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Successive 2‐km‐wide swath cross‐sections along the shear direction for increasing shear deformation at the base of the DEM model. Each dot indicates an induced crack colored according to its depth. Step 65 shows nucleation of crack clusters near the layer surface, which later expand downward to form Riedel shears. Sketches to the right illustrate time evolution of cracking within the brittle layer: (1) initiating from the base and propagating upward, (2) propagation both from top and base of crack fronts, and (3) formation of Riedel shears. L indicates the segment length.
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Geologic faults, including strike‐slip faults, are not continuous smooth structures. Detailed fault mapping and earthquake rupture traces show that they are rather formed by discontinuous segments bounded by jogs and bends. The structure of faults impacts the way a rupture propagates during an earthquake, and eventually where...
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... An increment in the interparticle friction also drastically increases the orientation angle of the main -bands from the beginning of the simulation and until steady-state, ( ≈ 6 • for num = 0.1 and ≈ 16 • for num = 0.6 ), Figures 4b and 5. Increasing num also increases the number of -bands formed during shearing, resulting in a reduced average distance between two successive bands. These results are consistent with Lefevre et al. (2020) and Jiao et al. (2021) who reproduced sandboxes with different widths and found a link between the internal friction angle and the distance between -bands. ...
Fault zones are usually composed of a granular gouge, coming from the wear material of previous slips, which contributes to friction stability. When considering a mature enough fault zone that has already been sheared, different types of infill materials can be observed, from mineral cementation to matrix particles that can fill the remaining pore spaces between clasts and change the rheological and frictional behaviors of the gouge. We aim to understand and reproduce the influence of grain‐scale characteristics on slip mechanisms and gouge rheology (Riedel bands) by employing the discrete element method. A 2D‐direct shear model is considered with a dense assembly of small polygonal cells of matrix particles. A variation of gouge characteristics such as interparticle friction, gouge shear modulus or the number of particles within the gouge thickness leads to different Riedel shear band formation and orientation that has been identified as an indicator of a change in slip stability. Interpreting results with slip weakening theory, our simulated gouge materials with high interparticle friction or a high bulk shear modulus, increase the possible occurrence of dynamic slip instabilities (small nucleation length and high breakdown energy). They may give rise to faster earthquake ruptures.
... Professor Haibing Li, based on some strong earthquake activities in the Qinghai-Tibet Plateau in the past 25 years, introduced the surface rupture zone caused by the earthquake (Pan et al., 2022a(Pan et al., , 2022b, and proposed that the geometric elements of the rupture, such as length, width and thickness, have certain regularity. Then the fault segmentation pattern in geometry was shown by means of numerical simulation (Jiao et al., 2021). Taking the 2014 Yutian earthquake and the 2022 Menyuan earthquake as typical cases, the relationship between aftershock sequence, focal mechanism, discrete element simulation and fault rupture was studied. ...
... Taking the 2014 Yutian earthquake and the 2022 Menyuan earthquake as typical cases, the relationship between aftershock sequence, focal mechanism, discrete element simulation and fault rupture was studied. The conclusions are as follows: (1) The numerical simulation results show that when the strong earthquake rupture extends from the deep source area to the near shallow surface, the surface echelon segmented shear fracture begins to develop and extend downward, and converges with the bottom spreading fracture to form a whole large-scale rupture zone ( Fig. 2) (Jiao et al., 2021). (2) The widthof the surface rupture zone of strike-slip strong earthquake is determined by the length of the echelon secondary fracture (Riedel shear fracture). ...
... Successive 2 km-wide swath cross-sections along the shear direction for increasing shear deformation at the base of the DEM model(Jiao et al., 2021). Each dot indicates an induced crack colored according to depth. ...
The second academic forum of the Committee on the Earthquake Hazard Chain, Seismological Society of China was held on 12 November 2022 in Beijing, China. The theme of this forum was theoretical research, technical application and popularization of science related to the earthquake hazard chain. It includes an opening ceremony and online lecture presentations. The work related to disaster prevention, mitigation, and relief for the earthquake hazard chain has been widely concerned. There are 49 speeches or lectures at the conference. The contents involve multiple stages and aspects of earthquake hazard chain, such as formation mechanism, database establishment, identification methods, risk assessment, monitoring and early warning, post-disaster rescue and reconstruction, and hazard prevention measures. This activity specially promotes the communication on the first few aspects. In future, the study on monitoring and early warning, emergency response and rescue, post-disaster reconstruction, and other related science and technology of earthquake hazard chain should be pay more attention.
... We thus try here to use Discrete Element Modeling (DEM) (e.g., Cundall & Strack, 1979), to explore whether that numerical approach (e.g., Jiao et al., 2018Jiao et al., , 2021Jiao et al., , 2022 can successfully generate the actual, observed, 3D Asian deformation, including great faults of all types, time-dependent step-by-step topographic uplift in different regions, and the large oceanic basins and rifts that formed around the southeastern corner of the continent since collision began (Jiao, 2016). The model results are then compared to observed fault geometries, ages, slip Tapponnier et al., 2001). ...
The Indian collision has deformed the eastern Asian continent in a multifaceted way, uplifting Tibet and surrounding mountains, activating ≥1,000 km‐long strike‐slip faults, and opening Tertiary rifts and oceanic basins up to ≈3,000 km away from the Himalayas. Modeling such broad‐scale tectonics has been challenging. While continent‐scale, lithospheric deformation appears to have been primarily taken‐up by long, narrow, inter‐connected shear‐zones with large offsets, the contribution of processes such as channel‐flow, collapse, delamination, etc… has remained contentious. Here, based on increasing ⁴G (Geological, Geophysical, Geochronological, Geodetic) evidence including kinematic and timing constraints on the main mechanisms at play, we use Discrete Element (DE) Modeling to simulate and further understand the evolution of 3D strain across east Asia since the onset of collision, ≈55 Ma ago. The planar, 50 million km², 125 km‐thick models are scaled for gravity. The approach permits mega‐fault generation and evolution without pre‐arranged initial settings. The results provide insight into fault birth, propagation and motion, as well as mountain building and plateau growth. They corroborate that continental crustal thickening across Tibet alternated with the extrusion of large blocks that rifted apart in the far field. Remarkably, without changes in boundary conditions or indentation rate, the DE model also vindicates slip reversal along initial strike‐slip shear zones.
... We describe the four major stages of the formation of a strike-slip fault zone in our experiments, that have already been thoroughly described in the literature (Tchalenko, 1970;Naylor et al., 1986;Hatem et al., 2017;Jiao et al., 2021). In order to illustrate the different stages of the fault zone formation, we carried out an experiment with grazing light and sedimented sand, which allows the structures to be clearly seen in the photos (E499bis, figure 4). ...
... Evolving faults intrinsically have variable amounts of slip, and hence maturity, along their length, being most mature near the middle of the fault length and least mature at the ends (e.g., ; no single measure of maturity is valid over the entire fault. Persistence of fault segmentation even for large cumulative displacements may reflect controls of crustal thickness and geological structures that compete with the tendency to progressively localize onto a single surface (e.g., Klinger, 2010;Jiao et al., 2021). Thus, maturation is not self-evidently linear with time or cumulative slip. ...
... Indeed, based on the geometrical analysis of the rupture trace (Klinger, 2010), it was shown that the length of the fault segments that ruptured during the 2013 Baluchistan event is ∼14 km (Lauer et al., 2020). This length is controlled by the width of the seismogenic zone (Jiao et al., 2021;Klinger, 2010;Lefevre et al., 2020), that is ∼15 km in kinematic slip inversions (maximum depth of the slip patch; Jolivet et al., 2014;Lauer et al., 2020). Hence, because C1 occurs only a few kilometers NE of C2, it cannot represent an inter-segment complexity. ...
Observations of recent earthquake surface ruptures show that ground deformations include a localized component occurring on faults, and an off‐fault component affecting the surrounding medium. This second component is also referred to as off‐fault deformation (OFD). The localized component generally occurs on complex networks of faults that connect at depth onto a unique fault plane, whereas OFD consists of distributed fracturing and diffuse deformation of the bulk volume, and occurs over scales of hundreds of meters to kilometers around the faults. High‐resolution optical image correlation presents a unique potential to characterize the complexity of the surface displacements, including on‐fault displacements and OFDs. In this study, we used sub‐pixel correlation of 0.5‐m resolution optical images to measure the surface displacement field with a <20 cm accuracy for a 30‐km long section of the 2013 Mw7.7 Baluchistan, Pakistan, rupture. Our results document significant variability in the fault displacements, associated with large proportions of OFD in regions of fault geometrical complexity. Conversely, in regions where the fault geometry is simple, surface deformation is entirely accommodated by the primary faults with 0% OFD. When combining the localized deformation on faults with the OFD, we show that the total surface displacement budget is constant along the strike of the rupture, despite strong variations observed in the rupture geometry. Based on this analysis, we propose an idealized scenario of earthquake surface deformation as a function of the rupture geometrical variations.
... Early in fault development, isolated fault segments may propagate and/or open, and with increasing displacement, the neighboring segments tend to link (Riedel, 1929). The distance between these segments depends on the thickness of the brittle portion of the crust (e.g., Jiao et al., 2021). Depending on the loading conditions and preexisting geometry of fault segments, the volume of crust between the tips of neighboring faults may develop contraction or extension (e.g., Cooke et al., 2013;Cunningham & Mann, 2007;Dooley & Schreurs, 2012;Lunn et al., 2008). ...
Accelerating geophysical activity is detected preceding some, but not all, large earthquakes. This observation may indicate that no precursors occur before some earthquakes, or that the instrumentation lacks the required sensitivity. To aid crustal monitoring efforts, we use discrete element method models to identify the locations and styles of deformation that may provide useful information about approaching fault reactivation. We model the reactivation of two healed rough faults in a variety of step over configurations, embedded in a host rock with varying amounts of damage subject to shear velocity loading parallel to the faults. Both the fault geometry and ratio of fault to host rock strength control the amount of off‐fault deformation. Consistent with field observations, models with larger steps and more preexisting host rock damage produce higher amounts of off‐fault deformation. We assess the size of the continuous regions of high velocities and strains to compare the value of the precursory information of each velocity and strain component. Comparing the three components of the velocity vector suggests that the fault‐parallel velocity produces the largest and most temporally continuous regions of elevated velocity. The size of these regions increases toward failure, indicating the usefulness of tracking this component. Comparing the volumetric and shear components of the three‐dimensional strain tensor suggests that during most of the interseismic period, the shear strain provides more information about approaching fault slip than the volumetric strain. However, in the days and months preceding fault reactivation, both the shear and volumetric strains provide similarly valuable information.
... It has been proposed that the principal parameter controlling the lateral extent of strike-slip fault segment would be the thickness of the brittle crust (Klinger, 2010). Analogue model experiments (Lefevre et al., 2020) as well as numerical models (Jiao et al., 2021) were used to test further this assumption and to demonstrate that a linear relation between the average lateral extent of fault structures and the thickness of the brittle material is observed for a wide range of thickness and that such relation seems to hold beyond only geomaterials (Cambonie et al., 2019). Thus, Chu et al. (2021) add to a set of independent observations that points to the existence of a permanent specific scaling of the strike slip fault segments consistent with the thickness of the crust (Figure 1), and likely independent of the fault maturity (Manighetti et al., 2021). ...
The geometry of continental fault systems, and more specifically the spatial organization of faults, is a central topic to understand how earthquake ruptures start, propagate, and stop. By exploring the origin of unexpected high frequency emission during earthquakes, Chu et al. (2021), (https://doi.org/10.1029/2021GL095271) show that the most likely source for these emissions is the interaction between nearby misaligned faults. Thus, this result emphasizes the discrete nature of the strike‐slip fault segments at seismogenic crustal scale, adding to a set of evidence for spatially structured fault systems drawn from independent observations in geophysics and geology. This observation should bring some new constrains to earthquake rupture scenario by limiting the range of possible ruptures included in these models.
... For instance, previous studies on Earth described a relation between the length of fault segments (deduced from rupture traces of large continental earthquakes) and the thickness of the brittle seismogenic layer (∼18 ± 5 km on Earth; Klinger, 2010). Using experimental and numerical models, Lefevre et al. (2020) and Jiao et al. (2021) have also, respectively, shown that the inter-Riedel distance (or assumed segment length) is dependent on the brittle material thickness. On Mars, thermal models of the Martian interior estimated before the InSight landing a seismogenic lithospheric thickness from 30 to 100 km (Plesa et al., 2018) to 40-150 km (Knapmeyer et al., 2006). ...
The NASA InSight mission to Mars successfully landed on 26 November 2018 in Elysium Planitia. It aims to characterize the seismic activity and aid in the understanding of the internal structure of Mars. We focus on the Cerberus Fossae region, a giant fracture network ∼1,200 km long situated east of the InSight landing site where M ∼3 marsquakes were detected during the past 2 years. It is formed of five main fossae located on the southeast of the Elysium Mons volcanic rise. We perform a detailed mapping of the entire system based on high‐resolution satellite images and Digital Elevation Models. The refined cartography reveals a range of morphologies associated with dike activity at depth. Width and throw measurements of the fossae are linearly correlated, suggesting a possible tectonic control on the shapes of the fossae. Widths and throws decrease toward the east, indicating the long‐term direction of propagation of the dike‐induced graben system. They also give insights into the geometry at depth and how the possible faults and fractures are rooted in the crust. The exceptional preservation of the fossae allows us to detect up to four scales of segmentation, each formed by a similar number of 3–4 segments/subsegments. This generic distribution is comparable to continental faults and fractures on Earth. We anticipate higher stress and potential marsquakes within intersegment zones and at graben tips.
... We describe the four major stages of the formation of a strike-slip fault zone in our experiments, that have already been thoroughly described in the literature (Tchalenko, 1970;Naylor et al., 1986;Hatem et al., 2017;Jiao et al., 2021). In order to illustrate the different stages of the fault zone formation, we carried out an experiment with grazing light and sedimented sand, which allows the structures to be clearly seen in the photos (E499bis, figure 4). ...
