding well to AE characteristic parameters weighted information entropy. Moreover, entropy values, both individual and weighted, when correlated with bond stress and slip variations in the test specimens, distinctly outline and predict various stress transfer mechanisms between the GFRP bar and concrete. In summary, this research underscores the utility of AE entropy as a valuable tool for damage monitoring in GFRP-reinforced structures. Its ability to capture microstructural deformations positions AE entropy as a promising candidate for improving critical damage identification and preventing premature failure

Comprehensive analysis of bond stress transfer mechanisms in glass fiber-reinforced polymer-reinforced concrete beams using acoustic emission monitoring

The present study investigates the critical bond characteristics between glass fiber-reinforced polymer (GFRP) bars, which is essential for the application bars as corrosion-resistant components in structural concrete. The interfacial bond deterioration and stress transfer mechanisms have been investigated in the present study by employing acoustic emission (AE) monitoring in hinged-type GFRP-reinforced concrete (GFRP-RC) beam specimens. The bond strength of the test specimens, governed by chemical adhesion, mechanical interlocking, and frictional resistance, has been intricately examined. Various AE signal parameters as well as historic and severity indices derived from the AE signal parameters have been meticulously evaluated and correlated with bond stress and rebar slip variations. The present study has also introduced an innovative approach of using the sentry function for the assessment of bond deterioration and associated mechanisms. The results of the present study demonstrate the reliability of AE parameters in monitoring debonding and bond strength variation, the effectiveness of the sentry function in evaluating damage progression, and the utility of historic and severity indices in capturing micro-mechanism transformations. The accurate localization of debonding and the qualitative distribution of bond stress have also been demonstrated by through correlations between cumulative AE parameters and rebar slip, Additionally, the present study also highlights the significance of peak frequency variations in AE signals, serving as a crucial tool for quantifying the mechanical interlocking and interfacial friction. The results contribute significantly to precise assessments and development of effective strategies for mitigating bond deterioration in GFRP-RC elements.

Influence of outer-rise faults on shallow décollement heterogeneity and sediment flux at the Japan trench

We investigate the impact of outer-rise normal fault subduction on the structural evolution of the décollement and frontal prism in a portion of the Japan trench that hosted the 2011 Tohoku earthquake. We use seismic reflection data to map the relative occurrence of sediment accretion, sediment subduction, and frontal tectonic erosion in the shallow portion of the subduction zone and correlate these deformation styles to the magnitude of outer-rise fault throw and incoming plate sediment thickness. These data reveal spatial heterogeneity in the modes of deformation over distances of 5-10 km that necessitate correlative heterogeneity in the geometry and composition of the shallow décollement over similar length-scales. We find that sediment accretion predominantly occurs in regions where incoming plate sediment thickness is greater than fault throw. In these areas, the décollement appears to be non-planar and compositionally homogenous. Conversely, frontal tectonic erosion and slope failures are predominantly observed in regions where fault throw is greater than sediment thickness. In these areas, the décollement may be planar but compositionally heterogeneous. Additionally, spatial variations in near trench slip appear to correlate with the dominant deformation modes, suggesting that both sediment thickness and outer-rise fault throw may be important controls on shallow megathrust behavior.

The behavior of Shear Connectors in Steel-Normal Concrete Composite Structure under Repeated Loads

In today's construction industry, the use of composite beams is becoming more and more important, particularly for long-span bridges that must withstand repeated loads from moving automobiles. This work investigates the behavior of composite beams through experimentation. Six push-out steel-concrete specimens are made and tested with various levels of static and repetitive loading applied. The specimens are made of rolled steel sections that are joined to concrete decks on both sides by stud shear connectors. Two approaches—one static and the other repeating—applied a push-out load to two sets of samples. One has a stud shear connector measuring 16 mm, and the other measures 25 mm. Three specimens were made for each group. To determine the final load, one specimen from each group underwent a static push-out test in the first stage. In the subsequent phase, repeated loads of 0-80% and 25-80% of the maximum static load were applied to the remaining ones. The analysis process measured the variation in slip between the concrete decks and the steel section over several load cycles. It was found that the recorded slip values at the ultimate load increased about four times just before the failure. The recorded values of the residual slip at the end of each load cycle decreased with the increase in load cycle numbers. Also, it was found that the values of the residual slip depend on the values of the lower and upper limits of the load level. Doi: 10.28991/CEJ-2024-010-01-013 Full Text: PDF

Wedge plasticity and a minimalist dynamic rupture model for the 2011 MW 9.1 Tohoku-Oki earthquake and tsunami

One crucial yet unanswered question about the 2011 MW 9.1 Tohoku-Oki earthquake and tsunami is what generated the largest tsunami (up to 40 m) along the Sanriku coast north of 39°N without large slip near the trench. A minimalist dynamic rupture model with wedge plasticity is presented to address this issue. The model incorporates the important variation of sediment thickness along the Japan Trench into the Japan Integrated Velocity Structure Model (JIVSM). By revising a heterogeneous stress drop model, the dynamic rupture model with a standard rate-and-state friction law can explain the GPS, tsunami, and differential bathymetry data (within data uncertainties) with minimum tuning. The rupture is driven by a large patch of stress drop up to ∼10 MPa near the hypocenter with significantly smaller stress drop (< 3 MPa) in the upper ∼10 km. The largest shallow slip reaches 75.67 m close to the trench north of hypocenter, which is caused by the large fault width, free surface, shallowly dipping fault geometry, and northwardly increasing sediment thickness, dominated by elastic off-fault response. North of large shallow slip zone, however, inelastic deformation of thick wedge sediments significantly controls the rupture propagation along trench, giving rise to slow rupture velocity (∼850 m/s), diminishing shallow slip, and efficient seafloor uplift. The short-wavelength inelastic uplift produces impulsive tsunami consistent with the observations off the Sanriku coast in terms of timing, amplitude, and pulse width. Wedge plasticity and variation of sediment thickness along the Japan Trench thus provides a self-consistent interpretation to the along-strike variation of near-trench slip and anomalous tsunami generation in the northern Japan Trench in this earthquake.

Stress and strain evolution in fault-related folds: insights from 2D geomechanical modelling

Fault-related folds are intriguing geological structures that develop in compressional and extensional regimes. These folds serve as structural traps for hydrocarbon resources, making their numerical models crucial for understanding the stress and strain evolution of hydrocarbon reservoirs. In our research, we utilize the two-dimensional finite element technique to simulate three representative categories of fault-related folds. Our investigation encompasses their geometric transformation over time, the distribution of stress and strain, variations in slip and uplift, and the effects that various mechanical properties have on these gradients. In our study, we uncovered essential findings about the behavior of fault-related folds. We ascertained that the fault slip gradient in the fault-bend fold model is less than in the fault-propagation fold model. Regarding the uplift gradient, the fault-propagation and fault-bend fold models displayed the greatest and the least degree of change, respectively. The trend of stress-strain evolution on the fold surface in all models was consistent, starting with an increase, transitioning to a constant phase, and ending with a decrease. This pattern proved to be more intricate and divergent than what was evident on the fault surface. Importantly, the internal friction angle, a crucial mechanical characteristic, had a significant influence on the development of these structures. This angle affected both the degree of uplift and stress; an increased angle resulted in enhanced uplift and stress, while a decrease resulted in a decline. Furthermore, the internal friction angle determined the compactness of the fold and the thickness of the forelimb, the part of the fold that inclines towards the advancing direction. These findings have enriched our knowledge of fault-related folds, highlighting the need to consider mechanical properties when studying their formation and evolution.

The 2021 Mw 5.2 Baicheng Earthquake: Implications for the Hazards of Extremely Shallow Earthquakes

Abstract On 23 March 2021, an Mw 5.2 earthquake struck Baicheng city at the southern foreland of the Tian Shan mountains and produced unexpected severe damages. Based on Interferometric Synthetic Aperture Radar observations, geological investigations, petroleum seismic-reflection profiles, and available seismological results, we found that (1) the earthquake rupture was sinistral-slip dominated and mostly concentrated at ≤2 km depth, suggesting an extremely shallow earthquake; (2) the earthquake produced a 4.1-km-long surface rupture zone, along which the lateral slip ranged from 0 to 135 cm and showed a significant short-wavelength variation; and (3) the causative fault is poorly developed (i.e., has low slip accumulation and slip rate) and cuts through a shallow-buried salt dome. These findings, along with those of previous studies, document some unique characteristics of moderate earthquakes at extremely shallow depths (≤3 km) relative to those at greater depths. First, shallow earthquakes occur on faults that are poorly developed and bracketed by rocks being able to behave as velocity weakening at shallow depth (including crystalline basement rocks, carbonites, volcanic rocks, or evaporites). Second, the surface rupture produced by shallow earthquakes has abnormally large length and slip, and possibly includes an abrupt slip variation. These characteristics highlight potential severe damages of the shallow moderate earthquake but enhance the challenge of identifying the earthquake causative fault (the earthquake source) prior to the event using traditional methods (e.g., geomorphic mapping, geophysical imaging surveys, and paleoseismic trenching).

Preparatory Slip in Laboratory Faults: Effects of Roughness and Load Point Velocity

AbstractAseismic slip may occur during a long preparatory phase preceding earthquakes, and what controls it remains poorly understood. In this study, we explored the role of load point velocity and surface roughness on slow slip during the preparatory stage prior to stick‐slip events. To that end, we conducted displacement‐rate controlled friction experiments by imposing varying load point velocities on sawcut granite samples with different surface roughness at a confining pressure of 35 MPa. We measured the average slip along the fault with the recorded far‐field displacements and strain changes, while acoustic emission sensors and local strain gages were used to capture local slip variations. We found that the average amount of aseismic slip during the preparatory stage increases with roughness, whereas precursory slip duration decreases with increased load point velocity. These results reveal a complex slip pattern on rough faults which leads to dynamic ruptures at high load point velocities.

Coseismic and post-seismic characteristics of the 2021 Ganaveh earthquake along the Zagros foredeep fault based on InSAR data

SUMMARY The Ganaveh earthquake on 2021 April 18 (Mw 5.8) occurred in the southwest of the Dezful embayment of the Zagros Mountain belt, Iran, as a mainly compressive event. The InSAR coseismic displacement maps reveal a maximum of 17 cm of surface displacement in the satellite line of sight direction. InSAR inversion indicates a low-angle NE-dipping causative fault plane with a maximum slip of 95 cm at ∼6 km depth. It highlights the occurrence of the Ganaveh earthquake within the competent layers of the Zagros sedimentary cover, beneath the Gachsaran formation. A slight sinistral slip component (2.9 cm) is retrieved which is compatible with the USGS focal mechanism. Time-series analysis of SAR images after the main shock until the end of 2021 indicates a maximum of 7 cm of post-seismic surface displacement with a similar strike and pattern as the coseismic phase. This similarity and the distribution of aftershocks suggest an afterslip mechanism for the post-seismic phase. The inversion of post-seismic cumulative displacement evaluates a maximum of 30 cm slip at a depth of ∼5 km along the coseismic causative fault. A regional compressional stress regime (N041°E for the direction of the σ1 stress axis) is constrained by using the focal mechanisms of 39 earthquakes occurring between 1968 and 2021, including the Ganaveh main shock and its five larger aftershocks. Applying this direction of compression on the Ganaveh fault plane also results in a minor sinistral movement, consistent with the geodetic results. The relocated main shock and aftershocks as well as our InSAR coseismic displacement situations on the hanging wall of the Zagros Foredeep fault highlight it as the causative fault of the Ganaveh earthquake. To fit the geometry of the Ganaveh rupture plane with the Zagros Foredeep fault, we modelled a listric fault plane and its slip distribution using the available geological data. The retrieved slip variation on the listric plane is in close agreement with the slip pattern on the modelled planar geometry. The low dip angle of the rupture plane combined with a listric geometry highlights the thin-skin characteristics of the Zagros Foredeep fault as the causative fault of the Ganaveh earthquake. The occurrence of this moderate magnitude earthquake on the Zagros Foredeep fault underlines its role as the western structural boundary for the recurrence of Mb &amp;gt; 5 events in the Dezful embayment.

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest Mw 7.1 Mainshock

AbstractThe variation of stress on faults is important for our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we use a new geodetic imaging technique to measure the 3D coseismic slip vectors along the 2019 Ridgecrest surface ruptures and invert them for the coseismic stress state. We find that the coseismic stresses show an eastward rotation that becomes increasingly transtensional from south‐to‐north along the rupture, that matches the known background stress state. We find that the main fault near the Mw 7.1 mainshock hypocenter was critically stressed. Coseismic slip was maximum there and decreased gradually along strike as the fault became less optimally oriented due its curved geometry. The variations of slip and stress along the curved faults are used to infer the static and dynamic fault friction assuming Mohr‐Coulomb failure. We find shear stresses of 4–9 MPa in the shallow crust (∼1.3 km depth) and that fault friction drops from a static, Byerlee‐type, value of 0.61 0.14 to a dynamic value of 0.29 0.04 during seismic slip. These values explain quantitatively the slip variations along a transpressional fault bend.

Cyclic Fault Slip Under the Magnifier: Co‐ and Postseismic Response of the Pamir Front to the 2015 Mw7.2 Sarez, Central Pamir, Earthquake

AbstractThe constant increase of geodetic instrumentation over the past decades enables us to not only detect ever smaller tectonic signals but also to monitor their evolution in time and space. We present spatial and temporal slip variations observed on a fault affected by a large, intermediate‐field earthquake: the 2015 Mw7.2 Sarez, Central Pamir, earthquake ruptured the sinistral, NE‐trending Sarez‐Karakul fault system. 120–170 km North of the main rupture, the thin‐skinned, E‐trending Pamir thrust system bounding the Pamir to the North was co‐seismically activated. We derived co‐seismic offsets and post‐seismic rates observed by two dense, high‐rate Global Positioning System (GPS) profiles crossing the Pamir thrust system at different longitudes. The continuous GPS observations of the western profile focus on the dextral, NW‐striking Aramkungey fault segment that connects two thrust faults with opposite dip. We compare inter‐, co‐ and post‐seismic displacement rates by complementing the continuous data with survey‐mode GPS data and East rates derived from satellite radar interferometric displacement time‐series. All the GPS stations were shifted toward the epicenter against the direction of the interseismic load with an increased gradient in the Aramkungey fault segment. During the postseismic stage, the fault‐parallel and fault‐perpendicular rates were affected differently, suggesting gradual re‐locking of the Aramkungey fault after its unlocking by right‐lateral co‐seismic slip.

Estimation Method of Relative Slip in Fretting Fatigue Contact by Digital Image Correlation

An experimental method that can quantify relative slip was developed using digital image correlation (DIC) in order to evaluate the sliding portion. The bridge-type test setup was designed to establish the fretting contact condition. The relative displacements between the contact surfaces were determined by DIC methods. Based on the evolution and distribution of relative slip, the transitions from gross slip to partial slip on the contact surface were found throughout all tests. This result indicated that the fretting scar was closely correlated to relative slip. The variation of relative slip corresponding to the stick-slip state was consistent with the tangential force coefficient. Besides, the load amplitude was an important factor for fretting fatigue damage, which can affect the stick-slip state.

Modelling of Off-Road Truck Tire-Rim Slip Using Finite Element Analysis

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Slip or relative rotation between the tire and rim is a significant concern for vehicle operation and wheel manufacturing since it leads to wheel imbalance and vibration as well as power losses. A slip situation typically occurs due to improper bead lubrication and mounting, irregularities in the bead seat, and extreme loading conditions with high torques and low tire pressures. Currently, there are relatively few published studies on the tire-rim interface, and they mainly focus on topics such as the mounting process, load transfer, and friction modelling. This leaves a gap to explore the measurement and variation of gross tire-rim slip under the dynamic conditions of a driven tire. In this paper, a previously developed and validated FEA truck tire model was modified to include a frictional contact surface between the tire and rim, and then the slip ratio between the tire and rim was measured under different operating conditions. The new model’s static behavior was compared to the previously validated model with the fixed tire-rim connection, then the model parameters such as vertical load, inflation pressure, drawbar load, longitudinal wheel speed, and tire-rim friction were varied and their effects on the tire-rim slip of the driven truck tire were investigated. It was discovered that factors affecting the torque transmitted through the wheel, including the tire-rim friction, vertical load, and inflation pressure, had the most significant effect, while the longitudinal wheel speed had a minimal effect on the tire-rim slip. The findings of this research work will be useful for determining the tire-rim slip under various operating conditions.&lt;/div&gt;&lt;/div&gt;

Effectiveness of Hybrid Fibers on the Fracture and Shear Behavior of Prestressed Concrete Beams

This study investigates the effectiveness of hybrid fibers (steel and macro-synthetic) on the shear behavior of prestressed concrete beams. The hybrid fiber combination was selected to avoid workability issues at high volume dosages and ensure effective crack arresting over the crack opening range. Fracture studies included testing notched concrete prisms to identify the role of hybrid fibers in the crack bridging mechanism. Seven hybrid fiber reinforced prestressed concrete (HFRPC) beams were tested at a low shear span (a) to depth (d) ratio of 2.4. The effects of hybrid fibers on load–deflection behavior and strain in the strand are reported. Similarly, the crack opening, crack slip and crack angle variation regarding applied shear were investigated using the digital image correlation (DIC) technique. Test results of HFRPC beams showed considerable improvements in peak load and the post-peak response with a higher hybrid fiber dosage. The crack opening and crack slip measurement across the major shear crack revealed continuous dilatant behavior. The kinematic response of critical shear crack reflects the sustained dilation response up to the ultimate load, which depends on the critical shear crack angle of the tested beams. As the fiber dosage increases, the shear crack slip and width are reduced, indicating the roles of hybrid fibers in improving ductility and the change in failure mode from brittle shear tension to relatively ductile shear tension.

Resolving co- and early post-seismic slip variations of the 2021 MW 7.4 Maduo earthquake in east Bayan Har block with a block-wide distributed deformation mode from satellite synthetic aperture radar data

On 21 May 2021 (UTC), an <i>M</i>_W 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau. The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake, and especially in proximity to the seismic gaps on the east Kunlun fault. Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake. Range offset displacements depict clear surface ruptures with a total length of ~170 km involving two possible activated fault segments in the earthquake. Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust. The well-resolved slip variations are characterized by five major slip patches along strike and 64% of shallow slip deficit, suggesting a young seismogenic structure. Spatial–temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations, and are well explained by time-dependent afterslip models. Analysis of Global Navigation Satellite System (GNSS) velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block, but exhibits significant lateral heterogeneities, as evidenced by magnetotelluric observations. The block-wide distributed deformation of the east Bayan Har block along with the significant co- and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults, especially the Tuosuo Lake and Maqên–Maqu segments of the Kunlun fault that are known as seismic gaps.

Slab metamorphism and interface earthquakes in Peru: Implications from three-dimensional hydrothermal variation in the subducted Nazca plate

Convergent plate dehydration is of significance in determining the coupling strength and seismicity activity at variable subduction contacts. Characterized by decadal M > 7.5 devastating earthquakes offshore and a lack of a magmatic arc in north-central Peru, the Peruvian megathrust remains enigmatic in terms of the along-strike heterogeneity of the thermal regime, slab dehydration, and seismotectonics. Hydrothermally controlled petrological metamorphism of multiple facies within the subducted oceanic lithosphere and subsequent fluid channeling and migration lead to fault instability and seismic and aseismic slips on the megathrusts. Based on 3D thermal modeling, we estimate the features of the Peruvian subduction hydrothermal regime. Our results show that (1) the shallow seismogenic zone (M > 7.5 earthquakes) along coastal Peru exhibits high slab dehydration rates and gradients and is associated with fault segmentation and the updip migration of fluids controlling the occurrence of great megathrust earthquakes; (2) the low slab dehydration rate (<0.01 wt%/km) in north Peru contributes to the absent volcanism in north Peru, while the high slab dehydration rate (>0.02 wt%/km) beneath south Peru facilitate the recurrence of magmatic volcanism; (3) the subduction-related slip behaviors at a certain depth resulting from heterogeneous variations in the coupled plate interface are determined by slab dehydration and petrological metamorphism in the subducted Nazca plate. The variation in slab dehydration contributes to the seismotectonic segmentation and slip variation associated with changes in the pore fluid pressure on the subducted megathrust.

Insights on fault reactivation during the 2019 November 11, Mw 4.9 Le Teil earthquake in southeastern France, from a joint 3-D geological model and InSAR time-series analysis

SUMMARY The 2019, Mw 4.9 Le Teil earthquake occurred in southeastern France, causing substantial damage in this slow deforming region. Field observations, remote sensing and seismological studies following the event revealed that coseismic slip concentrates at shallow depth along a ∼5 km long rupture associated with surface breaks and a thrusting mechanism. We further investigate this earthquake by combining geological field mapping, 3-D geology, InSAR time-series analysis and a coseismic slip inversion. From structural, stratigraphic and geological data collected around the epicentre, we first produce a 3-D geological model of the region surrounding the rupture using the GeoModeller software. Our model includes the geometry of the geological layers and the main faults, including the La Rouvière Fault, (LRF) the Oligocene normal fault that ruptured during the earthquake. We generate a time-series of surface displacement from Sentinel-1 SAR data ranging from early 2019 January to late 2020 January using the NSBAS processing chain. The spatio-temporal patterns of surface displacement for this time span show neither a clear pre-seismic signal nor significant post-seismic transient deformation. We extract the coseismic displacement pattern from the InSAR time-series, highlighting along-strike variations of coseismic surface slip. The maximum relative displacement along the line of sight is up to ∼16 cm and is located in the southwestern part of the rupture. We invert for the slip distribution on the fault from the InSAR coseismic surface displacement field. Constraining our fault geometry from the geological model, acceptable fault dip ranges between 55° and 60°. Our model confirms the reactivation of LRF, with reverse slip at very shallow depth and two main slip patches reaching, respectively, 30 and 24 cm of slip, both around 500 m depth. We finally discuss how the 3-D fault geometry and geological structure may have impacted the slip distribution and propagation during the earthquake. This study is a step to reassess the seismic hazard of the many faults similar to the La Rouvière one along the Cévennes fault system, in a densely populated area hosting several sensitive nuclear sites.

Spatial Variations of Slip and Creep Rates Along the Southern and Central Dead Sea Fault and the Carmel–Gilboa Fault System

AbstractCrustal deformation and seismic activity in the Levant is mainly related to the interplate Dead Sea Fault (DSF) and the intraplate Carmel–Gilboa Fault System (CGFS). In this study, we analyze the interseismic deformation along these fault systems using 23 years of Global Positioning System (GPS) measurements obtained from 209 campaign and 60 continuous stations. This GPS data set is the longest record and the densest data set for the DSF, the CGFS, and the Levant region. We use this data set to investigate the spatial variations of slip and creep rates along the southern and central sections of the DSF and the CGFS. Our inversion model results indicate that part of the tectonic motion is transferred from the DSF to the CGFS. We find that the left‐lateral strike‐slip motion along the DSF decreases in a rate of 0.9 ± 0.4 mm/year, from 4.8 ± 0.3 mm/year south to the intersection with the CGFS to 3.9 ± 0.4 mm/year north to this intersection. Along the CGFS, the left‐lateral strike‐slip motion ranges between ∼0.3 and 0.5 mm/year and the extension rate between ∼0.6 and 0.7 mm/year, indicating a total slip rate vector of 0.8 ± 0.4 mm/year in the DSF direction, in agreement with the reduction of slip rate along the DSF near the intersection with the CGFS. Shallow creep is found along the southern and central sections of the Dead Sea basin and the northern Jordan Valley section of the DSF, with creep rates of 3.4 ± 0.4 and 2.3 ± 0.4 mm/year, respectively. These creeping sections were identified as areas with thick Halite layers at the shallow subsurface. We suggest that shallow creep behavior along the DSF is govern by the presence and mechanical properties of the Halite, which probably allows plastic deformation and the transition to velocity strengthening at the shallow subsurface and promotes creep.

Diffuse Deformation and Surface Faulting Distribution from Submetric Image Correlation along the 2019 Ridgecrest, California, Ruptures

ABSTRACT The 2019 Mw 6.4 and 7.1 Ridgecrest, California, earthquake sequence (July 2019) ruptured consecutively a system of high-angle strike-slip cross faults (northeast- and northwest-trending) within 34 hr. The complex rupture mechanism was illuminated by seismological and geodetic data, bringing forward the issue of the interdependency of the two fault systems both at depth and at the surface, and of its effect on the final surface displacement pattern. Here, we use high-resolution (WorldView and Pleiades) optical satellite image correlation to measure the near-fault horizontal and vertical surface displacement fields at 0.5 m ground resolution for the two earthquakes. We point out significant differences with previous geodetic- and geologic-based measurements, and document the essential role of distributed faulting and diffuse deformation in producing the observed surface displacement patterns. We derive strain fields from the horizontal displacement maps, and highlight the predominant role of rotation and shear strain in the surface rupture process. We discuss the segmentation of the rupture based on the fault geometry and along-strike slip variations. We also image several northeast-trending faults with similar orientation to the deeply embedded shear fabric identified in aftershock studies, and show that these cross faults are present all along the rupture, including at a scale &amp;lt;100 m. Finally, we compare our results to kinematic slip inversions, and show that the surface diffuse deformation is primarily associated with areas of shallow slip deficit; however, this diffuse deformation cannot be explained using elastic modeling. We conclude that inelastic processes play an important role in contributing to the total surface deformation associated with the 2019 Ridgecrest sequence.