Earthquake relocation using a 3D velocity model and implications on seismogenic faults in the Beijing-Tianjin-Hebei region

To enhance the understanding of the geometry and characteristics of seismogenic faults in the Beijing-Tianjin-Hebei region,we relocated 14805 out of 16063 earthquakes(113°E-120°E,36°N-43°N)that occurred between January 2008 and December 2020 using the double-difference tomography method.Based on the spatial variation in seismicity after relocation,the Beijing-Tianjin-Hebei region can be divided into three seismic zones:Xingtai-Wen'an,Zhangbei-Ninghexi,and Tangshan.(1)The Xingtai-Wen'an Seismic Zone has a northeastsouthwest strike.The depth profile of earthquakes perpendicular to the strike reveals three northeast-striking,southeast-dipping,high-angle deep faults(>10 km depth),including one below the shallow(<10 km depth)listric,northwest-dipping Xinghe fault in the Xingtai region.Two additional deep faults in the Wen'an region are suggested to be associated with the 2006 M 5.1 Wen'an Earthquake and the 1967 M 6.3 Dacheng earthquake;(2)The Zhangbei-Ninghexi Seismic Zone is oriented north-northwest.Multiple northeast-striking faults(10-20 km depth),inferred from the earthquake-intensive zones,exist beneath the shallow(<10 km depth)Xiandian Fault,Xiaotangshan Fault,Huailai-Zhuolu Basin North Fault,Yangyuan Basin Fault and Yanggao Basin North Fault;(3)In the Tangshan Seismic Zone,earthquakes are mainly concentrated near the northeast-striking Tangshan-Guye Fault,Lulong Fault,and northwest-striking Luanxian-Laoting Fault.An inferred north-south-oriented blind fault is present to the north of the Tangshan-Guye Fault.The 1976 M 7.8 Tangshan earthquake occurred at the junction of a shallow northwest-dipping fault and a deep southeast-dipping fault.This study emphasizes that earthquakes in the region are primarily associated with deep blind faults.Some deep blind faults have different geometries compared to shallow faults,suggesting a complex fault system in the region.Overall,this research provides valuable insights into the seismogenic faults in the Beijing–Tianjin–Hebei region.Further studies and monitoring of these faults are essential for earthquake mitigation efforts in this region.

Optimal Configuration of Fault Location Measurement Points in DC Distribution Networks Based on Improved Particle Swarm Optimization Algorithm

The escalating deployment of distributed power sources and random loads in DC distribution networks hasamplified the potential consequences of faults if left uncontrolled. To expedite the process of achieving an optimalconfiguration of measurement points, this paper presents an optimal configuration scheme for fault locationmeasurement points in DC distribution networks based on an improved particle swarm optimization algorithm.Initially, a measurement point distribution optimization model is formulated, leveraging compressive sensing.The model aims to achieve the minimum number of measurement points while attaining the best compressivesensing reconstruction effect. It incorporates constraints from the compressive sensing algorithm and networkwide viewability. Subsequently, the traditional particle swarm algorithm is enhanced by utilizing the Haltonsequence for population initialization, generating uniformly distributed individuals. This enhancement reducesindividual search blindness and overlap probability, thereby promoting population diversity. Furthermore, anadaptive t-distribution perturbation strategy is introduced during the particle update process to enhance the globalsearch capability and search speed. The established model for the optimal configuration of measurement points issolved, and the results demonstrate the efficacy and practicality of the proposed method. The optimal configurationreduces the number of measurement points, enhances localization accuracy, and improves the convergence speedof the algorithm. These findings validate the effectiveness and utility of the proposed approach.

Multi-Branch Fault Line Location Method Based on Time Difference Matrix Fitting

The distribution network exhibits complex structural characteristics,which makes fault localization a challenging task.Especially when a branch of the multi-branch distribution network fails,the traditional multi-branch fault location algorithm makes it difficult to meet the demands of high-precision fault localization in the multi-branch distribution network system.In this paper,the multi-branch mainline is decomposed into single branch lines,transforming the complex multi-branch fault location problem into a double-ended fault location problem.Based on the different transmission characteristics of the fault-traveling wave in fault lines and non-fault lines,the endpoint reference time difference matrix S and the fault time difference matrix G were established.The time variation rule of the fault-traveling wave arriving at each endpoint before and after a fault was comprehensively utilized.To realize the fault segment location,the least square method was introduced.It was used to find the first-order fitting relation that satisfies the matching relationship between the corresponding row vector and the first-order function in the two matrices,to realize the fault segment location.Then,the time difference matrix is used to determine the traveling wave velocity,which,combined with the double-ended traveling wave location,enables accurate fault location.

Research on Asymmetric Fault Location of Wind Farm Collection System Based on Compressed Sensing

Aiming at the problem that most of the cables in the power collection systemof offshore wind farms are buried deep in the seabed,whichmakes it difficult to detect faults,this paper proposes a two-step fault location method based on compressed sensing and ranging equation.The first step is to determine the fault zone through compressed sensing,and improve the datameasurement,dictionary design and algorithmreconstruction:Firstly,the phase-locked loop trigonometric functionmethod is used to suppress the spike phenomenon when extracting the fault voltage,so that the extracted voltage valuewillnot have a large error due to the voltage fluctuation.Secondly,theλ-NIM dictionary is designed by using the node impedancematrix and the fault location coefficient to further reduce the influence of pseudo-fault points.Finally,the CoSaMP algorithmis improved with the generalized Jaccard coefficient to improve the reconstruction accuracy.The second step is to use the ranging equation to accurately locate the asymmetric fault of the wind farm collection system on the basis of determining the fault interval.The simulation results show that the proposedmethod ismore accurate than the compressedsensingmethod andimpedancemethod in fault section location and fault location accuracy,the relative error is reduced from 0.75%to 0.4%,and has a certain anti-noise ability.

FAULT LOCATION ESTIMATION FOR TWO-LINE FAULT INVOLVING DIFFERENT PHASES FROM EACH OF PARALLEL LINES

A novel numerical algorithm of fault location estimation for double line to ground fault involving different phases from each of two parallel lines is presented in this paper.It is based on the one terminal voltage and current data.The loop and nodal equations comparing faulted phase with non faulted phase of two parallel lines are introduced in the fault location estimation models,in which the source impedance of a remote end is not involved.The effects of load flow and fault resistance on the accuracy of fault location are effectively eliminated,therefore precise algorithms of locating fault are derived.The algorithm is demonstrated by digital computer simulations.

FAULT LOCATION AND RECORDING SYSTEM OF TRANSMISSION LINES BASED ON COMPUTER NETWORK

In this paper a fault location and recording system based on a computer network is presented. A brief description of the system structure and main features are given. Emphasis is placed on the accurate fault location method for extra high voltage and long distance transmission lines.

The MW5.5 earthquake on August 6,2023,in Pingyuan,Shandong,China:A rupture on a buried fault

On August 6,2023,a magnitude MW5.5 earthquake struck Pingyuan County,Dezhou City,Shandong Province,China.This event was significant as no large earthquakes had been recorded in the region for over a century,and no active fault had been previously identified.This study collects 1309 P-wave arrival times and 866 S-wave arrival times from 74 seismic stations less than 200 km to the epicenter to constrain the spatial distribution of the mainshock and its 125 early aftershocks by the double difference earthquake relocation method,and selects 864 P-waveforms from 288 stations located within 800 km of the epicenter to constrain the focal mechanism solution of the mainshock through centroid moment tensor inversion.The relocation and the inversion indicate,the Pingyuan MW5.5 earthquake was caused by a rupture on a buried fault,likely an extensive segment of the Gaotang fault.This buried fault exhibited a dip of approximately 75°to the northwest,with a strike of 222°,similar to the Gaotang fault.The rupture initiated at the depth of 18.6 km and propagated upward and northeastward.However,the ground surface was not broken.The total duration of the rupture was~6.0 s,releasing the scalar moment of 2.5895×1017 N·m,equivalent to MW5.54.The moment rate reached the maximum only 1.4 seconds after the rupture initiation,and the 90%scalar moment was released in the first 4.6 s.In the first 1.4 seconds of the rupture process,the rupture velocity was estimated to be 2.6 km/s,slower than the local S-wave velocity.As the rupture neared its end,the rupture velocity decreased significantly.This study provides valuable insights into the seismic characteristics of the Pingyuan MW5.5 earthquake,shedding light on the previously unidentified buried fault responsible for the seismic activity in the region.Understanding the behavior of such faults is crucial for assessing seismic hazards and enhancing earthquake preparedness in the future.

Modern Travelling Wave Based Fault Location Techniques for HVDC Transmission Lines

The modern travelling wave based fault location principles for transmission lines are analyzed.In order to apply the travelling wave principles to HVDC transmission lines,the special technical problems are studied.Based on this,a fault locating system for HVDC transmission lines is developed.The system can support modern double ended and single ended travelling wave princi- ples simultaneously,and it is composed of three different parts:travelling wave data acquisition and processing system,communication network and PC based master station.In the system,the fault generated transients are induced from the ground leads of the over-voltage suppression capacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 kV Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China.Some field operation experiences are summarized,showing that the system has very high reliability and accuracy,and the maximum location error is about 3 km(not more than 0.3%of the total line length). Obviously,the application of the system is successful,and the fault location problem has finally been solved completely since the line operation.

Fault locating for traveling-wave accelerators based on transmission line theory

Radio-frequency(RF)breakdown analysis and location are critical for successful development of high-gradient traveling-wave(TW)accelerators,especially those expected to generate high-intensity,high-power beams.Compared with commonly used schemes involving dedicated devices or complicated techniques,a convenient approach for breakdown locating based on transmission line(TL)theory offers advantages in the typical constant-gradient TW-accelerating structure.To deliver such an approach,an equivalent TL model has been constructed to equate the TW-accelerating structure based on the fun-damental theory of the TL transient response in the time domain.An equivalence relationship between the TW-accelerating structure and the TL model has been established via analytical derivations associated with grid charts and verified by TL circuit simulations.Furthermore,to validate the proposed fault-locating method in practical applications,an elaborate analysis via such a method has been conducted for the recoverable RF-breakdown phenomena observed at an existing prototype of a TW-accelerating-structure-based beam injector constructed at the Huazhong University of Science and Technology.In addition,further considerations and discussion for extending the applications of the proposed method have been given.This breakdown-locating approach involving the transient response in the framework of TL theory can be a conceivable supple-ment to existing methods,facilitating solution to construction problems at an affordable cost.

Adaptive restarting method for LCC-HVDC based on principle of fault location by current injection

The existing LCC-HVDC transmission project adopts the fixed-time delay restarting method.This method has disadvantages such as non-selectivity,long restart process,and high probability of restart failure.These issues cause a secondary impact on equipment and system power fluctuation.To solve this problem,an adaptive restarting method based on the principle of fault location by current injection is proposed.First,an additional control strategy is proposed to inject a current detection signal.Second,the propagation law of the current signal in the line is analyzed based on the distributed parameter model of transmission line.Finally,a method for identifying fault properties based on the principle of fault location is proposed.The method fully considers the influence of the long-distance transmission line with earth capacitance and overcomes the influence of the increasing effect of the opposite terminal.Simulation results show that the proposed method can accurately identify the fault properties under various complex fault conditions and subsequently realize the adaptive restarting process.

Fault Location Identification for Localized Intermittent Connection Problems on CAN Networks

The intermittent connection（IC）of the field-bus in networked manufacturing systems is a common but hard troubleshooting network problem,which may result in system level failures or safety issues.However,there is no online IC location identification method available to detect and locate the position of the problem.To tackle this problem,a novel model based online fault location identification method for localized IC problem is proposed.First,the error event patterns are identified and classified according to different node sources in each error frame.Then generalized zero inflated Poisson process（GZIP）model for each node is established by using time stamped error event sequence.Finally,the location of the IC fault is determined by testing whether the parameters of the fitted stochastic model is statistically significant or not using the confident intervals of the estimated parameters.To illustrate the proposed method,case studies are conducted on a 3-node controller area network（CAN）test-bed,in which IC induced faults are imposed on a network drop cable using computer controlled on-off switches.The experimental results show the parameters of the GZIP model for the problematic node are statistically significant（larger than 0）,and the patterns of the confident intervals of the estimated parameters are directly linked to the problematic node,which agrees with the experimental setup.The proposed online IC location identification method can successfully identify the location of the drop cable on which IC faults occurs on the CAN network.

Fault Location Method Based on EEMD and Traveling-Wave Speed Characteristics for HVDC Transmission Lines

This paper presents a method of Traveling Wave Fault location based on the improved Hilbert- Huang Transform. First, Intrinsic Mode Functions (IMF) of traveling waves are extracted by Ensemble Empirical Mode Decomposition (EEMD). Then Hilbert Transform is applied to calculate the corresponding instantaneous frequency of the highest frequency component (IMF1), the instantaneous frequency and corresponding time-frequency graph are obtained. Second, the arrival time and speed can be detected by the first instantaneous frequency’s mutational point. Finally, the improved two-terminal traveling wave fault location principle is used to calculate the fault distance. Relevant simulation results are performed to verify the correctness of the method by EMTDC software.

Overview of Distribution Network Fault Location

According to the existing research, the fault section location and fault location of passive distribution network and active distribution network are reviewed. Among them, fault location of passive distribution network mainly introduces fault segment location based on transient state and steady state quantity and fault location based on transient quantity. The active distribution network mainly introduces the fault segment location based on the current amount and the switching capacity based on the distribution network topology. On this basis, the difficulties of fault location in the distribution network at present are analyzed, and the future development is prospected.

Accurate Fault Location Modeling for Parallel Transmission Lines Considering Mutual Effect

:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance relay measures the impedance to the fault location which is the positive-sequence.The principle of summation the positive-,negative-,and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS.Also,the impedance of the transmission line to the fault location is determined.These algorithms are applied to single-line-to-ground(SLG)and double-line-to-ground(DLG)faults.To detect the fault location along the transmission line,its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area.TPTLS under study are fed from one-and both-ends.A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.

Method of Fault Area ＆ Section Location for Non-solidly Earthed Distribution System

中国中压配电网以架空线为主，多为小电流系统，单相接地故障占到电网故障总数的80％以上，但中国配网自动化系统基本上没有小电流接地故障定位功能，使配网自动化系统在提高可靠性的作用上大打折扣。给出一种小电流接地故障区段定位新方法，在线路上配置广域相量测量固定测点，获取小电流电网单相接地故障特征信息。基于测点相邻矩阵区段起始测点标识向量和故障路径标识向量概念，提出确定故障区间边界节点算法。物理模拟实验和挂网测试表明：该故障分区分段定位方法能够在线求解小电流接地故障段边界节点，缩小线路维护巡视范围。确定故障区间边界节点算法还可用于确定故障区相关负荷开关，为线路维护和馈线自动化提供依据。

Correlation Analysis Algorithm for Transmission Line Fault Location Based on Travelling Wave

This paper introduced correlation method to locate transmission line fault.First it described the principle of transmission line fault location based on traveling waves.The principle of correlation analysis is introduced,then the method using correlation analysis in fault location is given.Transmission line model is established with EMTP-ATP.Basing on the model,some kinds of fault are simulated.The feasibility of this algorithm is proved based on simulation results.By comparing with the classical wavelet analysis,this paper gave the advantages of this algorithm in two cases:noise influence suppression and accuracy of near distance fault location.Experiment is established to simulate transmission line grounding fault.The experiment result showed the correlation algorithm's validity.All the analysis result indicated that the correlation algorithm have a high precision.

Small-current grounding fault location method based on transient main resonance frequency analysis

The small-current grounding fault in distribution network is hard to be located because of its weak fault features.To accurately locate the faults,the transient process is analyzed in this paper.Through the study we take that the main resonant frequency and its corresponding component is related to the fault distance.Based on this,a fault location method based on double-end wavelet energy ratio at the scale corresponding to the main resonant frequency is proposed.And back propagation neural network(BPNN)is selected to fit the non-linear relationship between the wavelet energy ratio and fault distance.The performance of this proposed method has been verified in different scenarios of a simulation model in PSCAD/EMTDC.

Auxiliary Fault Location on Commercial Equipment Based on Supervised Machine Learning

As the fundamental infrastructure of the Internet,the optical network carries a great amount of Internet traffic.There would be great financial losses if some faults happen.Therefore,fault location is very important for the operation and maintenance in optical networks.Due to complex relationships among each network element in topology level,each board in network element level,and each component in board level,the con-crete fault location is hard for traditional method.In recent years,machine learning,es-pecially deep learning,has been applied to many complex problems,because machine learning can find potential non-linear mapping from some inputs to the output.In this paper,we introduce supervised machine learning to propose a complete process for fault location.Firstly,we use data preprocessing,data annotation,and data augmenta-tion in order to process original collected data to build a high-quality dataset.Then,two machine learning algorithms(convolutional neural networks and deep neural networks)are applied on the dataset.The evaluation on commercial optical networks shows that this process helps improve the quality of dataset,and two algorithms perform well on fault location.

Microearthquake reveals the lithospheric structure at midocean ridges and oceanic transform faults

Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics,but the deep structure of the oceanic lithosphere remains poorly understood.The large number of microearthquakes occurring along ridges and transforms provide valuable information for gaining an indepth view of the underlying detailed seismic structures,contributing to understanding geodynamic processes within the oceanic lithosphere.Previous studies have indicated that the maximum depth of microseismicity is controlled by the 600-℃isotherm.However,this perspective is being challenged due to increasing observations of deep earthquakes that far exceed this suggested isotherm along mid-ocean ridges and oceanic transform faults.Several mechanisms have been proposed to explain these deep events,and we suggest that local geodynamic processes(e.g.,magma supply,mylonite shear zone,longlived faults,hydrothermal vents,etc.)likely play a more important role than previously thought.

Fault Location Method for STATCOM Connected Transmission Lines Using CCM

Determining the fault location using conventional impedance based distance relay in the presence of FACTS controllers is a challenging task in a transmission line. A new distance protection method is developed to locate the fault in a transmission line compensated with STATCOM with simple calculations. The proposed protection method considers the STATCOM injected/absorbed current to correct the fault loop apparent impedance and accordingly calculates the actual distance to the fault location. The comprehensive equations needed for apparent impedance calculation are also outlined and the performance is evaluated and tested with a typical 400 KV transmission system for different fault types and locations using MATLAB/SIMULINK software. The evaluation results indicate that the new protection method effectively estimates the exact fault location by mitigating the impact of STATCOM on distance relay performance with error less than 0.3%.