STANDING‐WAVE PHENOMENA IN SHORT‐PERIOD SEISMIC NOISE

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1179-1186 ◽  
Author(s):  
Indra N. Gupta
Keyword(s):  
Steady State ◽  
Standing Wave ◽  
Seismic Noise ◽  
P Wave ◽  
Stratified Medium ◽  
Alternative Theory ◽  
Compressional Waves ◽  
Short Period ◽  
Wave Phenomena ◽  
Phase Spectra

Short‐period vertical seismometers are used in deep holes at several sites to obtain the change with depth in amplitude and phase spectra of short‐period seismic noise. Although the observed spectra can be explained by an arbitrary combination of several Rayleigh modes, an alternative theory is suggested here. An attempt is made to explain both amplitude and phase spectra of observed microseisms of period less than 6 sec in terms of standing‐wave phenomena caused by steady‐state plane harmonic compressional waves propagating vertically through a horizontally stratified medium. At most sites, the observed data indicate satisfactory agreement with the expected results. A considerable fraction of the short‐period noise may, therefore, be regarded as P‐wave noise propagating vertically from below.

POSSIBLE P‐WAVE OBSERVATIONS IN SHORT‐PERIOD SEISMIC NOISE

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1187-1190 ◽  
Author(s):  
A. J. Seriff ◽  
C. J. Velzeboer ◽  
R. J. Haase
Keyword(s):  
Seismic Noise ◽  
P Wave ◽  
Deep Hole ◽  
Frequency Range ◽  
The Past ◽  
Deep Well ◽  
Short Period ◽  
Noise Measurements ◽  
Deep Boreholes

For the past two years we have been engaged in a program of seismic noise measurements in deep boreholes; noise in a frequency range of approximately 0.2 to 5.0 cps has been studied. A special deep‐well seismometer designed by The Geotechnical Corporation has been used for recording noise at depths down to 14,000 ft in cased holes. The seismometer, which has a response almost identical to the typical short‐period Benioff, was clamped to the casing of the deep hole by a mechanical locking arm during observation periods. An identical seismometer has been used as a reference in a 500‐ft hole adjacent to the deep well. A surface array of four vertical Benioff seismometers was also recorded, with one seismometer near the well and three others at distances ranging from 0.5 to 1.0 km. Two horizontal seismometers were stationed near the wellhead.

Observations of the transition from linear polarization to complex polarization in short-period compressional waves

1991 ◽  
Vol 81 (2) ◽  
pp. 611-621
Author(s):  
William Menke ◽  
Arthur Lerner-Lam
Keyword(s):  
New York ◽  
New England ◽  
Linear Polarization ◽  
Compressional Wave ◽  
P Wave ◽  
Adirondack Mountains ◽  
Compressional Waves ◽  
Short Period ◽  
Shallow Crust ◽  
Complex Polarization

Abstract We measure the polarization of compressional waves from seismograms of chemical explosion of the Ontario-New York-New England refraction experiment recorded by the seven element ECO array in the New York Adirondack mountains. After careful instrument calibration, a precision of about 5° is achieved in measuring the azimuth of the compressional wave polarization direction. The azimuth of the polarization of the onset of the P wave differs from the geometrical source-receiver azimuth by as much as 20°, possible due to deflection of the first-arriving ray by lateral variation in crustal structure. Shortly after the onset of P, the polarization changes from the linear polarization expected of a compressional wave to become very complex. The time of this transition increases with source-receiver distance, from about 0.4 to 0.5 sec at 50 km distance and 0.7 to 0.8 sec at 150 km distance. The complex polarization may be due to the arrival of strongly scattered waves that have propagated mainly in the shallow crust, which would imply that the upper 1 to 2 km of the crust is particularly heterogeneous.

"Steady-state" competence for bacterial transformation

1968 ◽  
Vol 14 (3) ◽  
pp. 290-292
Author(s):  
Herbert H. Eichhorn ◽  
Shigeyo Arikawa ◽  
Stephen Zamenhof
Keyword(s):  
Bacillus Subtilis ◽  
Steady State ◽  
Continuous Culture ◽  
Generation Time ◽  
Bacterial Transformation ◽  
Short Period ◽  
Minimal Media ◽  
Harmful Effects ◽  
Specific Phase

The cells of Bacillus subtilis, grown in minimal media, are known to become competent for transformation for a short period at a specific phase of ceil growth. In the present work the cells (strain 168 ind−) were grown in continuous culture (chemostat; glucose limiting, generation time 4 h, 37 °C). Aliquots were removed at 20- to 24-h intervals and immediately tested for competence. The viability (41 h) was 97%. The initial very low competence increased up to 200-fold within the 24 h and remained at this high, slowly decreasing level for at least 168 h. It is concluded that a long-lasting competence may develop and persist in the cells in continuous culture ("steady-state"), without demonstrable harmful effects to the population.

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.

Short-period seismic noise

1967 ◽  
Vol 57 (1) ◽  
pp. 55-81
Author(s):  
E. J. Douze
Keyword(s):  
Surface Waves ◽  
Rayleigh Waves ◽  
Seismic Noise ◽  
Body Waves ◽  
Deep Hole ◽  
Period Range ◽  
Short Period ◽  
The Subject ◽  
Hole Arrays

abstract This report consists of a summary of the studies conducted on the subject of short-period (6.0-0.3 sec period) noise over a period of approximately three years. Information from deep-hole and surface arrays was used in an attempt to determine the types of waves of which the noise is composed. The theoretical behavior of higher-mode Rayleigh waves and of body waves as measured by surface and deep-hole arrays is described. Both surface and body waves are shown to exist in the noise. Surface waves generally predominate at the longer periods (of the period range discussed) while body waves appear at the shorter periods at quiet sites. Not all the data could be interpreted to define the wave types present.

scholarly journals Vertical to Horizontal Spectral Ratio (VHSR) Response of Seismic Wave Propagation in a Homogeneous Elastic – Poroelastic Medium Using The Spectral Finite Element Method

2021 ◽  
Vol 11 (1) ◽  
pp. 95
Author(s):  
Sudarmaji Saroji ◽  
Budi Eka Nurcahya ◽  
Nivan Ramadhan Sugiantoro
Keyword(s):  
Finite Element Method ◽  
Elastic Medium ◽  
Seismic Waves ◽  
Low Frequency ◽  
Seismic Wave Propagation ◽  
P Wave ◽  
Poroelastic Medium ◽  
Compressional Waves ◽  
Spectral Finite Element Method ◽  
Spectral Finite Element

<p>Numerical modeling of 2D seismic wave propagation using spectral finite element method to estimate the response of seismic waves passing through the poroelastic medium from a hydrocarbon reservoir has been carried out. A hybrid simple model of the elastic - poroelastic - elastic with a mesoscopic scale element size of about 50cm was created. Seismic waves which was in the form of the ricker function are generated on the first elastic medium, propagated into the poroelastic medium and then transmitted to the second elastic medium. Pororoelastic medium is bearing hydrocarbon fluid in the form of gas, oil or water. Vertical and horizontal component of velocity seismograms are recorded on all mediums. Seismograms which are recorded in the poroelastic and second elastic medium show the existence of slow P compressional waves following fast P compressional waves that do not appear on the seismogram of the first elastic medium. The slow P wave is generated when the fast P wave enters the interface of the elastic - poroelastic boundary, propagated in the poroelastic medium and is transmited to the second elastic medium. The curves of Vertical to horizontal spectrum ratio (VHSR) which are observed from seismograms recorded in the poroelastic and the second elastic medium show that the peak of VHSR values at low frequency correlated with the fluid of poroelastic reservoir. The highest VHSR value at the low frequency which is recorded on the seismogram is above the 2.5 Hz frequency for reservoirs containing gas and oil in the second elastic medium, while for the medium containing water is the highest VHSR value is below the 2.5 Hz frequency.</p>

Determination of source parameters of small earthquakes from P-wave rise time

1973 ◽  
Vol 63 (2) ◽  
pp. 599-614 ◽  
Author(s):  
M. E. O'Neill ◽  
J. H. Healy
Keyword(s):  
Rise Time ◽  
Source Parameters ◽  
P Wave ◽  
Simple Method ◽  
Zero Crossing ◽  
Basic Measurement ◽  
Earthquake Source Parameters ◽  
Short Period ◽  
Stress Drops

abstract A simple method of estimating source dimensions and stress drops of small earthquakes is presented. The basic measurement is the time from the first break to the first zero crossing on short-period seismograms. Graphs relating these measurements to rise time as a function of Q and instrument response permit an estimate of earthquake source parameters without the calculation of spectra. Tests on data from Rangely, Colorado, and Hollister, California, indicate that the method gives reasonable results.

Upper-mantle discontinuity from amplitude data of P′P′ and its precursors

1973 ◽  
Vol 63 (2) ◽  
pp. 587-597
Author(s):  
Ta-Liang Teng ◽  
James P. Tung
Keyword(s):  
Upper Mantle ◽  
Body Waves ◽  
P Wave ◽  
Specific Reference ◽  
Amplitude Data ◽  
Surface Displacements ◽  
Short Period ◽  
Mantle Velocity ◽  
Mantle Discontinuity ◽  
Upper Mantle Discontinuity

abstract Recent observations of P′P′ and its precursors, identified as reflections from within the Earth's upper mantle, are used to examine the structure of the uppermantle discontinuities with specific reference to the density, the S velocity, and the Q variations. The Haskell-Thomson matrix method is used to generate the complex reflection spectrum, which is then Fourier synthesized for a variety of upper-mantle velocity-density and Q models. Surface displacements are obtained for the appropriate recording instrument, permitting a direct comparison with the actual seismograms. If the identifications of the P′P′ precursors are correct, our proposed method yields the following: (1) a structure of Gutenberg-Bullen A type is not likely to produce observable P′P′ upper-mantle reflections, (2) in order that a P′P′ upper-mantle reflection is strong enough to be observed, first-order density and S-velocity discontinuities together with a P-wave discontinuity are needed at a depth of about 650 km, and (3) corresponding to a given uppermantle velocity-density model, an estimate can be made of the Q in the upper mantle for short-period seismic body waves.

Short-period P-wave attenuation along various paths in North America as determined from P-wave spectra of the SALMON nuclear explosion

1976 ◽  
Vol 66 (5) ◽  
pp. 1609-1622 ◽  
Author(s):  
Zoltan A. Der ◽  
Thomas W. McElfresh
Keyword(s):  
United States ◽  
North America ◽  
Wave Attenuation ◽  
Nuclear Explosion ◽  
P Wave ◽  
Western United States ◽  
Source Spectrum ◽  
Wave Spectra ◽  
Short Period ◽  
Q Values

abstract Average Q values were determined for ray paths to various LRSM stations from the SALMON nuclear explosion by taking ratios of observed P-wave spectra to the estimated source spectrum. Most Q values for P-wave paths throughout eastern North America are in the range 1600 to 2000 while those crossing over into the western United States are typically around 400 to 500. These differences in Q for intermediate distances can sufficiently explain the differences in the teleseismic event magnitudes observed, 0.3 to 0.4 magnitude units, in the western versus the eastern United States, if one assumes that the low Q layer under the western United States is located at depths less than 200 km.

The CIELO Seismic Experiment

2021 ◽  
Author(s):  
Heather A. Ford ◽  
Maximiliano J. Bezada ◽  
Joseph S. Byrnes ◽  
Andrew Birkey ◽  
Zhao Zhu
Keyword(s):  
Receiver Function ◽  
Function Analysis ◽  
P Wave ◽  
Crust And Upper Mantle ◽  
Waveform Data ◽  
Wyoming Craton ◽  
Sensor Orientation ◽  
Seismic Experiment ◽  
Short Period ◽  
Receiver Function Analysis

Abstract The Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny was a two-year deployment of 24 broadband, compact posthole seismometers in a linear array across the eastern half of the Wyoming craton. The experiment was designed to image the crust and upper mantle of the region to better understand the evolution of the cratonic lithosphere. In this article, we describe the motivation and objectives of the experiment; summarize the station design and installation; provide a detailed accounting of data completeness and quality, including issues related to sensor orientation and ambient noise; and show examples of collected waveform data from a local earthquake, a local mine blast, and a teleseismic event. We observe a range of seasonal variations in the long-period noise on the horizontal components (15–20 dB) at some stations that likely reflect the range of soil types across the experiment. In addition, coal mining in the Powder River basin creates high levels of short-period noise at some stations. Preliminary results from Ps receiver function analysis, shear-wave splitting analysis, and averaged P-wave delay times are also included in this report, as is a brief description of education and outreach activities completed during the experiment.

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