scholarly journals Rotaphone-CY: The Newest Rotaphone Model Design and Preliminary Results from Performance Tests with Active Seismic Sources

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 562
Author(s):  
Johana Brokešová ◽  
Jiří Málek ◽  
Jiří Vackář ◽  
Felix Bernauer ◽  
Joachim Wassermann ◽  
...  
Keyword(s):  
Performance Tests ◽  
Model Design ◽  
Small Aperture ◽  
Preliminary Results ◽  
Rigid Frame ◽  
Short Period ◽  
Reliable Instrument ◽  
Mutual Comparison ◽  
Mechanical Sensor ◽  
Field Deployment

Rotaphone-CY is a six-component short-period seismograph that is capable of the co-located recording of three translational (ground velocity) components along three orthogonal axes and three rotational (rotation rate) components around the three axes in one device. It is a mechanical sensor system utilizing records from elemental sensors (geophones) arranged in parallel pairs to derive differential motions in the pairs. The pairs are attached to a rigid frame that is anchored to the ground. The model design, the latest one among various Rotaphone designs based on the same principle and presented elsewhere, is briefly introduced. The upgrades of the new model are a 32-bit A/D converter, a more precise placing of the geophones to parallel pairs and a better housing, which protects the instrument from external electromagnetic noise. The instrument is still in a developmental stage. It was tested in a field experiment that took place at the Geophysical Observatory in Fürstenfeldbruck (Germany) in November 2019. Four Rotaphones-CY underwent the huddle-testing phase of the experiment as well as the field-deployment phase, in which the instruments were installed in a small-aperture seismic array of a triangular shape. The preliminary results from this active-source experiment are shown. Rotaphone-CY data are verified, in part, by various approaches: mutual comparison of records from four independent Rotaphone-CY instruments, waveform matching according to rotation-to-translation relations, and comparison to array-derived rotations when applicable. The preliminary results are very promising and they suggest the good functionality of the Rotaphone-CY design. It has been proved that the present Rotaphone-CY model is a reliable instrument for measuring short-period seismic rotations of the amplitudes as small as 10−7 rad/s.

scholarly journals INSTALLATION AND PRELIMINARY RESULTS FROM A SMALL APERTURE SEISMIC ARRAY IN TRIPOLI, GREECE

2004 ◽  
Vol 36 (3) ◽  
pp. 1499 ◽  
Author(s):  
M. Pirli ◽  
Ν. Voulgaris ◽  
J. Alexopoulos ◽  
K. Makropoulos
Keyword(s):  
Body Wave ◽  
Seismic Array ◽  
Small Aperture ◽  
Preliminary Results ◽  
Seismic Waveforms ◽  
Equipment Safety ◽  
Array Calibration ◽  
Array Performance ◽  
The University ◽  
Of Greece

A small aperture seismic array was installed by the University of Athens, in the area of Tripoli, Greece, on July 16th 2003, in order to test the performance of seismic array processing in the area of Greece and assess its contribution to earthquake location, especially in offshore areas not azimuthally covered by the existing, conventional seismological networks. The array consists of four three-component seismological stations, one of them in the middle of a small, almost equilateral triangle, formed by the deployment of the other three stations. Despite the fact that array siting is a compromise of array installation criteria, equipment safety and logistics, the test character of the experiment can be served successfully. The array transfer function depicts good azimuthal coverage nonetheless the existence of side-lobes and a rather wide main lobe is characteristic of spatial aliasing and low resolution in the two-dimensional wavenumber domain. The resolvable wavenumber passband of the array permits the determination of most of the common seismic body wave phases (Pn, Pg, Sn, Sg, etc.) for local and regional events in the area of Greece. Location of recorded events was performed using slowness and backazimuth data, calculated by f-k analysis of the seismic waveforms. Preliminary results have been compared to epicentres calculated by the Geodynamic Institute of the National Observatory of Athens. Although some differences are observed, these are not significant and location results as well as overall array performance can be improved by array calibration and travel-time, azimuth and slowness correction calculations.

scholarly journals Comparative Measurements of Local Seismic Rotations by Three Independent Methods

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5679
Author(s):  
Johana Brokešová ◽  
Jiří Málek
Keyword(s):  
Seismic Source ◽  
Medium Size ◽  
Period Range ◽  
Small Aperture ◽  
Technical Problems ◽  
Rotation Rates ◽  
Active Experiment ◽  
Short Period ◽  
Order Of Magnitude ◽  
The Given

A comparative active experiment that is aimed at collocated measurement of seismic rotation rates along three orthogonal axes by means of three different methods is described. The rotation rates in a short-period range of 6–20 Hz were obtained using three different methods: the 6C Rotaphone sensor system developed by the authors, the commercial R-1 rotational sensor by Eentec, and a small-aperture array of twelve standard velocigraphs in a rectangular arrangement. Those three methods are compared and discussed in detail. A medium-size quarry blast was used as a seismic source. At a distance of approximately 240 m, the rotation rates reached an amplitude of the order of magnitude of 10−4–10−5 rad/s. The array derived rotation rates displayed serious limitations, as clearly documented. The R-1 instruments have shown certain technical problems that partly limit their applicability. The measured rotation rates were compared to the relevant acceleration components according to rotation-to-translation relations. Out of all the three methods, the records best matching the acceleration components were made by Rotaphone. The experiment also revealed that rotation rates in the given short-period range noticeably changed over a distance as short as 2 m.

Radio wave Doppler studies of the Antarctic ionosphere

1977 ◽  
Vol 279 (963) ◽  
pp. 239-246 ◽  
Keyword(s):  
Energy Balance ◽  
Radio Wave ◽  
Antarctic Peninsula ◽  
Current Knowledge ◽  
Doppler Studies ◽  
Preliminary Results ◽  
Short Period ◽  
The Antarctic

The occurence of propagating wave-like disturbances in the atmosphere at ionospheric heights is well documented, but their causes and role in the energy balance of the atmosphere is poorly understood. This paper describes an experiment deployed in the Antarctic Peninsula region to investigate the morphology of the various classes of disturbance, with particular emphasis on the identification of their sources. Current knowledge of the phenomena is briefly reviewed and the reasons why observations in the peninsula region may be especially valuable are discussed. Some preliminary results from the first 3 months of operation are presented; these indicate the presence of waves with periods ranging from less than 1 min to more than 90 min. The short period waves (1-5 min) are unusually common in these data.

scholarly journals Precise Analytical Computation of Frozen-Eccentricity, Low Earth Orbits in a Tesseral Potential

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Martin Lara ◽  
Juan F. San-Juan ◽  
Luis M. López-Ochoa
Keyword(s):  
Model Design ◽  
Zonal Model ◽  
Period Effects ◽  
Short Period ◽  
Orbit Analysis ◽  
Low Earth Orbits ◽  
Tesseral Harmonics ◽  
Earth Orbits ◽  
Eccentricity Orbit

Classical procedures for designing Earth’s mapping missions rely on a preliminary frozen-eccentricity orbit analysis. This initial exploration is based on the use of zonal gravitational models, which are frequently reduced to a simpleJ2-J3analysis. However, theJ2-J3model may not be accurate enough for some applications. Furthermore, lower order truncations of the geopotential are known to fail in describing the behavior of elliptic frozen orbits properly. Inclusion of a higher degree geopotential, which also takes into account the short-period effects of tesseral harmonics, allows for the precise computation of frozen-eccentricity, low Earth orbits that show smaller long-period effects in long-term propagations than those obtained when using the zonal model design.

A Slug Damper for Compact Separators

2002 ◽  
Author(s):  
Gene E. Kouba
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Slug Flow ◽  
Dynamic Range ◽  
Liquid Flow Rate ◽  
Careful Consideration ◽  
The Body ◽  
Preliminary Results ◽  
Flow Fluctuations ◽  
Short Period

A common concern with the reduced capacity of compact gas/liquid separators, such as the GLCC©, is that flow fluctuations are passed through the separator with little dampening. Rate sensitive devices, e.g., meters, hydrocyclones, etc., located downstream of the compact separator often have a desired turn-down of less than 10 to 1. However, in slug flow, the instantaneous liquid flow rate in the body of a slug can easily exceed 10 times the average liquid flow rate, with a dynamic range closer to 100 to 1. Consequently, use of the GLCC requires careful consideration of the downstream systems and their susceptibility to flow fluctuations. The slug damper was developed to reduce the magnitude of short period flow fluctuations by providing an inexpensive way of increasing liquid retaining capacity of the inlet piping to the GLCC. These preliminary results show that the slug damper system does indeed dramatically reduce exiting flow rate fluctuations from incoming slug flow. Furthermore, the slug damper performed in a predictable manner with no observed instabilities or unusual operation modes.

scholarly journals HD 150136: towards one of the most massive systems?

2010 ◽  
Vol 6 (S272) ◽  
pp. 521-522
Author(s):  
Laurent Mahy ◽  
Eric Gosset ◽  
Hugues Sana ◽  
Gregor Rauw ◽  
Thomas Fauchez ◽  
...  
Keyword(s):  
Physical Parameters ◽  
Intensive Monitoring ◽  
Preliminary Results ◽  
Short Period ◽  
Period System ◽  
Orbital Solution ◽  
Three Components

AbstractWe present the preliminary results of an intensive monitoring devoted to HD 150136. Already quoted as an O3+O6 binary, we detected a third O-type component physically linked to the system, making it one of the nearest (1.3 kpc) most massive systems known until now (~134M⊙). To determine the physical parameters of this system, we applied a disentangling program to study individually the three components. It allows us to constrain their spectral types and to derive a new orbital solution for the short-period system.

scholarly journals Underground earth strain and seismic radiation measurements with a laser interferometer and a dense small-aperture seismic array

1997 ◽  
Vol 40 (5) ◽  
Author(s):  
A. Amoruso ◽  
L. Crescentini ◽  
G. De Luca ◽  
R. Scarpa ◽  
M. Abril ◽  
...  
Keyword(s):  
Laser Interferometer ◽  
High Sensitivity ◽  
Seismic Array ◽  
Seismic Zone ◽  
Small Aperture ◽  
Short Period ◽  
Physics Laboratories ◽  
Underground Physics ◽  
Very High ◽  
Radiation Measurements

This paper describes two geophysical instruments, installed in the underground physics laboratories of Gran Sasso (LNGS-INFN), located in the seismic zone of the Central Apennines, Italy. These instruments monitor strain and seismic radiation with very high sensitivity: one is a 90 m-long laser interferometer, sensitivity 3 x 10-12, frequency response 10-7-10-2 Hz, and has been operating since 1994. The other is a small-aperture seismic array composed of 21 three-component short period (Mark L4C-3D) and 3 broadband (Guralp CMG-3ESP) seismometers. This dense array will be in operation at the beginning of 1998.

scholarly journals Eclipsing Binary Stars from Space

2006 ◽  
Vol 2 (S240) ◽  
pp. 624-627
Author(s):  
Hans Bruntt ◽  
John Southworth
Keyword(s):  
Light Curve ◽  
High Precision ◽  
Binary Stars ◽  
Primary Component ◽  
Wide Field ◽  
Small Aperture ◽  
Eclipsing Binary ◽  
Preliminary Results ◽  
Eclipsing Binary Stars

AbstractWe have begun a programme to obtain high-precision photometry of bright detached eclipsing binary (dEB) stars with the Wide-field InfraRed Explorer (WIRE) satellite (Bruntt & Buzasi 2006). Due to the small aperture of WIRE, only stars brighter than V = 6 can be observed. We are collecting data for about a dozen dEB targets and here we present preliminary results for three of them. We have chosen dEBs with primary components of B and early A type. One of our aims is to combine the information from the light curve analyses of the eclipses with asteroseismic information from analysis of the pulsation of the primary component.

scholarly journals Lg-coda Q in the central part of the East European platform from small aperture array “Mikhnevo” data

2019 ◽  
Vol 1 (1) ◽  
pp. 57-66
Keyword(s):  
East European Platform ◽  
Seismic Attenuation ◽  
Tectonic Activity ◽  
Q Factor ◽  
Coda Q ◽  
Small Aperture ◽  
East European ◽  
Short Period ◽  
Lg Coda ◽  
Aperture Array

Whereas the quality factor Q is one of the basic parameters required in seismic hazard estimation, no systematic studies of seismic attenuation factors have been carried out in the central part of the East European Platform due to the lack of a dense seismic network and a small number of regional earthquakes. The main part of the events, recorded by the small aperture array “Mikhnevo” 80 km to the south of Moscow, consists of industrial explosions of different magnitude. The idea of the paper is to apply conventional seismic methods to the analysis of seismic waveforms of industrial explosions. The paper focuses on the Lg coda of the quarry blast in “Mikhailovsky” quarry 300 km from the array. Vertical components of the short-period and broad band records of the sensors positioned in the well at the depth 20 m are processed according to the SSR algorithm, suggested by Xie and Nuttli, 1988, and extensively used by Mitchell et al in different regions of the world. The advantages of the method imply exclusion of the source and site characteristics by taking spectral ratios of the successive time windows of the coda. Compared to the earthquake waveforms, the Lg coda of explosions is shorter, less regular and contains higher frequencies. The length of coda varies according to the noise level. We selected 14 events from the same quarry in different years, which demonstrate remarkable stability of the waveforms. All the events were processed individually to obtain the frequency dependence of Q in the form Q(f)=Q0 f , where Q0 is the Q factor at the frequency 1 Hz and  is the power. To produce stable estimates of Q0 and  individual values were averaged for frequency bands: 2-6 Hz, 2-7 Hz, 3-6 Hz, 3-7 Hz for different length of coda. The preferable frequency range for Lg coda Q studies of quarry blasts is suggested as 3-6 Hz, which avoids instability of coda in 1-3 Hz interval, presumably caused by local site effect, connected with the 3 km thick sedimentary layer. The Q estimate of Q0=584±89, =0.41±0.06 proves considerable heterogeneity of the upper crust in the region. Speaking about Q factor as an indicator of the tectonic activity, the studied area can be related to a region of moderate activity.

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