SEGJ Technical Conference

Consideration on the application of continuous wavelet transform to time series analysis for magnetotelluric data

Abstract It is important to calculate spectral data in the frequency domain to evaluate the responses of the natural electromagnetic field observed in the magnetotelluric (MT) survey. In transforming time-series data, however, there might be difference between the calculated signal values and the true ones due to the analytical errors. This paper suggests the way to analyze the ULF electromagnetic data by using the continuous wavelet transform (CWT), which can strike the proper balance between analytical accuracy of the time and frequency domain. In comparison with the result of Fourier transform accompanied with gradual decimation of time-series data, CWT is more effective to gain high-quality MT responses that are close to the true signal values. Moreover, this study indicates that the complex Morlet function with its wavelet parameter k set to be greater than or equal to 6 and smaller than 10 may be easy to restrain the analytical errors in the time and frequency domain throughout the range of ULF.