Rupture Characteristics Research Articles

Simulated and Experimental Investigation of the Mechanical Properties and Solubility of 3D-Printed Capsules for Self-Healing Cement Composites.

In the concrete industry, various R&D efforts have been devoted to self-healing technology, which can maintain the long-term performance of concrete structures, which is important in terms of sustainable development. Cracks in cement composites occur and propagate because of various internal and external factors, reducing the composite’s stability. Interest in “self-healing” materials that can repair cracks has led researchers to embed self-healing capsules in cement composites. Overcoming the limitations of polymer capsules produced by chemical manufacturing methods, three-dimensional (3D) printing can produce capsules quickly and accurately and offers advantages such as high material strength, low cost, and the ability to fabricate capsules with complex geometries. We performed structural analysis simulations, experimentally evaluated the mechanical properties and solubility of poly(lactic acid) (PLA) capsules, and examined the effect of the capsule wall thickness and printing direction on cement composites embedded with these capsules. Thicker capsules withstood larger bursting loads, and the capsule rupture characteristics varied with the printing angle. Thus, the capsule design parameters must be optimized for different environments. Although the embedded capsules slightly reduced the compressive strength of the cement composites, the benefit of the encapsulated self-healing agent is expected to overcome this disadvantage.

Modern Powder Metallurgy: Chemical Composition Design for Improved Heat Resistant Alloys

The modern approach to the design of heat-resistant metal alloys (HRAs) is analyzed, according to which the creep rupture characteristics of an alloy are mostly determined by the strength of interatomic bonding at grain boundaries (GBs) and in the bulk of a matrix phase. The main attention is paid to the concept of “low alloying additions” to polycrystalline alloys with transition metals, because of which the cohesive strength of the GBs and the cohesion energy of the alloy matrix are increased. This approach is especially important in relation to alloys obtained by powder metallurgy, which, in the compacted state, are fine-grained polycrystals. The methodology for calculating the key parameters of the theory (the energy of impurity segregation to the grain boundaries Egb and to the free surface Efs, as well as the values of the partial molar energy of the cohesion of the alloys) from the first principles is given. The results of applying the theory to the study of Ni-, Cr- and Ti-based alloys and the development of new HRAs based on them are presented. Typical defects in the microstructures of objects obtained using additive technologies (AT) and the application efficiency of standard methods of processing powder alloys (Hot Isostatic Pressing (HIP), heat treatment (HT)) to improve the microstructure and increase the mechanical properties are considered.

Seismic and Geodetic Analysis of Rupture Characteristics of the 2020 Mw 6.5 Monte Cristo Range, Nevada, Earthquake

ABSTRACT The largest earthquake since 1954 to strike the state of Nevada, United States, ruptured on 15 May 2020 along the Monte Cristo range of west-central Nevada. The Mw 6.5 event involved predominantly left-lateral strike-slip faulting with minor normal components on three aligned east–west-trending faults that vary in strike by 23°. The kinematic rupture process is determined by joint inversion of Global Navigation Satellite Systems displacements, Interferometric Synthetic Aperture Radar (InSAR) data, regional strong motions, and teleseismic P and SH waves, with the three-fault geometry being constrained by InSAR surface deformation observations, surface ruptures, and relocated aftershock distributions. The average rupture velocity is 1.5 km/s, with a peak slip of ∼1.6 m and a ∼20 s rupture duration. The seismic moment is 6.9×1018 N·m. Complex surface deformation is observed near the fault junction, with a deep near-vertical fault and a southeast-dipping fault at shallow depth on the western segment, along which normal-faulting aftershocks are observed. There is a shallow slip deficit in the Nevada ruptures, probably due to the immature fault system. The causative faults had not been previously identified and are located near the transition from the Walker Lane belt to the Basin and Range province. The east–west geometry of the system is consistent with the eastward extension of the Mina Deflection of the Walker Lane north of the White Mountains.

Plant-specific assessment of the natural circulation-induced creep rupture characteristics in the RCS pressure boundary during the SBO accident

In nuclear power plants (NPPs), one of the important yet uncertain phenomena during a station blackout (SBO) accident is the possibility for a counter-current natural circulation flow in the reactor coolant system (RCS) pressure boundary, which could divert the core melt progression and/or the in-vessel fission product (FP) distribution and, in turn, lead to a heatup and eventual creep rupture. From the risk and accident management points of view, one of key concerns is to predict more explicitly whether such a creep rupture can occur in the RCS pressure boundary, and if it indeed can, also predict the most probable time and the most likely location. This paper presents plant-specific analysis results on the potential characteristics of natural circulation-induced creep rupture of the RCS pressure boundary that could potentially take place during an SBO accident of a reference pressurized water reactor (APR1400). MELCOR-CFD (Computational Fluid Dynamics) coupled analysis was performed to determine more precisely the relevant physical parameter that could greatly influence on the behaviour of natural circulation and the ensuing creep rupture. Multiple sensitivity analyses were also carried out to investigate the influence that particular MELCOR modeling schemes and plant conditions have in estimating the RCS creep rupture characteristics. The analysis results and relevant insights were summarized in terms of particular points of interest.

Slip Model of the 2020 Yutian (Northwestern Tibetan Plateau) Earthquake Derived From Joint Inversion of InSAR and Teleseismic Data

AbstractInterferometric synthetic aperture radar and teleseismic P‐wave data were combined to investigate the source rupture characteristics of the 2020 Mw 6.3 Yutian, China, earthquake. We first utilized the near‐field displacements together with 29 broadband teleseismic P waveforms to investigate the uniform slip model by using a Bayesian bootstrap optimization nonlinear inversion method to resolve the nucleation point location, origin time and fault geometrical parameters. Based on these results, the kinematic rupture process of the earthquake was inverted. We conclude that the 2020 Yutian earthquake occurred on a west‐dipping blind normal fault with a dip of ∼60° at the junction of Bayan Har block (BHB) and western Kunlun block (WKB). The rupture nucleation point was located at longitude = 82.435°E, latitude = 35.619°N, and a depth of 6.377 km, making it shallower than estimated from other point source inversions. The earthquake started at 21:05:20 UTC on June 25, 2020 and was delayed by ∼2.07 s compared with GeoForschungsZentrum. The rupture lasted for ∼12 s, with a total seismic moment of ∼3.28 × 1018 Nm, corresponding to a moment magnitude of 6.3. The slip was mainly confined between ∼3.0 and 9.0 km in depth and the peak slip was ∼1.40 m, which occurred at a depth of ∼6.377 km. The slip was predominantly normal slip with slight right‐lateral strike‐slip components, which agrees with the southeastward movement of the BHB relative to the WKB.

Morphology of Acute Achilles Tendon Rupture by Intraoperative Evaluation

The purpose of this study was to clarify the morphology of acute Achilles tendon rupture (ATR) according to intraoperative evaluation. The morphology of 220 cases was evaluated retrospectively from intraoperative findings from June 2014 to December 2015. We noted 3 characteristics of rupture. First, we divided the ruptures into complete or partial type. Second, according to the level of rupture, we classified them into muscle-tendon junctional type, mid-substantial type, or calcaneal insertional avulsion type. Lastly, on the basis of the pattern of rupture, we divided them into transverse pattern, double-layer pattern, or Z-shaped pattern. All ruptured tendons were repaired with surgical procedures on the basis of the classification of rupture type or pattern. Of the total of 220 cases, 217 were complete ruptures (98.7%) and 3 partial ruptures (1.3%). Regarding the level of rupture, 5 cases were of the muscle-tendon junctional type (2.3%), 209 cases of the mid-substantial type (95%), and 6 cases of the calcaneal insertional avulsion type (2.7%). In terms of the pattern of rupture, there were 198 cases of the transverse pattern (90%), 10 cases of the double-layer pattern (4.5%), and 12 cases of the Z-shaped pattern (5.5%). There was significant gender difference only in the mid-substantial type. Although the morphology of a typical acute ATR was complete, of mid-substance type, and with transverse pattern, other types of ATR were recognized from the intraoperative investigation.

What controls the remobilization and deformation of surficial sediment by seismic shaking? Linking lacustrine slope stratigraphy to great earthquakes in South-Central Chile.

Remobilization and deformation of surficial subaqueous slope sediments create turbidites and soft sediment deformation structures, which are common features in many depositional records. Palaeoseismic studies have used seismically‐induced turbidites and soft sediment deformation structures preserved in sedimentary sequences to reconstruct recurrence patterns and – in some cases – allow quantifying rupture location and magnitude of past earthquakes. However, current understanding of earthquake‐triggered remobilization and deformation lacks studies targeting where these processes take place, the subaqueous slope and involving direct comparison of sedimentary fingerprint with well‐documented historical earthquakes. This study investigates the sedimentary imprint of six megathrust earthquakes with varying rupture characteristics in 17 slope sediment cores from two Chilean lakes, Riñihue and Calafquén, and evaluates how it links to seismic intensity, peak ground acceleration, bracketed duration and slope angle. Centimetre‐scale stratigraphic gaps ranging from ca 1 to 20 cm – caused by remobilization of surficial slope sediment – were identified using high‐resolution multi‐proxy core correlation of slope to basin cores, and six types of soft sediment deformation structures ranging from ca 1 to 25 cm thickness using high‐resolution three‐dimensional X‐ray computed tomography data. Stratigraphic gaps occur on slope angles of ≥2.3°, whereas deformation already occurs from slope angle 0.2°. The thickness of both stratigraphic gaps and soft sediment deformation structures increases with slope angle, suggesting that increased gravitational shear stress promotes both surficial remobilization and deformation. Seismic shaking is the dominant trigger for surficial remobilization and deformation at the studied lakes. Total remobilization depth correlates best with bracketed duration and is highest in both lakes for the strongest earthquakes (M w ca 9.5). In lake Riñihue, soft sediment deformation structure thickness and type correlate best with peak ground acceleration providing the first field‐based evidence of progressive soft sediment deformation structure development with increasing peak ground acceleration for soft sediment deformation structures caused by Kelvin‐Helmholtz instability. The authors propose that long duration and low frequency content of seismic shaking favours surficial remobilization, whereas ground motion amplitude controls Kelvin‐Helmholtz instability‐related soft sediment deformation structure development.

Frequency‐Dependent Rupture Characteristics of the 30 October 2016 Mw 6.5 Norcia, Italy Earthquake Inferred From Joint Multi‐Scale Slip Inversion

AbstractThe relationship between multi‐scale rupture characteristics and different frequency contents of the seismic waveforms has been revealed for moderate to great earthquakes by previous researches. To better understand such a relationship, we propose a two‐step strategy to perform finite fault inversion in the wavelet domain with multi seismic datasets, involving the seismic observations at both teleseismic and near‐field distances. In our two‐step strategy, the larger‐scale pattern of the seismic rupture is first constrained by using the lower‐frequency seismic waveforms and then based on the lower‐frequency rupture pattern, the higher‐frequency rupture features are obtained by performing inversion with higher‐frequency data. We apply this two‐step strategy with multi seismic datasets to study the 30 October 2016 Mw 6.5 Norcia, Italy earthquake, which is the largest event of the 2016–2017 central Italy seismic sequence. By analyzing the recovered slip patterns from different frequency bands, we notice the frequency‐dependent rupture features of this earthquake. The lower‐frequency slip concentrated at the shallower depths above the source, and the higher‐frequency slip appeared near the edges of the lower‐frequency slip patch, working as “barriers”, due to fault complexities in central Italy. The frequency‐dependent slip pattern of the 30 October 2016 Norcia earthquake shows a relation to the unevenly distributed pore fluid pressure, as indicated by Vp/Vs tomography from previous researches. Our results suggest that fault complexities and unevenly distributed fluids contribute to the frequency‐dependent rupture of this earthquake.

Simulation of near-fault ground strains and rotations from actual strike-slip earthquakes: case studies of the 2004Mw 6.0 Parkfield, the 1979Mw 6.5 Imperial Valley and the 1999Mw 7.5 Izmit earthquakes

SUMMARYPrevious studies have demonstrated that finite-fault simulations of actual or hypothetical earthquakes using deterministic, physics-based simulation techniques constitute an effective tool for characterizing near-fault ground strains and rotations in the low-frequency range. The characteristics of these motions are further investigated in this study by performing forward ground-motion simulations of three well-documented strike-slip earthquakes (i.e. 2004 Mw 6.0 Parkfield, 1979 Mw 6.5 Imperial Valley and 1999 Mw 7.5 Izmit) using models of the seismic source and crustal structure available in the literature. Time histories of ground strains and rotations are numerically generated at near-fault stations and at a dense grid of observation points extending over the causative fault. This is achieved by finite differencing translational motions simulated at very closely spaced stations using a kinematic modelling approach. The simulation results show that the three strike-slip earthquakes produce large-amplitude pulse-like shear strain and torsion in the forward direction of rupture propagation. The time histories of specific components of displacement gradient, strain and rotation at near-fault stations can be estimated from those of ground velocities using a phase velocity, whereas peak ground torsions in the near-fault region can be reasonably estimated from peak horizontal ground velocities using a scaling factor. However, both the phase velocity and the scaling factor exhibit significant variability in the near-fault region of the considered earthquakes. The concept of isochrones is also utilized to associate fault rupture characteristics with near-fault ground strains and rotations. The results indicate that the seismic energy radiated from the high-isochrone-velocity region of the fault—which encompasses areas of large slip locally driven by high stress drop—arrives at a near-fault station in a short time interval that coincides with the time window of the large-amplitude pulse-like shear strain and torsion.

Rupture and combustion characteristics of lithium-ion battery under overcharge

To clarify the evolution of thermal runaway of lithium-ion batteries under overcharge, the prismatic lithium-ion batteries are overcharged at various current rates in air and argon. The whole process with the charge rate higher than 0.1C in air includes three parts, which are expansion, rupture and combustion processes, respectively. The expansion process can be divided into two stages based on the change of surface temperature, and the temperatures at cell burst point are very close at various charge rates. The rupture process begins from the battery burst point. The pressure generated by rupture is less than 61 kPa at different charge rates, while it can reach 389 kPa in the following combustion process at 1C. The combustion process can be divided into four stages based on the obvious change of combustion phenomenon, which are ignition, violent combustion, stable combustion and extinguishing, respectively. Combustible gas was mainly CO, accounting for 32%. Three element factors of combustion under overcharge are clarified: combustible spouted out from the battery, high temperature electrode active substance, and oxygen in the environment, respectively. The results of this work can provide some information for the safety and fire protection of lithium-ion-battery based devices.

Quaternary Deposits Affect Coseismic Offset on Thrust Faults: Evidence from the 2008 Mw 7.9 Wenchuan, China, Earthquake

AbstractCoseismic offset is an important parameter to determine the characteristics of surface ruptures produced by large earthquakes and has significant implications for understanding fault-zone mechanics. To date, most studies have focused on broad-wavelength variations in coseismic offset and their related mechanisms. However, high-frequency variations in coseismic offset have been less commonly reported due to difficulty in field identification. Here, we show that three sites have typical abrupt changes in coseismic offset within short distances along surface ruptures produced by the 2008 Mw 7.9 Wenchuan earthquake. The Bailu, Qingping, and Xiaoyudong sites on different segments of the seismogenic faults show that coseismic vertical offsets can vary from ∼0.6 to ∼1.7 m at neighboring locations. Moreover, the offset gradients at the three sites are estimated from ∼2.5 to ∼30.9 m/km. Based on geologic and geophysical investigations at the three sites, we suggest that Quaternary deposits are the primary factor affecting coseismic offset. Specifically, thick and loosely packed deposits are more likely to yield smaller coseismic offsets than thin and densely packed deposits. Finally, through a compilation of recent thrust-type earthquakes, we suggest that the coseismic vertical offset gradient for thrust faults can vary greatly, which requires caution in seismic hazard assessments when designing linear infrastructure projects and constraining slip rates at specific sites.

Retrospective Analysis on Traumatic Rupture of Intracranial Internal Carotid Artery in 11 Cases.

Objective To retrospectively analyze the characteristics of the traumatic rupture of intracranial internal carotid artery in order to provide reference for forensic expertise examination and identification. Methods A total of 11 autopsy cases of traumatic rupture of intracranial internal carotid artery were collected. The gender, age, cause of injury, blood loss on the scene, location of internal carotid artery rupture, hardening degree of the rupture of the wall, brain injury, blood ethanol content and cause of death were also recorded. Results All 11 cases died on the scene, of which 7 died from traffic accidents, 2 falls from height and 2 from bare handed injuries. None of the 11 victims suffered serious head and body surface injury. The internal carotid artery rupture in the 9 cases of traffic injury and fall from height injury occurred in the cavernous segment. In all these cases, there were transverse fractures of the middle cranial fossa with the carotid sulcus involved, and minor intracranial hemorrhage and brain contusion. In 2 cases of bare handed injuries, internal carotid artery rupture occurred in the ophthalmic artery segment, accompanied by fatal intracranial hemorrhage and diffuse axonal injury, but no skull fracture. All 11 cases showed full-thickness rupture of the vessel wall, and the long axis of the wounds was perpendicular to those of the artery. Conclusion The incidence of intracranial internal carotid artery rupture in high-energy trauma events such as traffic accidents and high falls deserves attention. Injuries of the cavernous segment or ophthalmic segment might be more common. The main injury mechanism of intracranial internal carotid artery rupture might be that the blood vessels were pulled and the bone fragments caused damage.

Clinical characteristics of uterine rupture without previous Cesarean section: A 25‐year retrospective study

To investigate the clinical characteristics and risk factors of uterine rupture without preceding Cesarean section. The medical records of all deliveries at the Women's Hospital, Zhejiang University School of Medicine between 1992 and 2017 were reviewed. All cases of uterine rupture without previous Cesarean delivery were included. Two types of uterine rupture, incomplete and complete, were distinguished. The clinical characteristics of each patient were collected and analyzed, including demographic information, clinical manifestation, operative records, site of rupture, pregnancy and labor complication, obstetrics risk factors, and birth outcome. There were 222 418 deliveries in total during the study period. Nineteen cases of uterine rupture without previous Cesarean section were identified. As a result, the incomplete rupture group had significant advanced gestational age, decreased maternal gravidity, lower incidence of dilation and curettage, and lower perinatal mortality rate. In aspect of the rupture site, the involvement of the lower segment of the uterus was significantly more common in the incomplete rupture group. In the complete rupture group, the participants with a gestation age less than 28 weeks were more likely to have a history of dilation and curettage than those with a gestation age over 28 weeks. The history of dilation and curettage is the major risk factor of uterine rupture without Cesarean section. Our findings imply that obstetricians should be cautious of spontaneous uterine rupture in pregnant women who has a history of dilation and curettage.

Spatial patterns, controlling factors, and characteristics of landslides triggered by strike-slip faulting earthquakes: case study of Lefkada island, Greece

The correlation of coseismic landslides with the seismic and morphological parameters has been investigated in detail by many researchers, mainly after the devastating 2008 M8.0 Wenchuan, China earthquake. One of the goals of such studies is to examine the spatial distribution of the earthquake-induced landslides in order to establish a pattern depending on the type of the seismic fault. This research focusses on the island of Lefkada, Ionian Sea, Greece, that is considered one of the most prone to earthquakes regions in Europe due to its proximity to the Cephalonia Transform fault. Landslide data from the two shallow strike-slip faulting earthquakes that occurred on 2003 and 2015 are statistically analyzed in order to evaluate the landslide magnitude and area of slope failures and their frequency-area size distributions. Furthermore, the spatial distribution of failures was investigated in detail regarding its correlation to topography (slope angle, aspect, local relief, elevation), geology, and the characteristics of fault rupture. We conclude that the landslide pattern is not controlled by a single parameter and that it results from a combination and interaction of seismic, morphological, and geological factors. In particular, the parameters of slope angle, geology, and fault rupture/asperities are the ones that are clearly related to the highest landslide densities.

Standard MRI May Not Predict Specific Acute Anterior Cruciate Ligament Rupture Characteristics.

Background:There has been renewed interest in the concept of anterior cruciate ligament (ACL) suture repair (ACLSR). Morphologic characteristics of the ruptured ACL remnant play a role in deciding whether a patient is eligible for ACLSR. However, no classification of these characteristics of ACL rupture on magnetic resonance imaging (MRI) scans has yet been compared with intraoperative findings in the context of ACLSR.Purpose:To investigate the value of using preoperative MRI to predict specific characteristics of acute complete ACL rupture.Study Design:Cohort study (diagnostic); Level of evidence, 2.Methods:A total of 25 patients were included. Two radiologists classified ACL rupture location and pattern on preoperative 1.5-T MRI scans with a standard sequence; the results were compared with the corresponding findings at arthroscopy conducted by a single surgeon. The agreement between the MRI and surgical findings was calculated using Cohen κ values. Furthermore, the reliability coefficients of the MRI classifications within and between radiologists were calculated.Results:The agreement between MRI classification and arthroscopic findings for ACL rupture location was slight (Cohen κ, 0.016 [radiologist 1] and 0.087 [radiologist 2]), and for ACL rupture pattern, this was poor to slight (Cohen κ, <0 and 0.074). The intraobserver reliability of MRI classification for ACL rupture location was moderate for radiologist 1 and slight for radiologist 2 (Cohen κ, 0.526 and 0.061, respectively), and for ACL rupture pattern, this was slight for radiologist 1 and 2 (Cohen κ, 0.051 and 0.093, respectively). The interobserver reliability of MRI classification for ACL rupture location and pattern was slight between radiologists (Cohen κ, 0.172 and 0.040, respectively).Conclusion:In the current study, we found poor to slight agreement between MRI classification and arthroscopic findings of specific ACL rupture characteristics. In addition, the intra- and interobserver reliability for MRI classification of the ACL rupture characteristics was slight to moderate.

A novel method for automatic identification of rock fracture signals in microseismic monitoring

Microseismic (MS) monitoring technology is able to offer 3-dimensional and real-time rupture characteristics of rocks by capturing and analyzing detectable elastic waves released from rock fracture, which has been widely applied in rock/mining engineering. The prerequisite of MS analysis is to identify MS signals with high efficiency and accuracy. However, the identification work is inevitably disturbed by vibration signals from the blasting activities involved in rock/mining engineering. Currently, the classification work of MS and blasting signals is mainly carried out by the on-site operators based on their own experience, which is time-consuming and subjectively sensitive. In this work, a new discriminant method is developed to automatically recognize these signals based on their time-frequency spectrum characteristics to offer more reliable data for MS monitoring analysis. Singular value decomposition is adopted to reduce data volume and obtain unique features. Random Forest (RF) is applied to achieve automatic recognition and get the most important features based on the variation of ‘out-of-bag’ error and Gini Index. These most important features can be used to optimize the RF classifier. The numerical experiments are conducted to verify our new method. The results prove that the method reaches 95.99%±0.1% accuracy in 100 repetitions for events collected from the field, and the optimized RF produces a more accurate result (97%) using fewer characteristics, which is higher than the methods reported in the previous literature. The proposed method diminishes the sensitivity of operators in the classification and promotes the accuracy and efficiency of the identification of MS signals data in the application of MS monitoring technology. Moreover, this strategy also offers a new strategy to process the acquired monitoring signals in other monitoring techniques.

Comparative Study on Mineral-Scale Microcrack Propagation of Shale under Different Loading Methods

Producing a sufficient volume of multiscale crack networks is key to enhancing recovery of shale gas. The formation of crack network largely depends on initiation and propagation of microcracks. To reveal the influence of different loading methods on the propagation of mineral-scale microcracks, this study used the Voronoi tessellation technique to establish a cohesive zone model of shale mineral distribution and applied six different boundary conditions to represent different loading methods. Crack path characteristics, rupture characteristics, continuous crack propagation and turning, and en echelon intermittent crack propagation under different loading methods were compared and analyzed. The essence of different loading methods affecting the length and complexity of cracks was the spreading range of tensile microcracks. The mechanical properties of minerals led to dissimilarities in continuous crack propagation and turning. The formation and propagation of en echelon intermittent fractures of different scales were mainly impacted by the heterogeneity of minerals and mineral aggregates. The spreading direction and connection form of en echelon intermittent fractures were mainly affected by the loading method. Conclusions arising from mineral-scale simulations contribute to understanding the mechanism of microcrack propagation resulting from different loading methods, and these conclusions have a guiding significance to enhanced shale gas recovery.

Field Response and Surface-Rupture Characteristics of the 2020 M 6.5 Monte Cristo Range Earthquake, Central Walker Lane, Nevada

AbstractThe M 6.5 Monte Cristo Range earthquake that occurred in the central Walker Lane on 15 May 2020 was the largest earthquake in Nevada in 66 yr and resulted in a multidisciplinary scientific field response. The earthquake was the result of left-lateral slip along largely unmapped parts of the Candelaria fault, one of a series of east–northeast-striking faults that comprise the Mina deflection, a major right step in the north–northwest structural grain of the central Walker Lane. We describe the characteristics of the surface rupture and document distinct differences in the style and orientation of fractures produced along the 28 km long rupture zone. Along the western part of the rupture, left-lateral and extensional displacements occurred along northeasterly and north-striking planes that splay off the eastern termination of the mapped Candelaria fault. To the east, extensional and right-lateral displacements occurred along predominantly north-striking planes that project toward well-defined Quaternary and bedrock faults. Although, the largest left-lateral displacement observed was ∼20 cm, the majority of displacements were &amp;lt;5 cm and were distributed across broad zones up to 800 m wide, which are not likely to be preserved in the geologic record. The complex pattern of surface rupture is consistent with a network of faults defined in the shallow subsurface by aftershock seismicity and suggests that slip partitioning between east-striking left-lateral faults and north to northwest-striking right-lateral faults plays an important role in accommodating northwest-directed transtension in the central Walker Lane.

Variability of near‐fault seismic risk to reinforced concrete buildings based on high‐resolution physics‐based ground motion simulations

AbstractBroadband physics‐based simulated earthquake ground motions are utilized to characterize the regional‐scale seismic risk to modern reinforced concrete (RC) structures. A highly dense dataset of ground motions covering a 100‐km 40‐km domain was generated using kinematic fault rupture models with varying rupture characteristics to represent shallow crustal earthquakes and resolved up to frequencies of 5 Hz. Over 40,000 nonlinear response history simulations of short‐ and mid‐rise RC special moment frame buildings were conducted using simulation models that are capable of representing nonlinear behavior and component deterioration effects. The spatial variability of structural risk within a single earthquake scenario and between different rupture scenarios is examined, and the regions of strongest directivity effects and highest structural demands are identified. The structural demands may vary by factor of up to 8.0 at very short distances from the fault, and the large dispersion in the demands decreases significantly beyond a distance of 15 km. The interstory drift and member rotation demands are substantially impacted by important features of the geological structure and the characteristics of the rupture scenarios, particularly the presence of localized high‐slip regions. The frequency characteristics of the structures are found to play an important role in determining the effects of near‐fault ground motions on the structural response and expected damage. The results of this study suggest that the simulated ground motions, particularly those generated using the hybrid rupture approach, may offer reasonable structural risk estimates for low‐frequency structures and conservative estimates for high‐frequency structures.

Toward an Integrative Geological and Geophysical View of Cascadia Subduction Zone Earthquakes

The Cascadia subduction zone (CSZ) is an exceptional geologic environment for recording evidence of land-level changes, tsunamis, and ground motion that reveals at least 19 great megathrust earthquakes over the past 10 kyr. Such earthquakes are among the most impactful natural hazards on Earth, transcend national boundaries, and can have global impact.Reducing the societal impacts of future events in the US Pacific Northwest and coastal British Columbia, Canada, requires improved scientific understanding of megathrust earthquake rupture, recurrence, and corresponding hazards. Despite substantial knowledge gained from decades of research, large uncertainties remain about the characteristics and frequencies of past CSZ earthquakes. In this review, we summarize geological, geophysical, and instrumental evidence relevant to understanding megathrust earthquakes along the CSZ and associated uncertainties. We discuss how the evidence constrains various models of great megathrust earthquake recurrence in Cascadia and identify potential paths forward for the earthquake science community. ▪ Despite outstanding geologic records of past megathrust events, large uncertainty of the magnitude and frequency of CSZ earthquakes remains. ▪ This review outlines current knowledge and promising future directions to address outstanding questions on CSZ rupture characteristics and recurrence. ▪ Integration of diverse data sets with attention to the geologic processes that create different records has potential to lead to major progress.