Journal articles on the topic 'System identification- Geophysical signals'
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1
Lubis, Muhammad Zainuddin, Kasih Anggraini, Husnul Kausarian, and Sri Pujiyati. "Review: Marine Seismic And Side-Scan Sonar Investigations For Seabed Identification With Sonar System." Journal of Geoscience, Engineering, Environment, and Technology 2, no. 2 (June 1, 2017): 166. http://dx.doi.org/10.24273/jgeet.2017.2.2.253.
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Marine seismic reflection data have been collected for decades and since the mid-to late- 1980s much of this data is positioned relatively accurately. Marine geophysical acquisition of data is a very expensive process with the rates regularly ship through dozens of thousands of euros per day. Acquisition of seismic profiles has the position is determined by a DGPS system and navigation is performed by Hypack and Maxview software that also gives all the offsets for the equipment employed in the survey. Examples of some projects will be described in terms of the project goals and the geophysical equipment selected for each survey and specific geophysical systems according to with the scope of work. For amplitude side scan sonar image, and in the multi-frequency system, color, becoming a significant properties of the sea floor, the effect of which is a bully needs to be fixed. The main confounding effect is due to absorption of water; geometric spread; shape beam sonar function (combined transmit-receive sonar beam intensity as a function of tilt angle obtained in this sonar reference frame); sonar vehicle roll; form and function of the seabed backscatter (proportion incident on the seabed backscattered signal to sonar as a function of the angle of incidence relative to the sea floor); and the slope of the seabed. The different angles of view are generated by the translation of the sonar, because of the discrete steps involved by the sequential pings, the angular sampling of the bottom.
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Abramovych, А. О. "IMPROVING THE EDDY CURRENT IDENTIFIER OF METALS BASED ON THE CORRELATION APPROACH." Radio Electronics, Computer Science, Control, no. 4 (December 3, 2022): 7. http://dx.doi.org/10.15588/1607-3274-2022-4-1.
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Context. The article considers the problem of improving the eddy current device for metal identification on the basis of the correlation approach. This approach is convenient for the accumulation of a database of known leading materials, as well as for the comparison of the signal from an unknown metal object with the available standards in the database. The proposed approach allows to determine the type of metal from which the sample is made, without damaging its surface.
Objective. The aim of the work is the identification of metals by type on the feedback signals from the eddy current converter, due to the identification of new informative features and the creation of a database of images of metals.
Method. The paper presents the results of an experimental study of the proposed approach to increase the reliability of identification of metal objects that are detected using an eddy current device. These studies are conducted on the basis of a radio system that operates on the eddy current principle and has low-frequency magnetic loop antennas. The eddy current method allows the identification of metals by type remotely and without damaging their surface, in contrast to X-ray fluorescence, optical emission or chemical methods. A correlation approach for processing the response signal spectrum from a hidden metal object is proposed. The correlation approach allows to increase the reliability of the identification of metals by type when processing the signal in the spectral region based on the Fourier transform. Studies have been conducted on the example of metals that have similar spectral characteristics (silver, gold, lead). The updated approach allowed to increase the percentage difference between the information parameters of signals – responses from 1.87% to 5.02% for silver and gold, from 2.24% to 4.34% for silver and lead and from 0.36% to 0.7% for gold and lead.
Results. The developed radio system is a laboratory model, which consists of an analog part and a digital one. The analog part is an antenna unit, a signal amplifier and a bandpass filter, a digital part – a microcontroller with an ADC for digitizing and transmitting data to a laptop, which software implements the proposed approaches to signal processing. The paper experimentally confirmed the possibility of using a radio engineering system to solve the problem of metal identification within a subset of nonmagnetic and magnetic materials.
Conclusions. The development of modern eddy current devices is aimed at increasing the reliability of the identification the hidden metal objects, which is relevant in geophysical exploration, archeology, and law enforcement agencies in the search for hidden non-ferrous metals. The development and improvement of such systems includes both the development the hardware and the discovery new information parameters in the feedback signals from metals. One such direction may be the correlation approach to signal processing in the spectral region.
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Abazarsa, Fariba, Fariborz Nateghi, S. Farid Ghahari, and Ertugrul Taciroglu. "Blind Modal Identification of Non-Classically Damped Systems from Free or Ambient Vibration Records." Earthquake Spectra 29, no. 4 (November 2013): 1137–57. http://dx.doi.org/10.1193/031712eqs093m.
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A significant segment of system identification literature on civil structures is devoted to response-only identification, simply because lack of measurements of input excitations for civil structures is a fairly common scenario. In recent years, several researchers have successfully adapted a second-order blind identification (SOBI) technique—a method originally developed for “blind source separation” of audio signals—to response-only identification of mechanical and civil structures. However, this development had been confined to fully instrumented classically damped systems. While several approaches have been proposed recently for extending SOBI to non-classically damped systems, they all require additional data such as velocity or analytic signals. Herein, we present a version of SOBI that requires only acceleration signals recorded during free or ambient vibration tests, and yields the system's complex mode shapes, natural frequencies, and damping ratios. Performance of the proposed technique is demonstrated through two synthetic examples: a ten-story structure possessing a passive control system, and a soil-structure system with seven degrees of freedom (seven-DOF).
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Bodin, Jacques, Gilles Porel, Benoît Nauleau, and Denis Paquet. "Delineation of discrete conduit networks in karst aquifers via combined analysis of tracer tests and geophysical data." Hydrology and Earth System Sciences 26, no. 6 (April 1, 2022): 1713–26. http://dx.doi.org/10.5194/hess-26-1713-2022.
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Abstract. Assessment of the karst network geometry based on field data is an important challenge in the accurate modeling of karst aquifers. In this study, we propose an integrated approach for the identification of effective three-dimensional (3D) discrete karst conduit networks conditioned on tracer tests and geophysical data. The procedure is threefold: (i) tracer breakthrough curves (BTCs) are processed via a regularized inversion procedure to determine the minimum number of distinct tracer flow paths between injection and monitoring points, (ii) available surface-based geophysical data and borehole-logging measurements are aggregated into a 3D proxy model of aquifer hydraulic properties, and (iii) single or multiple tracer flow paths are identified through the application of an alternative shortest path (SP) algorithm to the 3D proxy model. The capability of the proposed approach to adequately capture the geometrical structure of actual karst conduit systems mainly depends on the sensitivity of geophysical signals to karst features, whereas the relative completeness of the identified conduit network depends on the number and spatial configuration of tracer tests. The applicability of the proposed approach is illustrated through a case study at the Hydrogeological Experimental Site (HES) in Poitiers, France.
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Akhi, A. V. "Akhi A.V. Efficiency of Identification of Complex Noise-Like Signal Classes by Dolphins (<i>Tursiops truncatus</i>) under Simultaneous Presentation Spatial Uncertainty." Fundamental and Applied Hydrophysics 16, no. 1 (April 23, 2023): 90–97. http://dx.doi.org/10.59887/fpg/vxe3-6531-nkup.
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The possibility of dolphin’s auditory system to solve the complex problem of identifying and classifying noise-like signals according to certain invariant features is considered under conditions of spatial uncertainty of their simultaneous presentation. There was studied the ability of bottlenose dolphins, which were trained to recognize and classify such signals, to select a certain class of signals from several that sound simultaneously. The dolphin had to recognize a positive class signal with a pair of simultaneously sounding signals: positive-negative (alternative choice) and with simultaneously sounding three signals: positive-negative-negative (multiple choice). It’s shown that the dolphin effectively solves the problem with a simple alternative choice of two signal sources, at the limit of reliability when choosing from three sources and unreliable when choosing from more sources.
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KOH, C. G., and M. J. PERRY. "STRUCTURAL DAMAGE QUANTIFICATION BY SYSTEM IDENTIFICATION." Journal of Earthquake and Tsunami 01, no. 03 (September 2007): 211–31. http://dx.doi.org/10.1142/s1793431107000134.
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After a disaster such as an earthquake has struck, the damage assessment of the affected buildings, bridges and other forms of structures is often urgently required for follow-up action. Research in using system identification for damage assessment in a quantifiable and non-destructive way has rapidly increased in recent years, due to advances in computing power and sensing technology. Though considerable progress has been made, many challenges still remain in achieving robust and effective identification of large structural systems using incomplete and noisy measurement signals. In this paper a novel strategy to tackle this problem is presented. A modified genetic algorithm (GA) strategy incorporating a search space reduction method, progressively and adaptively reduces the search space for each unknown parameter. By concurrent evolution of multiple species, it provides an excellent balance between exploration of the search space and exploitation of good solutions. The modified GA is incorporated into a damage detection strategy that works by comparing identified parameters for the undamaged and damaged structures and quantifies damage as a relative change in the stiffness of a member or a group of members. The additional information obtained from the analysis of the undamaged structure is used to greatly improve speed and accuracy in the identification of the damaged structure. Numerical studies on 10 and 20 degree-of-freedom (DOF) systems and an experimental study of a 7-storey small-scale steel frame are presented to illustrate the applicability of the method in accurately identifying even small amounts of damage.
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Zamora Santacruz, Mario Fernando, Mario RUIZ, and Jose OSORNO. "The Exploration of Hydrocarbons and Mining & Energy Resources Using Non-Seismic Methods - Nuclear Magnetic Resonance Technology." Technium: Romanian Journal of Applied Sciences and Technology 2, no. 7 (December 22, 2020): 372–89. http://dx.doi.org/10.47577/technium.v2i7.2258.
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Nuclear Magnetic Resonance-based technology is a geophysical method used in the exploration of hydrocarbons and other mineral resources, by studying electromagnetic signals from natural sources. The foregoing method has three phases: the first phase encompasses the identification of areas where hydrocarbons or other minerals are present at a regional level, using remote sensors; the anomalies identified are studied in detail in the second phase, during which the passive acquisition of electromagnetic signals on the surface with under 30m spacing be- tween points allows demarcating the areas with the highest and lowest intensity, to finally obtain stratigraphic columns at points selected after measuring the basic parameters using Vertical Probing with Electro – Resonance.
The study conducted for Agencia Nacional De Hidrocarburos (ANH) evaluated a total of 1083 Km2 spread over five areas whose topography, climate and vegetation restricted the acquisition of geological and geophysical data with traditional methods. Two of the five polygons are located in the part of the Chocó basin called Ánimas (163 km2) and Istmina (344 km2) while Timbiquí (159 km2), Remolino (200 km2) and Guayacana (217 km2) are in the Tumaco basin. The results of the satellite stage included the identification of 178 km2 of liquid hydrocarbon type anomalies in the Choco basin and 22 km2 of gaseous hydrocarbon-type anomalies in the Tumaco basin. The anomaly located in Animas was chosen for the field stage. It was detailed by demarcating the areas with the highest and lowest intensity, in which vertical probing took place, allowing for the in-depth characterization of nine parameters (H2O, CaCO3, Si, C10 H22, CH4, C21H44, Clays, Albite, Anorthite) in up to 4,000 m, identifying intervals showing a significant presence of hydrocarbons at 3,280 ft, 6,950 ft and 12,210 ft with a 36 ft.-average thickness, and an estimated basement depth of 12,650 ft. The correlation with seismic data allowed confirming the results, thus proving that the use of non-seismic methods in exploration and prospection processes allow for a better understanding of petroleum systems, while reducing uncertainty and exploratory hazards
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Munoz-Martin, Joan Francesc, Raul Onrubia, Daniel Pascual, Hyuk Park, Adriano Camps, Christoph Rüdiger, Jeffrey Walker, and Alessandra Monerris. "Untangling the Incoherent and Coherent Scattering Components in GNSS-R and Novel Applications." Remote Sensing 12, no. 7 (April 9, 2020): 1208. http://dx.doi.org/10.3390/rs12071208.
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As opposed to monostatic radars where incoherent backscattering dominates, in bistatic radars, such as Global Navigation Satellite Systems Reflectometry (GNSS-R), the forward scattered signals exhibit both an incoherent and a coherent component. Current models assume that either one or the other are dominant, and the calibration and geophysical parameter retrieval (e.g., wind speed, soil moisture, etc.) are developed accordingly. Even the presence of the coherent component of a GNSS reflected signal itself has been a matter of discussion in the last years. In this work, a method developed to separate the leakage of the direct signal in the reflected one is applied to a data set of GNSS-R signals collected over the ocean by the Microwave Interferometer Reflectometer (MIR) instrument, an airborne dual-band (L1/E1 and L5/E5a), multi-constellation (GPS and Galileo) GNSS-R instrument with two 19-elements antenna arrays with 4 beam-steered each. The presented results demonstrate the feasibility of the proposed technique to untangle the coherent and incoherent components from the total power waveform in GNSS reflected signals. This technique allows the processing of these components separately, which increases the calibration accuracy (as today both are mixed and processed together), allowing higher resolution applications since the spatial resolution of the coherent component is determined by the size of the first Fresnel zone (300–500 meters from a LEO satellite), and not by the size of the glistening zone (25 km from a LEO satellite). The identification of the coherent component enhances also the location of the specular reflection point by determining the peak maximum from this coherent component rather than the point of maximum derivative of the incoherent one, which is normally noisy and it is blurred by all the glistening zone contributions.
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Kaczmarek, Adrian, and Bernard Kontny. "Identification of the Noise Model in the Time Series of GNSS Stations Coordinates Using Wavelet Analysis." Remote Sensing 10, no. 10 (October 10, 2018): 1611. http://dx.doi.org/10.3390/rs10101611.
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Analysis of the time series of coordinates is extremely important in geodynamic research. Indeed, the correct interpretation of coordinate changes may facilitate an understanding of the diverse geophysical processes taking place in the earth’s crust. At present, when rigorously processing global navigation satellite system (GNSS) observations, the influence of deformations in the surface of the earth’s crust is not considered. This article presents signal modelling for the influence on the analysis of noise occurring in the time series of GNSS station coordinates. The modelling of coordinate time series was undertaken using the classic least-squares estimation (LSE) method and the inverse continuous wavelet transform (CWT). In order to determine the type of noise character, the coefficient spectral index was used. Analyses have demonstrated that the nature of noise in measurement data does not depend on the signal estimation method. The differences between classic modelling (LSE) of the time series with annual and semiannual oscillation and signal reconstruction are very small ( Δ κ = 0.0 ÷−0.2).
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Steinitz, G., P. Kotlarsky, and O. Piatibratova. "Indications for influence of artificial (man-made) activity on radon signals, in simulation experiments." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2195 (November 2016): 20160311. http://dx.doi.org/10.1098/rspa.2016.0311.
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Radon (Rn-222; a radioactive noble gas) is characterized by large temporal variations that differ significantly from variations of (i) other trace elements in geogas (noble gases); (ii) variation patterns of other dynamic geophysical systems (atmospheric, tidal). Consensus exists that there is no simple and straightforward understanding of the phenomena and its behaviour. This lacuna in the understanding of the underlying principles hampers the development of applications—such as radon as a proxy of processes in the seismogenic context. Using results from field investigations and simulation experiments the GSI suggested that an unidentified extraterrestrial component, probably in solar radiation, drives periodic radon signals in the diurnal and annual frequency bands. Recent findings from experimental investigations shed additional perspectives allowing a new evaluation of the issue. Particular transient signals, measured with alpha and gamma detectors, are interpreted to reflect the influence of artificial activity. Criteria are (i) signals lasting several hours that occur around midday on workdays (Sunday–Thursday); (ii) signals composed of a train of around 10 strong pulses, each lasting less than 15 min, occurring within several hours once a week, from Wednesday afternoon/evening to Thursday morning. A first interpretation is that an unidentified artificial activity of some sort (industrial?) generates and emits an unidentified agent that reaches enhanced confined mode experiments at the GSI laboratory, which respond to the incoming agent in the form of radon signals. Developing the capability of identification of such an earth-bound source generating an influencing agent is a key step towards understanding of external influence on radioactivity of radon.
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Mogilatov, V. S., V. V. Potapov, A. N. Shein, and V. A. Gur’ev. "Influences of the Earth’s Magnetic Field on the Transient Electromagnetic Process in the Geoelectric Field: an Experimental Study." Russian Geology and Geophysics 62, no. 12 (December 1, 2021): 1430–39. http://dx.doi.org/10.2113/rgg20204192.
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Abstract —A mathematical model of the influence of the Earth’s magnetic field (the Hall effect) on results of the controlled source transient electromagnetic (TEM) method has been elaborated. For identification of this effect, we propose a schematic layout of the experimental grounded system with a pulsed loop source and signals recording by radial receive lines equally spaced relative to the loop. The 2018–2019 special field experiments were conducted in the Tatar region of the West Siberian Lowland with an aim to estimate the Hall effect contributions to the TEM method. To detect the Hall effect, transient electromagnetic responses were measured mainly by four receive lines radiating from a 500×500 m square loop. Analysis of the TEM results processing aimed at improving the signal quality and reducing the interference revealed a great similarity in signals from the radial lines, which is theoretically possible only under the Hall effect. Comparison of the field signals with the theoretical ones enabled estimation of the components caused by the Hall effect, in particular, conductivity at ~0.002 S/m.
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Yang, Zhi, Jingtian Tang, Xiao Xiao, Qiyun Jiang, Xiangyu Huang, and Shuanggui Hu. "Application of powerline noise cancellation method in correlation identification of controlled source electromagnetic method." Journal of Geophysics and Engineering 18, no. 3 (June 2021): 339–54. http://dx.doi.org/10.1093/jge/gxab018.
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Abstract Powerline interference in the controlled source electromagnetic method has traditionally been one of the biggest conundrums plaguing geophysicists, and its conventional denoising methods primarily include filtering and noise estimation. The filter method leaches noise at specific frequency points, which might also filter useful signals; the noise estimation method significantly eliminates interference, whereas the premise is that the noise is stable after a short time and a recorder is necessary in the field. In the present study, using the periodicity and symmetry of powerline noise, we propose a subtraction and an addition method for cancellation of the powerline noise. First, the transmitted signal is optimized so that the equivalent transmitted signal is an m sequence; then the response signal is processed by using the cancellation method; subsequently, the correlation identification is applied and finally, we solve the earth impulse response by means of the Wiener filter deconvolution method. Simulation experiments and field data tests demonstrate that the powerline noise can be well suppressed by the cancellation method proposed in the present study, so that the system identification accuracy is greatly improved. The method is simple in principle and effective in removing powerline noise, which presents a novel perspective on noise elimination for system identification.
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Jiao, Zhonghu, Yumeng Hao, and Xinjian Shan. "A Spatially Self-Adaptive Multiparametric Anomaly Identification Scheme Based on Global Strong Earthquakes." Remote Sensing 15, no. 15 (July 31, 2023): 3803. http://dx.doi.org/10.3390/rs15153803.
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Earthquake forecasting aims to determine the likelihood of a damaging earthquake occurring in a particular area within a period of days to months. This provides ample preparation time for potential seismic hazards, resulting in significant socioeconomic benefits. Surface and atmospheric parameters derived from satellite thermal infrared observations have been utilized to identify pre-earthquake anomalies that may serve as potential precursors for earthquake forecasting. However, the correlation between these anomalies and impending earthquakes remains a significant challenge due to high false alarm and missed detection rates. To address this issue, we propose a spatially self-adaptive multiparametric anomaly identification scheme based on global strong earthquakes to establish the optimal recognition criteria. Each optimal parameter exhibits significant spatial variability within the seismically active region and indicates transient and subtle anomaly signals with a limited frequency of occurrences (<10 for most regions). In comparison to the fixed criterion for identifying anomalies, this new scheme significantly improves the positive Matthew’s correlation coefficient (MCC) values from ~0.03 to 0.122–0.152. Additionally, we have developed a multi-parameter anomaly synthesis method based on the best MCC value of each parameter anomaly. On average, the MCC increased from 0.143 to 0.186, and there are now more earthquake-prone regions with MCC values > 0.5. Our research emphasizes the critical importance of a multiparametric system in earthquake forecasting, where each geophysical parameter can be assigned a distinct weight, and the findings specifically identify OLR, including all-sky and clear-sky ones, as the most influential parameter on a global scale, highlighting the potential significance of OLR anomalies for seismic forecasting. Encouraging results imply the effectiveness of utilizing multiparametric anomalies and provide some confidence in advancing our knowledge of operational earthquake forecasting with a more quantitative approach.
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Wilson, Christopher J. L., Vladimir Luzin, Sandra Piazolo, Mark Peternell, and Daniel Hammes. "Experimental deformation of deuterated ice in 3D and 2D: identification of grain-scale processes." Proceedings of the Royal Society of Victoria 127, no. 1 (2015): 99. http://dx.doi.org/10.1071/rs15011.
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Major polar ice sheets and ice caps experience cycles of variable flow during different glacial periods and as a response to past warming. The rate and localisation of deformation inside an ice body controls the evolution of ice microstructure and crystallographic fabric. This is critical for interpreting proxy signals for climate change, with deformation overprinting and disrupting stratigraphy deep under ice caps due to the nature of the flow. The final crystallographic fabric in polar ice sheets provides a record of deformation history, which in turn controls the flow properties of ice during further deformation and affects geophysical sensing of ice sheets. For example, identification of layering in ice sheets, using seismic or ice radar techniques, is attributed to grain size changes and fabric variations. Such information has been used to provide information on climate state and its changes over time, and as the Fourth Intergovernmental Panel on Climate Change (IPCC) Report (Solomon et al. 2007) points out there is currently still a lack of understanding of internal ice-sheet dynamics. To answer this we have recently conducted experiments at the Australian Nuclear Science and Technology Organisation (ANSTO) to collect fully quantitative microstructural data from polycrystalline heavy water (D2O) ice deformed in a dynamic regime. The ice and temperature (–7°C) chosen for this study is used as a direct analogue for deforming natural-water ice as it offers a unique opportunity to link grain size and texture evolution in natural ice at –10°C. Results show a dynamic system where steady-state rheology is not necessarily coupled to microstructural and crystallographic fabric stability. This link needs to be taken into account to improve ice-mass-deformation modelling critical for climate change predictions.
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De Benedetto, Daniela, Francesco Montemurro, and Mariangela Diacono. "Mapping an Agricultural Field Experiment by Electromagnetic Induction and Ground Penetrating Radar to Improve Soil Water Content Estimation." Agronomy 9, no. 10 (October 15, 2019): 638. http://dx.doi.org/10.3390/agronomy9100638.
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A growing interest in proximal sensing technologies for estimating soil water content (SWC) will be highlighted. On this matter the objectives of this study were: (1) to use both the combined electromagnetic induction (EMI) sensor and Ground Penetrating Radar (GPR) to characterize an innovative field experiment located in southern Italy, in which different agricultural practices are tested, including a soil hydraulic arrangement; (2) to implement a geostatistical approach in order to merge different geophysical sensor data as auxiliary variables for SWC estimation. The multi-sensor recorded data were: (1) SWC data measured by gravimetric method; (2) Differential Global Positioning System height; (3) apparent electrical conductivity measured by an EMI sensor; (4) depths of soil discontinuities individuated by GPR radargrams interpretation; and (5) amplitude of GPR signal data at two different frequencies. Geostatistical techniques were used both to map all variables and improve the SWC estimation. The findings of this research indicate that: (1) the GPR radargrams identified four reflection events as a consequence of interfaces; (2) the EMI and GPR mapping provided identification of areas with high potential for water stagnation; and (3) the outputs of geophysical sensors can be effectively used as auxiliary tools to supplement the sampling of the target variable and to improve water content estimation.
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Kordelin, Kai, Johanna Virkki, Jaana Kordelin, Juhani Norokallio, Jari Heikkinen, Jyrki Liimatainen, Leena Ukkonen, and Lauri Sydänheimo. "Rock Type Effects on Radio Signal Attenuation." International Journal of Geophysics 2023 (February 1, 2023): 1–10. http://dx.doi.org/10.1155/2023/1209844.
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This research work is aimed at studying different rock types and the effect of their mineral contents on an active 434 MHz RFID card’s radio signal attenuation. This research was done at the ONKALO nuclear waste storage facility using radio frequency identification (RFID) equipment. First, the studied area and research plan, including the used system and equipment, are explained. After this, the researched areas of rock types and their effects on radio signals are presented. This work focused mainly on occupational safety, but it also investigated whether it would be possible to use RFID technology in producing mines as well, especially in the boundary layer of the ore body. This research can help the design of communication frequencies for autonomous devices.
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Aslanyan, A. M., I. Yu Aslanyan, R. R. Kantyukov, Yu Yu Petrova, and R. N. Minakhmetova. "Implementation of the Advanced Passive Acoustics Hardware and Software Complex for Well Integrity Diagnostics." Occupational Safety in Industry, no. 11 (November 2020): 56–62. http://dx.doi.org/10.24000/0409-2961-2020-11-56-62.
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To ensure operational stability of the unified gas supply system depending on the seasonal gas demand fluctuations, the underground gas storage facilities are effectively used. Well integrity diagnostics using the advanced logging techniques facilitate timely identification of potential problems (pinpointing cross-flows behind casing, detecting leaks in production casing and other well construction components, locating sustained annulus pressure sources etc.), and, thereby extension of the safe operation life of functioning of the underground gas storage facilities. The results of the complex of field and geophysical studies in several underground gas storage wells are given in this article. Different types of the underground gas storages are reviewed: the ones located in an aquifer, salt dome, and mature field. The diagnostics was carried out based on the complex of downhole logging including a passive acoustic tool. The passive acoustics hardware and software technology can capture and interpret acoustic signals generated by the wellbore or reservoir flows. To recognise and interpret the captured signals, the temporal coherence algorithms, data wavelet filtration, and neural networks are used. The use of this technology allows to significantly improve the safety of well operation. The information obtained is used both in the preparation of industrial safety expert reports and for the development of effective programs for major repairs of the underground gas storage wells located in the depleted gas and water fields, as well as in the salt caverns. Hardware and software technology of passive acoustics is being used in almost all the major oil and gas provinces in the world, receiving recognition from the largest domestic and foreign companies, however, this is the first time that underground gas storage facilities are used to check the technical condition of the wells.
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den Ouden, Olivier F. C., Jelle D. Assink, Pieter S. M. Smets, Shahar Shani-Kadmiel, Gil Averbuch, and Läslo G. Evers. "CLEAN beamforming for the enhanced detection of multiple infrasonic sources." Geophysical Journal International 221, no. 1 (January 8, 2020): 305–17. http://dx.doi.org/10.1093/gji/ggaa010.
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SUMMARY The detection and characterization of signals of interest in the presence of (in)coherent ambient noise is central to the analysis of infrasound array data. Microbaroms have an extended source region and a dynamical character. From the perspective of an infrasound array, these coherent noise sources appear as interfering signals that conventional beamform methods may not correctly resolve. This limits the ability of an infrasound array to dissect the incoming wavefield into individual components. In this paper, this problem will be addressed by proposing a high-resolution beamform technique in combination with the CLEAN algorithm. CLEAN iteratively selects the maximum of the f/k spectrum (i.e. following the Bartlett or the Capon method) and removes a percentage of the corresponding signal from the cross-spectral density matrix. In this procedure, the array response is deconvolved from the f/k spectral density function. The spectral peaks are retained in a ‘clean’ spectrum. A data-driven stopping criterion for CLEAN is proposed, which relies on the framework of Fisher statistics. This allows the construction of an automated algorithm that continuously extracts coherent energy until the point is reached that only incoherent noise is left in the data. CLEAN is tested on a synthetic data set and is applied to data from multiple International Monitoring System infrasound arrays. The results show that the proposed method allows for the identification of multiple microbarom source regions in the Northern Atlantic that would have remained unidentified if conventional methods had been applied.
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Green, David N., Alexandra Nippress, David Bowers, and Neil D. Selby. "Identifying suitable time periods for infrasound measurement system response estimation using across-array coherence." Geophysical Journal International 226, no. 2 (April 21, 2021): 1159–73. http://dx.doi.org/10.1093/gji/ggab155.
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SUMMARY Microbarometers deployed to measure atmospheric infrasound are often connected to, or housed within, a wind noise reduction system (WNRS). At infrasound arrays of the International Monitoring System (IMS), being deployed as part of Comprehensive Nuclear-Test-Ban Treaty verification measures, the WNRS typically comprises an 18 m diameter pipe array. Over the past decade an in situ method has been developed to estimate the measurement system (sensor + WNRS) response characteristics, by comparing its recordings with those made on a colocated reference sensor with known response and no WNRS. The method relies upon the identification of time periods for which the reference sensor and measurement system are subject to the same input pressure field. It has proven difficult to reliably identify such time periods at frequencies $\lt 0.1\,$ Hz using recordings at a single location, resulting in a negative bias in estimated measurement system gain values (the ‘dip artefact’) in the 0.02–0.1 Hz passband. The IMS is deploying arrays of microbarometers, and we show that a measure of across-array coherence can be used to identify time periods associated with acoustic signal propagation. Amplitude response estimates, using 1 yr of data from four IMS arrays, indicate that the dip artefact can be removed by retaining for analysis only those time periods that exhibit high across-array coherence. Moreover, our analysis confirms the hypothesis that the dip artefact is associated with time periods during which wind-generated pressure fluctuations dominate, leading to partial suppression of noise with length scales less than the extent of the WNRS. At two arrays within continental forests accurate amplitude responses are estimated across the 0.02–4 Hz passband, as acoustic signals at all frequencies can be identified. At two oceanic island arrays, the low numbers of time windows with above-noise acoustic signal in the 0.02–0.1 Hz passband make reliable response estimation at these frequencies difficult or impossible. It is recommended that the methodology for estimating the response of an infrasound measurement system at an array should incorporate a multichannel coherence measure; data centres may already routinely compute such measures in their signal detection algorithms.
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Song, Chunsheng, Yao Xiao, Chuanchao Yu, Wei Xu, and Jinguang Zhang. "H∞ active control of frequency-varying disturbances in a main engine on the floating raft vibration isolation system." Journal of Low Frequency Noise, Vibration and Active Control 37, no. 2 (August 21, 2017): 199–215. http://dx.doi.org/10.1177/1461348417725944.
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Reducing the vibration of marine power machinery can improve warships' capabilities of concealment and reconnaissance. Being one of the most effective means to reduce mechanical vibrations, the active vibration control technology can overcome the poor effect in low frequency of traditional passive vibration isolation. As the vibrations arising from operation of marine power machinery are actually the frequency-varying disturbances, the H∞ control method is adopted to suppress frequency-varying disturbances. The H∞ control method can solve the stability problems caused by the uncertainty of the model and reshape the frequency response function of the closed loop system. Two-input two-output continuous transfer function models were identified by using the system identification method and are validated in frequency domain of which all values of best fit exceeds 89%. The method of selecting the weighting functions on the mixed sensitivity problem is studied. Besides, the H∞ controller is designed for a multiple input multiple output (MIMO) system to suppress the single-frequency-varying disturbance. The numerical simulation results show that the magnitudes of the error signals are reduced by more than 50%, and the amplitudes of the dominant frequencies are attenuated by more than 10 dB. Finally, the single excitation source dual-channel control experiments are conducted on the floating raft isolation system. The experiment results reveal that the root mean square values of the error signals under control have fallen by more 74% than that without control, and the amplitudes of the error signals in the dominant frequencies are attenuated above 13 dB. The experiment results and the numerical simulation results are basically in line, indicating a good vibration isolation effect.
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Zobin, Vyacheslav. "Seismic signatures of atmospheric disturbances in the Western Pacific as a tool for reconstruction of their dynamics." Geofísica Internacional 60, no. 4 (October 1, 2021): 333–56. http://dx.doi.org/10.22201/igeof.00167169p.2021.60.4.2124.
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The wind and products of snowfalls and rainfalls touching the ground generate the seismic signals. During the decades, the study of seismic signatures of atmospheric disturbances, cyclones, was based on analysis of the ambient seismic noise in the low-frequency range which allowed identification of cyclones and location of the storm position. The methodology of monitoring of the atmospheric events using the short-period seismic signals recorded by a sensor installed at a height of about 4 km above sea level at the summit of dormant volcano Nevado de Colima is proposed. The methodology includes the indication of the seismic signatures of atmospheric disturbances on the daily helicorder displays of seismic signals with following analysis of waveforms, produced by the impact of rainfalls and snowfalls with the ground surface, and their Fourier spectral characteristics. Then, the reconstruction of the passage of the atmospheric events, based on the power spectral densities of the one-hour seismic records, which is performed mutually with the satellite observations. The methodology was applied to study the passage of hurricane Dora and its preceding tropical storm (June 2017) and the cold front system number 25 (January 2018). There were indicated the periods of actions of tropical storm, hurricane, and two stages of the cold front on the helicorder images. Then the characteristic waveforms for each period were selected. Analysis of the spectral characteristics of these waveforms demonstrated that the rainfalls, occurring during the tropical storm, hurricane and the initial stage of the cold front passage, generated the seismic signals within the frequency range between 1.0-1.8 Hz while the snowfall during the second stage of the cold front passage generated the seismic signals within the frequency range between 2.6 and 3.7 Hz. The reconstruction of dynamics of the passage of the atmospheric events based on the power spectral densities of the one-hour seismic records allowed to see the comparable intensity of tropical storm and hurricane, and two stages of the cold front. These results demonstrate a possibility for monitoring the passage of atmospheric disturbances in real time or to perform the reconstruction the dynamics of these events during past time using the short-period seismic signals recorded at the high heights.
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Ley-Cooper, Yusen, James Macnae, Terry Robb, and Julian Vrbancich. "Identification of calibration errors in helicopter electromagnetic (HEM) data through transform to the altitude-corrected phase-amplitude domain." GEOPHYSICS 71, no. 2 (March 2006): G27—G34. http://dx.doi.org/10.1190/1.2187741.
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We investigate the properties of EM signals in several different response-parameter domains to identify calibration errors in helicopter electromagnetic (HEM) data. In particular, we define a dimensionless response parameter α, derived from frequency-domain data, that is numerically identical to the historic wire-loop response parameter, and is closely related to the thin-sheet and half-space response parameters. The arctangent of α is the phase ϕ of the secondary field. We further define a dimensionless amplitude response parameter β, calculated as the ratio between inductive limits estimated from the data and from system geometry. The inductive limit calculated from geometry provides an initial altitude correction to the data amplitudes. Additional data corrections further correct phase effects and altimeter variations. The amplitude and phase errors in calibration become independent differences between the data and the fitted model in the ϕβ domain. This investigation was undertaken in the response-parameter domain rather than in the data domain, allowing the analysis to be independent of absolute values of conductivity and system frequencies. Statistical analysis in the ϕβ domain of recently acquired data suggests that amplitude calibration errors in HEM data may cause fitted models to have systematic depth errors of 1 to 2 m for near-surface conductors; variable altitude measurement errors are about 1.5 m over seawater.
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Andrushchenko, Yuriy, and Oleksandr Liashchuk. "GEODYNAMICS." GEODYNAMICS 2(31)2021, no. 2(31) (December 29, 2021): 84–91. http://dx.doi.org/10.23939/jgd2021.02.084.
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The aim of the work is to determine the possibility of using local seismological networks of nuclear power plants as elements of the seismological monitoring system of the territory of Ukraine. Estimation of local seismicity and specification of quantitative parameters of seismological influences is carried out on the basis of materials of seismological observations. Operational processing and analysis of seismic signals registered on the elements of local seismological networks of NPPs is carried out by the Main Center for Special Control of the State Space Agency of Ukraine (MCSC SSA of Ukraine). In the process of implementation of the “Seismic Hazard Assessment and Seismic Resistance Action Plan” of existing NPPs, seismic monitoring networks were deployed at Ukrainian NPPs. To date, the MCSC receives data from the local seismological networks of Rivne, Khmelnytsky and Zaporizhzhya NPPs in a continuous mode. The processing of geophysical information coming from the NPP to the FSC is carried out by the operational next shift of the center with the help of FSC hardware and software and provides reliable data on the parameters of seismic sources registered by stations, their location and energy characteristics. In total, in the period from 2017 to 2021, 36 local earthquakes were registered by NPP seismic networks in Ukraine. The epicenters of the vast majority of them are located within the Ivano-Frankivsk, Ternopil and Lviv regions. The experience of conducting instrumental observations at NPP seismic stations testifies to their high efficiency and possibility of use as full-fledged elements of the seismological monitoring system of the territory of Ukraine. According to the results of primary processing of seismic data of 2017-2021, a catalog of seismic events registered by NPP seismic stations was created. The system of interpretation of the obtained results was improved, which allowed to determine equally well local, regional and teleseismic events of different nature and energy level. The practical significance of the obtained results lies in their direct focus on solving a number of practical problems of processing and interpretation of seismological data. The use of NPP seismic stations as elements of the general system of seismological monitoring of Ukraine will increase the reliability of detection and localization of sources and the probability of correct identification of the nature of seismic phenomena, which in turn will improve the assessment of tectonic structures in Ukraine.
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SAVCHUK, S., and V. KERKER. "Determination of reference directions at a certified range using GNSS measurements." Modern achievements of geodesic science and industry 1, no. 45 (April 1, 2023): 89–97. http://dx.doi.org/10.33841/1819-1339-1-45-89-97.
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The relevance of PPP technology has greatly increased over the past 10 years. While the centimeter level of accuracy has already been practically ensured in most spheres of economic activity, first of all, in geodesy, the millimeter level for scientific tasks related to the study of the influence of geophysical factors on the environment is still the subject of research. The purpose of this work is to identify the real accuracy of the modification of the PPP-AR method using the example of data from four permanent GNSS stations: SULP (Lviv), FRAN (Ivano-Frankivsk), RAHI (Rakhiv), TERN (Ternopil), included in the European the EPN network (EUREF Permanent GNSS Network). Method. To fulfill the given task, we used data from four permanent GNSS stations. 3 weeks of observations were processed: one in July (2217 GPS week), one in August (2222 GPS week) and one in September (2226 GPS week). Processing of the observation files was carried out in the PRIDE PPP-AR software environment, which was pre-installed on the server with the Ubuntu operating system. The coordinates of each station were calculated with the same input parameters, namely, taking into account the second-order ionospheric correction and the function of displaying inclined zenith delays of signals from satellites in the direction of the VMF3 zenith. We compared the obtained sets of coordinates with the control coordinates of these stations. For the time periods we chose, the coordinates calculated by the relative method based on the formation of phase differences in the combined EPN processing center were taken as control. The results. The main results of our research were the difference of coordinates (comparison of the received coordinates with control ones). For each station, the obtained differences are unidirectional in nature and vary little between stations. The average value of the coordinate differences was from 0.6 to 7.2 mm and practically does not depend on the processing time interval. The root mean square error (RMS) of the coordinate differences is at the level of 1.5 – 3 mm and also changes little over time. It was found that the accuracy of determining the coordinates based on the processing of GNSS measurement data at permanent stations SULP, TERN, FRAN, RAHI using the PPP-AR method is quite high, but a systematic difference of several millimeters is noticeable, which may be caused by insufficient consideration of some factors of geophysical origin . Scientific novelty and practical significance. It is shown that the PPP-AR method at the current stage of development of GNSS technologies achieves the accuracy of the coordinate determination method based on phase differences and can be applied not only in geodesy tasks, but also in geodynamic studies, provided the results of daily GNSS observations are used. A promising direction for further research is the identification of unaccounted sources of systematic errors.
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den Ouden, Olivier F. C., Jelle D. Assink, Pieter S. M. Smets, and Läslo G. Evers. "A climatology of microbarom detections at the Kerguelen Islands: unravelling the ambient noise wavefield." Geophysical Journal International 229, no. 3 (January 4, 2022): 1646–64. http://dx.doi.org/10.1093/gji/ggab535.
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SUMMARY The ambient infrasonic noise field is complex due to the interference of spatially distributed infrasound sources. Microbaroms are one of the most dominant omnipresent infrasonic sources within this wavefield. These microbaroms are generated by nonlinear ocean surface wave interactions, and have a characteristic and continuous signature within the infrasound spectrum. Under noisy conditions, microbaroms can mask infrasonic signals of interest, such as infrasound from volcanoes or explosions, which limits detection and identification of such sources. This study performs an infrasonic climatology for infrasound array I23FR, using five years of data between 2015–2020. The array is located on the Kerguelen Islands, within the Southern Ocean, and is part of the International Monitoring System for the verification of the Comprehensive Nuclear-Test-Ban Treaty. The climatology analysis addresses the expected ambient noise levels, propagation paths and potential sources within the vicinity of an infrasound sensor. Time- and frequency-domain beamforming methods have been applied to analyse the infrasonic wavefield from the I23FR observations. A recently introduced method is applied to compute so-called soundscapes, to be compared with beamform results. Although the comparison indicates a disagreement in amplitude, there is a good agreement in directionality and frequency between both.
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Fleming, Sean W. "Artificial neural network forecasting of nonlinear Markov processes." Canadian Journal of Physics 85, no. 3 (March 1, 2007): 279–94. http://dx.doi.org/10.1139/p07-037.
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I assessed the performance characteristics of the feed-forward artificial neural network (ANN) as a first-order nonlinear Markov modelling technique. The ability to recover the underlying structure of five synthetic random time series was first tested. The method was then applied to an observed geophysical time series, and the results were compared against external empirical constraints and a simple representation of the underlying physics. The Monte Carlo experiments suggested that the ANN–Markov technique: (i) yields good prediction skill; (ii) in general, accurately retrieves the form of the iterative mapping, even for extremely noisy data; (iii) accomplishes the foregoing without any need to consider or adjust for the distributional characteristics of the data or driving noise; and (iv) accurately estimates the distribution of the strictly stochastic signal component. Application to a historical river-flow record again showed good forecast skill. Moreover, the robustness, flexibility, and simplicity of the method permitted easy identification of the fundamental nonlinear physical dynamics of this environmental system directly from the time series data, perhaps belying the common perception of ANNs as a strictly black-box prediction technique. The ANN–Markov technique may thus serve as a valuable data-driven tool for guiding the development of both process-based and parameteric statistical models. The lack of specific distributional assumptions and requirements notwithstanding, it was also found that manual distributional transformations may permit the method to be tuned to particular applications by emphasizing or de-emphasizing certain features of the data. Drawbacks to the method include substantial data-set length requirements, a general limitation of ANNs, as well as an inconsistent but potentially troubling tendency to partially imprint the form of the ANN activation function upon the estimated recursion relationship. PACS Nos.: 02.50.Ga, 05.10.–a, 05.45.Tp, 07.05.Mh, 02.50.Ey, 92.40.Fb
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Shalvi, O., and E. Weinstein. "System identification using nonstationary signals." IEEE Transactions on Signal Processing 44, no. 8 (1996): 2055–63. http://dx.doi.org/10.1109/78.533725.
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Descherevsky, A. V., A. A. Lukk, A. Y. Sidorin, G. V. Vstovsky, and S. F. Timashev. "Flicker-noise spectroscopy in earthquake prediction research." Natural Hazards and Earth System Sciences 3, no. 3/4 (August 31, 2003): 159–64. http://dx.doi.org/10.5194/nhess-3-159-2003.
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Abstract. The problem of earthquake prediction and the methods of identification of geophysical precursory signals are discussed. To get information on the dynamics of earthquake preparation processes, fluctuations in geophysical time series are analyzed with the method of flicker-noise spectroscopy. Integral indices – power spectra and various moments ("structural functions") – are used as information relations. We demonstrate that the method allows us to reveal earthquake precursors.
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Alihan, N. S. A., D. D. Wijaya, A. H. M. Din, and A. H. Omar. "THE PRESENCE OF GEOPHYSICAL LOADINGS IN GPS OBSERVATIONS USING GENERAL LEAST SQUARES APPROACHES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W16 (October 1, 2019): 101–7. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w16-101-2019.
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Abstract. The earth’s crust undergoes natural deformation due to the geophysical loadings that consist of the earth body tide, ocean tide loading, atmospheric pressure loading and pole tide. This periodic displacement is generated by the changes of the gravitational attraction between the moon and the sun acting upon the earth’s rotation, along with the temporal atmospheric changes and the variability of the ocean tide. The study of the geophysical loadings is important in the geodesy field as the magnitude of the signals is significant and can contribute to errors in space geodetic measurements such as Global Positioning System (GPS), Very-Long Baseline Interferometry (VLBI) and Altimeter. This study is conducted to evaluate the percentage of geophysical loadings in GPS observations by adopting general least square approaches. The presence of the geophysical loadings indicates that as many as 76% to 93% of the geophysical loadings signal are contained in the GPS time series. The findings reveal that earth body tide signals are more significant if compared to ocean tide loading signals because the magnitude of the earth body tide is greater than that of the ocean tide loading and it affects the coordinate system particularly at up component. Results illustrated the potential of GPS to provide the local parameters of the geophysical loadings that are beneficial for earth tidal modelling and that can be used to improve the quality of space geodetic measurements.
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Zarrop, M. B. "Book Review: Perturbation Signals for System Identification:." International Journal of Electrical Engineering & Education 31, no. 3 (July 1994): 229. http://dx.doi.org/10.1177/002072099403100304.
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Tsumura, K. "Optimal Quantization of Signals for System Identification." IEEE Transactions on Automatic Control 54, no. 12 (December 2009): 2909–15. http://dx.doi.org/10.1109/tac.2009.2033859.
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El-Fandi, M., I. A. Henderson, J. McGhee, and P. McGlone. "Uncorrelated multisymbol signals for MIMO system identification." IEEE Transactions on Instrumentation and Measurement 47, no. 5 (1998): 1133–38. http://dx.doi.org/10.1109/19.746570.
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Barker, H. A., K. R. Godfrey, and A. J. Tucker. "Nonlinear System Identification with Multilevel Perturbation Signals." IFAC Proceedings Volumes 33, no. 15 (June 2000): 1175–78. http://dx.doi.org/10.1016/s1474-6670(17)39913-5.
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Pintelon, R., J. Schoukens, and G. Vandersteen. "Frequency domain system identification using arbitrary signals." IEEE Transactions on Automatic Control 42, no. 12 (1997): 1717–20. http://dx.doi.org/10.1109/9.650025.
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TELESCA, LUCIANO, GERARDO COLANGELO, VINCENZO LAPENNA, JENS HEINICKE, and ULRICH KOCH. "QUANTITATIVE DYNAMICS IN GEOPHYSICAL PARAMETERS SIMULTANEOUSLY RECORDED IN THE SOOS NATURE PARK (CZECH REPUBLIC)." Fluctuation and Noise Letters 03, no. 01 (March 2003): L73—L82. http://dx.doi.org/10.1142/s0219477503001105.
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Time dynamics of self-potential, geochemical and meteorological parameters, simultaneously recorded in a CO 2 degassing area at Soos, NW-Bohemia (Czech Republic), have been investigated. The power spectra, behaving as power-law function of the frequency, show the presence of colored-noise-type dynamics. The Higuchi analysis reveals the observed geophysical signals to have the property of fractal curves, with the identification of different scaling regimes. The Detrended Fluctuation Analysis, removing trends and non-stationarities, has shown that the signals present clear fingerprints of long-range correlated fluctuations.
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Meyer, Matthias, Samuel Weber, Jan Beutel, and Lothar Thiele. "Systematic identification of external influences in multi-year microseismic recordings using convolutional neural networks." Earth Surface Dynamics 7, no. 1 (February 4, 2019): 171–90. http://dx.doi.org/10.5194/esurf-7-171-2019.
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Abstract. Passive monitoring of ground motion can be used for geophysical process analysis and natural hazard assessment. Detecting events in microseismic signals can provide responsive insights into active geophysical processes. However, in the raw signals, microseismic events are superimposed by external influences, for example, anthropogenic or natural noise sources that distort analysis results. In order to be able to perform event-based geophysical analysis with such microseismic data records, it is imperative that negative influence factors can be systematically and efficiently identified, quantified and taken into account. Current identification methods (manual and automatic) are subject to variable quality, inconsistencies or human errors. Moreover, manual methods suffer from their inability to scale to increasing data volumes, an important property when dealing with very large data volumes as in the case of long-term monitoring. In this work, we present a systematic strategy to identify a multitude of external influence sources, characterize and quantify their impact and develop methods for automated identification in microseismic signals. We apply the strategy developed to a real-world, multi-sensor, multi-year microseismic monitoring experiment performed at the Matterhorn Hörnligrat (Switzerland). We develop and present an approach based on convolutional neural networks for microseismic data to detect external influences originating in mountaineers, a major unwanted influence, with an error rate of less than 1 %, 3 times lower than comparable algorithms. Moreover, we present an ensemble classifier for the same task, obtaining an error rate of 0.79 % and an F1 score of 0.9383 by jointly using time-lapse image and microseismic data on an annotated subset of the monitoring data. Applying these classifiers to the whole experimental dataset reveals that approximately one-fourth of events detected by an event detector without such a preprocessing step are not due to seismic activity but due to anthropogenic influences and that time periods with mountaineer activity have a 9 times higher event rate. Due to these findings, we argue that a systematic identification of external influences using a semi-automated approach and machine learning techniques as presented in this paper is a prerequisite for the qualitative and quantitative analysis of long-term monitoring experiments.
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Uski, Marja. "Event detection and location performance of the FINESA array in Finland." Bulletin of the Seismological Society of America 80, no. 6B (December 1, 1990): 1818–32. http://dx.doi.org/10.1785/bssa08006b1818.
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Abstract The experimental seismic array FINESA in Finland is designed to monitor weak seismic events at regional and teleseismic distances. The array geometry currently comprises 15 short-period vertical seismometers in three concentric rings (A-, B-, and C-rings), with a diameter of the outer ring of about 2 km. In late 1989, the data acquisition system of the array was completely modernized. Signals are now transferred continuously via high-speed telephone lines to the processing centers at the Institute of Seismology in Helsinki and NORSAR in Norway, therefore allowing automatic real-time processing of the recorded data. In this paper, the detection performance of the array in the current configuration has been evaluated. The results are encouraging: during a 2-week test period, FINESA detected at least one P and one S phase for 84 per cent of the events reported in the regional bulletin of the University of Helsinki, and 99 per cent of the events in the weekly teleseismic bulletins. Many additional events at both distance ranges were also found. The estimated phase velocities obtained by the broadband frequency-wave-number analysis confidently identify the phase type (teleseismic Pgional PgionalS). However, the resolution of the analysis is not sufficient to separate Pg from Pn and Lg from Sn. The estimated backazimuths are reliable for phase association, the standard deviation of the estimates being 7° for regional P phases, 6° for regional S phases, and 23° for teleseismic P phases. Finally, preliminary results from FINESA's on-line event location capability showed that the average error in the location estimates is 21 per cent of the true epicentral distance. The greatest error sources are uncertainty in the estimated azimuths and occasional misidentification of secondary phases (Lg, Sn and Rg). The error could be reduced by constructing a regional correction term for the azimuth estimates and “tuning” the phase identification algorithms for FINESA. The characteristics of the Rg-phase need to be especially considered.
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Eberle, D. G., and B. Siemon. "Identification of buried valleys using the BGR helicopter-borne geophysical system." Near Surface Geophysics 4, no. 2 (June 1, 2005): 125–33. http://dx.doi.org/10.3997/1873-0604.2005038.
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Anderson, S. R., P. Dean, V. Kadirkamanathan, C. R. S. Kaneko, and J. Porrill. "System Identification From Multiple Short-Time-Duration Signals." IEEE Transactions on Biomedical Engineering 54, no. 12 (December 2007): 2205–13. http://dx.doi.org/10.1109/tbme.2007.896593.
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McCormack, A. S., K. R. Godfrey, and J. O. Flower. "Design of multilevel multiharmonic signals for system identification." IEE Proceedings - Control Theory and Applications 142, no. 3 (May 1, 1995): 247–52. http://dx.doi.org/10.1049/ip-cta:19951844.
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McKelvey, T., and H. Akçay. "Subspace based system identification with periodic excitation signals." Systems & Control Letters 26, no. 5 (December 1995): 349–61. http://dx.doi.org/10.1016/0167-6911(95)00035-6.
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Barker, H. A., and K. R. Godfrey. "System identification with multi-level periodic perturbation signals." Control Engineering Practice 7, no. 6 (June 1999): 717–26. http://dx.doi.org/10.1016/s0967-0661(99)00033-7.
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Song, Wenzhan, Fangyu Li, Maria Valero, and Liang Zhao. "Toward Creating a Subsurface Camera." Sensors 19, no. 2 (January 14, 2019): 301. http://dx.doi.org/10.3390/s19020301.
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In this article, the framework and architecture of a Subsurface Camera (SAMERA) are envisioned and described for the first time. A SAMERA is a geophysical sensor network that senses and processes geophysical sensor signals and computes a 3D subsurface image in situ in real time. The basic mechanism is geophysical waves propagating/reflected/refracted through subsurface enter a network of geophysical sensors, where a 2D or 3D image is computed and recorded; control software may be connected to this network to allow view of the 2D/3D image and adjustment of settings such as resolution, filter, regularization, and other algorithm parameters. System prototypes based on seismic imaging have been designed. SAMERA technology is envisioned as a game changer to transform many subsurface survey and monitoring applications, including oil/gas exploration and production, subsurface infrastructures and homeland security, wastewater and CO2 sequestration, and earthquake and volcano hazard monitoring. System prototypes for seismic imaging have been built. Creating SAMERA requires interdisciplinary collaboration and the transformation of sensor networks, signal processing, distributed computing, and geophysical imaging.
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Krishnamoorthy, Siddharth, Daniel Bowman, Emalee Hough, Zach Yap, John D. Wilding, Jamey Jacob, Brian R. Elbing, et al. "Development of balloon-based seismology for venus through earth-analog experiments and simulations." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A278. http://dx.doi.org/10.1121/10.0018837.
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Balloon-based seismology through the study of low-frequency seismo-acoustic signals (infrasound) has gained acceptance as a viable way to study seismic activity on Venus. Balloon-based barometers have the potential to detect and characterize atmospheric waves launched by venusquakes and volcanic eruptions while offering substantially longer instrument lifetimes in the Venus middle atmosphere, where temperature and pressure are significantly more benign (0–100°C, ∼1 atm) as compared to the surface (>460 °C, ∼90 atm). One of the major challenges in performing balloon-based seismology on Venus is the absence of ground-truth data for event identification and discrimination. To address this challenge, our activities are aimed at building a catalog of terrestrial balloon-recorded infrasound signals of geophysical provenance, using which signal predictions can be extended to Venus and the detectability of events can be analyzed. We will highlight our recently concluded Balloon-based Acoustic Seismology Study (BASS) flight campaign, which served as Earth-analog experiments for Venus balloon-based seismology. Data collected were used to validate seismo-acoustic simulation tools, which are being expanded to include the Venus atmosphere. These tools will used to generate predictions of infrasound signals from geophysical events on Venus. We will also provide perspective on directions for future instrument development for Venus balloon flights.
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Liu, Qunli, Ghatu Subhash, and Harold A. Evensen. "Behavior of a Novel Iterative Deconvolution Algorithm for System Identification." Journal of Vibration and Control 11, no. 7 (July 2005): 985–1003. http://dx.doi.org/10.1177/1077546305055537.
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This paper demonstrates the effectiveness and versatility of an iterative deconvolution algorithm in dealing with noise-rendered, truncated signals when signal averaging is not an option. An iterative deconvolution algorithm for system identification and signal restoration is presented, and its effectiveness and robustness are validated through the analysis of several artificially generated signals that are intended to mimic practically measured signals. Its application is intended for use in improving the quality of system identification by reducing the detrimental effect of information leakage caused by windowing. System identification was conducted for various scenarios, in which the input and output signals were rendered with noise and subjected to different truncation levels at the heads and/or tails. The ability of the algorithm to restore the truncated portion of signals is demonstrated. It is concluded that the algorithm has superior performance compared to currently available traditional approaches, such as the fast Fourier transform and autoregressive moving average methods.
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Ma, Shexiang, and Xin Guo. "Frequency estimation of satellite-based automatic identification system signals." Journal of Computational Methods in Sciences and Engineering 16, no. 1 (March 11, 2016): 29–37. http://dx.doi.org/10.3233/jcm-160599.
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Barker, H. A., A. H. Tan, and K. R. Godfrey. "Optimal Levels of Perturbation Signals for Nonlinear System Identification." IEEE Transactions on Automatic Control 49, no. 8 (August 2004): 1404–7. http://dx.doi.org/10.1109/tac.2004.832860.
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Barker, H. Anthony, Ai Hui Tan, and Keith R. Godfrey. "Object-oriented creation of input signals for system identification." IET Control Theory & Applications 8, no. 10 (July 3, 2014): 821–29. http://dx.doi.org/10.1049/iet-cta.2013.0259.
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Szilágyi, Nóra, and Eszter Láng. "System identification and signal processing methods for cardiovascular signals." International Journal of Psychophysiology 11, no. 1 (July 1991): 79. http://dx.doi.org/10.1016/0167-8760(91)90332-r.
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Widanage, W. D., J. Stoev, and J. Schoukens. "Design and Application of Signals for Nonlinear System Identification*." IFAC Proceedings Volumes 45, no. 16 (July 2012): 1605–10. http://dx.doi.org/10.3182/20120711-3-be-2027.00095.
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