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Seismic signal de noising using time–frequency peak fltering based on empirical wavelet transform

Liu Naihao, Yang Yang, Li Zhen, Gao Jinghuai, Jiang Xiudi, Pan Shulin

Acta Geophysica

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2020

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Vol. 68, no. 2

425--434

EN

Seismic noise suppression plays an important role in seismic data processing and interpretation. The time–frequency peak fltering (TFPF) is a classical method for seismic noise attenuation defned in the time–frequency domain. Nevertheless, we obtain serious attenuation for the seismic signal amplitude when choosing a wide window of TFPF. It is an unsolved issue for TFPF to select a suitable window width for attenuating seismic noise efectively and preserving valid signal amplitude efectively. To overcome the disadvantage of TFPF, we introduce the empirical wavelet transform (EWT) to improve the fltered results produced by TFPF. We name the proposed seismic de-noising workfow as the TFPF based on EWT (TFPFEWT). We frst introduce EWT to decompose a non-stationary seismic trace into a couple of intrinsic mode functions (IMFs) with diferent dominant frequencies. Then, we apply TFPF to the chosen IMFs for noise attenuation, which are selected by using a defned reference formula. At last, we add the fltered IMFs and the unprocessed ones to obtain the fltered seismic signal. Synthetic data and 3D feld data examples prove the validity and efectiveness of the TFPF-EWT for both attenuating random noise and preserving valid seismic amplitude.

2

Identyfikacja wybranych parametrów źródeł wahań napięcia z wykorzystaniem ulepszonej empirycznej transformaty falkowej

Kuwałek Piotr

Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej

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2019

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Nr 66

33--36

PL

W artykule przedstawiono wyniki wstępnych badań dotyczących nowatorskiej metody pozyskiwania informacji o wybranych parametrach źródeł wahań napięcia z wykorzystaniem ulepszonej empirycznej transformaty falkowej. Dla przeprowadzonych badań założono, że oddziaływanie źródeł wahań napięcia można identyfikować jako modulację amplitudową sygnału napięcia. Uwzględniając to założenie, daną wejściową dla ulepszonej empirycznej transformaty falkowej była obwiednia sygnału napięciowego, wyznaczona z zastosowaniem transformaty Hilberta. Poprawność działania metody zweryfikowano w oparciu o wykonane symulacje numeryczne dla sygnału deterministycznego z wykorzystaniem programu MATLAB.

EN

The article presents the results of preliminary research on an innovative method of analysis of voltage fluctuation sources with the use of an enhanced empirical wavelet transform. For the tests, it was assumed that the influence of voltage fluctuation sources can be identified as the amplitude modulation of the voltage signal. Given this assumption, the input data for the enhanced empirical wavelet transform was a voltage signal envelope derived from the use of the Hilbert transform. The correctness of the method was verified on the basis of performed simulation tests for a deterministic signal using the MATLAB program.

3

An empirical wavelet transform based approach for multivariate data processing application to cardiovascular physiological signals

Singh O., Sunkaria R. K.

Bio-Algorithms and Med-Systems

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2018

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Vol. 14, no. 4

art. no. 20180030

EN

Background: This article proposes an extension of empirical wavelet transform (EWT) algorithm for multivariate signals specifically applied to cardiovascular physiological signals. Materials and methods: EWT is a newly proposed algorithm for extracting the modes in a signal and is based on the design of an adaptive wavelet filter bank. The proposed algorithm finds an optimum signal in the multivariate data set based on mode estimation strategy and then its corresponding spectra is segmented and utilized for extracting the modes across all the channels of the data set. Results: The proposed algorithm is able to find the common oscillatory modes within the multivariate data and can be applied for multichannel heterogeneous data analysis having unequal number of samples in different channels. The proposed algorithm was tested on different synthetic multivariate data and a real physiological trivariate data series of electrocardiogram, respiration, and blood pressure to justify its validation. Conclusions: In this article, the EWT is extended for multivariate signals and it was demonstrated that the component-wise processing of multivariate data leads to the alignment of common oscillating modes across the components.

4

Comparison of gravimetric excitation functions derived from equivalent water thickness, based on ﬁltered GRACE data sets

Nagalski T.

Reports on Geodesy

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2012

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z. 1/92

201--211

EN

We can estimate the Equivalent Water Thickness (EWT) from results of observations of the Earth gravity field from the Gravity Recovery and Climate Experiment (GRACE) gravimetric mission. However the maps of EWT obtained from raw gravimetric data contain typical stripes. To eliminate these disturbances we need to filter the raw data to improve the signal to noise ratio. The distribution of EWT obtained from the GRACE mission can be used to determine the gravimetric excitation function. In this paper it was investigated the filter influence on the EWT distribution and the amplitude of the gravimetric excitation functions. We use the EWT data sets derived from Stokes coefficients made accessible and filtered by the International Centre for Global Earth Models (ICGEM). The data sets available on ICGEM website were imported from three research centers GFZ, JPL and CSR. The anisotropic filter, with three degrees of smoothing DDK3, DDK2 and DDK1 is described in (Kusche et al., 2009).

5

Cz. II. Recykling a fundusze z UE

Gola-Sienkiewicz R.

Recykling

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2009

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nr 2

32-33

PL

Dofinansowanie przyznane Polsce przez Unię Europejską wspomoże rodzimą gospodarkę. Kolejną grupę programów, z których może skorzystać branża zagospodarowywania odpadów, stanowi Europejska Współpraca Terytorialna. Będzie ona realizowana w latach 2007-2013.