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Limberger, Fabian, Georg Rümpker, Michael Lindenfeld i Hagen Deckert. "The impact of seismic noise produced by wind turbines on seismic borehole measurements". Solid Earth 14, nr 8 (18.08.2023): 859–69. http://dx.doi.org/10.5194/se-14-859-2023.
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Abstract. Seismic signals produced by wind turbines can have an adverse effect on seismological measurements up to distances of several kilometres. Based on numerical simulations of the emitted seismic wave field, we study the effectivity of seismic borehole installations as a way to reduce the incoming noise. We analyse the signal amplitude as a function of sensor depth and investigate effects of seismic velocities, damping parameters and geological layering in the subsurface. Our numerical approach is validated by real data from borehole installations affected by wind turbines. We demonstrate that a seismic borehole installation with an adequate depth can effectively reduce the impact of seismic noise from wind turbines in comparison to surface installations. Therefore, placing the seismometer at greater depth represents a potentially effective measure to improve or retain the quality of the recordings at a seismic station. However, the advantages of the borehole decrease significantly with increasing signal wavelength.
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Howie, John A., i Ali Amini. "Numerical simulation of seismic cone signals". Canadian Geotechnical Journal 42, nr 2 (1.04.2005): 574–86. http://dx.doi.org/10.1139/t04-120.
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Numerical analysis can provide insight into the effect of ground conditions on seismic signals recorded in downhole seismic testing. As part of a study of the interpretation of seismic cone data in complex ground conditions, this paper deals with the cases of wave propagation in (i) homogeneous soil and (ii) soil of increasing stiffness with depth. The main purpose of this study was to assess the validity of the use of the finite difference program FLAC for the simulation of the downhole seismic test. For realistic assumptions of material stiffness and damping, the main characteristics of field seismic cone penetration test (SCPT) seismic data were reproduced in the simulated data. Both displayed the same general shape of signal, number of oscillations, signal attenuation, frequency content, compression wave component (near-field effect), signal widening, and shift of the peak of the frequency spectrum with depth. Damping was shown to cause signal widening and dispersion, and the shear wave velocity, Vs, interpreted from the simulated wave traces varied with the interval method used to determine it. For a case history of field data, it was found that Vs varied by about 3%, depending on the analysis method used. The results show that finite difference modeling of wave propagation can provide useful insights into the factors affecting the interpretation of downhole seismic tests.Key words: seismic cone testing, shear wave velocity, signal widening, near-field effect, numerical simulation, finite difference.
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Zhang, Xingli, Yan Chen, Ruisheng Jia i Xinming Lu. "Two-dimensional variational mode decomposition for seismic record denoising". Journal of Geophysics and Engineering 19, nr 3 (1.06.2022): 433–44. http://dx.doi.org/10.1093/jge/gxac032.
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Abstract Seismic signal denoising is the main task of seismic data processing. This study proposes a novel method for the denoising seismic record on the basis of a two-dimensional variational mode decomposition (2D-VMD) algorithm and permutation entropy (PE). 2D-VMD is a recently introduced adaptive signal decomposition method in which $K$ and $\alpha $ are important decomposing parameters to determine the number of modes, and have a predictable effect on the nature of detected modes. We present a novel method to address the problems of selecting appropriate $K$ and $\alpha $ values and apply these values to the proposed method. First, for a 2D seismic signal, the 2D-VMD method can decompose it into $K$ modes with specific direction and vibration characteristics. Next, the PE value of each mode is calculated. Random noise components are eliminated according to the PE value. Finally, the signal components are reconstructed to acquire the denoised seismic signal. Experimental and simulation results indicate that the proposed method has remarkable denoising effect on synthetic and real seismic signals. We hope that this new method can inspire and help evaluate new ideas in this field.
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Landrø, Martin. "The effect of noise generated by previous shots on seismic reflection data". GEOPHYSICS 73, nr 3 (maj 2008): Q9—Q17. http://dx.doi.org/10.1190/1.2894453.
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In marine seismic acquisition, the typical time interval between two adjacent shots is about [Formula: see text]. This interval is considered sufficient to avoid the signal from one shot interfering with the signal from the next shot. However, when we are looking for very weak signals or weak changes in a given signal (time-lapse seismic), the influence of the shot-generated noise can be of importance. In the present work, shot records with a recording time of [Formula: see text] are used to analyze the influence of the shot-generated noise from the previous shot. Simple decay models are used to match the observed rms decay curves. These calibrated models are used to estimate variations in signal-to-noise ratio versus shot time interval and source strength. For instance, if the source strength is doubled and the time interval between two shots is increased from [Formula: see text], an improvement in the signal-to-shot-generated noise from the previous shot of [Formula: see text] is expected. Especially for time-lapse seismic using permanently installed receivers, this way of increasing the S/N might be useful.
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Li, Bo, Lixin Zhang, Qiling Zhang i Shengmei Yang. "An EEMD-Based Denoising Method for Seismic Signal of High Arch Dam Combining Wavelet with Singular Spectrum Analysis". Shock and Vibration 2019 (10.03.2019): 1–9. http://dx.doi.org/10.1155/2019/4937595.
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Due to complicated noise interference, seismic signals of high arch dam are of nonstationarity and a low signal-to-noise ratio (SNR) during acquisition process. The traditional denoising method may have filtered effective seismic signals of high arch dams. A self-adaptive denoising method based on ensemble empirical mode decomposition (EEMD) combining wavelet threshold with singular spectrum analysis (SSA) is proposed in this paper. Based on the EEMD result for seismic signals of high arch dams, a continuous mean square error criterion is used to distinguish high-frequency and low-frequency components of the intrinsic mode functions (IMFs). Denoised high-frequency IMF using wavelet threshold is reconstructed with low-frequency components, and SSA is implemented for the reconstructed signal. Simulation signal denoising analysis indicates that the proposed method can significantly reduce mean square error under low SNR condition, and the overall denoising effect is superior to EEMD and EEMD-Wavelet threshold denoising algorithms. Denoising analysis of measured seismic signals of high arch dams shows that the performance of denoised seismic signals using EEMD-Wavelet-SSA is obviously improved, and natural frequencies of the high arch dams can be effectively identified.
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Zheng, Gong Ming, Yuan Yuan Shen i Ling Ling Song. "Vibroseis Nonlinear Scanning Signal Simulation Analysis". Applied Mechanics and Materials 318 (maj 2013): 191–95. http://dx.doi.org/10.4028/www.scientific.net/amm.318.191.
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Vibrator nonlinear scan is an important means of high frequency seismic exploration. With the propagation of seismic waves, High frequency components continue to be absorbed, due to the filtering effect of the earth. Nonlinear scanning technology can get some degree of compensation to the seismic wave loss in the high frequency part in the propagation, by extending the vibration of the high frequency component time. This article through MATLAB simulation, this paper analyzed the nonlinear scanning signals in scanning signals and logarithmic index scanning signals, and the similarities and differences between the two signals are summarized.
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Cai, Jianxian, Li Wang, Jiangshan Zheng, Zhijun Duan, Ling Li i Ning Chen. "Denoising Method for Seismic Co-Band Noise Based on a U-Net Network Combined with a Residual Dense Block". Applied Sciences 13, nr 3 (19.01.2023): 1324. http://dx.doi.org/10.3390/app13031324.
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To address the problem of waveform distortion in the existing seismic signal denoising method when removing co-band noise, further improving the signal-to-noise ratio (SNR) of seismic signals and enhancing their quality, this paper designs a seismic co-band denoising model Atrous Residual Dense Block U-Net (ARDU), which uses a U-shaped convolutional neural network (U-Net) as a basic framework and combines atrous convolution and the residual dense block (RDB). In the ARDU model, atrous convolution is connected with residual dense blocks to form the feature extraction unit of the model encoder. Among them, the residual dense blocks can deepen the network’s depth and enhance the feature extraction ability of the network on the premise of mitigating the gradient-vanishing and gradient-exploding problem. Atrous convolution can enlarge receptive fields, reduce waveform distortion, and protect effective signals without increasing network parameters. To test the denoising performance of the ARDU model, the Stanford Global Seismic dataset was used to construct a training set and a test set and the model was trained and tested on it. The experimental results of the ARDU model for different types of seismic co-band noise showed that this model can effectively remove seismic co-band noise, protect effective signals, improve the SNR of seismic signals, and enhance the quality of seismic signals. To further verify the denoising effect of the model, this model was compared with the wavelet threshold denoising U-Net model and the denoising residual dense block (DnRDB) model, and the results showed that the ARDU model has the best SNR, r (correlation coefficient), and root-mean-square error (RMSE) and the least distortion of the seismic signal waveform.
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Juarzan, Laode Ihksan. "ANALISIS SINYAL SEISMIK DAN SELF POTENTIAL (SP) DARI FENOMENA SEIMOELEKTRIK DI GUNUNG LUMPUR BLEDUG KUWU JAWA TENGAH". Jurnal Rekayasa Geofisika Indonesia 4, nr 01 (30.04.2022): 60. http://dx.doi.org/10.56099/jrgi.v4i01.27456.
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Abstarct Bledug Kuwu is one of the mud volcano (gunung lumpur) in Java. Bledug Kuwu eruption periodically occured with a frequency of more than five times in one minute, pointed by the release of gas bubbles and mud. This study aims to observe the signals of the seismic and self potential (SP) from seismoelectric phenomenon generated by Bledug Kuwu eruption. Measurements were performed by placed seismic sensor around the main crater point of Bledug Kuwu mud volcano, while the SP sensor placed in the vertical, the radial and tangential direction from the point of the main crater of a Bledug Kuwu mud volcano.. The result of analysis shows that the dominant frequency of seismic events is 0,2 Hz, while dominant frequency of SP signals is 48,0 Hz. The arrival time difference between seismic and SP signals predominantly in the range of time (0,0 to 1,5 second) which indicates that the appears of the seismic signal causes the appearance of the signal SP as a result of the transfer fluid as described in the seismoelectric phenomenon.The average value of the amplitude of seismic events for Z, NS and EW component is 0,6694, 0,4848 and 0,5158 Count/Volt. The average value of the amplitude of SP events for Z, NS and EW component is 1,338, 1,249 and 0,909 mVolt. SP events will appear if amplitude of seismic events more than 0,2 Count value. Amplitude of sesmic events proportional to the amplitude of the SP event with value of the correlation coefficient between the both is more than 80.0%, the seismic events caused the material in its path have excessive pressure that pore fluid in the material move and cause the separation of charge is the source of the appear of SP signal, the greater the amplitude of the seismic event the pressure exerted on the material so that the larger the amplitude of the SP events formed also getting bigger, this is in accordance with the theory of the seismoelectric phenomenon by electrokinetic effect mechanismKeyword: Bledug Kuwu, Self Potential (SP), seismic, dominant frequency, different arrival time, amplitude and seismoelectric effect.
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Wu, Jing, Li Wu, Miao Sun, Ya-ni Lu i Yan-hua Han. "Application of Boundary Local Feature Scale Adaptive Matching Extension EMD Endpoint Effect Suppression Method in Blasting Seismic Wave Signal Processing". Shock and Vibration 2021 (13.08.2021): 1–9. http://dx.doi.org/10.1155/2021/2804539.
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The intrinsic endpoint effect of empirical mode decomposition (EMD) will lead to serious divergence of the intrinsic mode function (IMF) at the endpoint, which will lead to the distortion of IMF and affect the decomposition accuracy of EMD. In view of this phenomenon, an EMD endpoint effect suppression method based on boundary local feature scale adaptive matching extension was proposed. This method can consider both the change trend of the signal at the endpoint and the change rule of the signal inside. The simulation results showed that the proposed method had better suppression effect on the intrinsic endpoint effect of EMD than the traditional EMD endpoint effect suppression method and achieved high-precision IMF. The endpoint effect suppression method of EMD based on boundary local feature scale adaptive matching extension was used to process the actual blasting seismic signal. The decomposition results showed that the method can effectively suppress the endpoint effect of EMD of blasting seismic signal and are helpful to extract the detailed characteristic parameters of blasting seismic signal.
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Zhao, Binghui, Liguo Han, Pan Zhang i Yuchen Yin. "Weak Signal Enhancement for Passive Seismic Data Reconstruction Based on Deep Learning". Remote Sensing 14, nr 21 (24.10.2022): 5318. http://dx.doi.org/10.3390/rs14215318.
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In conventional passive seismic exploration, it is often necessary to make a long-period seismic record. On the one hand, the passive seismic records with long period allowed us to screen several good passive seismic records with long period for seismic interferometry reconstruction and perform piecewise stacking on them. On the other hand, a sufficiently long recording time can help us avoid noise interference generated by nonpassive sources during the recording process, such as animal activities, construction operations, industrial electrical interference, etc. Compared with the passive seismic records with short period, the passive seismic records with long period can obtain higher signal-to-noise ratio after seismic interferometry reconstruction. However, they also cause huge consumptions of manpower, material resources, and time. Based on this, this paper proposes a seismic interferometry reconstruction method using passive signals of short-period recordings. Based on deep learning technology, the effective information is extracted and enhanced, the strong coherent noise after reconstruction is suppressed and weakened, the SNR of reconstructed recording is improved, and the effective information is mined. It can effectively reduce the time of passive seismic recording required for acquisition and improve acquisition efficiency. In addition, it also has a certain monitoring effect on real-time changes in underground structures.
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Ouyang, Zhiyuan, Liqi Zhang, Huazhong Wang i Kai Yang. "High-Dimensional Seismic Data Reconstruction Based on Linear Radon Transform–Constrained Tensor CANDECOM/PARAFAC Decomposition". Remote Sensing 14, nr 24 (11.12.2022): 6275. http://dx.doi.org/10.3390/rs14246275.
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Random noise and missing seismic traces are common in field seismic data, which seriously affects the subsequent seismic processing flow. The complete noise-free high-dimensional seismic dataset in the frequency–space (f-x) domain under the local linear assumption are regarded as a low-rank tensor, and each high dimensional seismic dataset containing only one linear event is a rank-1 tensor. The tensor CANDECOM/PARAFAC decomposition (CPD) method estimates complete noise-free seismic signals by characterizing high-dimensional seismic signals as the sum of several rank-1 tensors. In order to improve the stability and effect of the tensor CPD algorithm, this paper proposes a linear Radon transform–constrained tensor CPD method (RCPD) by using the sparsity of factor matrix in the Radon domain after high-dimensional seismic signal tensor CPD and uses alternating direction multiplier method (ADMM) to solve the established optimization problem. This proposed method is an essential realization of the high-dimensional linear Radon transform, and the results of synthetic and field data reconstruction prove the effectiveness of the proposed method.
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Lurka, Adam, Grzegorz Mutke i Piotr Małkowski. "Dynamic Influence of Near-Source Seismic Ground Motion on Underground Mine Working Stability Using Time-Frequency Analysis". Shock and Vibration 2021 (2.08.2021): 1–16. http://dx.doi.org/10.1155/2021/9023550.
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Peak particle velocity parameter is very useful in assessing underground mine working stability. Its application is widespread and requires additional analysis of the dominant frequency of the seismic signal. In order to properly analyze the velocity amplitudes of strong ground motions generated from seismic sources, time-frequency properties of near-source seismic signals in underground mines should be quantified. Using numerical calculations, the continuous wavelet transform (CWT) of the recorded near-source seismic signals in three perpendicular directions was obtained to characterize its time-frequency properties. The properties of recorded strong ground motion velocity seismograms for two high energy seismic events and two blasts from two underground coal mines in Poland have been extracted with the use of continuous wavelet transform spectrograms showing the duration time of each frequency group. Assuming a constant peak particle velocity amplitude on the analyzed seismograms, the duration time of each frequency group starts to play a key role. The longer the duration time of the lower frequency group is on the CWT spectrogram, the more the damaging effect on underground mining excavations can be observed. Varying bandwidths of dominant frequencies in separate time intervals for the analyzed seismic signals have had significantly different influence on the potentially damaging effect on underground mining excavations.
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Wuenschel, Paul C. "Removal of the detector‐ground coupling effect in the vertical seismic profiling environment". GEOPHYSICS 53, nr 3 (marzec 1988): 359–64. http://dx.doi.org/10.1190/1.1442469.
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In a “controlled” experiment with the Gulf VSP tool, the detector‐ground coupling was measured and removed from the recorded signal using the Washburn‐Wiley algorithm. Repeat measurements were made at a common detector depth with two coupling configurations, the first to permit the true ground motion to be recorded and the second to ensure that a coupling resonance existed within the seismic frequency band. The algorithm removed the distortion of the body‐wave portion of the seismogram caused by the coupling resonance for the second configuration and recovered true ground motion. However, lowering the coupling resonance into the seismic band also caused the tool to become sensitive to tube waves. This observation is helpful in evaluating current VSP tools; it implies that any VSP tool that is sensitive to tube waves has a coupling resonance within the seismic frequency band, and that the signal recorded with such a tool does not measure true ground motion. This test also showed that a detector used to monitor source signature variations must have a bandwidth comparable to the VSP signal.
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Wehner, Daniel, i Martin Landrø. "Low-frequency acoustic signal created by rising air-gun bubble". GEOPHYSICS 82, nr 6 (1.11.2017): P119—P128. http://dx.doi.org/10.1190/geo2016-0674.1.
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In the seismic industry, there is increasing interest in generating and recording low frequencies, which leads to better data quality and can be important for full-waveform inversion. The air gun is a seismic source with a signal that consists of the (1) main impulse, (2) oscillating bubble, and (3) rising of this air bubble. However, there has been little investigation of the third characteristic. We have studied a low-frequency signal that could be created by the rising air bubble and find the contribution to the low-frequency content in seismic acquisition. We use a simple theory and modeling of rising spheres in water and compute the acoustic signal created by this effect. We conduct tank and field experiments with a submerged buoy that is released from different depths and record the acoustic signal with hydrophones along the rising path. The experiments simulate the signal from the rising bubble separated from the other two effects (1 and 2). Furthermore, we use data recorded below a single air gun fired at different depths to investigate if we can observe the proposed signal. We find that the rising bubble creates a low-frequency signal. Compared with the main impulse and the oscillating bubble effect of an air-gun signal, the contribution of the rising bubble is weak, on the order of 1/900 depending on the bubble size. By using large air-gun arrays tuned to create one big bubble, the contribution of the signal can be increased. The enhanced signal can be important for deep targets or basin exploration because the low-frequency signal is less attenuated.
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Wu, Haofeng, Weiguo Xiao i Haoran Ren. "Automatic Time Picking for Weak Seismic Phase in the Strong Noise and Interference Environment: An Hybrid Method Based on Array Similarity". Sensors 22, nr 24 (16.12.2022): 9924. http://dx.doi.org/10.3390/s22249924.
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The extraction of travel-time curve of seismic phase is very important for the subsequent inference of the structural properties of underground media in seismology. In recent years, with the increase in the amount of data, manual processing is facing significant challenges, and automatic signal processing has gradually become the mainstream. According to the similarity of array signals and considering the elimination of outliers, we propose an improved multi-channel cross-correlation method using the L1 norm measure to obtain preliminary results, which builds on a new controllable measurement mode. Then, the post-correction step is carried out in combination with the signal gain property of beamforming technique. Based on these two methods, this paper proposes a new scheme of automatic arrival time picking. We apply the scheme to actual data to verify the effects of the two methods step by step. The entire scheme achieves fine results: direct water waves, seismic waves refracted by the crust and seismic waves reflected by the upper mantle are automatically detected. In addition, compared with the two traditional methods, the scheme proposed in this paper has a better overall effect and a reasonable computation cost.
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Zhang, Hui, Hao Zhai, Ke Zhang, Lujun Wang, Xing Zhao i Jianmin Wei. "Feature Extraction and Analysis of Microseismic Signal Based on Convolutional Neural Network". Journal of Physics: Conference Series 2143, nr 1 (1.12.2021): 012017. http://dx.doi.org/10.1088/1742-6596/2143/1/012017.
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Abstract Seismic detection technology has been widely used in safety detection of engineering construction abroad. Although it has just started in the field of engineering in our country, its role is becoming more and more important. Through computer technology, micro-seismic detection can provide accurate data for the construction safety detection of large-scale projects, which has important practical significance for the rapid and effective identification of micro-seismic signals. Based on this, the purpose of this article is to study the feature extraction and classification of microseismic signals based on neural games. This article first summarizes the development status of microseismic monitoring technology. Using traditional convolutional neural networks for analysis, a multi-scale feature fusion network is proposed on the basis of convolutional neural networks and big data, the multi-scale feature fusion network is used to research and analyze microseismic feature extraction and classification. This article systematically explains The principle of microseismic signal acquisition and the construction of multi-scale feature fusion network. And use big data, comparative analysis method, observation method and other research methods to study the theme of this article. Experimental research shows that the db7 wavelet base has little effect on the Megatron signal.
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Liu, Shu Cong, Er Gen Gao i Chun Sheng Guo. "Seismic Signal Wavelet-Packet Denoising and Fast Spectrum Analysis". Applied Mechanics and Materials 229-231 (listopad 2012): 1772–76. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.1772.
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Noise mixed in the recorded seismic signals often affects the data analysis result. To solve this problem, wavelet packet decomposition technology is selected to reduce the noise. The principle, denoising steps and algorithm of wavelet packet decomposition technology are introduced with its effectiveness and reliability verified by computer simulation. Meanwhile, split-radix FFT algorithm is used to rapidly perform spectral analysis for seismic signals. Compared with radix-2 FFT and radix-4 FFT, split-radix algorithm can significantly reduce calculation amount and improve the speed of data analysis. Field tests showed that wavelet packet denoising technology and split-radix FFT algorithm have good effect.
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Flinders, Ashton F., Ingrid A. Johanson, Phillip B. Dawson, Kyle R. Anderson, Matthew M. Haney i Brian R. Shiro. "Very-Long-Period (VLP) Seismic Artifacts during the 2018 Caldera Collapse at Kīlauea, Hawai‘i". Seismological Research Letters 91, nr 6 (16.09.2020): 3417–32. http://dx.doi.org/10.1785/0220200083.
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Abstract Throughout the 2018 eruption of Kīlauea volcano (Hawai‘i), episodic collapses of a portion of the volcano’s summit caldera produced repeated Mw 4.9–5.3 earthquakes. Each of these 62 events was characterized by a very-long-period (VLP) seismic signal (>40 s). Although collapses in the later stage of the eruption produced earthquakes with significant amplitude clipping on near-summit broadband seismometers, the first 12 were accurately recorded. For these initial collapse events, we compare average VLP seismograms at six near-summit locations to synthetic seismograms derived from displacements at collocated Global Positioning System stations. We show that the VLP seismic signal was generated by a radially outward and upward ramp function in displacement. We propose that at local distances the period of the VLP seismic signal is solely dependent on the duration of this ramp function and the instrument transfer function, that is, the seismic VLP is an artifact of the bandlimited instrument response and not representative of real ground motion. The displacement ramp function imposes a sinc-function velocity amplitude spectrum that cannot be fully recovered through standard seismic instrument deconvolution. Any near-summit VLP signals in instrument-response-corrected velocity or displacement seismograms from these collapse events are subject to severe band limitation. Similarly, the seismic amplitude response is not flat through the low-frequency corner, for example, instrument-response-uncorrected seismograms scaled by instrument sensitivity are equally prone to band limitation. This observation is crucial when attempting to clarify the different contributions to the VLP source signature. Not accounting for this effect could lead to misunderstanding of the magmatic processes involved.
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Li, Huai Liang, Xian Guo Tuo i Ming Zhe Liu. "Distributed Wireless Acquisition System for Seismic Signal with Vibration and Noise". Applied Mechanics and Materials 340 (lipiec 2013): 75–79. http://dx.doi.org/10.4028/www.scientific.net/amm.340.75.
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This work presented the design and implementation of a wireless acquisition system for seismic signal. 4 distributed signal acquisition stations were integrated to the low-power prototype which composed of 48 acquisition channels, and a star-shaped wireless network was built which is suitable for seismic data transmission using the networking mode of multi-pipe and multi-address switching. A distributed seismic data acquisition system was accomplished which has the function of synchronous control and asynchronous transmission. The key technical problems and solutions of time balance distribution between multi-channel time-sharing switching acquisition and temporary storage, and wireless seismic data transmission is analyzed in detail in this paper. Thus the additional accessories of traditional wired seismograph were greatly reduced, to improve its cable layout trouble and low efficiency of construction in an adverse environment. This system increased efficiency more than 50% and took same exploration effect compared with wired mode in the field application.
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Day, Ryan D., Robert D. McCauley, Quinn P. Fitzgibbon, Klaas Hartmann i Jayson M. Semmens. "Exposure to seismic air gun signals causes physiological harm and alters behavior in the scallop Pecten fumatus". Proceedings of the National Academy of Sciences 114, nr 40 (18.09.2017): E8537—E8546. http://dx.doi.org/10.1073/pnas.1700564114.
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Seismic surveys map the seabed using intense, low-frequency sound signals that penetrate kilometers into the Earth’s crust. Little is known regarding how invertebrates, including economically and ecologically important bivalves, are affected by exposure to seismic signals. In a series of field-based experiments, we investigate the impact of exposure to seismic surveys on scallops, using measurements of physiological and behavioral parameters to determine whether exposure may cause mass mortality or result in other sublethal effects. Exposure to seismic signals was found to significantly increase mortality, particularly over a chronic (months postexposure) time scale, though not beyond naturally occurring rates of mortality. Exposure did not elicit energetically expensive behaviors, but scallops showed significant changes in behavioral patterns during exposure, through a reduction in classic behaviors and demonstration of a nonclassic “flinch” response to air gun signals. Furthermore, scallops showed persistent alterations in recessing reflex behavior following exposure, with the rate of recessing increasing with repeated exposure. Hemolymph (blood analog) physiology showed a compromised capacity for homeostasis and potential immunodeficiency, as a range of hemolymph biochemistry parameters were altered and the density of circulating hemocytes (blood cell analog) was significantly reduced, with effects observed over acute (hours to days) and chronic (months) scales. The size of the air gun had no effect, but repeated exposure intensified responses. We postulate that the observed impacts resulted from high seabed ground accelerations driven by the air gun signal. Given the scope of physiological disruption, we conclude that seismic exposure can harm scallops.
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Jimenez, Cesar, Nabilt Moggiano, Erick Mas, Bruno Adriano, Yushiro Fujii i Shunichi Koshimura. "Tsunami Waveform Inversion of the 2007 Peru (Mw8.1) Earthquake". Journal of Disaster Research 9, nr 6 (1.12.2014): 954–60. http://dx.doi.org/10.20965/jdr.2014.p0954.
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An earthquake shook the central-southern coast of Peru on August 15, 2007, as a coseismic effect a tsunami was generated, which flooded some villages and beach resorts and killed 3 people. From the analysis and signal processing of 10 tidal records, we obtained the parameters of the seismic source and the initial coseismic deformation through an inversion modeling, in which the synthetic signals are compared with the observed signals by a non-negative least square method. The maximum slip located on the southern part of the rupture geometry is 7.0 m. The calculated scalar seismic moment isM0= 1.99 × 1021Nm, equivalent to a magnitude ofMw8.1. We used these parameters to obtain a heterogeneous seismic source model, which was used as initial condition to simulate the tsunami propagation and inundation. We used the field survey observations to validate our source model.
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Panea, Ionelia, Stefan Prisacari, Victor Mocanu, Mihnea Micu i Marius Paraschivoiu. "The use of seismic modeling for the geologic interpretation of deep seismic reflection data with low signal-to-noise ratios". Interpretation 5, nr 1 (1.02.2017): T23—T31. http://dx.doi.org/10.1190/int-2016-0046.1.
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We have performed a deep seismic reflection study, DACIA-PLAN, based on the data recorded along a crooked line across the southeastern Romanian Carpathians. The signal-to-noise ratio (S/N) of these data varies along the seismic profile, and its variation is considered to be an effect of the rough topography, complex subsurface geology, and varying surface conditions encountered during seismic data acquisition. The migrated time section that covers the mountainous area is clear, without visible reflections, making the geologic interpretation very difficult. We used a seismic modeling technique to explain the poor S/N of the recorded data and to generate synthetic seismic sections that can be useful for the geologic interpretation of the field seismic section (migrated time section). We used ray-tracing modeling to obtain the expected seismic expression of horizons of interest. Subsurface illumination modeling indicates that the complex subsurface geology and irregularly deployed sources and receivers are responsible for the incomplete and/or uneven illumination of the subsurface and can lead to strong amplitude variations. We then used 2.5D acoustic finite-difference modeling to analyze the effect of a crooked line on seismic wave propagation. The synthetic shot gathers prove that crooked line arrival times for reflected and head waves contain static time shifts relative to a straight line regular sampling geometry. Some geologic interfaces of interest are not well-imaged on the synthetic seismic section, and this is considered to be an effect of poor positioning during seismic data acquisition. We used the velocity model from the tomographic inversion of first-arrival traveltimes and synthetic and field crooked line deep seismic reflection data to create a structural image for the southeastern Romanian Carpathians and the Focsani Basin, which tie well with the geologic model built for this area on the basis of geologic and well data only.
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Ji, Chang Peng, Mo Gao i Jie Yang. "Study on Threshold Detection of Micro-Seismic Signal Based on Constraint Judgment". Advanced Materials Research 255-260 (maj 2011): 2898–903. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.2898.
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Double threshold detection based on constraint judgment is proposed for micro-seismic signal detection. The improvement effect on Probability of False Alarm and influence on Probability of Detection are quantitatively analyzed with constraint judgment. The mathematical models of total PFA and PD of double threshold detection based on constraint judgment are built, and the validity of the mathematical model is verified by simulation tests and experiments. The results show that the signal-to-noise ratio under scheduled PFA and PD Call be decreased by introducing constraint judgment to double threshold detection, and improve the identification accuracy of micro-seismic signal.
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Lowe, Maximilian, Jörg Ebbing, Amr El-Sharkawy i Thomas Meier. "Gravity effect of Alpine slab segments based on geophysical and petrological modelling". Solid Earth 12, nr 3 (19.03.2021): 691–711. http://dx.doi.org/10.5194/se-12-691-2021.
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Abstract. In this study, we present an estimate of the gravity signal of the slabs beneath the Alpine mountain belt. Estimates of the gravity effect of the subducting slabs are often omitted or simplified in crustal-scale models. The related signal is calculated here for alternative slab configurations at near-surface height and at a satellite altitude of 225 km. We apply three different modelling approaches in order to estimate the gravity signal from the subducting slab segments: (i) direct conversion of upper mantle seismic velocities to density distribution, which are then forward calculated to obtain the gravity signal; (ii) definition of slab geometries based on seismic crustal thickness and high-resolution upper mantle tomography for two competing slab configurations – the geometries are then forward calculated by assigning a constant density contrast and slab thickness; (iii) accounting for compositional and thermal variations with depth within the predefined slab geometry. Forward calculations predict a gravity signal of up to 40 mGal for the Alpine slab configuration. Significant differences in the gravity anomaly patterns are visible for different slab geometries in the near-surface gravity field. However, different contributing slab segments are not easily separated, especially at satellite altitude. Our results demonstrate that future studies addressing the lithospheric structure of the Alps should have to account for the subducting slabs in order to provide a meaningful representation of the geodynamic complex Alpine area.
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Wang, Ruizhen, Jinkuan Wang, Haidong Li, Hongliang Cui, Meizhen Tang i Jingtao Zhao. "A Study on the Acquisition Technology for Weak Seismic Signals from Deep Geothermal Reservoirs". Energies 16, nr 6 (15.03.2023): 2751. http://dx.doi.org/10.3390/en16062751.
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There are rich geothermal resources in China and they are widely distributed. After years of continuous exploration and production, most of the shallow geothermal resources have been explored and the current exploration mainly focuses on deep ones. Among a great many geophysical exploration methods, seismic survey is the most effective means of geothermal resource exploration and production, but its weak seismic reflection signal, low S/N ratio and poor imaging of thermal reservoirs due to the seismic geological conditions restrict the production and utilization of deep geothermal resources. It considers through the analysis of the geophysical characteristics of the thermal reservoir that the main causes for the weak seismic reflection signals from deep thermal reservoirs are (1) the shielding effect of the strong wave impedance interface between the thermal reservoir and the caprocks; (2) the small reflection coefficient inside the thermal reservoir; and (3) the serious absorption and attenuation of high-temperature fluids such as hydrothermal fluids and steam in the thermal reservoirs by seismic waves. Accordingly, a series of seismic data acquisition technologies are proposed based on the high-precision vibroseis low-frequency shooting, high-sensitivity geophones long-spread receiving and small bin size highfold technologies, and their application in the seismic acquisition of dry-hot rocks (HDR) in Gonghe Basin, Qinghai, shows a very good application effect.
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KASLOVSKY, DANIEL N., i FRANÇOIS G. MEYER. "NOISE CORRUPTION OF EMPIRICAL MODE DECOMPOSITION AND ITS EFFECT ON INSTANTANEOUS FREQUENCY". Advances in Adaptive Data Analysis 02, nr 03 (lipiec 2010): 373–96. http://dx.doi.org/10.1142/s1793536910000537.
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Huang's Empirical Mode Decomposition (EMD) is an algorithm for analyzing nonstationary data that provides a localized time-frequency representation by decomposing the data into adaptively defined modes. EMD can be used to estimate a signal's instantaneous frequency (IF) but suffers from poor performance in the presence of noise. To produce a meaningful IF, each mode of the decomposition must be nearly monochromatic, a condition that is not guaranteed by the algorithm and fails to be met when the signal is corrupted by noise. In this work, the extraction of modes containing both signal and noise is identified as the cause of poor IF estimation. The specific mechanism by which such "transition" modes are extracted is detailed and builds on the observation of Flandrin and Goncalves that EMD acts in a filter bank manner when analyzing pure noise. The mechanism is shown to be dependent on spectral leak between modes and the phase of the underlying signal. These ideas are developed through the use of simple signals and are tested on a synthetic seismic waveform.
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Liang, Xiaofeng, Sicheng Zuo, Shilin Li i Yongge Feng. "Burial Process of a Seismic Station by Moving Dunes in Tarim Basin". Seismological Research Letters 91, nr 5 (17.06.2020): 2936–41. http://dx.doi.org/10.1785/0220200116.
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Abstract A temporary seismometer vault was buried by a moving sand dune in the Taklimakan Desert at northwestern China in October 2019. The dune gradually covered the solar panel and the power supply to the seismic station was subsequently cut off. Here, we show that the burial process can be diagnosed according to the temperature record from the thermometer in the data-logger, an ultra-low-frequency seismic signal, and the change of high-frequency noise level from the continuous seismograms recorded by the broadband seismometer. The ultra-low-frequency seismic signal reflects the thermoelastic effect of the suspension spring in the seismometer corresponding to the temperature gradient in the sensor vault. At the same time, the variation of high-frequency noise level correlates well with the temperature profile and the ultra-low-frequency seismic signal, indicating the ground wind intensity. The peak frequency shifts and their different responses on three-component waveforms for the high-frequency noise might reflect the distance from the moving dunes to the station and their moving directions. This observation shows a potential usage of continuous seismograms to study rapid environment change around a temporary seismic station.
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Gao, Yongxin, Dongdong Wang, Jian Wen, Hengshan Hu, Xiaofei Chen i Cheng Yao. "Electromagnetic responses to an earthquake source due to the motional induction effect in a 2-D layered model". Geophysical Journal International 219, nr 1 (5.07.2019): 563–93. http://dx.doi.org/10.1093/gji/ggz303.
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Summary Movement of the conductive earth medium in the ambient geomagnetic field can generate an electromotive force and a motional induction current, which further cause the disturbances of the electromagnetic (EM) fields. Such a mechanoelectric coupling is known as the motional induction (MI) effect and has been proposed to be a possible mechanism for the generation of the observed EM signals during earthquakes. In this paper, we study the EM responses to an earthquake source due to such a MI effect in a 2-D horizontally layered model. First we transform the governing equations that couple the elastodynamic equations and Maxwell equations into a set of first-order ordinary depth-dependent differential equations. Then we solve the seismic and EM responses to a moment tensor source. Finally, we transform the 2-D seismic and EM responses to 3-D responses using a simple amplitude correction method. We conduct several numerical examples to investigate the properties of the EM signals generated by the earthquake source. The results show that two types of EM signals can be observed. The first one is the coseismic electric/magnetic field that accompanies the seismic P and S waves as well as the Rayleigh wave. The second one is the early EM signal which arrives before the P wave. The numerical results show that the EM signals change with the inclination angle of the geomagnetic field, the azimuth angle between the wave propagation plane and the geomagnetic vertical plane, and the medium conductivity. Increase in the conductivity can enhance the coseismic electric and magnetic signals. Our simulation also shows that an EM wave can be generated by a seismic wave at the interface separating two different media. The radiation pattern of the interface EM wave generated by a P wave is similar to that of a horizontal electric dipole located on the interface.
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Dmitriev, A. N. "RESULTS OF WORK BY THE METHOD OF REFLECTED WAVES IN AN ELECTRICALLY PERTURBED SURROUNDINGS". Oil and Gas Studies, nr 5 (30.10.2018): 45–50. http://dx.doi.org/10.31660/0445-0108-2018-5-45-50.
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The article is devoted to the actual topic of improving the direct search for hydrocarbon deposits by the method of reflected waves. A method for detecting hydrocarbon deposits by the method of reflected waves in the superimposed electric field is developed. The anomalous effect of the deposit is detected by the parameter P . This parameter is the ratio of the normalized energy of the seismic signal after the excitation of the medium by an electric field to the normalized energy of the seismic signal before excitation by this field in different time windows. Field verification seismic works on the known oil deposit have been performed. The interpretation of the proposed method gave positive results. The deposit is confidently allocated in a seismic field on depth and laterals due to preliminary influence by an electric field on a geological section with a deposit.
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He, Li, i Dong Wang Zhong. "The Blasting Test with Precise Delayed Time Interval and Wavelet Pocket Analysis for Vibration Signals’ Energy". Advanced Materials Research 1023 (sierpień 2014): 198–204. http://dx.doi.org/10.4028/www.scientific.net/amr.1023.198.
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As a physical carrier, blasting vibration signal includes much information about blasting method, explosive charge structure and propagation medium. Based on the indoor concrete slope test with millisecond blasting and wavelet pocket analysis technology, the blasting seismic signal was analyzed in the features of energy distribution in order to control the blasting vibration hazard better. The attenuation law of the energy and the peak vibration velocity (PPV) with distance decreased were researched. The effects of delayed time interval on PPV and energy are investigated, and the paper have analyzed the weakening degree of energy and PPV of vibration signals when damping ditch exists, so was its effect on the distribution of energy. The conclusions show that: the impact is great about delayed time interval on the total energy of signals in millisecond blasting; the damping ditch made the predominant frequency for energy concentrate on the low frequency band, damping effect of the damping ditch reduced with the delay time interval increasing. When the propagation distance increased, the attenuation trend of the PPV and total energy slowed down gradually near blasting area. The PPV and energy are not necessarily meanwhile the maximum; the energy of the vibration signal is not only determined by the PPV.
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Godano, Cataldo, Vincenzo Convertito i Nicola Alessandro Pino. "The Signal to Noise Ratio and the Completeness Magnitude: The Effect of the COVID-19 Lockdown". Atmosphere 12, nr 5 (21.04.2021): 525. http://dx.doi.org/10.3390/atmos12050525.
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We analyse the earthquakes catalogues for Italy, South California, and Greece across the COVID-19 lockdown period for each country. The results for Italy and Greece show that, even if the reduction of the signal to noise ratio has improved the earthquake detection capability, the completeness magnitude remains substantially unchanged, making the improved detection capability ineffective from the statistical point of view. A slight reduction (0.2) of the completeness magnitude is observed for South California, likely related to the relatively higher number of seismic stations located close to urban areas. Our findings suggest that—given the present configuration of the seismic network considered here—only an important decrease in the station spacing can produce a significant decrease of the completeness magnitude.
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Li, Qiuzi, Harry W. Deckman, Deniz Ertaş i Lang Feng. "The magneto-seismic method in geoscience". Leading Edge 40, nr 3 (marzec 2021): 194–201. http://dx.doi.org/10.1190/tle40030194.1.
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Key concepts and potential applications associated with a phenomenon hitherto unexplored by the geoscience community, which we have named the magneto-seismic effect, are introduced. The method is based on the simple principle that when an electric charge moves in the presence of an external magnetic field, the charge carrier experiences an instantaneous force, which is equal to the vector cross product of the current it carries and the magnetic field that is present. This “Lorentz force” can create both compressional and shear sound waves in electrical conductors by passing an alternating current through them via an electromagnetic source. In laboratory settings, this magneto-seismic effect can produce readily detectable rock frame displacements. This opens up the possibility of developing new experimental methods to interrogate elastic and poroelastic response of rocks in a broad frequency range from subhertz to megahertz, potentially closing the frequency gap between traditional ultrasonic characterization and properties of interest in the seismic frequency band. In exploration settings, electric current dipole/bipole sources, or novel rotating magnetic dipole sources, can be used to generate electric currents at depth. These currents produce seismic waves at interfaces (or boundaries) where conductivity abruptly changes. The amplitude and propagation directions of these generated seismic waves depend on the relative orientation of the interfaces (or boundaries) with respect to the earth's magnetic field. These seismic waves can then be recorded by receivers at the surface and, in principle, might be processed to yield a resistivity map with seismic resolution. It is shown that processing to obtain a signal from deep targets is significantly limited by seismic background noise. However, an acceptable signal-to-noise ratio might be achieved for shallower targets. The difference between the magneto-seismic response and the previously well-studied electro-seismic response will be discussed.
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Li, Lei, Pierre Boué i Michel Campillo. "Observation and explanation of spurious seismic signals emerging in teleseismic noise correlations". Solid Earth 11, nr 1 (30.01.2020): 173–84. http://dx.doi.org/10.5194/se-11-173-2020.
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Abstract. Deep body waves have been reconstructed from seismic noise correlations in recent studies. The authors note their great potential for deep-Earth imaging. In addition to the expected physical seismic phases, some spurious arrivals having no correspondence in earthquake seismograms are observed from the noise correlations. The origins of the noise-derived body waves have not been well understood. Traditionally, the reconstruction of seismic phases from inter-receiver noise correlations is attributed to the interference between waves from noise sources in the stationary-phase regions. The interfering waves emanating from a stationary-phase location have a common ray path from the source to the first receiver. The correlation operator cancels the common path and extracts a signal corresponding to the inter-receiver ray path. In this study, with seismic noise records from two networks at teleseismic distance, we show that noise-derived spurious seismic signals without correspondence in real seismograms can arise from the interference between waves without a common ray path or common slowness. These noise-derived signals cannot be explained by traditional stationary-phase arguments. Numerical experiments reproduce the observed spurious signals. These signals still emerge for uniformly distributed noise sources, and thus are not caused by localized sources. We interpret the presence of the spurious signals with a less restrictive condition of quasi-stationary phase: providing the time delays between interfering waves from spatially distributed noise sources are close enough, the stack of correlation functions over the distributed sources can still be constructive as an effect of finite frequencies, and thereby noise-derived signals emerge from the source averaging.
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Boudjada, M. Y., K. Schwingenschuh, H. K. Biernat, J. J. Berthelier, J. Blecki, M. Parrot, M. Stachel, Ö. Aydogar, G. Stangl i J. Weingrill. "Similar behaviors of natural ELF/VLF ionospheric emissions and transmitter signals over seismic Adriatic regions". Natural Hazards and Earth System Sciences 8, nr 6 (24.11.2008): 1229–36. http://dx.doi.org/10.5194/nhess-8-1229-2008.
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Abstract. We report on the analysis of ELF/VLF emissions observed by the Instrument Champ Electrique (ICE) experiment onboard the DEMETER micro-satellite. We consider principally selected seismic events reported by Molchanov et al. (2006). These authors studied the VLF signals radiated by ground transmitters and received on board the DEMETER micro-satellite. They revealed a drop of the signals (scattering spot) connected with the occurrence of large earthquakes. In our investigations, we proceed to a spectral analysis of ICE observations with the aim to find if the natural ionospheric VLF/ELF emissions show, or not, a similar ''drop'' in the intensity as it is the case of the VLF transmitter signal. We combine our results with those of Molchanov et al. (2006), and we discuss the origin of such interesting ionospheric features in the frame of the investigation of the pre-seismic electromagnetic emissions. We show that the geomagnetic activity is a key parameter which could disturb the natural VLF ionospheric emissions, and also the transmitter signal. We find that it is not possible to conclude the presence, or not, of a preseismic effect when the Kp-index is higher than one.
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Cordery, Simon. "An effective data processing workflow for broadband single-sensor single-source land seismic data". Leading Edge 39, nr 6 (czerwiec 2020): 401–10. http://dx.doi.org/10.1190/tle39060401.1.
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Examples of raw and processed broadband single-sensor single-source land seismic data acquired in the Middle East region have been found to be significantly noisy, and very low-frequency signal has been either missing or unrecoverable. In response, an effective and pragmatic processing workflow has been developed that substantially improves the quality of the final processed data, to the extent where we can say that original survey objectives can be met. The new workflow includes early deterministic deconvolution for a number of filtering effects in the recorded signal wavelet, with the aim of flattening the signal wavelet amplitude spectrum over the vibroseis sweep frequencies and zeroing the wavelet phase. This includes the key innovative step of converting the recorded particle motion to that of the vibroseis far-field signal, those respectively being particle acceleration and particle displacement. This significantly boosts low-frequency amplitudes relative to higher frequencies such that it becomes possible to deterministically compensate for earth's absorption using a large gain limit with less concern for overamplifying high-frequency noise. An application of a source designature compensates for the nonflat design of the pilot sweep, further increasing signal amplitudes over the low-frequency ramp-up portion of the sweep. With the flattened signal spectrum, it is possible to better assess trace noise characteristics across the full bandwidth and perform better QC for its removal. Subsequent statistical deconvolution becomes more of a correction for residual effects on the signal wavelet, and the use of trace supergrouping further mitigates the effect of noise on statistical deconvolution and other data-adaptive processes.
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Beresnev, Igor A., i Kuo-Liang Wen. "The possiblity of observing nonlinear path effect in earthquake-induced seismic wave propagation". Bulletin of the Seismological Society of America 86, nr 4 (1.08.1996): 1028–41. http://dx.doi.org/10.1785/bssa0860041028.
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Abstract Observations of the dependence of elastic-wave velocities on stress in the lithosphere, ultrasonic modeling, and field experiments using controllable sources reveal that significant nonlinear elastic effects may occur in seismic wave propagation. Theoretical modeling involving nonlinear wave equation shows that the most pronounced and practically observable implication of the nonlinear elasticity in broadband-signal propagation is the gradual enrichment of the spectra in high-frequency components. We check the significance of nonlinear path effects using the strong ground motion data from two accelerograph arrays in Taiwan. The data cover the motions with peak ground accelerations from 1 to 161 Gal (cm/sec2) and peak surface strains from 10−4 to 10−7. The differences between the average spectra of seismic waves recorded by groups of stations separated by distances of 20 to 40 km are examined to identify the possible nonlinear path effect. Mixed results have been obtained. In the SMART2 array, the increase in high-frequency energy is detected in compliance with the theory, which corroborates elastic nonlinearity. On the other hand, in the NCCU array, no symptoms of nonlinear wave propagation are found. Poor signal-to-noise conditions and restrictions imposed by the frequency band of standard instrumentation might be accountable for the negative result.
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Marchetti, Emanuele, Alec van Herwijnen, Marc Christen, Maria Cristina Silengo i Giulia Barfucci. "Seismo-acoustic energy partitioning of a powder snow avalanche". Earth Surface Dynamics 8, nr 2 (2.06.2020): 399–411. http://dx.doi.org/10.5194/esurf-8-399-2020.
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Abstract. While flowing downhill, a snow avalanche radiates seismic waves in the ground and infrasonic waves in the atmosphere. Seismic energy is radiated by the dense basal layer flowing above the ground, while infrasound energy is likely radiated by the powder front. However, the mutual energy partitioning is not fully understood. We present infrasonic and seismic array data of a powder snow avalanche, which was released on 5 February 2016, in the Dischma valley above Davos, Switzerland. A five-element infrasound array, sensitive above 0.1 Hz, and a seven-element seismic array, sensitive above 4.5 Hz, were deployed at a short distance (<500 m) from each other and close (<1500 m) to the avalanche path. The avalanche dynamics were modelled by using RAMMS (rapid mass movement simulation) and characterized in terms of front velocity and flow height. The use of arrays rather than single sensors allowed us to increase the signal-to-noise ratio and to identify the event in terms of back-azimuth angle and apparent velocity of the recorded wave fields. Wave parameters, derived from array processing, were used to identify the avalanche path and highlight the areas, along the path, where seismic and infrasound energy radiation occurred. The analysis showed that seismic energy is radiated all along the avalanche path, from the initiation to the deposition area, while infrasound is radiated only from a limited sector, where the flow is accelerated and the powder cloud develops. The recorded seismic signal is characterized by scattered back-azimuth angle, suggesting that seismic energy is likely radiated by multiple sources acting at once. On the contrary, the infrasound signal is characterized by a clear variation of back-azimuth angle and apparent velocity. This indicates that infrasound energy radiation is dominated by a moving point source, likely consistent with the powder cloud. Thanks to such clear wave parameters, infrasound is revealed to be particularly efficient for avalanche detection and path identification. While the infrasound apparent velocity decreases as the flow moves downhill, the seismic apparent velocity is quite scattered but decreases to sound velocity during the phase of maximum infrasound radiation. This indicates an efficient process of infrasound to seismic energy transition, which, in our case, increases the recorded seismic amplitude by ∼20 %, at least in our frequency band of analysis. Such an effect can be accounted for when the avalanche magnitude is estimated from seismic amplitude. Presented results clearly indicate how the process of seismo-acoustic energy radiation by a powder avalanche is very complex and likely controlled by the powder cloud formation and dynamics, and the process is hence affected by the path geometry and snow characteristics.
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Kværna, Tormod, i Frode Ringdal. "Seismic threshold monitoring for continuous assessment of global detection capability". Bulletin of the Seismological Society of America 89, nr 4 (1.08.1999): 946–59. http://dx.doi.org/10.1785/bssa0890040946.
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Abstract Continuous seismic threshold monitoring is a technique that has been developed over the past several years to assess the upper magnitude limit of possible seismic events that might have occurred in a geographical target area. The method provides continuous time monitoring at a given confidence level. In this article we expand upon previous work to apply the method to a global network of seismic stations and give examples of applications from a prototype system that will be installed at the International Data Center for monitoring the Comprehensive Nuclear Test Ban Treaty. Using a global grid of 2562 geographical aiming points, we computed site-specific threshold traces for each grid point and applied spatial interpolation to obtain full global coverage. For each grid point, the procedure is in principle to “focus” the network by tuning the frequency filters and array beams using available information on signal and noise characteristics at each station-site combination. Standard global P-phase attenuation relationships and travel-time tables (IASP91) are used in this initial implementation, but the system lends itself easily to applying station-site-specific corrections (magnitudes, travel times, etc.) to each seismic phase. We give examples of two main types of applications based on data from a worldwide seismic network: (a) an estimated continuous global threshold level and (b) an estimated continuous global detection capability. The first application provides a continuous view of the global seismic “background field” as calculated from the station data, with the purpose of assessing the upper magnitude limit of any seismic event that might have occurred anywhere on Earth. The second application introduces detection thresholds for each station and provides a simplified estimate, continuously in time, of the n-station detection capability of the network. The latter approach naturally produces higher threshold values, with the difference typically being 0.5-1 magnitude unit. We show that both these approaches are useful especially during large earthquakes, where conventional capability maps based on statistical noise and signal models cannot be applied. In order to illustrate the usefulness of combining global monitoring with site-specific monitoring for areas of special interest, we consider a large earthquake aftershock sequence in Kamchatka and its effect on the threshold trace in a very different region (the Novaya Zemlya nuclear test site). We demonstrate that the effects of the aftershock signals on the thresholds calculated for Novaya Zemlya are modest, partly because of the emphasis on high-frequency signals. This indicates that threshold monitoring could provide significantly improved seismic monitoring during aftershock sequences compared with conventional methods, for which the large number of detected phases tends to saturate the phase association process.
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Shatskaya, A. A., M. M. Nemirovich-Danchenko i D. A. Terre. "Modeling of inclined fracture network and calculation of fracture effect on seismic signal spectrum". IOP Conference Series: Earth and Environmental Science 21 (28.08.2014): 012016. http://dx.doi.org/10.1088/1755-1315/21/1/012016.
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Cao, Guobin, Guangde Zhang, Huaibang Zhang, Shengqiang Mu, Guoxu Shu, Mengcheng Shu i Shoudong He. "Research on Noise Suppression Technology of "Black Triangle" of Vibroseis Seismic Data". Highlights in Science, Engineering and Technology 9 (30.09.2022): 8–13. http://dx.doi.org/10.54097/hset.v9i.1708.
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The "black triangle" noise, harmonic interference, and adjacent gun interference in the seismic data collected by the controllable vibrator seriously affect the signal-to-noise ratio of the seismic data. With the emergence of high-efficiency acquisition technology, the "black triangle" noise the impact is getting bigger and bigger. At present, the geological tasks are often accomplished through higher-level seismic data acquisition and indoor fine processing. In order to suppress the "black triangle" noise of controllable seismic data, the effective suppression of the "black triangle" noise has been achieved through the research of high-resolution time-frequency analysis, "black triangle" noise feature extraction, and Wiener filtering. The "black triangle" noise suppression processing of the actual controllable seismic data in the Shun 8 well area of the Tarim Basin has achieved good results. It is of great significance for optimizing the processing effect of the seismic data collected by the controllable seismic source and popularizing the scope of application of the controllable seismic source.
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Shih, Pei-Ju Rita, i Marcel Frehner. "Laboratory evidence for Krauklis-wave resonance in fractures and implications for seismic coda wave analysis". GEOPHYSICS 81, nr 6 (listopad 2016): T285—T293. http://dx.doi.org/10.1190/geo2016-0067.1.
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Krauklis waves are of major interest because they can lead to resonance effects in fluid-filled fractures. This resonance is marked by seismic signals with a dominant signature frequency, which may reveal fracture-related rock properties. In our laboratory study, we used homogeneous Plexiglas samples containing a single well-defined (i.e., manufactured) fracture. We recorded the signals obtained from propagating ultrasonic P- and S-waves (source frequency: 0.6, 1, and 2.25 MHz) along a sample without a fracture and samples with a fracture with different inclination angles of 30°, 45°, and 60° with respect to the short axis. The experimental results obtained from an incident S-wave confirmed that the presence of the fracture led to resonance effects at frequencies lower than the dominant source frequency, which slowly decayed over time in the recorded seismic coda after the first arrival. The resonance frequency was independent of the fracture orientation and the source frequency. We have interpreted this narrow-banded coda signal as a resonance in the fracture, and the frequency at which this occurred was an intrinsic property of the fracture size and elastic properties. To verify our laboratory results, we used an analytical solution, which provided a relationship between the fracture width, fracture length, resonance frequency, and temporal quality factor (i.e., exponential decay over time). The temporal quality factor obtained from our laboratory data agreed very well with the analytical solution. Hence, we concluded that the observed signature frequency (approximately 0.1 MHz) in the seismic coda was indeed a resonance effect. Finally, we have developed possible applications on the reservoir scale to infer fracture-related properties based on seismic coda analysis.
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Libak, Audun, Behzad Alaei i Anita Torabi. "Fault visualization and identification in fault seismic attribute volumes: Implications for fault geometric characterization". Interpretation 5, nr 2 (31.05.2017): B1—B16. http://dx.doi.org/10.1190/int-2016-0152.1.
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Fault seismic attribute volumes (such as volumetric coherence and curvature) represent an efficient and objective way to visualize and identify faults in seismic cubes. Fault geometric attributes such as length, height, and fault segmentation can be extracted from such fault seismic attribute volumes. We evaluate the strengths and pitfalls of using coherence volumes for characterization of fault geometry. The results are obtained using a database from the Barents Sea, which contains 35 3D seismic cubes, together with conceptual synthetic seismic models. A high signal-to-noise ratio is a requirement for the extraction of accurate fault geometric data. Noise attenuation methods improve fault visualization, but our results indicate that the effect of noise attenuation on the extracted fault geometric attributes is only clear in areas of low signal-to-noise ratios. The choice of coherence algorithm is important when extracting fault length data. Semblance-based coherence performs better than gradient structure tensor-based coherence in low-displacement areas near the fault tips, and it produces more accurate fault length data. Faults can appear segmented in coherence volumes if relatively similar reflectors are juxtaposed across a fault. In such areas, it is important that the interpreter does not overlook the fault. The size of the analysis window used in coherence calculations controls the resolution and continuity of the imaged faults. Our results support an optimal temporal window size of one to two times the dominant period of the seismic data (typically 7–17 samples in conventional 4 ms sampled 3D seismic data). Larger temporal window sizes can result in an overestimation of fault height, especially for small faults. A large spatial window can smear out segmentation along the fault and make the fault traces wider. Even though a large spatial window can have some positive effects, we recommend using a relatively small spatial window (five traces) when extracting subtle fault geometric attributes.
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Kuponiyi, Ayodeji Paul, i Honn Kao. "Temporal Variation in Cultural Seismic Noise and Noise Correlation Functions during COVID-19 Lockdown in Canada". Seismological Research Letters 92, nr 5 (28.04.2021): 3024–34. http://dx.doi.org/10.1785/0220200330.
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Abstract The COVID-19 pandemic of 2020 led to a widespread lockdown that restricted human activities, particularly land, air, and maritime traffic. The “quietness” on land and ocean that followed presents an opportunity to measure an unprecedented reduction in human-related seismic activities and study its effect on the short-period range of ambient noise cross-correlation functions (NCFs). We document the variations in seismic power levels and signal quality of short-period NCFs measured by four seismographs located near Canadian cities across the pandemic-defined timeline. Significant drops in seismic power levels are observed at all the locations around mid-March. These drops coincide with lockdown announcements by the various Canadian provinces where the stations are located. Mean seismic power reductions of ∼24% and ∼17% are observed near Montreal and Ottawa, respectively, in eastern Canada. Similar reductions of ∼27% and 17% are recorded in western Canada near Victoria and Sidney, respectively. None of the locations show full recovery in seismic power back to the pre-lockdown levels by the end of June, when the provinces moved into gradual reopening. The overall levels of seismic noise during lockdown are a factor of 5–10 lower at our study locations in western Canada, relative to the east. Signal quality of NCF measured in the secondary microseism frequency band for the station pair in western Canada is maximum before lockdown (late February–early March), minimum during lockdown (mid–late March), and increased to intermediate levels in the reopening phase (late May). A similar pattern is observed for the signal quality of the eastern Canada station pair, except for a jump in levels at similar periods during the lockdown phase. The signal quality of NCF within the secondary microseism band is further shown to be the lowest for the western Canada station pair during the 2020 lockdown phase, when compared with similar time windows in 2018 and 2019.
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Der, Zoltan A., Robert H. Shumway i Michael R. Hirano. "Time domain waveform inversion—A frequency domain view: How well we need to match waveforms?" Bulletin of the Seismological Society of America 81, nr 6 (1.12.1991): 2351–70. http://dx.doi.org/10.1785/bssa0810062351.
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Abstract Waveform modeling in the time domain matches the various frequency components of seismic signals unevenly; the agreement is better at low frequencies and becomes progressively worse towards higher frequencies. The net effect of this kind of time-domain modeling is that the resolution in the spatial details of the source is less than optimal since the high-frequency components of the signal with their short wavelengths to resolve finer details do not fit the data. These problems are demonstrated by numerical simulations and by the reanalysis of some aspects of the El Golfo earthquake in using a new seismic imaging technique based on a generalization of an f-k algorithm. This procedure computes a statistic that can be used to derive confidence limits of the parameters sought in the inversion, thus providing a quantitative measure of the uncertainties in the results.
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Fei, Jianbo, i Yanchun Wang. "Interactive Multimedia Data Coscattering Point Imaging for Low Signal-to-Noise Ratio 3D Seismic Data Processing". Wireless Communications and Mobile Computing 2022 (4.08.2022): 1–12. http://dx.doi.org/10.1155/2022/6904653.
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In this paper, low signal-to-noise ratio 3D seismic data are processed by the method of coscattered point imaging, and the imaging method is analyzed in combination with interactive multimedia for 3D seismic data. The reconstruction is carried out using a convex set projection algorithm based on the curvilinear wave transform. The track set is extracted from the 3D data body and transformed into the common offset distance-center point tract set to achieve the reconstruction of seismic data in the common offset distance track set domain and through comparison. It is concluded that the reconstruction effect is better in the common. The reconstruction results are better in the common offset distance track set domain. To shorten the processing time and obtain better reconstruction results, this paper proposes the idea of direct reconstruction of frequency slices. Experiments on the actual seismic three-component wavefield based on velocity-type and acceleration-type three-component geophones are carried out to reveal the signal characteristics of the actual seismic wavefield under the mining space. Due to the limitation of the construction observation space and the particularity of the actual needs of mine detection, the application of the scattered wave imaging method in the mine must be based on the corresponding detection space and detection purpose. The implementation of this thesis improves the signal-to-noise ratio, resolution, and fidelity of the 3D seismic data of the Shawan Formation, which is more conducive to the search for lithological traps. Combined with the seismic geological data, several traps were finally found and implemented, indicating that the fidelity of the resultant information is good and can meet the needs of interpretation and comprehensive research. The multiwave scattering imaging method in this paper can complete multiwave field imaging of longitudinal, transverse, and slot waves, which has the advantages of data redundancy, high superposition number, and more accurate imaging than conventional reflection wave imaging and provides field application value for ensuring mine safety production.
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Pérez-Campos, Xyoli, Víctor H. Espíndola, Daniel González-Ávila, Betty Zanolli Fabila, Víctor H. Márquez-Ramírez, Raphael S. M. De Plaen, Juan Carlos Montalvo-Arrieta i Luis Quintanar. "The effect of confinement due to COVID-19 on seismic noise in Mexico". Solid Earth 12, nr 6 (16.06.2021): 1411–19. http://dx.doi.org/10.5194/se-12-1411-2021.
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Abstract. The world experienced the beginning of the COVID-19 pandemic by the end of 2019 to the beginning of 2020. Governments implemented strategies to contain it, most based on lockdowns. Mexico was no exception. The lockdown was initiated in March 2020, and with it, a reduction in the seismic noise level was witnessed by the seismic stations of the national and Valley of Mexico networks. Stations located in municipalities with more than 50 000 people usually experience larger seismic noise levels at frequencies between 1 and 5 Hz, associated with human activity. The largest noise levels are recorded in Mexico City, which has the largest population in the country. The largest drop was observed in Hermosillo, Sonora; however, it was also the city with the fastest return to activities, which seems to correlate with a quick increase in confirmed COVID-19 cases. Mexico initiated a traffic-light system to modulate the re-opening of economic activities for each state. Therefore, since 1 June, noise levels have generally reflected the colour of the state traffic light. Furthermore, the reduction in the noise level at seismic stations has allowed identification of smaller earthquakes without signal processing. Also, people in cities have perceived smaller or more distant quakes.
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Potylitsyn, Vadim, Danil Kudinov, Alekseev Dmitry, Ekaterina Kokhonkova, Sergey Kurkov, Ivan Egorov i Aleksandra Pliss. "Study of the Seismoelectric Effect of the Second Kind Using Molecular Sensors". Sensors 21, nr 7 (25.03.2021): 2301. http://dx.doi.org/10.3390/s21072301.
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The article is devoted to the study of the potential possibilities of using molecular-electronic sensors of seismic waves for field work using the seismoelectric method to explore the hydrocarbon deposits. The introduction provides an analytical review of the current state of research based on data from science magazines and patents. It is shown that at present, seismoelectric effects are at the stage of experimental implementation into the practice of field work for oil and gas geophysical prospecting. Further in the article, theoretical estimates and results of mathematical modeling of the manifestation of seismoelectric (SE) phenomena in the regions of hydrocarbon anomalies are presented, numerical estimates of the values of the seismic and secondary electromagnetic fields are given. The analysis of the results (on a tank and real gas condensate field) showed that the use of molecular-electronic geophones, which have a higher sensitivity and operate in a wider frequency range (up to 0.1 Hz), allows one to obtain higher signal-to-noise ratio. Thus, it has been experimentally established that the use of molecular sensors for recording seismic electric effects when searching for deposits is more preferable when carrying out field work.
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Hamarbitan, N. S., i G. F. Margrave. "Spectral analysis of a ghost". GEOPHYSICS 66, nr 4 (lipiec 2001): 1267–73. http://dx.doi.org/10.1190/1.1487074.
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A seismic line was shot such that the source‐ghost effect from two different dynamite source patterns could be compared. Two 15‐shot seismic datasets were created that were identical in all respects except that one used 4 kg of explosives in a single 18‐m hole, while the other used 2 kg of explosives in each of two 9‐m holes. After identical processing, the final stacked sections of the 18‐m and 9‐m datasets are dramatically different in character and temporal resolution. An f‐x spectral analysis of the stacked sections reveals that the 18‐m data shows a loss in power and phase coherence from 45 to 58 Hz, while the 9‐m data shows a similar effect from 65 to 78 Hz. A spectral notch, centered near 55 Hz, due to a source ghost is suggested as the reason for the lower power in the 18‐m dataset. The 9‐m data is consistent with a spectral notch at a higher central frequency near 72 Hz. Above its spectral notch, 18‐m data shows a reemergence of weak signal that persists to near 80 Hz; the 9 m dataset shows little signal above 65 Hz. Examination of raw shot records shows that these effects are very difficult to observe in field records. Without specialized deghosting, the 9‐m dataset shows greater temporal resolution; however, the 18‐m dataset has a broader signal bandwidth and is potentially superior.
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Alzamil, Nour, Weichang Li, Hua‐Wei Zhou i Harold Merry. "Frequency‐dependent signal‐to‐noise ratio effect of distributed acoustic sensing vertical seismic profile acquisition". Geophysical Prospecting 70, nr 2 (29.12.2021): 377–87. http://dx.doi.org/10.1111/1365-2478.13165.
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Li, Guofa, Hao Zheng, Jingjing Wang i Wei Huang. "Inversion-based directional deconvolution to remove the effect of a geophone array on seismic signal". Journal of Applied Geophysics 130 (lipiec 2016): 91–100. http://dx.doi.org/10.1016/j.jappgeo.2016.04.014.
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