scholarly journals Low-Frequency Seismic Node Based on Molecular-Electronic Transfer Sensors for Marine and Transition Zone Exploration

2017 ◽  
Vol 34 (8) ◽  
pp. 1743-1748 ◽  
Author(s):  
Alexander Antonov ◽  
Anna Shabalina ◽  
Andrey Razin ◽  
Svetlana Avdyukhina ◽  
Ivan Egorov ◽  
...  
Keyword(s):  
Seismic Station ◽  
Low Frequency ◽  
Molecular Electronic ◽  
Operational Conditions ◽  
Transition Zones ◽  
Electronic Transfer ◽  
Digital Electronics ◽  
Seismic Sensors ◽  
Battery Module ◽  
Subsurface Formation

AbstractA self-contained seismic station that has a modular structure adjustable to different operational conditions—like onshore, offshore to 500-m depth, and at transition zones—has been developed and field tested. The station operation frequency band is 1–300 Hz, which is wider than that of the majority of seismic stations based on using standard (10 Hz) geophones. Such improvement was achieved through the use of molecular-electronic transfer seismic sensors that allow for covering a low-frequency part of the spectrum that is needed for broadband processing and receiving information on subsurface formation. Basically, the system includes a module of sensing elements, a module of digital electronics, and a battery module. Optionally, a self-surfacing module could be used. The field test of the station was performed in August 2016 in the Sea of Azov.

scholarly journals Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors

2012 ◽  
Vol 1 (2) ◽  
pp. 85-101 ◽  
Author(s):  
E. Kozlovskaya ◽  
A. Kozlovsky
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Geomagnetic Latitude ◽  
Low Frequency ◽  
Auroral Oval ◽  
Polar Regions ◽  
Geomagnetic Pulsations ◽  
Seismic Sensors ◽  
Magnetic Poles ◽  
Magnetic Disturbances

Abstract. Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude), where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF) magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT) between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003). The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

scholarly journals Results of the infrasonic array on the Valaam Island primary data processing

2020 ◽  
Vol 2 (1) ◽  
pp. 85-91
Author(s):  
Vladimir Karpinsky ◽  
Vladimir Asming
Keyword(s):  
Data Processing ◽  
Seismic Station ◽  
Sampling Rate ◽  
Low Frequency ◽  
Primary Data ◽  
Joint Analysis ◽  
Main Task ◽  
Significant Difference ◽  
Infrasound Signal ◽  
Short Time

The infrasound array VALS developed in Kola Branch GS RAS has been installed in June 2016 on the Valaam Island in addition to the continuously operating seismic station VALR. The array consists of 3 spaced low-frequency microphones. The data with a sampling rate of 100 Hz is stored continuously at the acquisition computer; the timing is carried out using GPS. In addition to the acquisition system, an infrasound signal detector is installed on the computer. It works in near real-time mode and enables us to find signals and compute their back azimuths. At the end of 2018, a new version of the detector was developed at the Kola Branch GS RAS. The detector began to work much faster, which enabled us to carry out data processing for 2.5 years in two frequency ranges in a short time. The main task of the array is acoustic monitoring, the detection of infrasound events, the determination of their parameters, and the selection of events of natural origin. The data are also used (in combination with the VALR seismic station data) to locate near seismic events, especially weak ones. The analysis of the obtained data revealed the prevailing directions to the signal sources. The change of directions to sources in time was investigated, seasonal features were revealed. Acoustic events were detected in the frequency bands 1–5 Hz and 10–20 Hz, and a significant difference was found in the azimuthal distribution of events for these ranges. A joint analysis of acoustic and seismic data showed that the part of events with both acoustic and seismic components is low – it is almost completely exhausted by career explosions. It was also noted that in addition to explosions in nearby quarries (Kuznechnoye, Pitkäranta) located at a distance of 50–60 km, according to acoustic data, events corresponding to explosions at quarries located at a distance of 100 km or more were repeatedly identified.

scholarly journals Non-Contact Damage Detection under Operational Conditions with Multipoint Laservibrometry

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 732 ◽  
Author(s):  
Xiaodong Cao ◽  
Christian Rembe
Keyword(s):  
Low Frequency ◽  
Operational Conditions ◽  
Mechanical Coupling ◽  
Vibration Behavior ◽  
Damage Indices ◽  
Highly Sensitive ◽  
Vibration Responses ◽  
Common Technique ◽  
Measurement Object ◽  
Response Vector

Scanning laser–Doppler vibrometry (SLDV) can localize and visualize damages in mechanical structures. In order to enable scanning, it is necessary to repeat the vibration. Therefore, this technique is not suited to detect emerging hazards in working machinery that change the vibration behavior. A common technique for such cases is monitoring the vibration excited by machine operation with accelerometers. This technique requires mechanical coupling between sensors and the measurement object, which influences the high-frequency vibration responses. However, in the low-frequency range, local damages do not shift resonances or distort operational deflection shapes (ODS) significantly. These alterations in the vibration behavior are tiny and hard to detect. This paper shows that multipoint laservibrometry (MPV) with laser excitation can measure these effects efficiently, and it further demonstrates that damages influence ODSs at frequencies above 20 kHz much stronger than at frequencies below 20 kHz. In addition, ODS-based damage indices are discussed; these are highly sensitive to minute visible changes of the ODSs. In order to enhance the sensitivity of hazard detection, the response vector assurance criterion value is computed and evaluated during operation. The capabilities and limitations of the methodology on the example of a cantilever with manually emerging damage are demonstrated.

scholarly journals Small-Scale Volcanic Structures of the Aeolian Volcanic Arc Revealed by Seismic Attenuation

2021 ◽  
Vol 9 ◽  
Author(s):  
Ignacio Castro-Melgar ◽  
Janire Prudencio ◽  
Andrea Cannata ◽  
Edoardo Del Pezzo ◽  
Jesús M. Ibáñez
Keyword(s):  
Seismic Station ◽  
Low Frequency ◽  
Seismic Attenuation ◽  
Fault System ◽  
Small Scale ◽  
Aeolian Islands ◽  
Seismic Scattering ◽  
Intrinsic Attenuation ◽  
Scattering Attenuation ◽  
The World

We present the first two-dimensional (2-D) spatial distribution of seismic scattering and intrinsic attenuation beneath the Aeolian Islands arc. The Aeolian Islands archipelago represents one of the best examples of a small dimension volcanic island arc characterised by the alternation of different structural domains. Using the seismic wave diffusion model as the basis for the analysis, and using data from an active seismic experiment (TOMO-ETNA), we analysed more than 76,700 seismic paths marked by epicentre-seismic station pairs. Based on frequencies of 4–24 Hz, we identified high regional attenuation, comparable with other volcanic areas of the world. We used two different seismogram lengths, reflecting two different sampling depths, which allowed us to observe two different attenuative behaviours. As in most volcanic regions, scattering attenuation predominates over intrinsic attenuation, but some characteristics are area-specific. Volcanic structures present the highest contribution to scattering, especially in the low frequency range. This behaviour is interpreted to reflect the small size of the islands and the potentially relatively small size of individual magmatic feeding systems. In addition, strong scattering observed in one zone is associated with the northernmost part of the so-called Aeolian-Tindari-Letojanni fault system. In contrast, away from the volcanic islands, intrinsic attenuation dominates over scattering attenuation. We interpret this shift in attenuative behaviour as reflecting the large volume of sedimentary material deposited on the seabed. Owing to their poorly consolidated nature, sediments facilitate intrinsic attenuation via energy dissipation, but in general present high structural homogeneity that is reflected by low levels of scattering. Our results show that this region is not underlain by a large volcanic structural complex such as that beneath nearby Mt. Etna volcano. Instead, we observe dimensionally smaller and isolated subsurface volcanic structures. The identification of such features facilitates improved geological interpretation; we can now separate consolidated marine structures from independent subsurface volcanic elements. The results of this study provide a model for new research in similar regions around the world.

scholarly journals Analysis of the dynamic characteristics of the mixed structure building using mobile seismic station of new generation

2019 ◽  
Author(s):  
Дж.К. Карапетян ◽  
О.Ю. Айрапетян ◽  
Д.А. Мхитарян
Keyword(s):  
Dynamic Characteristics ◽  
Seismic Station ◽  
Complex Structure ◽  
Residential Building ◽  
Technical Condition ◽  
Similar Data ◽  
Seismic Sensors ◽  
Instrumental Observations ◽  
Short Time ◽  
New Generation

В статье рассматриваются вопросы изучения поведения зданий и сооружений в натурных условиях. Статья посвящена теме исследования динамических характеристик жилого здания с неполным каркасом. Авторы предложили осуществлять изучение поведения зданий с помощью мобильной сейсмостанции нового поколения, состоящей из трех сейсмоприемников – типа модернизированных сейсмодатчиков СМ-3, логгер, производства ИГИС НАН РА, оснащённых беспроводной сетью, что обеспечивает связь с ноутбуком. Приводятся результаты исследований динамических характеристик жилого здания комплексной конструкции с помощью специальной мобильной сейсмостанции, разработанной в ИГИС НАН РА. В процессе эксплуатации зданий их техническое состояние изменяется. Это выражается изменением количественных характеристик работоспособности (надёжности), в частности, динамических характеристик зданий. Нами была поставлена задача: исследование динамических характеристик жилого здания комплексной конструкции и проверка его технического состояния, сравнение динамических характеристик с данными, полученными в ранее проведённых работах], а также сопоставление динамических характеристик грунтов их оснований. Замер колебаний осуществлен с помощью микросейсм. При таких измерениях необходимо избегать влияния движения транспортных средств и других постоянных источников генерации колебаний грунтов и зданий. Поэтому измерения были произведены в ночное время для того, чтобы колебания грунта и здания были вызваны только естественными микросейсмами. Одним из важнейших преимуществ микросейсмических исследований является то, что количество микроимпульсов, регистрируемых на поверхности Земли и на зданиях и сооружениях, чрезвычайно велико, поэтому имеется возможность за короткие сроки без особых затрат получать большое количество информации для спектрального анализа. Эта информация позволяет решать ряд важных задач научного и практического характера. Проведен сравнительный анализ полученных путем инструментальных наблюдений динамических характеристик здания и имевшихся ранее аналогичных данных. Выявлены закономерности изменения динамических характеристик в зависимости от длительности эксплуатации здания, в результате чего произведена оценка его фактического технического состояния. The article deals with the study of the behavior of buildings and structures in natural conditions. The article is devoted to the study of the dynamic characteristics of a residential building with an incomplete frame. The authors proposed to study the behavior of buildings using a mobile seismic station of a new generation consisting of three seismic receivers, such as the upgraded SM-3 seismic sensors, a logger, produced by IGES NAS RA, equipped with a wireless network that provides communication with a laptop. The article presents the results of studies of the dynamic characteristics of a residential building of a composite structure with the help of a special mobile seismic station developed at IGES NAS RA. During the operation of buildings, their technical condition changes. This is expressed by a change in the quantitative characteristics of performance (reliability), in particular, the dynamic characteristics of buildings. We set the task: to study the dynamic characteristics of a residential building with a complex structure and to check its technical condition, to compare the dynamic characteristics with data obtained in earlier works, and also to compare the dynamic characteristics of the grounds of their bases. Measurement of vibrations were carried out with the help of microseisms. In such measurements it is necessary to avoid the influence of the movement of vehicles and other permanent sources of generation of vibrations of soils and buildings. Therefore, measurements were made at night to ensure that the vibrations of the soil and buildings were caused only by natural microseisms. One of the most important advantages of microseismic research is that the number of micropulses recorded on the surface of the Earth and on buildings and structures is extremely large, so it is possible to obtain a large amount of information for spectral analysis in a short time without much expense. This information allows you solving a number of important tasks of a scientific and practical nature. A comparative analysis of the dynamic characteristics of the building obtained by instrumental observations and previously available similar data was carried out. The regularities of changes in the dynamic characteristics depending on the duration of the building's operation were revealed, as a result of which an assessment of its actual technical condition was made.

Experimental Validation and Updating of the Flexible Multibody Model of a Commercial 3R Planar Manipulator

2011 ◽  
Author(s):  
Stefano Fiorati ◽  
Emiliano Mucchi ◽  
Raffaele Di Gregorio ◽  
Giorgio Dalpiaz
Keyword(s):  
Ad Hoc ◽  
Low Frequency ◽  
Experimental Tests ◽  
Low Speed ◽  
Operational Conditions ◽  
Multibody Model ◽  
Planar Manipulators ◽  
Flexible Multibody ◽  
Modes Of Vibration ◽  
Synthesis Methodology

Serial planar manipulators are diffusely used either as stand-alone machines or as part of more complex cells, and many commercial planar manipulators are available on the market. These commercial machines are mainly destined to accomplish low-speed tasks, and they are designed by taking into account their flexibility at most in the joints. Unfortunately, there are particular installation conditions in which even low-speed tasks can generate low-frequency vibrations that highly interfere with the task. This aspect is highlighted here with reference to a commercial 3R planar manipulator, and how to manage this problem is explained. In this sight, a flexible multibody model is developed where the flexibility of the frame, the manipulator is fixed to, is modeled over the flexibility of the joints, that is introduced as lumped stiffness. In particular, the flexible frame is included in the model by using a Component Mode Synthesis methodology, in which only the natural modes of vibration and the static constrain modes are accounted. The model is validated through an experimental campaign. The experimental tests consist of several modal analyses, together with acceleration and laser Doppler measurements in operational conditions. This methodology allows to provide a model which takes into account the installation conditions, and gives a tool for studying ad-hoc solutions which prevent the occurrence of low-frequency vibrations.

Development of a Compact Broadband Ocean-Bottom Seismometer

2021 ◽  
Author(s):  
Masanao Shinohara ◽  
Tomoaki Yamada ◽  
Hajime Shiobara ◽  
Yusuke Yamashita
Keyword(s):  
Low Frequency ◽  
Plate Boundaries ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Broadband Seismometer ◽  
Seismic Sensors ◽  
Slow Earthquakes ◽  
Short Period ◽  
Ocean Bottom Seismometers

Abstract Studies of very-low-frequency earthquakes and low-frequency tremors (slow earthquakes) in the shallow region of plate boundaries need seafloor broadband seismic observations. Because it is expected that seafloor spatially high-density monitoring requires numerous broadband sensors for slow earthquakes near trenches, we have developed a long-term compact broadband ocean-bottom seismometer (CBBOBS) by upgrading the long-term short-period ocean-bottom seismometer that has seismic sensors with a natural frequency of 1 Hz and is being mainly used for observation of microearthquakes. Because many long-term ocean-bottom seismometers with short-period sensors are available, we can increase the number of broadband seafloor sensors at a low cost. A short-period seismometer is exchanged for a compact broadband seismometer with a period of 20 or 120 s. Because the ocean-bottom seismometers are installed by free fall, we have no attitude control during an installation. Therefore, we have developed a new leveling system for compact broadband seismic sensors. This new leveling system keeps the same dimensions as the conventional leveling system for 1 Hz seismometers so that the broadband seismic sensor can be installed conveniently. Tolerance for leveling is less than 1°. A tilt of up to 20° is allowed for the leveling operation. A microprocessor controls the leveling procedure. Some of the newly developed ocean-bottom seismometers were deployed in the western Nankai trough, where slow earthquakes frequently occur. The data from the ocean-bottom seismometers on the seafloor were evaluated, and we confirmed that the long-term CBBOBS is suitable for observation of slow earthquakes. The developed ocean-bottom seismometer is also available for submarine volcanic observation and broadband seafloor observation to estimate deep seismic structures.

Causality of manufacturing processes with significant time delays

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 725-738
Author(s):  
SHELDON WANG ◽  
YU GUO
Keyword(s):  
Flow Rate ◽  
Time Delays ◽  
Low Frequency ◽  
Paper Mill ◽  
Frequency Range ◽  
Operational Conditions ◽  
Significant Time ◽  
Extraneous Information ◽  
Stock Flow ◽  
Synchronization Procedure

In this paper, the effects of flow rate, fiber consistency, and pressure fluctuation on basis weight variations were studied based on a set of paper mill operation data that include thick stock flow rate, consistency at eight different stock preparation stages, inlet and outlet pressure of the pressure pulsation attenuator, scanner position, β gauge, and scanner basis weight measurements. In order to focus on the important spectra and correlations within the low frequency range, a boxcar averaging procedure to eliminate high frequency extraneous information was employed. Moreover, two complete sets of data have been obtained for consistent and problematic operational conditions; namely, with and without a stuff box flow control system. The transfer function between the input and output spectra of certain components or processes within approach flow systems is also studied. Particular emphasis is placed on the synchronization procedure necessary for the study of low frequency range signals, as well as the correlation between two signals. All analysis results presented here are derived with an in-house developed program targeted for systems with significant time delays.

Burial Process of a Seismic Station by Moving Dunes in Tarim Basin

2020 ◽  
Vol 91 (5) ◽  
pp. 2936-2941
Author(s):  
Xiaofeng Liang ◽  
Sicheng Zuo ◽  
Shilin Li ◽  
Yongge Feng
Keyword(s):  
High Frequency ◽  
Noise Level ◽  
Seismic Station ◽  
Low Frequency ◽  
Seismic Signal ◽  
Frequency Noise ◽  
Temperature Record ◽  
Environment Change ◽  
Broadband Seismometer ◽  
High Frequency Noise

Abstract A temporary seismometer vault was buried by a moving sand dune in the Taklimakan Desert at northwestern China in October 2019. The dune gradually covered the solar panel and the power supply to the seismic station was subsequently cut off. Here, we show that the burial process can be diagnosed according to the temperature record from the thermometer in the data-logger, an ultra-low-frequency seismic signal, and the change of high-frequency noise level from the continuous seismograms recorded by the broadband seismometer. The ultra-low-frequency seismic signal reflects the thermoelastic effect of the suspension spring in the seismometer corresponding to the temperature gradient in the sensor vault. At the same time, the variation of high-frequency noise level correlates well with the temperature profile and the ultra-low-frequency seismic signal, indicating the ground wind intensity. The peak frequency shifts and their different responses on three-component waveforms for the high-frequency noise might reflect the distance from the moving dunes to the station and their moving directions. This observation shows a potential usage of continuous seismograms to study rapid environment change around a temporary seismic station.

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