Determination of a seismometer’s generator constant, azimuth, and orthogonality in three-dimensional space using a reference seismometer

Tasič, Izidor; Runovc, Franc

doi:10.1007/s10950-012-9355-y

Cited by 11 publications

(7 citation statements)

References 6 publications

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“…We corrected the potential misalignment angles between seismometers based on three-dimensional (3D) rotational algorithm of raw seismic traces to maximize coherence, which is similar in principle to that of previous studies (Tasič and Runovc 2013;Gerner et al 2017). The raw data were deconvolved with instrument response of both seismometers and data loggers.…”

Section: Analysis and Resultsmentioning

confidence: 99%

“…Several studies (Holcomb 1990;Sleeman and Melichar 2012;Tasič and Runovc 2013;Gerner and Bokelmann 2013;Ringler et al 2015aRingler et al , 2015bGerner et al 2017) have shown that sensor misalignment is an important source of error during self-noise testing of seismometers based on collocation methods. A synthetic test was conducted to quantify the effect of sensor misalignment as a function of signal-to-noise ratio (SNR) on the self-noise estimate.…”

Section: Introductionmentioning

confidence: 99%

“…This implied that these types of measurements should be performed at seismically quiet locations or the misalignment error must be well corrected before the correlation analysis to avoid the misinterpretation of test result. Considering that an ideal seismically quiet location can hardly be found and misalignment error can hardly be guaranteed to be less than 1° (Ekström and Busby 2008;Ringler et al 2013), the correction based on the trace rotation is a good option and different rotational schemes have been developed to correct the effect of sensor misalignment (Tasič and Runovc 2013;Gerner and Bokelmann 2013;Gerner et al 2017). The timing errors between sensor records contribute to the incoherent-noise estimates and are related to the SNR of the records (Ringer et al, 2011); however, this effect is increasingly negligible because the timing clock inside modern data acquisition systems can be well synchronized once the inside global navigation satellite system (GNSS) module is normally operated.…”

Section: Introductionmentioning

confidence: 99%

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A case study of seismograph self-noise test from Trillium 120QA seismometer and Reftek 130 data logger

Yuan

2019

J Seismol

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Seismograph self-noise has become a de facto standard for instrument comparisons and their performance assessment and is considered as one of the most vital parameters for instrument comparison. For self-noise testing of modern force-balance feedback broadband seismometers, several factors have been thoroughly discussed and thought to be attributable to the self-noise estimate, including the data selection criteria, sensor alignment correction, timing error, correlation analysis method, and computational parameter selection during the computational process. This study focuses on some other factors, such as local site conditions, temperature insulating methods, and data logger self-noise interferences, with an aim to differentiate the self-noise contribution of these sources and their dependencies on time and frequency. A series of experiments were conducted at the Beijing National Earth Observatory using a Trillium 120QA seismometer and Reftek-130 data acquisition system at three different locations ranging from the ordinary equipment warehouse to global seismographic network level cave with a hardrock base. Results show that noise-free site is necessary for the self-noise test in a frequency band greater than approximately 0.1 Hz. However, for a frequency band less than 0.1 Hz, the insulation method and installation procedures are far more important, although the influence of the site location cannot be neglected fully. A suitable preamp should be selected in the data logger configurations to ensure that the low-noise amplitude of the sensor signal is above the digitizer noise level.

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Section: Analysis and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A case study of seismograph self-noise test from Trillium 120QA seismometer and Reftek 130 data logger

Yuan

2019

J Seismol

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“…Finally, an attempt was made to cast the inverse problem with all three Euler angles (Bronshtein et al, ) in a way similar to the method suggested by Tasič and Runovc (), but the very small expected deviations from the vertical cause a significant trade‐off between the azimuth and the nutation angle around the perturbed vertical direction. This could be minimized if the generator constants and orientations of all three components of a reference station are assumed to be perfectly known to reduce the severity of coupling between each axis.…”

Section: Discussionmentioning

confidence: 99%

“…If one or more of the unknowns are fixed, then there is a chance that these equations could be solved for the other unknowns. Tasič and Runovc () show that if the generator constants (and digitizer gains) are known for one instrument, inversion of the Euler matrix for a second instrument with unknown orientation recording the same signal can give the generator constants (and gains) for a second instrument along with the relative orientation of the second with respect to the first. Here the assumption is that the generator constants and gains are not known for any component for any instrument.…”

Section: Methodsmentioning

confidence: 99%

Calibrating Dense Spatial Arrays for Amplitude Statics and Orientation Errors

Langston

2018

JGR Solid Earth

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An iterative procedure is designed to calibrate dense arrays of three‐component seismic instruments for station amplitude statics and horizontal component orientation errors. Station amplitude statics refers to differences in sensor and digitizer gains and amplification effects due to local site and installation conditions. Amplitude statics and orientation errors can seriously affect computation of the wavefield gradient tensor that is the basis of seismic strain and rotation computations as well as analysis of wave field attributes through wave gradiometry since wave spatial gradients rely on first‐order differences of the wavefield between sensors in an array. The technique is based on the assumption of a common wave field observed over a small array using teleseismic earthquake observations. In situ calibration of the broad band, 800‐m aperture array at Pinyon Flat, California, achieves relative amplitude precision for vertical components of the array from 0.16% to 0.25% and horizontal components from 0.16% to 0.61%. Relative sensor orientations can be determined to a precision better than 0.35°. Comparison of horizontal strains computed from array observations of a regional M4.9 earthquake and strains from the Gladwin Tensor borehole strain meter at Pinyon Flat shows excellent correspondence over the frequency band of 0.05 to 2 Hz. Agreement of borehole measured strains and seismic array strains for regional/local seismic events gives confidence that a borehole strain meter and single, three‐component, colocated seismometer can be used as a “point array” for deducing wavefield attributes from wave gradiometry.

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Local Variations in Broadband Sensor Installations: Orientations, Sensitivities, and Noise Levels

Ringler

Anthony

2021

Pure Appl. Geophys.

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As seismologists continue to place more stringent demands on data quality, accurately described metadata are becoming increasingly important. In order to better constrain the orientation and sensitivities of seismometers deployed in U.S. Geological Survey networks, the Albuquerque Seismological Laboratory (ASL) has recently begun identifying true north with a fiber optic gyroscope (FOG) and has developed methodologies to constrain mid-band, vertical component sensitivity levels to less than 1% in a controlled environment. However, questions remain regarding the accuracy of this new alignment technique as well as if instrument sensitivities and background noise levels are stable when the seismometers are installed in different environmental settings. In this study, we examine the stability and repeatability of these parameters by reinstalling two high-quality broadband seismometers (Streckeisen STS-2.5 and Nanometrics T-360 Global Seismographic Network (GSN) version) at different locations around the ASL and comparing them to each other and a reference STS-6 seismometer that stayed stationary for the duration of the experiment. We find that even in different environmental conditions, the sensitivities of the two broadband seismometers stayed stable to within 0.1% and that orientations attained using the FOG are generally accurate to within a degree. However, one install was off by 5° due to a mistake made by the installation team. These results indicate that while technology and methodologies are now in place to calibrate and orient a seismometer to within 1°, human error both during the installation and while producing the metadata is often a limiting factor. Finally, we find that background noise levels at short periods (0.1–1 s) become noisier when the sensors are emplaced in unconsolidated materials, whereas the noise levels at long periods (30–100 s) are not sensitive to local geological structure on the vertical components.

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Determination of a seismometer’s generator constant, azimuth, and orthogonality in three-dimensional space using a reference seismometer

Cited by 11 publications

References 6 publications

A case study of seismograph self-noise test from Trillium 120QA seismometer and Reftek 130 data logger

A case study of seismograph self-noise test from Trillium 120QA seismometer and Reftek 130 data logger

Calibrating Dense Spatial Arrays for Amplitude Statics and Orientation Errors

Local Variations in Broadband Sensor Installations: Orientations, Sensitivities, and Noise Levels

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