Fault Model Research Articles

Authentic fault models and dispersive tsunami simulations for outer-rise normal earthquakes in the southern Kuril Trench

The southern Kuril Trench is one of the most seismically active regions in the world. In this study, marine surveys and observations were performed to construct fault models for possible outer-rise earthquakes. Seismic and seafloor bathymetric surveys indicated that the dip angle of the outer-rise fault was approximately 50°–80°, with a strike that was slightly oblique to the axis of the Kuril Trench. The maximum fault length was estimated to be ~ 260 km. Based on these findings, we proposed 17 fault models, with moment magnitudes ranging from 7.2 to 8.4. To numerically simulate tsunami, we solved two-dimensional dispersive wave and three-dimensional Euler equations using the outer-rise fault models. The results of both simulations yielded identical predictions for tsunami with short-wavelength components, resulting in significant dispersive deformations in the open ocean. We also found that tsunami generated by outer-rise earthquakes were affected by refraction and diffraction because of the source location beyond the trench axis. These findings can improve future predictions of tsunami hazards.Graphical

Development of high-fidelity air handling unit fault models for FDD innovation: lessons learned and recommendations

Interest in automated building analytics, including fault detection and diagnostics has been increasing; however, developers of these solutions have lacked access to ground-truth-validated data across a wide range of weather conditions for algorithm development and performance assessment. This study presents the development, and validation of faulted and fault-free models for air handling units (AHUs) – a common HVAC system design. Detailed models for the single-duct AHU (Modelica) and dual-duct AHU (HVACSIM+) were used to conduct annual simulations, for common sensor, mechanical, and control sequence faults. We report lessons learned during the efforts, including challenges and insights regarding how these simulation models, typically used for design applications, can be purposed to accurately reflect real-world system operational behaviours. Finally, we highlight considerations for researchers and FDD developers who may wish to leverage this dataset to assess the performance of their algorithms, and evolving performance of FDD solutions over time.

Multilevel assessment method for post-earthquake functionality of medical buildings considering component–department–floor interdependencies

The assessment of the post-earthquake functionality of medical buildings (PEFMB) is critical for the post-earthquake emergency response, recovery, and resilience-based seismic design of medical buildings. Hospitals are complex functional systems that exhibit multilevel functional coupling from components to departments to floors. Existing methods have challenges, including the difficulty of considering the impact of different departments located on different floors on medical functions, and a lack of multilevel performance improvement strategies for enhancing post-earthquake medical functionality. A multilevel assessment method for the PEFMB that considers component–department–floor interdependencies (CDFI) was developed in this study. This method establishes a functional logical relationship between components and departments using fault tree models of typical departments. A multilevel functional coupling relationship among the components, departments, and floors was established by incorporating floor nodes to reflect the impact of departments located on different floors. This enabled the assessment of the PEFMB considering the CDFI. Furthermore, methods for identifying critical failure paths in the PEFMB were developed, and multilevel performance improvement strategies by adjusting medical equipment and departments along the critical failure path were recommended. The proposed method is demonstrated using an outpatient building. The main conclusions are as follows. (1) The proposed multilevel assessment method enables quantitative assessment of the PEFMB and exhibits good scalability. (2) This method provides a clear and intuitive visualization of the critical failure path in healthcare functionality under seismic conditions. The proposed multilevel improvement strategies can enhance the post-earthquake functionality of medical buildings at multiple levels, which provides a valuable reference for the seismic design of medical buildings.

On the effect of background seismicity in physics-based earthquake simulations

Physics-based simulations have been extensively employed to generate synthetic earthquake catalogs over the past decade. In this kind of simulation, primary known faults are typically modeled, while smaller and intermediate faults are often neglected. As a result, the location of earthquakes in the simulation is confined to the modeled faults. Furthermore, due to the elimination of off-fault seismicity, a complete match of the frequency-magnitude distribution of the synthetic catalog with observed data is not achieved. This paper presents an approach to include off-fault seismicity (or background seismicity) within the simulation. First, background earthquakes are separated from the primary faults’ earthquakes, and a fault section is assigned to each event. By employing a scaling relationship, the dimensions of these fault sections are determined according to the magnitude of the corresponding event. The fault section’s slip rates are estimated based on the observed frequency-magnitude distribution. Combining the background fault model with the primary fault model results in a comprehensive model that accounts for all stress interactions between fault elements within the simulator in actual locations. As a result, a broader range of frequency-magnitude distribution in the synthetic catalog can be matched to the observations. A case study using one of the available simulators, Virtual Quake, on a sample area is presented. The results demonstrate that eliminating off-fault seismicity could lead to an underestimated assessment of the earthquake probabilities for the whole region and a biased estimation of earthquake rates in individual faults.

A novel auxiliary signal design algorithm for weak fault isolation based on zonotopic optimization

A novel active isolation method for weak faults based on zonotopes is proposed. First, a zonotopic filter is designed to estimate the system state; subsequently, an auxiliary signal is designed based on the obtained state set, and the auxiliary signal is added to both the normal and fault models to ensure that the intersection of their state sets is empty. Then, the intersection solution process is transformed into an optimization problem. Finally, simulation results from a numerical simulation and an experiment on a DC–DC circuit platform verify that the auxiliary signal designed using this method is more optimal and less conservative compared with other auxiliary signal design methods.

Virtualized Fault Injection Framework for ISO 26262-Compliant Digital Component Hardware Faults

Simulation-based Fault Injection (FI) is crucial for validating system behaviour in safety-critical applications, such as the automotive industry. The ISO 26262 standard’s Part 11 extension provides failure modes for digital components, driving the development of new fault models to assess software-implemented mechanisms against random hardware failures (RHF). This paper proposes a Fault Injection framework, QEFIRA, and shows its ability to achieve the failure modes proposed by Part 11 of the ISO 26262 standard and estimate relevant metrics for safety mechanisms. QEFIRA uses QEMU to inject permanent and transient faults during runtime, whilst logging the system state and providing automatic post-execution analysis. Complemented with a confusion matrix, it allows us to gather standard compliant metrics to characterise and evaluate different designs in the early stages of development. Comparatively to the native QEMU implementation, the tool only shows a slowdown of 1.4× for real-time microcontroller-based applications.

Production optimization in a fractured carbonate reservoir with high producing GOR

The Gas-Oil Ratio (GOR) is a crucial production parameter in oil reservoirs. An increase in GOR results in higher gas production and lower oil production, potentially leading to well shut-ins due to economic infeasibility. This study focuses on a real fractured oil field that requires urgent production operations to reduce the producing GOR. In this study, the static model for the field was developed using commercial software, involving steps such as data collection, fault modeling, meshing, and statistical analysis to prepare for dynamic simulation. The dynamic model incorporates geometry, gridding, and rock properties from the static model, utilizing a dual-porosity approach for the naturally fractured reservoir and the Peng-Robinson equation for fluid phase behavior. Initial reservoir conditions, production history, and rock-fluid interactions were defined, with relative permeability curves indicating a water-wet reservoir and low critical gas saturation affecting the GOR. To better understand the relationship between reservoir and production parameters, a detailed sensitivity analysis was performed using the Response Surface Methodology (RSM). Following the sensitivity analysis, a history matching process was conducted using the Designed Exploration and Controlled Evolution (DECE) optimizer to validate the model for future forecasts. Six operational scenarios were defined to decrease the production GOR and enhance final recovery from the field. The results indicate that the water injection scenario is effective in preventing the GOR increase by maintaining reservoir pressure, thereby sustaining production over a longer period. This scenario also improves oil recovery by approximately 6% compared to the base case. Finally, optimization was carried out using the DECE optimizer for each scenario to fine-tune the operational parameters. The goal was to maximize oil revenue for each scenario during the optimization process. This study stands out as one of the few that provides a comprehensive analysis of production behavior and development planning for a real fractured reservoir with high producing GOR.

Source Parameters and Seismogenic Fault Model of the 2024 Mw 7.0 Wushi (Xinjiang, China) Earthquake Revealed by InSAR Observations

Source Parameters and Seismogenic Fault Model of the 2024 Mw 7.0 Wushi (Xinjiang, China) Earthquake Revealed by InSAR Observations

Robust Fixed-Time Adaptive Fault-Tolerant Control for Dynamic Positioning of Ships with Thruster Faults

The ship dynamic positioning system has long been a subject of great interest due to the intricate and unpredictable nature of the maritime environment, which affects its dependability and timeliness. This study focuses on the issue of developing a robust, efficient, and adaptable fault-tolerant control system for ship dynamic positioning systems that experience thruster malfunctions. Firstly, we build the motion model of the ship’s dynamic positioning system with three degrees of freedom, as well as the model for faults in the thruster. A second-order fast fixed-time nonsingular sliding mode surface is formulated, and a robust adaptive control technique is introduced to counteract external environmental disturbances and model errors. The objective is to ensure rapid convergence of the system within a predetermined time frame. Simultaneously, combined with the fault-tolerant control technique, it is ensured that the dynamic positioning ship can still achieve system stability when thruster faults occur. In addition, the analysis of the Lyapunov stability criterion proves that the proposed fixed-time adaptive fault-tolerant control scheme can make the system tracking error converge within a fixed time. Finally, the effectiveness of the proposed control scheme is verified by numerical simulation results.

Three-dimensional fault model and features of chained hazards of the Luding MS 6.8 earthquake, Sichuan Province, China

The MS 6.8 Luding earthquake in 2022 is located on the NNW-trending Moxi segment of the Xianshuihe fault with left-lateral strike-slip behavior. This area is where the Xianshuihe, Anninghe, Daliangshan and Longmenshan faults intersect. China Earthquake Administration has identified that intersection area, among the Moxi segment of the Xianshuihe fault, the Anninghe fault, the Daliangshan fault and the southern part of the Longmenshan fault, as a high-magnitude earthquake hazard area. According to existing data on the Luding earthquake, including the focal parameters, the spatial distribution of re-located aftershocks, dominated azimuth of the earthquake intensities and earthquake-induced ground fissures, we built a 3D earthquake fault model. We found that two discontinuous NNW-trending vertical strike-slip faults with left stepping were the seismogenic faults of the Luding earthquake. Its coseismic left-lateral dislocation triggered transtensional slips and aftershocks on the NW-trending secondary faults at its northernmost tensile area. Meanwhile, local crustal coseismic shortening on the side of Mt. Gongga triggered the aftershocks on the NE- and NW-trending secondary conjugated strike-slip faults, which were confirmed by GNSS observations and InSAR deformation field around the epicenter. This earthquake rupturing pattern also controlled the spatial distribution of the earthquake intensity IX area and earthquake chain hazards. The Coulomb stress calculation shows that the Luding earthquake increases the risk of high-magnitude earthquake occurrence on the southernmost part of the Xianshuihe fault and the Anninghe fault. Finally, we suggested doing good monitoring of the Anninghe fault and the southernmost part of the Xianshuihe fault and avoiding active faults with seismogenic capacity and areas prone to earthquake-chained hazards during the site selection and planning of reconstruction.

Predictive Model for Incipient Faults in Oil-Filled Transformers

Predictive Model for Incipient Faults in Oil-Filled Transformers

Analytical Fault Modeling of Droop-Controlled IIDG and its Cluster

Analytical Fault Modeling of Droop-Controlled IIDG and its Cluster

Reliable communication in dynamic networks with locally bounded byzantine faults

The Byzantine tolerant reliable communication primitive is a fundamental building block in distributed systems that guarantees the authenticity, integrity, and delivery of information exchanged between processes.We study the implementability of such a primitive in a distributed system with a dynamic communication network (i.e., where the set of available communication channels changes over time). We assume the f-locally bounded Byzantine fault model and identify the conditions on the dynamic communication networks that allow reliable communication between all pairs of processes. In addition, we investigate its implementability on several classes of dynamic networks and provide insights into its use in asynchronous distributed systems.

Research on new distributed distribution network hidden fault remote automatic recovery technology

Abstract To solve a series of chain reactions in which a fault in the distribution network triggers the shutdown of other components, a new distributed distribution network hidden fault remote automatic recovery technology research is proposed. The traditional chain fault model about line protection describes that when a fault occurs on one or some lines of the system, the line protection devices will operate with a certain probability, and the misoperation or inappropriate action of these line protection devices will lead to the expansion of the fault and ultimately form a wide range of power outages. This study quantitatively gives the interaction relationship between the components in the system. Firstly, the difference between the distribution network chained fault and the main network chained fault mechanism is analyzed; secondly, the topology of the distribution network is modeled; then, the fault transfer model of the distribution network and the chained fault model based on the line dynamics model are constructed based on this model; finally, the detailed distribution network chained fault algorithm process is given based on the proposed model.

Fault prioritisation for Air Handling units using fault modelling and actual fault occurrence data

Fault impact analysis is an important step in developing Fault Detection and Diagnosis (FDD) tools for Heating, Ventilation and Air-Conditioning (HVAC) systems. It provides an insight into how HVAC systems react in the presence of operational faults and helps to prioritise which faults to focus on. The research in the existing literature has mostly focused on modelling several faults occurring in various HVAC systems and components to evaluate the effect of the fault on energy performance and the predicted thermal comfort of occupants. However, the real frequency of fault occurrence, an important factor which affects the overall impact a fault has on the system’s performance, has barely been addressed in the reviewed literature. This paper addresses this gap by considering real fault occurrence frequency data in addition to the effect of the faults on the energy performance of the building to assess their total energy impact. A real office building in the Netherlands was modelled using DesignBuilder and its energy performance was simulated using EnergyPlus. Air Handling Unit (AHU) faults were introduced using the native fault object and Energy Management System (EMS) features available in EnergyPlus. The fault occurrence data was extracted from AHU work orders using text mining. The fault modelling and text mining results were combined to get the total energy impact of the fault and, subsequently, the faults were prioritised using the Pareto principle. The research identified that fan failure, Heat Recovery Wheel (HRW) failure, fan stuck at 50% and Heating Coil Valve (HCV) stuck at 0% are the priority faults for winter and fan failure is the priority fault for summer.

Fault-Tolerant Control Study of Four-Wheel Independent Drive Electric Vehicles Based on Drive Actuator Faults

Failure of any of the drive systems in a Four-Wheel Independent Drive (4WID) electric vehicle may affect the control performance and driving safety of the whole vehicle. Therefore, in this paper, a fault-tolerant controller (FTC) for 4WID electric vehicles considering drive actuator failures is proposed. First, a comprehensive characterization of multiple fault types is achieved by establishing a generalized fault model and designing a comprehensive fault factor. Second, based on the comprehensive fault factor, an LPV model with faults is constructed. Further, a fault-tolerant controller based on LPV/H∞ output feedback is designed by combining the weighting function. Finally, the effectiveness of the FTC in this paper is verified by simulation and hardware-in-the-loop (HIL) experiments. The experimental results show that the FTC designed in this paper can improve the stability of the vehicle traveling while ensuring tracking accuracy when the drive system fails.

Study on fault-slip process and seismic mechanism under dynamic loading of hard roof fracture disturbance

The dynamic stress disturbance induced by mining is a significant factor triggering fault-slip. To better understand the impact of mining-induced hard roof fracture on fault-slip, combined with the geological conditions of a longwall face in contact with the fault, a dynamic and static numerical model was established using FLAC3D. The influence of dynamic loading from hard roof fracture on fault stability was investigated. The characteristics of changes in fault shear stress, shear displacement, slip area, and seismic moment under dynamic loading were analyzed. Simultaneously, numerical results were compared and analyzed against microseismic (MS) monitoring records in the mining, validating the accuracy of the numerical results. The results indicate that dynamic loading is a critical factor in inducing fault-slip. As a geological weak surface, the fault impedes the transmission of shock waves and causes their attenuation. Under dynamic loading, when the fluctuation of fault shear stress and friction coefficient exceeds the threshold, the fault-slip. During the fault-slip process, accompanied by a sharp increase in shear displacement, the seismic moment increases. Finally, the influence of changes in seismic parameters (e.g. longwall–fault distance, seismic energy, and seismic location) on the fault-slip mechanism was analyzed. This study contributes to a better understanding of the disturbance mechanism of mining-induced dynamic loading on fault-slip and provides a theoretical basis for fault-slip rock bursts.

A quantitative internal-short-circuit diagnosis method of lithium-ion batteries for float charging systems

The diagnosis of internal short circuit (ISC) faults in lithium-ion batteries (LIBs) plays an important role in improving battery safety and reducing the occurrence of fire and explosion accidents. Traditional ISC diagnosis methods mainly focus on dynamic operating conditions, and rarely consider stable float charging scenarios with high risks. This paper proposes a quantitative diagnosis strategy for ISC faults in LIBs under different float charging conditions. First, a simulation model of ISC faults for single cells and battery modules under float charging conditions is established. Then, for the LIB packs without a balancing system, three quantitative diagnosis methods (namely Map-based, constant-voltage-source based, and intermittent-charging based) for the ISC faults applicable to different simple and complex float charging systems are proposed. Finally, the method is verified through simulation and experiments, and the results show that an ISC of 0–500 Ω can be detected in various scenarios, and the proposed methods are low-cost, high-precision, and easy to implement for early ISC diagnosis of float charging systems for energy storage.

Seismic and Potential Field Constraints on Upper Crustal Architecture of Inner Bering Shelf, Offshore Southwestern Alaska

Southwestern Alaska encompasses a group of fault-bounded tectonostratigraphic terranes that were accreted to North America during the Mesozoic and Paleogene. To characterize the offshore extension of these terranes and several significant faults identified onshore, we reprocessed three intersecting multichannel deep seismic reflection profiles totaling ∼750 line-km that were shot by the R/V Ewing across part of the inner Bering continental shelf in 1994. Since the uppermost seismic section is often contaminated by high amplitude water layer multiples from the hard and shallow seafloor, the migrated reflection images are supplemented with high-resolution P wave velocity models derived by traveltime tomography of the recorded first-arrivals to depths of up to 2000 m. Additionally, other geophysical datasets such as seismicity, well logs, high resolution satellite-altimetry gravity, air-borne magnetics, ship-board gravity and magnetics, are also incorporated into an integrated regional interpretation. We delineate the offshore extension of the major mapped geological elements, including the Togiak fault (TGF), East Kulukak fault (EKF), Chilchitna fault (CF), Lake Clark fault (LCF), Togiak terrane (TT), Goodnews terrane (GT), Peninsular terrane (PT), Northern Kahiltna flysch (NKF) and Southern Kahiltna flysch (SKF) deposits, and the regional suture zone. The geophysical evidence from this study suggest that the major faults and terrane boundaries of southwestern Alaska, excluding the LCF, not only extend beneath the Bering shelf offshore but also appear to rotate, forming a trend parallel to the inactive Beringian margin. The LCF extends offshore but likely terminates in the northeastern part of the Bristol Bay basin. Additionally, the constraints from seismicity data indicates that while the major faults in southwestern Alaska exihibit some activity onshore, they remain dormant in the offshore region. These new findings will contribute to a better understanding of terrane accretion processes and existing fault models of southwestern Alaska.

Insights on the dip of fault zones in Southern California from modeling of seismicity with anisotropic point processes

Accurate models of fault zone geometry are important for scientific and hazard applications. While seismicity can provide high-resolution point measurements of fault geometry, extrapolating these measurements to volumes may involve making strong assumptions. This is particularly problematic in distributed fault zones, which are commonly observed in immature faulting regions. In this study, we focus on characterizing the dip of fault zones in Southern California with the goal of improving fault models. We introduce a novel technique from spatial point process theory to quantify the orientation of persistent surficial features in seismicity, even when embedded in wide shear zones. The technique makes relatively mild assumptions about fault geometry and is formulated with the goal of determining the dip of a fault zone at depth. The method is applied to 11 prominent seismicity regions in Southern California. Overall, the results compare favorably with the geometry models provided by the SCEC Community Fault Model and other focused regional studies. More specifically, we find evidence that the Southern San Andreas and San Jacinto fault zones are both northeast dipping at seismogenic depths at the length scales of 1.0–4.0 km. In addition, we find more limited evidence for some depth dependent variations in dip that suggest a listric geometry. The developed technique can provide an independent source of information from seismicity to augment existing fault geometry models.