scholarly journals Source mechanisms and near-source wave propagation from broadband seismograms

1994 ◽  
Vol 37 (6) ◽  
Author(s):  
J. Virieux ◽  
A. Deschamps ◽  
J. Perrot ◽  
J. Campos
Keyword(s):  
Wave Propagation ◽  
Coordinate System ◽  
Ray Tracing ◽  
Dynamic Range ◽  
Time Derivative ◽  
Quality Data ◽  
Heterogeneous Structure ◽  
Spherical Coordinate ◽  
Seismic Rupture ◽  
Converted Phases

Recording seismic events at teleseismic distances with broadband and high dynamic range instruments provides new high-quality data that allow us to interpret in more detail the complexity of seismic rupture as well as the heterogeneous structure of the medium surrounding the source where waves are initially propagating. Wave propagation analysis is performed by ray tracing in a local cartesian coordinate system near the source and in a global spherical coordinate system when waves enter the mantle. Seismograms are constructed at each station for a propagation in a 2.5-D medium. Many phases can be included and separately analyzed; this is one of the major advantages of ray tracing compared to other wave propagation techniques. We have studied four earthquakes, the 1988 Spitak Armenia Earthquake (Ms = 6.9), the 1990 Iran earthquake (Ms = 7.7), the 1990 romanian earthquake (Ms = 5.8) and the 1992 Erzincan, Turkey earthquake (Ms = 6.8). These earthquakes exhibit in different ways the complexity of the rupture and the signature of the medium surrounding the source. The use of velocity seismograms, the time derivative of displacement, increases the difficulty of the fit between synthetic seismograms and real seismograms but provides clear evidence for a need of careful time delay estimations of the different converted phases. We find that understanding of the seismic rupture as well as the influence of the medium surrounding the source for teleseismically recorded earthquakes requires a multi-stop procedure: starting with ground displacement seismograms, one is able to give a first description of the rupture as well as of the first-order influence of the medium. Then, considering the ground velocity seismograms makes the fit more difficult to obtain but increases our sensitivity to the rupture process and early converted phases. With increasing number of worldwide broadband stations, a complex rupture description is possible independently of field observations, which can be used to check the adequacy of such complicated models.

Comparison Considerations Toward Investigating the Factors of Load and Age Group on the Maximum Reach Envelope

2020 ◽  
pp. 001872082096501
Author(s):  
Heather Johnston ◽  
Colleen Dewis ◽  
John Kozey
Keyword(s):  
Coordinate System ◽  
Three Dimensional ◽  
Spherical Coordinate System ◽  
Upper Body ◽  
Group Differences ◽  
Anthropometric Measures ◽  
Younger Adults ◽  
Present Measurement ◽  
Spherical Coordinate ◽  
Cylindrical Coordinate

Objective The objectives were to compare cylindrical and spherical coordinate representations of the maximum reach envelope (MRE) and apply these to a comparison of age and load on the MRE. Background The MRE is a useful measurement in the design of workstations and quantifying functional capability of the upper body. As a dynamic measure, there are human factors that impact the size, shape, and boundaries of the MRE. Method Three-dimensional reach measures were recorded using a computerized potentiometric system for anthropometric measures (CPSAM) on two adult groups (aged 18–25 years and 35–70 years). Reach trials were performed holding .0, .5, and 1 kg. Results Three-dimensional Cartesian coordinates were transformed into cylindrical ( r, θ , Z) and spherical ( r, θ, ϕ) coordinates. Median reach distance vectors were calculated for 54 panels within the MRE as created by incremented banding of the respective coordinate systems. Reach distance and reach area were compared between the two groups and the loaded conditions using a spherical coordinate system. Both younger adults and unloaded condition produced greater reach distances and reach areas. Conclusions Where a cylindrical coordinate system may reflect absolute reference for design, a normalized spherical coordinate system may better reflect functional range of motion and better compare individual and group differences. Age and load are both factors that impact the MRE. Application These findings present measurement considerations for use in human reach investigation and design.

Optimal Design and Structural Precision Analysis for a Spherical Coordinate System 3D Scanner Guiding Device

2014 ◽  
Vol 705 ◽  
pp. 164-168
Author(s):  
Sang Wook Park ◽  
Hee Young Maeng ◽  
Ju Wook Park
Keyword(s):  
Optimal Design ◽  
Data Collection ◽  
Reverse Engineering ◽  
Coordinate System ◽  
Fem Analysis ◽  
Spherical Coordinate System ◽  
3D Scanner ◽  
Spherical Coordinate ◽  
Overall Performance ◽  
Improved Design

Recently, automatic 3D scanning devices are commonly researched and developed for better productivity of the reverse engineering fields. In this paper, a 3D scanner utilizing a spherical coordinate system was designed and analyzed using FEM analysis. The system was designed for optimal performance, high precision, minimal deflection, and speed of data collection. FEM analysis allowed us to properly design the system to achieve these goals, with focus on the deflection of the cantilever arm. Results of the FEM analysis and figures showing the apparatus design are provided. Successive prototypes are shown to increase in overall performance and reliability through improved design and analysis.

Research on Outdoor Positioning Based on Ray Tracing Method

2014 ◽  
Vol 556-562 ◽  
pp. 3039-3042
Author(s):  
Xian Qiang Peng
Keyword(s):  
Wave Propagation ◽  
Ray Tracing ◽  
Radio Waves ◽  
Complex Environment ◽  
Simulation Experiments ◽  
Outdoor Environments ◽  
Positioning Method ◽  
Tracking Point ◽  
Set Up ◽  
Tracing Method

GPS can’t detect the signal because of the cell complex environment in the outdoor and poor radio wave propagation conditions, so that the positioning result is not ideal. However, the positioning method using the ray tracing prediction of radio waves, the tracking point of the scene from all the source radiation, record the relevant parameters, and then positioned within the microcell environment can satisfy the demand. The principle of ray tracing was firstly introduced in this paper, then an outdoor positioning model was set up, finally, the corresponding simulation experiments was implemented to demonstrate the effectiveness of ray tracing positioning in the outdoor environments.

scholarly journals Design and Validation of Probes and Sensors for the Characterization of Magneto-Ionic Radio Wave Propagation on Near Vertical Incidence Skywave Paths

Sensors ◽  
2019 ◽  
Vol 19 (11) ◽  
pp. 2616
Author(s):  
Ben A. Witvliet ◽  
Rosa M. Alsina-Pagès ◽  
Erik van Maanen ◽  
Geert Jan Laanstra
Keyword(s):  
Magnetic Field ◽  
Wave Propagation ◽  
Radio Wave ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Radio Wave Propagation ◽  
Direct Digital Synthesis ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
Propagation Of Waves

This article describes the design and validation of deployable low-power probes and sensors to investigate the influence of the ionosphere and the Earth’s magnetic field on radio wave propagation below the plasma frequency of the ionosphere, known as Near Vertical Incidence Skywave (NVIS) propagation. The propagation of waves that are bent downward by the ionosphere is dominated by a bi-refractive mechanism called ‘magneto-ionic propagation’. The polarization of both downward waves depends on the spatial angle between the Earth’s magnetic field and the direction of propagation of the radio wave. The probes and sensors described in this article are needed to simultaneously investigate signal fading and polarization dynamics on six radio wave propagation paths. The 1-Watt probes realize a 57 dB signal-to-noise ratio. The probe polarization is controlled using direct digital synthesis and the cross-polarization is 25–35 dB. The intermodulation-free dynamic range of the sensor exceeds 100 dB. Measurement speed is 3000 samples/second. This publication covers design, practical realization and deployment issues. Research performed with these devices will be shared in subsequent publications.

Sign in / Sign up

Export Citation Format

Share Document