Calibrating the 2016 IRIS Wavefields Experiment Nodal Sensors for Amplitude Statics and Orientation Errors

2021 ◽  
Author(s):  
Oluwaseyi J. Bolarinwa ◽  
Charles A. Langston
Keyword(s):  
Signal To Noise Ratio ◽  
Vertical Component ◽  
Calibration Method ◽  
Horizontal Component ◽  
High Signal ◽  
Correction Factors ◽  
Small Aperture ◽  
S Waves ◽  
Amplitude Correction ◽  
Array Calibration

ABSTRACT We used teleseismic P and S waves recorded in the course of the 2016 Incorporated Research Institutions for Seismology (IRIS) community-planned experiment in northern Oklahoma, to estimate amplitude correction factors (ACFs) and orientation correction factors (OCFs) for the gradiometer’s three-component Fairfield nodal sensors and two other gradiometer-styled subarray nodal sensors. These subarrays were embedded in the 13 km aperture nodal array that was also fielded during the 2016 IRIS experiment. The array calibration method we used in this study is based on the premise that a common wavefield should be recorded over a small-aperture array using teleseismic observation. In situ estimates of ACF for the gradiometer vary by 2.3% (standard deviation) for the vertical components and, typically, variability is less than 4.3% for the horizontal components; associated OCFs generally dispersed by 3°. For the two subarrays, the vertical-component ACF usually vary up to 2.4%; their horizontal-component ACFs largely spread up to 3.6%. OCFs for the subarrays generally disperse by 6.5°. ACF and OCF estimates for the gradiometer are seen to be stable across frequency bands having high signal coherence and/or signal-to-noise ratio. Gradiometry analyses of calibrated and uncalibrated gradiometer records from a local event revealed notable improvements in accuracy of attributes obtained from analyzing the calibrated horizontal-component waveforms in the light of catalog epicenter-derived azimuth. The improved waveform relative amplitudes after calibration, coupled with the enhanced wave attribute accuracy, suggests that instrument calibration for amplitude statics and orientation errors should be encouraged prior to doing gradiometry analysis in future studies.

scholarly journals A Geometric Calibration Method of Hydrophone Array Based on Maximum Likelihood Estimation with Sources in Near Field

2020 ◽  
Vol 8 (9) ◽  
pp. 678
Author(s):  
Nan Zou ◽  
Zhenqi Jia ◽  
Jin Fu ◽  
Jia Feng ◽  
Mengqi Liu
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimation ◽  
Signal To Noise Ratio ◽  
Near Field ◽  
Likelihood Estimation ◽  
Calibration Method ◽  
Optimization Method ◽  
High Signal ◽  
Geometric Calibration ◽  
Environment Experiment

Considering the requirement of the near-field calibration under strong underwater multipath condition, a high-precision geometric calibration method based on maximum likelihood estimation is proposed. It can be used as both auxiliary-calibration and self-calibration. According to the near-field geometry error model, the objective function of nonlinear optimization problem is constructed by using the unconditional maximum likelihood estimator. The influence of multipath on geometric calibration is studied. The strong reflections are considered as the coherent sources, and the compensation strategy for auxiliary-calibration is realized. The optimization method (differential evolution, DE) is used to solve the geometry errors and sources’ position. The method in this paper is compared with the eigenvector method. The simulation results show that the method in this paper is more accurate than the eigenvector method especially under high signal-to-noise ratio (SNR) and multipath environment. Experiment results further verify the effectiveness.

SEISMIC NOISE ESTIMATION USING HORIZONTAL COMPONENTS

Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 617-632
Author(s):  
Thomas F. Potter ◽  
Robert B. Roden
Keyword(s):  
Signal To Noise Ratio ◽  
Single Point ◽  
Vertical Component ◽  
Horizontal Component ◽  
Noise Component ◽  
Physical Separation ◽  
Noise Rejection ◽  
Particle Orbit ◽  
Circular Rings ◽  
Noise Models

The use of seismometer arrays containing both horizontal‐ and vertical‐component instruments for attenuation of surface‐wave noise has been studied theoretically. If a process can be defined to estimate the vertical noise component by operating on the outputs of one or more horizontal‐component seismometers, the estimate may be subtracted from the vertical‐component record to improve signal‐to‐noise ratio. The exact waveforms of vertically‐incident signals must be preserved in an operation of this kind. Formulas are developed to describe the response of a system employing three components measured at a single point. This system is found to be useful only in cases where the noise is strongly directional. A physical separation between the vertical‐ and horizontal‐component instruments is necessary to resolve the difficulties caused by uncertainties in the sense of the propagation velocity vector and particle orbit vector. Formulas, derived for systems consisting of circular rings of radially‐oriented horizontals and a central vertical show, that useful noise rejection can be obtained even in the most unfavorable case of uniform azimuthal noise distribution. The performance of arrays of this kind is not affected very much by uncorrelated noise or Love‐wave noise. Comparisons with similar arrays containing only vertical‐component seismometers indicate that, for some of the noise models studied, the multicomponent array should provide useful noise rejection over a greater bandwidth and at longer wavelengths than an all‐vertical array with the same dimensions.

Detector coupling corrections for vector infidelity of multicomponent OBC data

Geophysics ◽  
2007 ◽  
Vol 72 (3) ◽  
pp. V67-V77 ◽  
Author(s):  
James E. Gaiser
Keyword(s):  
Vertical Component ◽  
Low Frequency ◽  
Radial Component ◽  
Horizontal Component ◽  
Ocean Bottom ◽  
S Wave ◽  
S Waves ◽  
Resonance Modes ◽  
The Time Domain ◽  
Phase Distortions

Differences in the frequency response of horizontal and vertical detectors (vector infidelity) in ocean bottom cable (OBC) surveys can cause problems for multicomponent processing, such as S-wave birefringence and amplitude variation with azimuth (AVA) analyses, and combining vertical and hydrophone data for water-born multiple suppression. One source of this problem is poor detector coupling with the seabed that produces resonances and phase distortions. Coupling and data quality are generally excellent for the inline component. However, the crossline component often exhibits low-frequency resonance compared to the inline. Also, OBCs are susceptible to rotational modes about the cable axis that produce spurious S-waves on the vertical component. I derive a method for correcting the crossline and vertical components based on a model of OBC detector coupling, and design vector operators in the frequency domain from shots over many offsets and azimuths. The crossline data are corrected,relative to the inline, assuming linear polarization of early, near-offset arrivals on the radial-horizontal component. Thus, the transverse-horizontal component provides a convenient error or objective function to be minimized for operator design. Using the corrected crossline, as a model of rotational modes, leads to an estimate of spurious S-waves on the vertical component, which are adaptively subtracted. Data examples from the Gulf of Mexico and offshore Nigeria are presented to illustrate improvements in crossline frequency content and match to inline data. Typically there is [Formula: see text] reduction in error using the rms ratio of transverse-to-radial component data computed in the time domain. Suppression of spurious S-waves from the vertical component without undesirable effects of low-cut or [Formula: see text] filters is shown for prestack and poststack data. Also, vector operators indicate they contain important information related to resonance modes of crossline coupling and rotational modes associated with seabed-deployed versus buried OBCs.

scholarly journals Amplitude of PcP, PcS, ScS, and ScP in deep-focus earthquakes*

1953 ◽  
Vol 43 (1) ◽  
pp. 63-83
Author(s):  
Kazim Ergin
Keyword(s):  
Systematic Study ◽  
Transverse Wave ◽  
Vertical Component ◽  
Horizontal Component ◽  
P Waves ◽  
S Waves ◽  
Core Boundary ◽  
Deep Focus ◽  
The Waves ◽  
Good Agreement

abstract A systematic study has been made of the ratios of (displacementperiod) of PcP, PcS, ScS, and ScP to that of the corresponding incident wave {e.g.,(displacementperiod)PcP/(displacementperiod)P}, using intermediate and deep-focus earthquake seismograms. The results indicate that the observed ratios of the horizontal components of the waves that are reflected as P waves (i.e., PcP/P and ScP/S) and that of the vertical component of the waves that are reflected as S waves (i.e., ScS/S and PcS/P) at the mantle-core boundary are considerably larger than the theoretical ones, whereas the observed ratios of the vertical component of the first group and that of the horizontal component of the second group are in fairly good agreement with the theoretical values. Theoretical computations were based on the assumption that in the case of a longitudinal wave the vibration is in the direction of propagation and in the case of a transverse wave the vibration is perpendicular to the direction of propagation. It is further found that the behavior of the direct P and S waves is in accord with the theory, but the vibration of the ground is not in the direction of propagation for PcP and ScP and is not perpendicular to the direction of propagation for PcS and ScS.

The G-calibration: A new method for an absolute in situ calibration of long-period accelerometers, tested on the Streckeisen instruments of the GEOSCOPE network

1991 ◽  
Vol 81 (4) ◽  
pp. 1360-1372
Author(s):  
P. Bernard ◽  
J.-F. Karczewski ◽  
M. Morand ◽  
B. Dole ◽  
B. Romanowicz
Keyword(s):  
Gravitational Field ◽  
Rotation Axis ◽  
Vertical Component ◽  
Calibration Method ◽  
High Accuracy ◽  
Horizontal Component ◽  
Force Balance ◽  
Absolute Calibration ◽  
Calibration System

Abstract The sensitivity of the Streckeisen's very broadband (VBB) accelerometers is routinely measured on tilt tables by the manufacturer, with an announced accuracy of about 1 per cent. Nevertheless, the transportation of the station or different in situ environmental conditions may modify the sensitivity. As one may expect that a high accuracy in the wave amplitude will be required in the future by seismologists, we developed and tested an in situ absolute calibration method, which does not require the seismometers to be moved. Its principle is simple: A mass is moving in the vicinity of the force-balance accelerometer, and the perturbation of the gravitational field is measured. This calibration method, because it requires the use of G, the gravitational constant, is termed the G-calibration. At a distance of 0.5 m, the gravitational field of a 30 kg mass is 8 × 10−9 m.sec−2, which is 2 order of magnitude greater than the instrumental noise. At the test station of SBB, this acceleration is still 50 times above the seismic noise level for the vertical component, but little above the seismic horizontal noise. The calibration system consists into a small telescope platform (diameter 0.5 m) supporting a horizontal bar of 1 m. Two metallic cylinders of equal mass (about 30 kg) are placed at the two ends of the bar, symmetrically with respect to the vertical rotation axis of the platform. The rotation velocity of the system is controlled with a high accuracy. The accelerometers are located at less than 1 m from the system axis. For the vertical component, we measured the sensitivity at various periods between 2000 and 50 sec, and the result was within 10 per cent of the specified sensitivity; this difference was of the same order as the expected accuracy. For the horizontal component, a slight asymmetry of the two masses with respect to the rotation center and an irregular coupling of the platform to the ground induced a periodic variation of the tilt, dominating over the gravitational signal of the masses at the frequencies of interest, which made the sensitivity measurement less accurate. Nevertheless, the result was still close to the announced sensitivity. We expect that an improved version of our calibration system will allow an accuracy of 1 per cent for the vertical, with a few hours of calibration. This will require an accuracy of a few millimeters in the geometry of the calibration system. Improving the results for the horizontal component will require a careful installation in order to eliminate the tilt perturbation and should lead to an accuracy of a few per cent.

Passive seismic measurement of seismic attenuation in Delaware Basin

2019 ◽  
Vol 38 (2) ◽  
pp. 138-143 ◽  
Author(s):  
Małgorzata Drwiła ◽  
Miłosz Wcisło ◽  
Denis Anikiev ◽  
Leo Eisner ◽  
Randy Keller
Keyword(s):  
Sedimentary Basin ◽  
Signal To Noise Ratio ◽  
Peak Frequency ◽  
Seismic Attenuation ◽  
High Signal ◽  
Earthquake Activity ◽  
Frequency Method ◽  
P Waves ◽  
S Waves ◽  
Delaware Basin

Local earthquake activity can be employed to measure attenuation (the effective quality factor [Q]) and characterize production in the Delaware Basin, Texas, USA. To illustrate this, we employed data from the recently installed Texas Seismic Network (TexNet) seismic stations collected in the west Texas area between April 2017 and March 2018. Earthquake activity in the Delaware Basin has increased in comparison to the previous 20 years, which has resulted in numerous high-quality events suitable for this analysis. The high signal-to-noise ratio events were used to estimate effective Q factors using the peak frequency method on the sediments of the Delaware Basin. The effective attenuation of the sedimentary basin is 90 for P-waves and 140 for S-waves (both with uncertainty of approximately 30), indicating an unusually low attenuation (high Q) for S-waves relative to the P-waves. This is consistent with attenuation of a saturated sedimentary basin because the saturation results in less attenuation of S-waves. Additionally, we observe an increase of the effective Q factor with distance between the station and events consistent with rays sampling the deeper, less-attenuating, and less-saturated portions of the basin and even basement. Inverted effective attenuation coefficients were used to calculate moment magnitudes, which were consistent with those seen in the TexNet array.

A compact guided-wave EMAT with pulsed electromagnet for ferromagnetic tube inspection

2020 ◽  
Vol 64 (1-4) ◽  
pp. 951-958
Author(s):  
Tianhao Liu ◽  
Yu Jin ◽  
Cuixiang Pei ◽  
Jie Han ◽  
Zhenmao Chen
Keyword(s):  
Power Plants ◽  
Signal To Noise Ratio ◽  
Small Diameter ◽  
Performance Testing ◽  
Guided Wave ◽  
High Signal ◽  
Receiver Coil ◽  
Signal To Noise ◽  
Corrosion Defects

Small-diameter tubes that are widely used in petroleum industries and power plants experience corrosion during long-term services. In this paper, a compact inserted guided-wave EMAT with a pulsed electromagnet is proposed for small-diameter tube inspection. The proposed transducer is noncontact, compact with high signal-to-noise ratio and unattractive to ferromagnetic tubes. The proposed EMAT is designed with coils-only configuration, which consists of a pulsed electromagnet and a meander pulser/receiver coil. Both the numerical simulation and experimental results validate its feasibility on generating and receiving L(0,2) mode guided wave. The parameters for driving the proposed EMAT are optimized by performance testing. Finally, feasibility on quantification evaluation for corrosion defects was verified by experiments.

Application of Novel Low Current OBIRCH Amplifier and Nanoprobing to Identify Subtle Leakages in Advanced Node Technologies

2018 ◽  
Author(s):  
Satish Kodali ◽  
Liangshan Chen ◽  
Yuting Wei ◽  
Tanya Schaeffer ◽  
Chong Khiam Oh
Keyword(s):  
Signal To Noise Ratio ◽  
Semiconductor Industry ◽  
Fault Isolation ◽  
Ring Oscillator ◽  
High Signal ◽  
The Novel ◽  
Resistance Change ◽  
Three Samples ◽  
Relative Threshold ◽  
First Time

Abstract Optical beam induced resistance change (OBIRCH) is a very well-adapted technique for static fault isolation in the semiconductor industry. Novel low current OBIRCH amplifier is used to facilitate safe test condition requirements for advanced nodes. This paper shows the differences between the earlier and novel generation OBIRCH amplifiers. Ring oscillator high standby leakage samples are analyzed using the novel generation amplifier. High signal to noise ratio at applied low bias and current levels on device under test are shown on various samples. Further, a metric to demonstrate the SNR to device performance is also discussed. OBIRCH analysis is performed on all the three samples for nanoprobing of, and physical characterization on, the leakage. The resulting spots were calibrated and classified. It is noted that the calibration metric can be successfully used for the first time to estimate the relative threshold voltage of individual transistors in advanced process nodes.

A novel and sensitive LC-MS/MS method for the quantitation of ceftiofur in pharmaceutical preparations and milk samples

2020 ◽  
Vol 23 ◽  
Author(s):  
Serkan Levent ◽  
Saniye Özcan ◽  
Aysun Geven ◽  
Nafiz Öncü Can
Keyword(s):  
Quantitative Estimation ◽  
Signal To Noise Ratio ◽  
Multiple Reaction Monitoring ◽  
Pharmaceutical Preparations ◽  
Calibration Method ◽  
Negative Ion ◽  
Cow Milk ◽  
Tandem Mass ◽  
Ionization Source ◽  
Liquid Chromatography Tandem Mass

Introduction:: In the present study, a sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was described for the determination of ceftiofur (CEF) in cow milk and pharmaceutical preparations. CEF is an antibiotic compound, which is commonly used in the treatment of animal diseases such as respiratory system, soft tissue, and foot infections, as well as postpartum acute puerperal metritis. One of the critical features of CEF is its prescription while breastfeeding of cows; in accordance, its quantitative estimation is essential to assess its residual amounts. Methods:: In the method reported herein, after simple protein precipitation using acetonitrile, the pre-treated samples were introduced in to an LC-MS/MS instrument equipped with a Chromolith® High-Resolution RP-18 series HPLC column (100 mm × 4.6 mm from Merck KGaA, Germany). Electrospray ionization was employed as the ionization source in the triplequadrupole tandem mass spectrometer. Results:: For the calibration method using solvent-based standards; LOQ was 3.038 ng/mL, 12.15 ng/mL, and LOD was 1.215 ng/mL and 6.076 ng/mL for ESI+ and ESI- modes, respectively. On the other hand, for the method of matrix-matched standards; LOQ was 1.701 ng/mL, 10.13 ng/mL, and LOD was 0.486 ng/mL and 5.929 ng/mL for ESI+ and ESI- modes, respectively as obtained from signal to noise ratio. Conclusion:: Applicability of both positive and negative ion modes was tested, and the analyte was detected via multiple reaction monitoring. The distorting effects of the milk matrix on the MS ionization and quantitation of CEF were overcome by using matrix-matched calibration for the first time.

Galilean Relativity

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
Inertial Frame ◽  
Vertical Component ◽  
Horizontal Component ◽  
The Other ◽  
One Dimension ◽  
Everyday Experience ◽  
Low Speed ◽  
Principle Of Relativity ◽  
Galilean Relativity ◽  
Laws Of Motion

Galilean relativity is a useful description of nature at low speed. Galileo found that the vertical component of a projectile’s velocity evolves independently of its horizontal component. In a frame that moves horizontally along with the projectile, for example, the projectile appears to go straight up and down exactly as if it had been launched vertically. The laws of motion in one dimension are independent of any motion in the other dimensions. This leads to the idea that the laws of motion (and all other laws of physics) are equally valid in any inertial frame: the principle of relativity. This principle implies that no inertial frame can be considered “really stationary” or “really moving.” There is no absolute standard of velocity (contrast this with acceleration where Newton’s first law provides an absolute standard). We discuss some apparent counterexamples in everyday experience, and show how everyday experience can be misleading.

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