Amplification of seismic body waves by low-velocity surface layers

1971 ◽  
Vol 61 (1) ◽  
pp. 109-145 ◽  
Author(s):  
J. R. Murphy ◽  
A. H. Davis ◽  
N. L. Weaver
Keyword(s):  
Seismic Waves ◽  
Dynamic Range ◽  
Repeated Measurements ◽  
Body Waves ◽  
Recording Site ◽  
Low Velocity ◽  
Frequency Dependent ◽  
Near Surface ◽  
Wide Range ◽  
Analytic Models

abstract Frequency-dependent amplification of seismic waves by near-surface low-velocity layers is a well-known phenomenon. This phenomenon was examined from both the analytic and experimental viewpoints for body waves (P, SV, SH). Groundmotion data, recorded in conjunction with the underground nuclear testing program at the Nevada Test Site, are used to provide experimental validation of the analytic models. Experimental amplification factors are derived from these data for a variety of recording-site near-surface geological configurations (alluvium, mine tailings, fill) and a wide dynamic range of ground-motion intensity (10−5 to 100 g). The variability in the mean amplification observed at a site for repeated measurements is described statistically. This analysis shows that, although the amplification at a given site varies on the average by a factor of about 1.4 across the frequency band of interest, from detonation to detonation, the frequency and magnitude of the dominant amplification are fairly consistent. The quality of the comparisons of the observed and calculated amplification indicates that the available linear analytic models are capable of describing the major features of the frequency-dependent amplification observed for this wide range of groundmotion intensity and recording-site geology.

Fault zone trapped seismic waves

1990 ◽  
Vol 80 (5) ◽  
pp. 1245-1271 ◽  
Author(s):  
Y.-G. Li ◽  
P. C. Leary
Keyword(s):  
Fault Zone ◽  
Seismic Waves ◽  
Fault Plane ◽  
Body Wave ◽  
Velocity Model ◽  
Trapped Waves ◽  
Low Velocity ◽  
Near Surface ◽  
San Andreas ◽  
Borehole Seismic

Abstract Two instances of fault zone trapped seismic waves have been observed. At an active normal fault in crystalline rock near Oroville in northern California, trapped waves were excited with a surface source and recorded at five near-fault borehole depths with an oriented three-component borehole seismic sonde. At Parkfield, California, a borehole seismometer at Middle Mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the San Andreas fault zone. At Oroville recorded particle motions indicate the presence of both Love and Rayleigh normal modes. The Love-wave dispersion relation derived for an idealized wave guide with velocity structure determined by body-wave travel-time inversion yields seismograms of the fundamental mode that are consistent with the observed Love-wave amplitude and frequency. Applying a similar velocity model to the Parkfield observations, we obtain a good fit to the trapped wavefield amplitude, frequency, dispersion, and mode time separation for an asymmetric San Andreas fault zone structure—a high-velocity half-space to the southwest, a low-velocity fault zone, a transition zone containing the borehole seismometer, and an intermediate velocity half-space to the northeast. In the Parkfield borehole seismic data set, the locations (depth and offset normal to fault plane) of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone. We conclude that it is feasible to obtain near-surface borehole records of fault zone trapped waves. Because trapped modes are excited only by events close to the fault zone proper—thereby fixing these events in space relative to the fault—a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body-wave/tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane. It is an open question whether near-surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device.

The Nature of Intrinsic Attenuation

2020 ◽  
Author(s):  
Yu-Chang Wu ◽  
Cheng-Ju Wu
Keyword(s):  
Seismic Waves ◽  
Body Waves ◽  
Northwestern Pacific ◽  
The Novel ◽  
Low Velocity ◽  
High Attenuation ◽  
Intrinsic Attenuation ◽  
Novel Method ◽  
The Difference ◽  
The Relationship

<p>Intrinsic attenuation plays an important role in investigating the interior structure of Earth, especially for the Lithosphere-asthenosphere system, the best place to understand the physical mechanics of plate tectonic. The dissipation, the high attenuation of seismic waves in the low-velocity zones, and the frequency dependence are the characteristic of intrinsic attenuation. However, N. Takeuchi, et al. measured the Northwestern Pacific Ocean’s lithosphere-asthenosphere system, and state the attenuation of the asthenosphere is 50 times larger than the attenuation of lithosphere attenuation. The attenuation of the lithosphere shows strong frequency dependency, but the attenuation of the asthenosphere does not. Previous theories of attenuation failed to explain this phenomenon. Here we demonstrate an explicit attenuation formulation to explain the high attenuation of seismic waves in the low-velocity zones and to show the mechanisms of spectral of teleseismic body waves rapidly fall off as frequency bigger than 1 Hz by perturbing the wave equation with the novel method we proposed. The result also indicates that the difference between the attenuation of the lithosphere and asthenosphere is because their attenuation governs by different physics mechanisms and mathematical models. Moreover, we illustrate the explicit formulation of the relationship between apparent t*, wave velocity, and frequency.</p>

Surface and near-surface effects on seismic waves—theory and borehole seismometer results

1987 ◽  
Vol 77 (4) ◽  
pp. 1168-1196
Author(s):  
P. M. Shearer ◽  
J. A. Orcutt
Keyword(s):  
Free Surface ◽  
Plane Wave ◽  
Seismic Waves ◽  
Wave Model ◽  
Body Waves ◽  
P Wave ◽  
Surface Velocity ◽  
Ocean Bottom ◽  
Near Surface ◽  
Borehole Seismic

Abstract A simple plane wave model is adequate to explain many surface versus borehole seismometer data sets. Using such a model, we present a series of examples which demonstrate the effects of the free-surface, near-surface velocity gradients, and low impedance surface layers on the amplitudes of upcoming body waves. In some cases, these amplitudes are predictable from simple free-surface and impedance contrast expressions. However, in other cases these expressions are an unreliable guide to the complete response, and the full plane wave calculation must be performed. Large surface amplifications are possible, even without focusing due to lateral heterogeneities or nonlinear effects. Both surface and borehole seismometer site responses are almost always frequency-dependent. Ocean bottom versus borehole seismic data from the 1983 Ngendei Seismic Experiment in the southwest Pacific are consistent with both a simple plane wave model and a more complete synthetic seismogram calculation. The borehole seismic response to upcoming P waves is reduced at high frequencies because of interference between the upgoing P wave and downgoing P and SV waves reflected from the sediment-basement interface. However, because of much lower borehole noise levels, the borehole seismometer enjoys a P-wave signal-to-noise advantage of 3 to 7 dB over nearby ocean bottom instruments.

scholarly journals Observed Evidences of Frequency-Dependent Site Spectral Amplification due to Strong Structural Control of Active Reverse Faults at Different Three Localities in Japan

2021 ◽  
Author(s):  
Mostafa Thabet
Keyword(s):  
Fault Zone ◽  
Structural Control ◽  
Active Fault ◽  
Low Frequency ◽  
Fault Zones ◽  
Low Velocity ◽  
Frequency Dependent ◽  
Near Surface ◽  
High Frequencies ◽  
The Impact

Abstract In the present study, observed active fault zone related site amplification is calculated based on Fourier acceleration spectrum (FAS) at three different localities in Japan. For this purpose, the FASs are calculated using 26432 earthquakes recorded at 126 K-NET and KiK-net seismic stations, which are distributed on the fault zones and upthrown and downthrown sides. This observed amplification is strongly frequency-dependent because of the presence of the near-surface low-velocity flower fault structure and the deeper fault zone. Moreover, the amplification patterns at each study area are tectonic-specific patterns. Sources inside the active fault zones could produce amplification at high frequencies at stations on both fault zone and far away from the fault zone. This is because of the impact of the near-surface fault zone. Sources outside the active fault zones could not produce significant amplification at high frequencies, whereas remarkable high amplification at low frequencies exhibits a gradual increase through stations on hanging walls, fault zones, and footwalls. Remarkably, low-frequency amplification due to sources outside the active fault zones at stations on footwalls is much higher than those observed on hanging walls. Interestingly, the peaks of the low-frequency amplification are corresponding to wavelengths that approximately equalize the width of the fault zone. Diffuse field theory inversion using earthquake horizontal-to-vertical spectral ratio (EHVSR) could successfully detect the presence of fault zone low-velocity layers. However, analyzing the fault zone related site effects using HVSR is not effective because of the strong amplification related structural control of the active fault zones on the ground motions.

scholarly journals Observed Evidences of Frequency-Dependent Site Amplification Due to Structural Control of Active Reverse Faults at Different Localities in Japan

2021 ◽  
Author(s):  
Mostafa Thabet
Keyword(s):  
Fault Zone ◽  
Structural Control ◽  
Active Fault ◽  
Site Amplification ◽  
Fault Zones ◽  
Low Velocity ◽  
Frequency Dependent ◽  
Low Frequencies ◽  
Near Surface ◽  
The Impact

Abstract Observed active fault zone related site amplification is calculated based on Fourier acceleration spectrum (FAS) at three different localities in Japan. The FASs are calculated using 26432 earthquakes recorded at 126 K-NET and KiK-net seismic stations, which are distributed on the fault zones, upthrown and downthrown sides. This observed amplification is strongly frequency-dependent because of the presence of the near-surface low-velocity flower fault structure and the deeper fault zone. Moreover, the amplification patterns at each study area are tectonic-specific patterns. Sources inside the active fault zones could produce amplification at high frequencies at stations on both fault zone and far away from the fault zone, because of the impact of the near-surface fault zone. Sources outside the active fault zones yield remarkable high amplification at low frequencies exhibiting a gradual increase through stations on hanging walls, fault zones, and footwalls. Interestingly, the peaks of the low-frequency amplification are corresponding to wavelengths that approximately equalize the width of the fault zone. The presence of fault zone low-velocity layers could be successfully detected by the diffuse field theory inversion.

scholarly journals Detectivity optimization to detect of ultraweak light fluxes with an EM-CCD as binary photon counter array

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ibtissame Khaoua ◽  
Guillaume Graciani ◽  
Andrey Kim ◽  
François Amblard
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Photon Counting ◽  
Detection Methods ◽  
Strong Nonlinearity ◽  
Wide Range ◽  
Depth Analysis ◽  
Spatially Extended ◽  
Extended Sources ◽  
Photon Counting Mode

AbstractFor a wide range of purposes, one faces the challenge to detect light from extremely faint and spatially extended sources. In such cases, detector noises dominate over the photon noise of the source, and quantum detectors in photon counting mode are generally the best option. Here, we combine a statistical model with an in-depth analysis of detector noises and calibration experiments, and we show that visible light can be detected with an electron-multiplying charge-coupled devices (EM-CCD) with a signal-to-noise ratio (SNR) of 3 for fluxes less than $$30\,{\text{photon}}\,{\text{s}}^{ - 1} \,{\text{cm}}^{ - 2}$$ 30 photon s - 1 cm - 2 . For green photons, this corresponds to 12 aW $${\text{cm}}^{ - 2}$$ cm - 2 ≈ $$9{ } \times 10^{ - 11}$$ 9 × 10 - 11 lux, i.e. 15 orders of magnitude less than typical daylight. The strong nonlinearity of the SNR with the sampling time leads to a dynamic range of detection of 4 orders of magnitude. To detect possibly varying light fluxes, we operate in conditions of maximal detectivity $${\mathcal{D}}$$ D rather than maximal SNR. Given the quantum efficiency $$QE\left( \lambda \right)$$ Q E λ of the detector, we find $${ \mathcal{D}} = 0.015\,{\text{photon}}^{ - 1} \,{\text{s}}^{1/2} \,{\text{cm}}$$ D = 0.015 photon - 1 s 1 / 2 cm , and a non-negligible sensitivity to blackbody radiation for T > 50 °C. This work should help design highly sensitive luminescence detection methods and develop experiments to explore dynamic phenomena involving ultra-weak luminescence in biology, chemistry, and material sciences.

scholarly journals Evaluation of the Quality of Irrigation Machinery by Monitoring Changes in the Coefficients of Uniformity and Non-Uniformity of Irrigation

Agronomy ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1499
Author(s):  
Ján Jobbágy ◽  
Peter Dančanin ◽  
Koloman Krištof ◽  
Juraj Maga ◽  
Vlastimil Slaný
Keyword(s):  
Repeated Measurements ◽  
Joint Stock Company ◽  
Stock Company ◽  
Uniformity Coefficient ◽  
Quality Of Work ◽  
Total Length ◽  
Irrigation Uniformity ◽  
Wide Range ◽  
The Impact

Recently, the development of agricultural technology has been focused on achieving higher reliability and quality of work. The aim of the presented paper was to examine the possibilities of evaluating the quality of work of wide-area irrigation machinery by monitoring the coefficients of uniformity and non-uniformity of irrigation. The object of the research was pivot irrigation machinery equipped with sprinklers with a total length from 230 to 540 m. The commonly applied quality of work parameter for wide-range irrigators is the irrigation uniformity coefficient according to Heermann and Hein CUH. Work quality evaluations were also carried out through other parameters applicable in practice, such as irrigation uniformity coefficients calculated according to Christiansen CU, Wilcox and Swailes Cws, and our introduced parameters, the coefficient ar (derived from the degree of unevenness according to Oehler) and the degree of uniformity γr (derived from the degree of non-uniformity according to Voight). Other applied parameters for determining the quality of work of wide-range irrigation machinery were the coefficients of irrigation uniformity according to Hart and Reynolds CUhr, further according to Criddle CUcr and subsequently according to Beale and Howell CUbr. Next, the parameters of the non-uniformity coefficient according to Oehler a, the coefficient of variation according to Stefanelli Cv, the degree of non-uniformity according to Voigt γ and the degree of non-uniformity according to Hofmeister Ef were evaluated. Field tests were performed during the growing season of cultivated crops (potatoes, corn and sugar beet) in the village of Trakovice (agricultural enterprise SLOV-MART, southwest of the Slovakia) and in the district of Piešťany (Agrobiop, joint stock company). During the research, the inlet operating parameters (speed stage, inlet pressure, irrigation dose), technical parameters (number of sprayers, total length, number of chassis) and weather conditions (wind speed and temperature) were recorded. The obtained results were examined by one-way ANOVA analysis depending on the observed coefficient or input conditions and subsequently verified by Tukey and Duncan tests as needed. Irrigation uniformity values ranged from 67.58% (Cws) to 95.88% (CUbh) depending on the input conditions. Irrigation non-uniformity values ranged from 8.58 (a, Ef) to 32.42% (Cv). The results indicate a statistically significant effect of the site of interest and thus the impact of particular field conditions (p < 0.05). When evaluating the application of different coefficients of irrigation uniformity, the results showed a statistically significant effect only in the first test (p = 0.03, p < 0.05). During further repeated measurements, the quality of work increased due to the performed inspection of all sprayers and the reduction in the influence of the wind.

scholarly journals Bulk Relativistic Motion in a Complete Sample of Radio Selected AGN

1987 ◽  
Vol 121 ◽  
pp. 287-293
Author(s):  
C.J. Schalinski ◽  
P. Biermann ◽  
A. Eckart ◽  
K.J. Johnston ◽  
T.Ph. Krichbaum ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Radio Sources ◽  
Relativistic Motion ◽  
Complete Sample ◽  
Superluminal Motion ◽  
Spectrum Radio ◽  
Wide Range ◽  
Show Evidence

A complete sample of 13 flat spectrum radio sources is investigated over a wide range of frequencies and spatial resolutions. SSC-calculations lead to the prediction of bulk relativistic motion in all sources. So far 6 out of 7 sources observed with sufficient dynamic range by means of VLBI show evidence for apparent superluminal motion.

scholarly journals Optical whispering-gallery mode barcodes for high-precision and wide-range temperature measurements

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jie Liao ◽  
Lan Yang
Keyword(s):  
High Precision ◽  
Dynamic Range ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Temperature Measurements ◽  
Laser Source ◽  
Multiple Modes ◽  
Whispering Gallery ◽  
Wide Range ◽  
Thermal Sensing

AbstractTemperature is one of the most fundamental physical properties to characterize various physical, chemical, and biological processes. Even a slight change in temperature could have an impact on the status or dynamics of a system. Thus, there is a great need for high-precision and large-dynamic-range temperature measurements. Conventional temperature sensors encounter difficulties in high-precision thermal sensing on the submicron scale. Recently, optical whispering-gallery mode (WGM) sensors have shown promise for many sensing applications, such as thermal sensing, magnetic detection, and biosensing. However, despite their superior sensitivity, the conventional sensing method for WGM resonators relies on tracking the changes in a single mode, which limits the dynamic range constrained by the laser source that has to be fine-tuned in a timely manner to follow the selected mode during the measurement. Moreover, we cannot derive the actual temperature from the spectrum directly but rather derive a relative temperature change. Here, we demonstrate an optical WGM barcode technique involving simultaneous monitoring of the patterns of multiple modes that can provide a direct temperature readout from the spectrum. The measurement relies on the patterns of multiple modes in the WGM spectrum instead of the changes of a particular mode. It can provide us with more information than the single-mode spectrum, such as the precise measurement of actual temperatures. Leveraging the high sensitivity of WGMs and eliminating the need to monitor particular modes, this work lays the foundation for developing a high-performance temperature sensor with not only superior sensitivity but also a broad dynamic range.

Energy absorbed ability and damage analysis for honeycomb sandwich material of bio-inspired micro aerial vehicle under low velocity impact

2020 ◽  
pp. 095440622097542
Author(s):  
Jianxun Du ◽  
Peng Hao ◽  
Mabao Liu ◽  
Rui Xue ◽  
Lin’an Li
Keyword(s):  
Honeycomb Structure ◽  
Low Velocity Impact ◽  
Parameter Study ◽  
Low Velocity ◽  
Micro Aerial Vehicle ◽  
Thin Walled Structures ◽  
Wide Range ◽  
Aerial Vehicle ◽  
Thin Walled ◽  
The Impact

Because of the advantages of light weight, small size, and good maneuverability, the bio-inspired micro aerial vehicle has a wide range of application prospects and development potential in military and civil areas, and has become one of the research hotspots in the future aviation field. The beetle’s elytra possess high strength and provide the protection of the abdomen while being functional to guarantee its flight performance. In this study, the internal microstructure of beetle’s elytra was observed by scanning electron microscope (SEM), and a variety of bionic thin-walled structures were proposed and modelled. The energy absorption characteristics and protective performance of different configurations of thin-walled structures with hollow columns under impact loading was analyzed by finite element method. The parameter study was carried out to show the influence of the velocity of impactor, the impact angle of the impactor and the wall thickness of honeycomb structure. This study provides an important inspiration for the design of the protective structure of the micro aerial vehicle.

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