WITHDRAWN: Source Duration of Stress‐ and Water‐Induced Seismicity as Derived from Experimental Analysis of P Wave Pulse Width in Granite

2012 ◽  
Vol 39 (24) ◽  
Author(s):  
Koji Masuda ◽  
Takashi Satoh
Keyword(s):  
Experimental Analysis ◽  
Induced Seismicity ◽  
Pulse Width ◽  
P Wave ◽  
Wave Pulse ◽  
Source Duration

Some numerical solutions for Lamb's problem

1974 ◽  
Vol 64 (2) ◽  
pp. 473-491
Author(s):  
Harold M. Mooney
Keyword(s):  
Rayleigh Wave ◽  
Poisson’S Ratio ◽  
Pulse Width ◽  
Numerical Solutions ◽  
Pulse Height ◽  
P Wave ◽  
Poisson's Ratio ◽  
Wave Form ◽  
Lamb’S Problem ◽  
Wave Forms

abstract We consider a version of Lamb's Problem in which a vertical time-dependent point force acts on the surface of a uniform half-space. The resulting surface disturbance is computed as vertical and horizontal components of displacement, particle velocity, acceleration, and strain. The goal is to provide numerical solutions appropriate to a comparison with observed wave forms produced by impacts onto granite and onto soil. Solutions for step- and delta-function sources are not physically realistic but represent limiting cases. They show a clear P arrival (larger on horizontal than vertical components) and an obscure S arrival. The Rayleigh pulse includes a singularity at the theoretical arrival time. All of the energy buildup appears on the vertical components and all of the energy decay, on the horizontal components. The effects of Poisson's ratio upon vertical displacements for a step-function source are shown. For fixed shear velocity, an increase of Poisson's ratio produces a P pulse which is larger, faster, and more gradually emergent, an S pulse with more clear-cut beginning, and a much narrower Rayleigh pulse. For a source-time function given by cos2(πt/T), −T/2 ≦ T/2, a × 10 reduction in pulse width at fixed pulse height yields an increase in P and Rayleigh-wave amplitudes by factors of 1, 10, and 100 for displacement, velocity and strain, and acceleration, respectively. The observed wave forms appear somewhat oscillatory, with widths proportional to the source pulse width. The Rayleigh pulse appears as emergent positive on vertical components and as sharp negative on horizontal components. We show a theoretical seismic profile for granite, with source pulse width of 10 µsec and detectors at 10, 20, 30, 40, and 50 cm. Pulse amplitude decays as r−1 for P wave and r−12 for Rayleigh wave. Pulse width broadens slightly with distance but the wave form character remains essentially unchanged.

Shallow Prospecting on Land by Means of a Novel Electroacoustical P-Wave Pulse Generator

1985 ◽  
pp. 585-593
Author(s):  
G. B. Cannelli ◽  
E. D’Ottavi ◽  
S. Santoboni
Keyword(s):  
Pulse Generator ◽  
P Wave ◽  
Wave Pulse

Application of square wave pulse-width-variable laser using temporal shaping

2004 ◽  
Author(s):  
Li Wang ◽  
Yu Zhao ◽  
Yong Tian ◽  
Jinfeng Zhou ◽  
Liu Huang
Keyword(s):  
Pulse Width ◽  
Wave Pulse ◽  
Square Wave

COUPLING OF EXPLOSIVE ENERGY IN THREE‐DIMENSIONAL MODELS

Geophysics ◽  
1970 ◽  
Vol 35 (2) ◽  
pp. 220-233
Author(s):  
Dhari S. Bahjat ◽  
Carl Kisslinger
Keyword(s):  
Pulse Width ◽  
Surrounding Medium ◽  
Three Dimensional ◽  
P Wave ◽  
Elastic Response ◽  
Laboratory Model ◽  
Cavity Radius ◽  
General Validity ◽  
Short Period ◽  
Tightly Coupled

The coupling of explosive generated P waves to the surrounding medium was investigated in a three‐dimensional laboratory model. For tightly coupled charges the amplitude was found to increase as [Formula: see text], and the pulse width as [Formula: see text], where W is the charge mass. Only a few hundredths of one percent of the energy in the explosion was transmitted in the initial P wave. When charges were fired in air‐filled cavities, the amplitude of the energy in the P wave increased to a maximum and then decreased with increasing cavity radius. The amplitudes from cavity shots were never less than the amplitudes for the tightly coupled shots. As the cavity radius increased, the pulse width of the P wave decreased to a minimum, an indication of a decrease in the size of the equivalent cavity, and then increased with further increase in cavity size. The period minimum is interpreted as corresponding to the transition from nonelastic to elastic response of the cavity wall. The cavity pressure at this transition is about one‐half the nominal tensile strength of the material. Scaling to the Sterling nuclear event is examined, and the conclusion is that the disagreement between field tests of decoupling and our experiments is due to the dominance of short period energy in our experiments. The results cast doubt on the general validity of partial decoupling.

The SPWM Pulse Width Signal Spectrum Analysis Based on MATLAB

2013 ◽  
Vol 756-759 ◽  
pp. 4147-4151
Author(s):  
Zi Tao ◽  
Li Zhi ◽  
Jia Long
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Pulse Wave ◽  
Sampling Methods ◽  
Sine Wave ◽  
Signal Spectrum ◽  
Modulation Scheme ◽  
Wave Pulse ◽  
Advantages And Disadvantages ◽  
Key Points

Based on the analysis of the characteristics of sine-wave pulse-width modulation (SPWM) and space vector pulse width modulation (SVPWM) [, the key points are the algorithm of various sampling methods of PWM signals and the analysis of those signals spectrum with MATLAB[4]. The foundational features of the harmonic distributions and advantages and disadvantages of various sampling methods are obtained. According to the analysis, some suggest can be given for the evaluation of pulse width modulation scheme. In the same time, some methods of optimization of pulse wave are advised to provide theoretical guidance for the system design.

Empirical Green's functions: A comparison between pulse width measurements and deconvolution by spectral division

1999 ◽  
Vol 89 (1) ◽  
pp. 178-189
Author(s):  
Nicholas Deichmann
Keyword(s):  
Initial Phase ◽  
Pulse Width ◽  
Circular Crack ◽  
P Wave ◽  
Far Field ◽  
Velocity Pulse ◽  
Zero Crossing ◽  
Northern Switzerland ◽  
Field Displacement ◽  
Width Measurements

Abstract Data from a microearthquake cluster in northern Switzerland and synthetic seismograms simulating the observed signals are used to compare two different techniques of obtaining information about earthquake source-time functions. Comparisons between the observed P-wave velocity pulse widths and the rise times of far-field displacement pulses obtained from empirical Green's function (EGF) deconvolutions show significant discrepancies. Whereas the observed velocity pulse widths of the larger events scale with seismic moment over a broad range, this scaling is practically lost in the deconvolutions. The reason is that velocity pulse widths are usually measured at high trace magnifications from the first break to the first zero crossing. At lower magnifications, these pulse widths are seen to include an emergent onset, which can be attributed to an initial phase of gradual rupture acceleration and whose duration scales with moment. Synthetic simulations, based on a source model of a circular crack with constant stress drop and rupture propagating outward from the center with a gradually increasing velocity, correctly reproduce these emergent onsets. Deconvolutions using the synthetic signals show that the slow initial phase is masked by the noise amplification and stabilizing measures inherent in the deconvolution. Therefore, despite the uncertainties in the necessary corrections for attenuation and scattering along the path, relative pulse width measurements are more reliable and provide better resolution for small earthquakes than rise-time measurements on far-field displacement pulses obtained from EGF deconvolutions by spectral division.

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