Event detection and location performance of the FINESA array in Finland

1990 ◽  
Vol 80 (6B) ◽  
pp. 1818-1832
Author(s):  
Marja Uski
Keyword(s):  
High Speed ◽  
Epicentral Distance ◽  
Correction Term ◽  
Wave Number ◽  
Average Error ◽  
Phase Identification ◽  
Secondary Phases ◽  
Frequency Wave ◽  
Real Time Processing ◽  
Short Period

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.

The October 6, 1974 Acapulco earthquake: An example of the importance of short-period surface waves in strong ground motion

1978 ◽  
Vol 68 (6) ◽  
pp. 1663-1677
Author(s):  
Stephen H. Hartzell ◽  
James N. Brune ◽  
Jorge Prince
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Epicentral Distance ◽  
Source Region ◽  
Crystalline Rock ◽  
Body Waves ◽  
Wave Number ◽  
Source Depth ◽  
Moment Estimate ◽  
Short Period

abstract The Acapulco earthquake of October 6, 1974 (mb = 5.0, Ms = 4.75) resulted in 0.5 g accelerations in Acapulco at an epicentral distance of about 35 km. Extrapolation of the peak acceleration to the source region gives a near source acceleration of at least 1.0 g. If the teleseismically estimated source depth of 51 km is assumed, the Acapulco accelerogram must be interpreted as composed of primarily body waves. This assumption yields a moment estimate of 3.3 ×1023 dyne-cm and a stress drop of 1.5 kbar. However, strong evidence indicates that the source depth is only about 1.0 km and that the record is composed mainly of high frequency (1.0 to 4.0 Hz) surface waves. The character of the record is that of a normally dispersed surface wave. The relatively simple form and high acceleration may be attributed to the high rigidity, crystalline rock types in the region. The three component record is fitted by summing the fundamental and first higher mode Rayleigh and Love waves using a model consisting of a single layer over a homogeneous half-space. The results are also checked using a direct wave-number integration program developed by Apsel and Luco. The moment estimate from the surface-wave synthetics is 2.0 ×1023 dyne-cm.

scholarly journals On the validity of the planar wave approximation to compute synthetic seismograms of teleseismic body waves in a 3-D regional model

2020 ◽  
Vol 224 (3) ◽  
pp. 2060-2076
Author(s):  
Vadim Monteiller ◽  
Stephen Beller ◽  
Bastien Plazolles ◽  
Sébastien Chevrot
Keyword(s):  
Epicentral Distance ◽  
Spectral Element ◽  
Synthetic Seismograms ◽  
Body Waves ◽  
Earth Model ◽  
Secondary Phases ◽  
P Waves ◽  
Short Period ◽  
Wide Range ◽  
Injection Methods

SUMMARY Injection methods are a very efficient means to compute synthetic seismograms of short-period teleseismic body waves in 3-D regional models. The principle is to inject an incident teleseismic wavefield inside a regional 3-D Cartesian spectral-element grid. We have developed an opern-source package that allows us to inject either an incident plane wave, computed with a frequency–wavenumber method, or the complete wavefield, computed in a spherically symmetric reference earth model with AxiSEM. The computations inside the regional spectral-element grid are performed with SPECFEM3D_Cartesian. We compare the efficiency and reliability of the two injection methods for teleseismic P waves, considering a wide range of epicentral distance and hypocentral depths. Our simulations demonstrate that in practice the effects of wave front and Earth curvature are negligible for moderate size regional domains (several hundreds of kilometres) and for periods larger than 2 s. The main differences observed in synthetic seismograms are related to secondary phases that have a different slowness from the one of the reference P phase.

scholarly journals Laser Lens Size Measurement Using Swept-Source Optical Coherence Tomography

2020 ◽  
Vol 10 (14) ◽  
pp. 4936
Author(s):  
Pingping Jia ◽  
Hong Zhao ◽  
Yuwei Qin
Keyword(s):  
Optical Coherence Tomography ◽  
High Speed ◽  
Wave Number ◽  
Radius Of Curvature ◽  
Optical Coherence ◽  
Swept Source ◽  
Laser Focusing ◽  
Fitting Algorithm ◽  
Laser Confocal Microscope ◽  
Focusing Lens

A high-speed, high-resolution swept-source optical coherence tomography (SS-OCT) is presented for focusing lens imaging and a k-domain uniform algorithm is adopted to find the wave number phase equalization. The radius of curvature of the laser focusing lens was obtained using a curve-fitting algorithm. The experimental results demonstrate that the measuring accuracy of the proposed SS-OCT system is higher than the laser confocal microscope. The SS-OCT system has great potential for surface topography measurement and defect inspection of the focusing lens.

scholarly journals A new evaluation and prediction model of sound quality of high-speed permanent magnet motor based on genetic algorithm-radial basis function artificial neural network

2021 ◽  
Vol 104 (3) ◽  
pp. 003685042110311
Author(s):  
Kai Hu ◽  
Guangming Zhang ◽  
Wenyi Zhang
Keyword(s):  
Neural Network ◽  
Genetic Algorithm ◽  
Artificial Neural Network ◽  
Basis Function ◽  
High Speed ◽  
Objective Evaluation ◽  
Sound Quality ◽  
Average Error ◽  
Permanent Magnet Motor ◽  
Predicted Model

Sound quality (SQ) has become an important index to measure the competitiveness of motor products. To better evaluate and optimize SQ, a novelty SQ evaluation and prediction model of high-speed permanent magnet motor (HSPMM) with better accuracy is presented in this research. Six psychoacoustic parameters of A-weighted sound pressure level (ASPL), loudness, sharpness, roughness, fluctuation strength (FS), and perferred-frequency speech interference (PSIL) were adopted to objectively evaluate the SQ of HSPMM under multiple operating conditions and subjective evaluation was also conducted by the combination of semantic subdivision method and grade scoring method. The evaluation results show that the SQ is poor, which will have a certain impact on human psychology and physiology. The correlation between the objective evaluation parameters and the subjective scores is analyzed by coupling the subjective and objective evaluation results. The average error of multiple linear regression (MLR) model is 7.10%. It has good accuracy, but poor stability. In order to improve prediction accuracy, a new predicted model of radial basis function (RBF) artificial neural network was put forward based on genetic algorithm (GA) optimization. Compared with MLR, its average error rate is reduced by 3.16% and the standard deviation is reduced by 1.841. In addition, the weight of each objective parameter was analyzed. The new predicted model has a better accuracy. It can evaluate and optimize the SQ exactly. The research methods and conclusions of this paper can be extended to the evaluation, prediction, and optimization of SQ of other motors.

scholarly journals Internal face finishing for a cooling channel using a fluid containing free abrasive grains

2021 ◽  
Author(s):  
Mitsugu Yamaguchi ◽  
Tatsuaki Furumoto ◽  
Shuuji Inagaki ◽  
Masao Tsuji ◽  
Yoshiki Ochiai ◽  
...  
Keyword(s):  
High Speed ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Cooling Channel ◽  
H13 Steel ◽  
Channel Diameter ◽  
Abrasive Grains ◽  
Low Viscosity ◽  
Short Period ◽  
Internal Pressures

AbstractIn die-casting and injection molding, a conformal cooling channel is applied inside the dies and molds to reduce the cycle time. When the internal face of the channel is rough, both cooling performance and tool life are negatively affected. Many methods for finishing the internal face of such channels have been proposed. However, the effects of the channel diameter on the flow of a low-viscosity finishing media and its finishing characteristics for H13 steel have not yet been reported in the literature. This study addresses these deficiencies through the following: the fluid flow in a channel was computationally simulated; the flow behavior of abrasive grains was observed using a high-speed camera; and the internal face of the channel was finished using the flow of a fluid containing abrasive grains. The flow velocity of the fluid with the abrasive grains increases as the channel diameter decreases, and the velocity gradient is low throughout the channel. This enables reduction in the surface roughness for a short period and ensures uniform finishing in the central region of the channel; however, over polishing occurs owing to the centrifugal force generated in the entrance region, which causes the form accuracy of the channel to partially deteriorate. The outcomes of this study demonstrate that the observational finding for the finishing process is consistent with the flow simulation results. The flow simulation can be instrumental in designing channel diameters and internal pressures to ensure efficient and uniform finishing for such channels.

A Spectral Finite Element Model for Wave Propagation Analysis in Laminated Composite Plate

2006 ◽  
Vol 128 (4) ◽  
pp. 477-488 ◽  
Author(s):  
A. Chakraborty ◽  
S. Gopalakrishnan
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Shear Deformation ◽  
Mechanical Response ◽  
Laminated Composite ◽  
Wave Number ◽  
Single Element ◽  
Element Formulation ◽  
Frequency Wave ◽  
Spectral Finite Element

A new spectral plate element (SPE) is developed to analyze wave propagation in anisotropic laminated composite media. The element is based on the first-order laminated plate theory, which takes shear deformation into consideration. The element is formulated using the recently developed methodology of spectral finite element formulation based on the solution of a polynomial eigenvalue problem. By virtue of its frequency-wave number domain formulation, single element is sufficient to model large structures, where conventional finite element method will incur heavy cost of computation. The variation of the wave numbers with frequency is shown, which illustrates the inhomogeneous nature of the wave. The element is used to demonstrate the nature of the wave propagating in laminated composite due to mechanical impact and the effect of shear deformation on the mechanical response is demonstrated. The element is also upgraded to an active spectral plate clement for modeling open and closed loop vibration control of plate structures. Further, delamination is introduced in the SPE and scattered wave is captured for both broadband and modulated pulse loading.

Short-period Lg magnitudes: Instrument, attenuation, and source effects

1983 ◽  
Vol 73 (6A) ◽  
pp. 1835-1850
Author(s):  
Robert B. Herrmann ◽  
Andrzej Kijko
Keyword(s):  
United States ◽  
Epicentral Distance ◽  
P Wave ◽  
Magnitude Scale ◽  
Source Effects ◽  
Anelastic Attenuation ◽  
Basic Conclusion ◽  
Short Period ◽  
Central United States ◽  
Definition Of

Abstract The applicaton of the Nutli (1973) definition of the mbLg magnitude to instruments and wave periods other than the short-period WWSSN seismograph is examined. The basic conclusion is that the Nuttli (1973) definition is applicable to a wider range of seismic instruments if the log10(A/T) term is replaced by log10A. For consistency and precision, the notation mbLg should be applied only to magnitudes based upon 1.0 Hz observations. The mbLg magnitude definition was constrained to be consistent with teleseismic P-wave mb estimates from four Central United States earthquakes. In general, for measurements made at a frequency f, the notation mLg(f) should be used, where m L g ( f ) = 2.94 + 0.833 log ⁡ 10 ( r / 10 ) + 0.4342 γ r + log ⁡ 10 A , and r is the epicentral distance in kilometers, γ is the coefficient of anelastic attenuation, and A is the reduced ground amplitude in microns. Given its stability when estimated from different instruments, the mLg(f) magnitude is an optimum choice for an easily applied, standard magnitude scale for use in regional seismic studies.

Effects of Parameters on the Two-Phase Flow Instability in a Microchannel

2018 ◽  
Author(s):  
Yefei Liu ◽  
Yang Liu ◽  
Xingtuan Yang ◽  
Liqiang Pan
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Flow Instability ◽  
Working Fluid ◽  
Two Phase ◽  
Short Period ◽  
Period Oscillation ◽  
Data Acquisition Card ◽  
Series Of Experiments ◽  
Vertical Microchannel

Series of experiments are conducted in a single microchannel, where subcooled water flows upward inside a transparent and vertical microchannel. The cross section of the channel is rectangle with the hydraulic diameter of 2.8mm and the aspect ratio of 20. The working fluid is 3–15K subcooled and surface heat flux on the channel is between 0–3.64 kW/m2, among which two-phase instability at low vapor quantity may occur. By using a novel transparent heating technique and a high-speed camera, visualization results are obtained. The parameters are acquired with a National Instruments Data Acquisition card. In the experiments, long-period oscillation and short-period oscillation are observed as the primary types of instability in a microchannel. Instability characteristics represented from signals correspond well with the flow pattern. Moreover, effects of several parameters are investigated. The results indicate that the oscillating period generally increases with the heat flux density and decreases with inlet subcooling, while the effects of inlet resistance are more complex.

Sign in / Sign up

Export Citation Format

Share Document