Fault Moment Research Articles

A smoothed stochastic earthquake rate model considering seismicity and fault moment release for Europe

EC-Research FP7-projects, SHARE, under grant agreement No. 226967 and NERA, under grant agreement No. 262330

A New Algorithm of Phase to Ground Fault Location for Electric Power Feeder

t is a great significance for power supply reliability and smart grid to locate feeder fault quickly and accurately for distribution network. A new ground fault traveling-wave signal time-frequency analysis method is proposed, which decomposes the aerial mode component and zero mode component of fault current based on EMD to get multi-stage stable intrinsic mode function (IMF). The first IMF contains high frequency components which can reflect the mutation of signal. Hilbert-Huang transformation is done for the first IMF to get the instantaneous frequency of signal. And then check the moment of traveling wave arrival by the instantaneous frequency in the figure of IMF time-frequency. The fault distance is computed based on the time difference between the moments of wave arrived of aerial mode component and zero mode components. Simulation shows that this method is able to accurately give the distance of fault without the influence of the random fault condition such as fault transition resistance and the moment of fault.

Research on the Control Strategy of DFIG Grid Side Converter under Unbalanced Grid Voltage Conditions

This paper studies on the electromagnetic transient model of doubly-fed wind turbine grid-side converter under the imbalanced grid condition. And on this basis, the paper analysis the impact of doubly-fed converter when grid voltage asymmetric drop. It puts forward a dual PLL and dual current control combination of doubly-fed converter grid side control strategy. This strategy achieves grid voltage positive and negative sequence fast separation when asymmetric grid voltage drop occur, achieves the active output power secondary fluctuate suppression under the imbalanced grid voltage condition, avoids DC voltage rise at the fault moment and also achieves converter reactive power support under the imbalanced grid fault. The simulation and experimental results show that the proposed control strategy is correct and with the application value of engineering

Study of Failure Rate Model for a Large-Scale Water Supply Network in Southern China Based on Different Diameters

This paper studies on the electromagnetic transient model of doubly-fed wind turbinegrid-side converter under the imbalanced grid condition. And on this basis, the paper analysis theimpact of doubly-fed converter when grid voltage asymmetric drop. It puts forward a dual PLL anddual current control combination of doubly-fed converter grid side control strategy. This strategyachieves grid voltage positive and negative sequence fast separation when asymmetric grid voltagedrop occur, achieves the active output power secondary fluctuate suppression under the imbalancedgrid voltage condition, avoids DC voltage rise at the fault moment and also achieves converterreactive power support under the imbalanced grid fault. The simulation and experimental resultsshow that the proposed control strategy is correct and with the application value of engineering.

First evidences of fast creeping on a long-lasting quiescent earthquake normal-fault in the Mediterranean

SUMMARY A key issue in our understanding of the earthquake cycle and seismic hazard is the behaviour of an active fault during the interseismic phase. Locked and creeping faults represent two end-members of mechanical behaviours that are given two extreme rupturing hazard levels, that is, high and low, respectively. Geophysical and space geodetic analyses are carried out over the Pollino Range, an extensional environment within the Africa–Eurasia plate boundary, to disclose the behaviour of the long-lasting quiescent Castrovillari normal fault. Fault trenching evidenced at least four large earthquakes (6.5–7.0 Mw) in the past and an elapsed time of 1200 yr since the last event. Inversion of Differential Interferometric Synthetic Aperture Radar and Global Positioning System over a decade shows fast creeping at all depths of the fault plane. The velocity-strengthening creeping zone reaches maximum rates 20 mm yr −1 against an average rate of about 3–9 mm yr −1 . It limits the southern-weakening locked part of the fault. An essential condition for the generation of a large earthquake on the Castrovillari fault, as has occurred in the past, is a rupture through the velocity-strengthening zone. The Castrovillari fault yields the best evidence for being both a strong and weak fault during its earthquake cycle. Creeping at rates faster than its tectonically driven ones, it must thus consist of a mix of unstable and conditionally stable patches ready to sustain a sizeable earthquake. Quantifying and mapping the slip rate over the fault plane is important because they influence fault moment budget estimate and helps to constrain constitutive laws of fault zones. Aseismic slip also redistributes stress in the crust, thereby affecting the locations of future earthquakes.

Spatial structures in earthquakes and faults: quantifying similarity in simulated stress fields and natural data sets

This paper presents an adaptation for fault analysis of the coherence method of Kagan and Knopoff [Kagan, Y.Y., Knopoff, L., 1985b. The two-point correlation function of the seismic moment tensor. Geophysical Journal of the Royal Astronomical Society 83, 637–656], understanding coherence as a measure of the similarity between fault-slip data for two faults, which can be analytically computed from earthquake or fault moment tensors. Through the use of a customized GIS routine, the degree and distribution of similarity in synthetic and natural fault populations can be calculated as a function of distance between fault/earthquake pairs and their relative orientation. Stress simulations using synthetic data sets reveal that fault populations, which developed under homogeneous stress fields, have a high degree of similarity that increases with the slip tendency of faults. Stress ratio variations, and especially stress axis rotations, lower the coherence values. Spatial analysis of natural earthquake and fault data sets from the Umbria–Marche region (Northern Apennines, Italy) reveals a common pattern of coherence spatial cyclicities in faults/earthquakes controlled by two consecutive tectonic phases, Miocene compression and Plio-Pleistocene extension. The proposed interpretation attributes the spatial cyclicities of Miocene data to syn- to post-faulting folding, in agreement with wavelengths derived from field data. The observed periodicities in earthquakes (1997 Colfiorito–Sellano Umbria–Marche seismic sequence) could, in turn, have been controlled by the Miocene thrust structures, with possible spatial stress field axis rotations and/or stress ratio variations. The spatial characteristics of younger fault/earthquake populations are thus possibly controlled by the characteristics of older tectonic structures, such as fold wavelength or fault spacing.

Application of GIS to spatial analysis of mesofault populations

This paper presents a GIS approach to spatial analysis of fault populations. Coherence between fault moment tensors, a concept borrowed from the geophysical works of Kagan and Knopoff [1985a. Geophysical Journal of the Royal Astronomical Society 81(2), 429–444; 1985b. Geophysical Journal of the Royal Astronomical Society 83(3), 637–656], is the parameter used for quantifying the degree of similarity between faults. Fault datasets from various structural sites can be imported into a GIS software such as ArcView®; using a series of customized GIS tools, data can then be checked and their spatial dependence may be investigated. This customization may be used to investigate the distribution of coherence values based on fault types (i.e. normal, left-lateral, etc.) and/or on the distance between faults. The analysis of a natural dataset reveals that, depending on the movement type, faults can display different coherence distributions with increasing distance ranges, and in some cases also a cyclic behavior. These findings can help reconstruct the history and understand the kinematic significance of fault populations.

The investigation of the multi-shielding system of the superconducting generator

In this paper the electromagnetic shielding behavior of the multi-shielding system in superconducting synchronous generators, the influence of one screen upon the others and the sharing of fault moment among the different screens have been investigated. Definition of magnetic penetrability has been made for describing the electromagnetic shielding behaviors of screens. The influence of operation temperature of inner screen on the system was investigated too, and a method of determining the mean temperature of inner screen was proposed.