Wide-area Situational Awareness Application Developments

This dissertation expands the topics from the wide-area situational awareness application development, system architecture design, to power system disturbance analysis. All the works are grounded on the wide-area Frequency Monitoring Network (FNET). The FNET system takes GPS-synchronized wide-area measurements in a low-cost, easily deployable manner at 120V single-phase power outlet. These synchronized observations enables the monitoring of bulk power systems, and provides critical information for understanding power system disturbances and system operations. Firstly, the work addresses the viability of angle measurement to serve different types of situational awareness applications, including the development of new angle-based event location estimation methods, the design of real-time system visualization framework using angle measurement. Secondly, a sound FNET power system event monitoring and automatic event reporting system framework is introduced, with NERC Frequency Response Initiative (FRI) tasks included to improve power system situational awareness capability. Lastly, the work covers different types of power system disturbance analysis, including the statistical analysis of frequency disturbances in NA power grid from 2008 to 2011; analysis of typical frequency response characteristics of the generation and load loss events in Europe power grid; analysis of some major disturbances in NA power grid from 2010 to 2011; and the inter-area oscillation modal analysis in the WECC system

Data-driven Localization and Estimation of Disturbance in the Interconnected Power System

Identifying the location of a disturbance and its magnitude is an important component for stable operation of power systems. We study the problem of localizing and estimating a disturbance in the interconnected power system. We take a model-free approach to this problem by using frequency data from generators. Specifically, we develop a logistic regression based method for localization and a linear regression based method for estimation of the magnitude of disturbance. Our model-free approach does not require the knowledge of system parameters such as inertia constants and topology, and is shown to achieve highly accurate localization and estimation performance even in the presence of measurement noise and missing data

Automatic processing of induced seismicity at the geothermal reservoirs Landau and Insheim

Besides political and striking uncertainty, induced seismicity is a fundamental risk to the success of geothermal projects. The geothermal reservoirs Landau and Insheim are located on the western rim of the Upper Rhine Graben where the highest fluid temperatures in Germany provide a good foundation for geothermal energy production while the complex tectonic structure provides a difficult set-up for geophysical investigations. In this thesis I advance automatic processing algorithms and apply them to assess characteristics of induced seismicity at the two geothermal reservoirs. Key objectives are to complete existing detection catalogs, determine the reliability of automatic processing results and to identify characteristics of induced earthquakes at the geothermal reservoirs which in future may be linked to operational parameters of the power plants. Challenging the completeness of existing catalogs a complementary offline similarity detection approach which considers multiple master events per reservoir is proposed. The second algorithm is an autoregressive prediction (AR)-Akaike Information Criterion (AIC)-cost-function arrival time determination approach which is straightforward trainable for different datasets on different scales and able to reliably pick robust seismic P- and S-phase arrival times on single- and multi-component data. The resulting hypocenter offsets standard deviations are approximately 1 km horizontally as well as vertically. Finally from hypocenter relative relocations, I am able to identify a spatial separation of the Insheim earthquake clusters retrieved by the similarity detection algorithm. Two orientations of seismicity are found to coincide with the stress regimes, firstly a south-east to north-west orientation during graben activity, and secondly a rather south-to-north orientation of the recently more dominant stress regime from Alpine denudation

Bayesian inference of focal mechanisms and backprojection methods for source kinematics characterization

The general goal of this thesis has been to characterize the seismic source of an earthquake. A source can be characterized by macroscopic characteristics in the approximation of a point source, as the location of the hypocenter, moment magnitude of the event and the focal mechanism. Moreover, we can also provide characteristics of the extended source, as its spatial dimensions or the final slip map on the fault plane rather than an average value. Another punctual quantity that can be provided is rupture velocity. We have focused not only on the moderate-to-large events, but we have also tried to infer characteristics for micro-seismicity, believing that the latter is a key to understanding more large-scale mechanisms (De Matteis, 2012). In particular, we focused on the estimation of focal mechanism of microearthquakes (Mw< 3). Firstly, we have developed an algorithm in an evolutionary Bayesian framework to give a rapid estimation of the earthquake focal mechanism using the few seconds of P-wave since the origin time of a set of recording stations for moderate earthquakes (Mw 4.5 to 6.5). Then, opportunely modifying this procedure allowing for the inclusion of S/P amplitude and inclusion of polarity, we tried to infer the focal mechanism also of micro-earthquakes (local magnitude < Ml 3.0). We then investigated two different approaches for back-projection. We performed the back projection as in Marcklin et al,2012 but near source and applied to a moderate event, the 6.5 Mw 2016 Norcia earthquake, retrieving the dominant rupture propagation toward south. Moreover, the duration (~8s) is in agreement with references. This approach beamforms and stacks displacement amplitude directly on the fault plane to retrieve slip rate and slip on the plane. There is also a different strategy to perform the back-projection (Xie & Meng, 2020) which locates the seismic radiators, that are sub-events of an earthquake. We applied the Multi-array Back-projection to study 3 different earthquakes at local and regional scales, in different tectonic regimes, to determine the location of seismic radiators and we used the distance from seismic radiators as source-to-site distance metric to considering for the path effect in local Ground Motion Prediction Equations. This technique does not require the discretization of the source in sub-sources, neither to orient the fault plane in the space. It works to match the coherency of waveforms to locate seismic radiators, which distribution reflects the main direction of the rupture and also the rupture length. We used the distance of stations to radiators at local scale in an evolutionary approach to obtain estimation of Peak Ground Acceleration (PGA) in time, predicting in good agreement the observed PGA some seconds before

Real-time compression of IEC 61869-9 sampled value data

Fast-acting, yet cost-effective, communications is critical for smarter grid monitoring, protection, and control. This paper demonstrates a new approach for the real-time compression of Sampled Value (SV) data based on the IEC 61869-9 recommendations. This approach applies simple compression rules, yet yields excellent compression performance---typically compressing data to less than half of the original size. This leads to a significant and beneficial reduction in encoding time (in the merging unit producing the SV data) and decoding time (at the end application), as well as the main benefit of reduced Ethernet transmission times resulting from the reduced frame size. As well as reducing the absolute bandwidth requirements in typical applications, this has system-wide benefits due to reducing Ethernet queuing delays and the consequent network jitter. The approach has been validated on a real-time platform to accurately measure all contributions to the end-to-end delay. This work will help enable low-latency and bandwidth-sensitive applications involving the SV protocol, such as phasor measurement units and wide-area protection

Strain partitioning and the seismicity distribution within a transpressive plate boundary : SW Iberia-NW Nubia

Tese de doutoramento, Geologia (Geodinâmica Interna), Universidade de Lisboa, Faculdade de Ciências, 2017The Gulf of Cadiz offshore SW Iberia is an area linked with episodic destructive seismic and tsunamigenic events, such as the M~8.8, 1st November 1755 Lisbon earthquake among others. The association of active faults to this kind of high magnitude event has been extensively studied specially due to the contribution of several international projects for more than two decades. However, the meaning of the persistent small to intermediate magnitude seismicity recognized in this region is still particularly not fully understood. This is, at least, related to the lack of an accurate hypocenter location of these events resulting from an asymmetrical geographical distribution of the permanent seismic network. One of the main purposes of the NEAREST project (Integrated observation from NEAR shore sourcES of Tsunamis: towards an early warning system GOCE, contract n. 037110) was the identification and characterization of seismogenic and tsunamigenic structures in the Gulf of Cadiz area, source region of the Lisbon 1755 earthquake and tsunami. To address this problem 24 broadband Ocean Bottom Seismometers (OBS) and a seafloor multiparametric station GEOSTAR (Geophysical and Oceanographic Station for Abyssal Research) acquired between August 2007 and July 2008 passive seismic data in this region. The results delivered a detailed record of the local seismicity, revealing 3 main clusters of earthquakes, two of them coinciding with the location of the 3 larger instrumental earthquakes in the area: i) the 28th February 1969 (Mw~8.0); ii) the 12th February 2007 (Mw=6.0) and iii) the 17th December 2009 (Mw=5.5). Focal mechanisms show a mixed pattern, mostly strike-slip and reverse dip-slip with a very few normal mechanisms. The results show that of the recorded events are located in the mantle (at depths between 30 and 60 km). This implies the existence of tectonically active structures located much deeper than the ones mapped by Multichannel seismic reflection. A thorough analysis shows that the seismicity clusters are offset with respect to the upper crustal active thrusts. The wide-range solutions of focal mechanisms also imply that the related source processes are complex. This can reflect the interaction of different active geological features, such as faults and rheological boundaries. To understand these new results in the context of the seismotectonics of the Gulf of Cadiz a review of some available geophysical data (reflection and refraction seismic profiles interpretation) in this area is presented as well as novel work on seismic reflection profile IAM GB1 across a rheologic boundary and seismicity cluster. Our study shows that the seismicity clusters are located at faults intersections mapped at the seafloor and shallow crust, suggesting that the crustal tectonic faults are replicated in the lithospheric mantle. These fault interferences are associated with boundaries of lithospheric domains prone to localize stress and seismic strain. Active crustal faults are either locked or move through slow aseismic slip. Frictional slip in crustal faults is probably limited to high magnitude earthquakes. Serpentinization probably induces tectonic decoupling limiting micro-seismicity to depths below the serpentinized layer. It is expected that during highmagnitude events seismic rupture is favored by weakening mechanisms and propagates upwards through the serpentinized layer up to the surface. The results obtained in this work improve our knowledge about the local seismicity and related active faults in the Gulf of Cadiz area, giving a new contribution to access to the seismic hazard in the Nubia-Iberia plate boundary in the Northeast Atlantic Region.O Golfo de Cádis é uma região com uma sismicidade moderada embora se conheça, tanto no registo histórico como instrumental, eventos de elevada magnitude. O sismo de 1 de Novembro de 1755 é um exemplo paradigmático com uma magnitude estimada de 8.8 e um tsunami associado com Mt = 8.5. Já o sismo de 28 de Fevereiro de 1969, é o mais importante registado instrumentalmente, teve uma Ms de 7.9, ao qual esteve associado um pequeno tsunami. Mais recentemente, salientam-se os sismos de 12 de Fevereiro de 2007, com Mw=6.0 e o de 17 de Dezembro de 2009, com Mw =5.5 (EMSCEuropean-Mediterranean Seismological Centre). No entanto, a sismicidade nesta região é descrita como de magnitude baixa a intermédia, com uma distribuição em profundidade acima dos 60 km. Correlacionar esta sismicidade com potenciais estruturas sismogénicas no Golfo de Cádis constituiu um dos objectivos do projecto NEAREST (Integrated observation from NEAR shore sourcES of Tsunamis: towards an early warning system GOCE, contract n. 037110). Neste contexto, foram necessárias uma caracterização e localização mais precisas dos eventos sísmicos ocorridos nesta região, até agora limitadas pelos constrangimentos inerentes à distribuição geográfica das estações permanentes terrestres. Por isso, foi desenvolvida uma campanha de aquisição de dados contínuos utilizando uma rede de sismómetros de fundo do mar. A rede sísmica NEAREST operou de modo contínuo num período de 11 meses, entre Agosto de 2007 Julho de 2008, integrando 24 sismómetros de fundo do mar (OBS) e uma estação multiparamétrica- GEOSTAR. Durante as campanhas de colocação e recuperação dos instrumentos, as manipulações dos OBS e GEOSTAR estiveram a cargo do Alfred Wegener Institute for Polarand Marine Research e do Istituto Nazionale di Geofisica e Vulcanologia – INGV, respectivamente. Os OBS foram construídos pela K.U.M. Umwelt- und Meerestechnik Kiel GmbH, Germany e incorporavam sismómetros de banda larga Güralp CMG-40T e um hidrofone. A GEOSTAR é um observatório que integra diversos equipamentos para a recolha de dados geofísicos e oceanográficos em contínuo. Nesta estação estão incluídos um sismómetro de banda larga com 3 componentes e um hidrofone usados nesta campanha. As estações terrestres estão a cargo do Instituto Português do Mar e da Atmosfera (IPMA) e Instituto Dom Luiz (IDL) correspondendo a sismómetros de banda larga também com 3 componentes. Os registos nestas estações foram apenas utilizados para constranger as soluções dos mecanismos focais. Em trabalhos futuros, prevê-se a sua inclusão na localização dos eventos identificados pela rede NEAREST. Durante o período de aquisição foram registados na rede terrestre, para a área delimitada pela rede NEAREST, cerca de 270 sismos locais. Durante o período de funcionamento da rede NEAREST foram identificados cerca de 750 eventos observados em mais de 3 estações. Deste total 590 sismos estavam localizados na área da rede NEAREST. A localização hipocentral foi testada usando diferentes metodologias e modelos de velocidades: a) inversão conjunta das posições hipocentrais e correcções de estações; b) o método das diferenças duplas e c) a inversão conjunta do modelo de velocidades-localizações hipocentrais e correcções de estações. O catálogo final inclui 443 eventos identificados em mais de 6 estações e localizados na área da rede NEAREST. De um modo geral, a maioria dos hipocentros estão localizados a mais de 30 km de profundidade, portanto no manto. As magnitudes locais variam entre 1.2 e 4.8. As localizações epicentrais e hipocentrais baseadas na rede NEAREST divergem das soluções conhecidas para a rede terrestre (providenciadas pelo IPMA), estando deslocadas para SW e sendo mais profundas. A diferença de profundidade pode atingir os 40 km. A campanha do projecto NEAREST permitiu a identificação de uma grande quantidade de eventos não detectada pela rede terrestre. Esta campanha permitiu ainda uma redefinição da distribuição da sismicidade na região, até então considerada difusa. Destes resultados foi possível reconhecer 3 enxames de sismicidade, dois destes coincidentes com 3 dos maiores eventos observados no registo instrumental. Tanto os sismos de 28 de Fevereiro de 1969 (Mw~8.0) como 12 de Fevereiro de 2007 (Mw=6.0) na proximidade da Falha da Ferradura e 17 de Dezembro de 2009 (ML=6.0) na região do canhão de São de Vicente. Os mecanismos focais do catálogo NEAREST são consistentes com estes eventos bem como com soluções de tensores de momento publicadas para esta região. No enxame do canhão de São Vicente é onde estão localizados a maioria dos eventos. Os hipocentros encontram-se a profundidades entre os 20 e os 55 km. A distribuição dos epicentros apresenta um alinhamento ≈ NE-SW ao longo do canhão de São Vicente e prolongando-se para o limite NE da Falha da Ferradura. Os mecanismos focais dominantes são de desligamento e oblíquos, combinando movimento de desligamento com uma menor contribuição de movimento inverso. Foram ainda registados raros eventos em falha normal. A compressão máxima é aproximadamente sub-paralela ao SHmax, com uma direcção ≈NW-SE. Os epicentros localizados no enxame a SW da Falha da Ferradura, tem um alinhamento aproximadamente NW-SE, sub-paralelo à direcção de SHmax regional. Neste enxame os hipocentros são mais profundos localizando-se entre os 30 e os 55km. Os mecanismos focais são na sua maioria de desligamento puro existindo alguns eventos em falha inversa e também raras soluções em falha normal. Importa salientar que as soluções de desligamento apresentam frequentemente um plano subparalelo à orientação das falhas de desligamento SWIM (≈WNW-ESE a E-W). A compressão máxima é aproximadamente NW-SE e NNW-SSE, a W e E do enxame de sismicidade, respectivamente. As direcções de SHmax são mais uma vez coincidentes com a direção de compressão máxima. No enxame do Banco do Gorringe maioria dos sismos estão localizados no bordo SW deste relevo submarino, sub-paralelos à falha do Gorringe. Os eventos são menos profundos quando comparados com os outros dois enxames, na sua maioria acima dos 40 km. Os mecanismos focais são na sua maioria de desligamento e em falha inversa. Também neste enxame foram registados alguns sismos em falha normal. A direcção de compressão máxima e o SHmax são NNW-SSE. O facto de estes eventos se localizarem predominantemente no manto constitui um dos principais resultados deste trabalho. Neste contexto, tendo em consideração a profundidade dos eventos sísmicos, a correlação da sismicidade com as estruturas sismogénicas na região do Golfo de Cádis é particularmente complexa. Esta comparação foi desenvolvida com base nos dados de sísmica de reflexão e refração disponíveis. Do nosso estudo resulta que a sismicidade parece estar concentrada em zonas de interferência de falhas localizadas no manto subcrustal litosférico. Estas deverão ser uma replicação do padrão observado a níveis crustais e parecem ser coincidentes com transições entre diferentes domínios litosféricos. Estas zonas de interferência de falhas deverão ser áreas favoráveis à acumulação de tensões e deformação sísmica. As falhas activas crustais deverão estar ou bloqueadas ou movimentar-se de modo assísmico. A movimentação sísmica pode estar associada apenas a sismos de maior magnitude. A existência de níveis serpentinizados no Golfo de Cádis é suportada por dados de sísmica refracção e furos de sondagens profundas. Estes podem funcionar como planos de descolamento para as grandes falhas inversas, acomodando a movimentação asísmica e impedindo a micro-sismicidade de se propagar aos níveis crustais. Durante os sismos de elevada magnitude estes níveis serpentinizados deverão funcionar como zona enfraquecida, de baixo atrito, favorecendo a propagação da ruptura sísmica até à superfície. Os resultados obtidos neste trabalho melhoram o nosso conhecimento sobre a sismicidade e a sua relação com as falhas activas na região do limite de placas litosféricas no Golfo de Cádis, contribuindo para o estudo do risco sísmico associada a sismos devastadores

Frequency Monitoring Network (FNET) Data Center Development and Data Analysis

Frequency Monitoring Network (FNET) is an Internet-based, wide-area phasor measurement system that collects power system data using Frequency Disturbance Recorders (FDRs) that are installed at the distribution level. The FNET data center enables the monitoring of bulk power systems, and provides wide-area situational awareness and disturbance analysis for understanding power system disturbances and system operations. Therefore, the data center plays a very critical role in the entire FNET system framework. In recent years, many potential challenges brought by the rapid expansion of the FNET system have underlined the importance of designing the next-generation FNET data center. More discussions about the motivation and guidelines to design the next-generation FNET data center will be presented in Chapter 2, along with a brief introduction of the new infrastructure composing of multiple data storage and application layers. A distributed alarming agent that communicates between real-time applications and near-real-time applications is discussed in detail. Chapter 3 proposes the data storage solutions for FNET time-series measurement data, configuration data and analysis records. Chapter 4 addresses the challenges of the real-time application development. The algorithm, configuration parameters and data processing procedures of the real-time event detection, oscillation detection, and islanding detection are presented in detail. Chapter 5 introduces the implementation of the FNET map-based web display using the measurement data feed provided by the openHistorian data publisher service. Besides contributing to the situation awareness applications, the researches presented here explore novel data analysis perspectives to investigate power grids’ behavior. Chapter 6 introduces a frequency distribution probability calculation method, applies this method to frequency measurement data from 2005-2013 collected by the FNET system, investigates the distribution probability of frequency data over North American and also worldwide power grids, and compares the distribution patterns during different years, seasons, days of a week and periods of a day. Chapter 7 presents a solution method to produce replay videos based on FDRs’ normalized voltage magnitude data and investigates the voltage magnitude pattern changes over the Eastern Interconnection (EI) during events and days by using historical FNET measurement data. Conclusions and possible future research topics are given in Chapter 8

A multi-technology analysis of the 2017 North Korean nuclear test

On 3 September 2017 official channels of the Democratic People's Republic of Korea announced the successful test of a thermonuclear device. Only seconds to minutes after the alleged nuclear explosion at the Punggye-ri nuclear test site in the mountainous region in the country's northeast at 03:30:02 (UTC), hundreds of seismic stations distributed all around the globe picked up strong and distinct signals associated with an explosion. Different seismological agencies reported body wave magnitudes of well above 6.0, consequently estimating the explosive yield of the device on the order of hundreds of kT TNT equivalent. The 2017 event can therefore be assessed as being multiple times larger in energy than the two preceding North Korean events in January and September 2016. This study provides a multi-technology analysis of the 2017 North Korean event and its aftermath using a wide array of geophysical methods. Seismological investigations locate the event within the test site at a depth of approximately 0.6&thinsp;km below the surface. The radiation and generation of P- and S-wave energy in the source region are significantly influenced by the topography of the Mt. Mantap massif. Inversions for the full moment tensor of the main event reveal a dominant isotropic component accompanied by significant amounts of double couple and compensated linear vector dipole terms, confirming the explosive character of the event. The analysis of the source mechanism of an aftershock that occurred around 8&thinsp;min after the test in the direct vicinity suggest a cavity collapse. Measurements at seismic stations of the International Monitoring System result in a body wave magnitude of 6.2, which translates to an yield estimate of around 400&thinsp;kT TNT equivalent. The explosive yield is possibly overestimated, since topography and depth phases both tend to enhance the peak amplitudes of teleseismic P waves. Interferometric synthetic aperture radar analysis using data from the ALOS-2 satellite reveal strong surface deformations in the epicenter region. Additional multispectral optical data from the Pleiades satellite show clear landslide activity at the test site. The strong surface deformations generated large acoustic pressure peaks, which were observed as infrasound signals with distinctive waveforms even at distances of 401&thinsp;km. In the aftermath of the 2017 event, atmospheric traces of the fission product 133Xe were detected at various locations in the wider region. While for 133Xe measurements in September 2017, the Punggye-ri test site is disfavored as a source by means of atmospheric transport modeling, detections in October 2017 at the International Monitoring System station RN58 in Russia indicate a potential delayed leakage of 133Xe at the test site from the 2017 North Korean nuclear test.</p