スパースアレイ・レーダにおける信号処理技術

Tohoku University佐藤源之課

Estimation of turbidity in water treatment plant using hammerstein-wiener and neural network technique

Turbidity is a measure of water quality. Excessive turbidity poses a threat to health and causes pollution. Most of the available mathematical models of water treatment plants do not capture turbidity. A reliable model is essential for effective removal of turbidity in the water treatment plant. This paper presents a comparison of Hammerstein Wiener and neural network technique for estimating of turbidity in water treatment plant. The models were validated using an experimental data from Tamburawa water treatment plant in Kano, Nigeria. Simulation results demonstrated that the neural network model outperformed the Hammerstein-Wiener model in estimating the turbidity. The neural network model may serve as a valuable tool for predicting the turbidity in the plant

A multidisciplinary geophysical approach to recognize and quantify the gas occurrence in the Northern Adriatic

L'Adriatico settentrionale \ue8 caratterizzato da una presenza diffusa di gas nel sottosuolo, testimoniata da vari segni distintivi sul fondo mare e nei sedimenti sottostanti. Nel 2009 e nel 2014, OGS ha effettuato nell'area due campagne di sismica a riflessione 2D , finalizzate ad indagare la relazione tra le emissioni di gas, i cammini di migrazione e l'assetto geologico della regione. Inoltre, si voleva caratterizzare da un punto petrofisico i fluidi all'interno della successione sedimentaria. In questa tesi, due linee sismiche perpendicolari del dataset sono state selezionate ed analizzate. L'obiettivo era la determinazione della distribuzione del gas e la stima della sua concentrazione lungo le due linee sismiche, all'interno della successione sedimentaria Plio-Quaternaria e correlando log di pozzo e attributi sismici. Un approccio multidisciplinare \ue8 stato applicato sia nell'analisi che nell'interpretazione dei dati, integrando l'informazione geologica e quella geofisica. La caratterizzazione del gas nell'area di studio ha due implicazioni importanti: 1) Una valutazione complessiva della presenza di gas e della sua dinamica di migrazione all'interno della successione sedimentaria pu\uf2 vincolare il ruolo delle strutture tetttoniche identificate 2) L'approccio innovativo e multidisciplinare usato pu\uf2 essere applicato in altre aree di studio, caratterizzate dalla presenza di gas nei sedimenti e in simili assetti geologici. Inoltre, considerato il fondale molto basso dell'area, il trasferimento di gas dai sedimenti alla colonna d'acqua e nell'atmosfera potrebbe essere rapido e significativo. Comprendere a fondo i meccanismi di fuoriuscita di gas ha quindi importanti implicazioni climatologiche, dato che il metano, il componente principale del gas nell'area, ha un ruolo di spicco come gas serra.The Northern Adriatic is characterized by widespread occurrence of gas in the subsurface, testified by the presence of fluid related seabed and sub-seabed features (Donda et al., 2015, and references therein). In 2009 and 2014 OGS carried out two 2D multichannel seismic surveys in the area to constrain the relationship between gas emissions, migration paths and the regional geological setting. A further aim was to characterize the gas-charged fluids occurring within the sedimentary succession. Two seismic lines from these datasets were analyzed in the framework of this PhD thesis (GEA project, \u2019Gas Emissions in the Northern Adriatic Sea\u2019). The objective of this thesis is to determine the distribution of gas and estimate its concentration along the two selected perpendicular seismic profiles within the Plio-Quaternary sedimentary succession, through the petrophysical characterization of the sediments with the use of well-log to seismic attributes correlation. A multidisciplinary approach was applied both in the analysis and in the interpretation of the data, through the integration of geological information with geophysical wireline logs and seismic data. The proper characterization of the gas occurrence in the study area has two direct implications: 1. The comprehensive evaluation of both the gas occurrence and its migration within the sedimentary succession will constrain the role of the identified tectonic features; 2. The innovative and multidisciplinary approach used in this thesis could be applied to other areas characterized by gas-charged fluids in similar geological settings. Moreover, due to the shallow water in the Northern Adriatic, the potential transfer of gas from sediment to the water column and then into the atmosphere could be significant. Therefore, understanding the mechanisms of natural gas seepage has important climatological implications, since methane, the main component of the gas in the area (Donda et al., accepted), plays a major role as a greenhouse gas

Using Three-Component Data for Seismic Interferometry Studies at the Kylylahti Mine, Eastern Finland

The reflection seismic surveying method is useful when conducting mineral exploration in the crystalline bedrock because of its good depth extent and resolution. However, the traditional experiments with active sources are expensive and difficult to carry out, especially in remote areas or in conservation areas where mineral exploration is limited due to environmental reasons. Recently, a number of theoretical advances have proven that passive soundings utilizing ambient seismic noise can provide new opportunities for seismic imaging and contribute to data generation for reflection seismic surveys, without the need for explosive or vibratory sources. One of the most promising new methods is seismic interferometry (SI), where the impulse response between two receivers is reconstructed by correlating their signals with each other. COGITO-MIN is a joint project between the University of Helsinki, the Geological Survey of Finland, Polish Academy of Sciences, and industrial partners with the aim of investigating and developing new cost-effective seismic exploration methods in the crystalline bedrock. Within the framework of the project, a passive seismic experiment was carried out in which 45 three-component geophones were deployed for a month in the vicinity of the polymetallic Kylylahti Mine in Polvijärvi, northern Karelia, where the mining operator is the Swedish metal company Boliden. The original purpose of these geophones was to collect data suitable for detecting underground cavities related to underground nuclear explosions. The institute that collected the data was CTBTO (Comprehensive Test Ban Treaty Organization) whose task is to monitor the treaty in the pre-ratification stage. The purpose of this Master's thesis was to develop an SI workflow for the three-component data and to investigate the method's performance in an area where local geology is known after nearly 40 years of exploration and consequent mining operations. The specific scientific objectives of the thesis are (1) to demonstrate the usefulness of collecting three-component data in conjunction with or instead of single-component data, (2) to assess the noise-based SI methods used in previous studies and to improve their stability in the crystalline bedrock, and (3) to investigate the possibilities of SI from an operational perspective. Seismic velocities obtained through laboratory measurements were merged with geological and density models of the target area provided by Boliden. The resulting velocity and density grids were then used as the basis for waveform modelling, and the results from SI were validated against them. The starting point for SI was the noise-driven approach where 'each sample matters'. The interferometric workflow is built on the Seismic Unix suite together with self-written algorithms that are based on theoretical evaluations. SI is followed by an imaging workflow, which provides the basis for the reflectivity profiles. The thesis work focuses on five components of the Green's tensor and the vertical, radial and transverse component of the impulse response. With the horizontal components, one can access the S-wave patterns in addition to the P-waves. As a specialty, the so-called sign bit normalization (SBN) method was also tested. The technique involves destroying much of the amplitude information of the original seismograms by only retaining the sign bit of each sample. According to the results outlined in this thesis, SBN can make it easier to image the weak reflectors of the subsurface. This type of seismic interferometry seems particularly suitable for the early stage of mineral exploration, where the explorer does not yet fully understand the target they are studying. The most important advantage of seismic interferometry, however, is its cost effectiveness, and its potential for reducing risks for the environment.Den reflektionsseismiska mätmetoden är nyttig då man bedriver mineralprospektering i den kristallina berggrunden på grund av dess bra djupdimension och upplösning. De traditionella experimenten med aktiva källor är dock dyra och svåra att utföras, särskilt i avlägsna trakter eller i naturskyddsområden där mineralprospektering är begränsad på grund av miljöskäl. Under den senaste tiden har ett antal teoretiska framsteg bevisat att passiva lodningar som utnyttjar omgivningens seismiska brus kan ge nya möjligheter till seismisk avbildning och bidra till datagenerering för reflektionsseismiska undersökningar, utan att det behövs några explosions- eller vibrationskällor. En av de mest lovande nya metoderna är seismisk interferometri där impulsresponsen mellan två mottagare rekonstrueras genom att korrelera deras signaler mot varandra. COGITO-MIN är ett gemensamt projekt mellan Helsingfors universitet, Geologiska forskningscentralen, Polska vetenskapsakademien och industripartner med syfte att undersöka och utveckla nya kostnadseffektiva seismiska prospekteringsmetoder i den kristallina berggrunden. Inom ramen för projektet genomfördes ett passivt-seismiskt experiment där 45 trekomponentsgeofoner distribuerades under en månad i närheten av den polymetalliska Kylylahtigruvan i Polvijärvi, norra Karelen, där gruvoperatören är det svenska metallföretaget Boliden. Det ursprungliga syftet med de här geofonerna var att samla in data som är lämpliga för att upptäcka underjordiska hålor relaterade till kärnvapenexplosioner. Institutet som samlade in datan var CTBTO (Comprehensive Test Ban Treaty Organization) vars uppgift är att övervaka det omfattande testförbudsfördraget i världen innan det har ratificerats. Syftet med denna magisteravhandling var att utveckla ett interferometriskt arbetsflöde för seismiska trekomponentsdata och att utreda metodens prestanda i ett område där den lokala geologin redan är välkänd efter nästan 40 år prospekteringar och efter den därpå följande gruvbrytningen. De specifika vetenskapliga målen till avhandlingen är (1) att påvisa nyttan med att samla in trekomponentsdata i sammanhang med eller i stället för enkomponentsdata, (2) att forska de brusbaserade interferometrimetoder som använts i tidigare studier och förbättra deras stabilitet i den kristallina berggrunden samt (3) att utreda möjligheterna för seismisk interferometri ur ett operativt perspektiv. Hastighetsvärden som erhållits genom laboratoriemätningar slogs ihop med Bolidens geologiska modell över målområdet. De resulterande hastighets- och täthetsrutnäten användes sedan som basen för vågformsmodellering, och resultaten från seismisk interferometri validerades mot dem. Utgångspunkten för seismisk interferometri var det brusstyrda tillvägagångssättet där "varje sampel räknas". Det interferometriska arbetsflödet bygger på Seismic Unix -produkten och självskrivna algoritmer som baserar sig på teoretiska resonemang. Interferometrin följs av ett avbildningssteg som utgör en grund för de seismiska tvärsnitten. Avhandlingsarbetet fokuserar på fem komponenter i Greentensoren samt den vertikala, radiella och transversa komponenten av impulssvaret. Med de horisontala komponenterna kan man komma åt S-vågor förutom P-vågorna. Som specialitet testades också den så kallade teckenbitnormaliseringen där amplitudinformationen hos de ursprungliga seismogrammen hade förstörts genom att endast lämna kvar teckenbiten på varje sampel. Enligt resultaten kan teckenbitnormaliseringen göra det lättare att avbilda markens svaga reflektorer. Denna typ av seismisk interferometri verkar särskilt lämplig för det tidiga prospekteringssteget, där prospekteraren ännu inte har fullständig förståelse för det föremål han studerar. Den viktigaste fördelen med seismisk interferometri är dock dess kostnadseffektivitet och potentialen för minskningen av miljöriskerna

High‐Resolution Seismic Imaging of Fault‐Controlled Basins: A Case Study From the 2009 Mw 6.1 Central Italy Earthquake

We present the first seismic reflection images of the Paganica and Bazzano basins, two tectonic basins developed in the hanging wall of the Paganica-San Demetrio Fault System, the causative fault of the 2009 Mw 6.1 L'Aquila earthquake, Italy. Five high-resolution seismic profiles were acquired along a main, 7 km long transect cutting across the strands of an active fault system in urbanized areas with widespread sources of seismic noise. Three processing approaches were chosen to tackle a variable and site-dependent data quality . To aid interpretation of this complex setting, we complemented seismic amplitude images with energy and similarity attributes as well with post-stack acoustic impedance inversion. The final seismic sections expose, with unprecedented resolution, the basins' structure and the uppermost splays of the 2009 earthquake. The seismic data show fine details of the subsurface stratigraphic setting, revealing continental depocenters carved in the marine Meso-Cenozoic substratum and displaced by a series of conjugate normal faults, mostly unknown before this study. Several of the imaged fault strands connect to the 2009 coseismic surface ruptures. Matching the seismic interpretation with constraints from surface geology and shallow boreholes, published data from field surveys and scientific drilling, we present a structural map of the Bazzano and Paganica basins with an estimation of the depth of the Meso-Cenozoic substratum. This map highlights a different structure, evolution, and age of the two basins, with the older Bazzano basin that likely began to form in late Pliocene