Hanieh Mardomi; Mir Sattar Meshinchi Asl; Hamid Reza Siahkoohi
Abstract
Magnetotellurics is an exploration method which is based on measurement of natural electric and magnetic fields of the Earth and is increasingly used in geological applications, petroleum industry, geothermal sources detection and crust and lithosphere studies. In this work, discrete wavelet transform ...
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Magnetotellurics is an exploration method which is based on measurement of natural electric and magnetic fields of the Earth and is increasingly used in geological applications, petroleum industry, geothermal sources detection and crust and lithosphere studies. In this work, discrete wavelet transform of magnetotelluric signals was performed. Discrete wavelet transform decomposes signals into coefficients in multi-scales. Noise and signal portions are separable in multi-scale mode. Therefore, noise can be discarded in each scale; a threshold value is constructed dependent to coefficients of the scale then, the noise coefficients are discarded by thresholding the coefficients with the proper values. Proportional threshold values can be used to remove white and 1/f noise from time series. After that, a new signal is constructed using clean coefficients. This method is widely used in various fields of sciences from image processing to seismic studies. This work tried to show the effectiveness of this technique in decreasing pervasive noise from magnetotelluric signals. The results emphasized the advantageous effect of wavelet techniques in magnetotelluric data noise removing process.
S Shokrzade; B Voosoghi; M Amighpey
Abstract
In this paper, the Bam post-seismic annual deformations in period from 2004 to 2010 have been obtained using synthetic aperture radar interferometry. The time series of deformations have been constructed using Persistent Scatterer Radar Interferometry technique. When displacements rate in the area are ...
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In this paper, the Bam post-seismic annual deformations in period from 2004 to 2010 have been obtained using synthetic aperture radar interferometry. The time series of deformations have been constructed using Persistent Scatterer Radar Interferometry technique. When displacements rate in the area are low and the pixels are with temporal decorrelation, this technique is more effective. The technique also largely reduces the topography residuals and atmospheric delay. Because of the low rates of post-seismic displacements, this technique is very useful for measuring such earth surface displacements. The results illustrate that the maximum amount of uplift and subsidence displacements for Line Of Sight (LOS) direction during 2004 to 2010 after the earthquake are 4.5± 0.5 and -4.3± 0.5 centimeter, respectively. Comparison of displacement fields demonstrates that the displacements reduction rates are approaching to the co-seismic phase. In addition, the results of post-seismic modeling proves that displacements field, follows exponential or logarithmic function.
