Data Processing Procedures for Minami-Kayabe Magnetotelluric Soundings

Abstract

MT and AMT surveys were conducted in the Minami-Kayabe area, southern Hokkaido, over a period of about two months in the fall of 1988. In this survey, 161 sites were arranged in a square lattice shape. FFT techniques were used in the initial data processing in 1998. Here we describe improved data processing using the cascade decimation technique. Data were processed efficiently by constructing a system using coherency and remote-reference. More than 10 sets of threshold values for the coherencies of (Ex, Hy) and (Ey, Hx) were then determined. Power spectra were sorted by these threshold values and then stacked. Satisfactory results were obtained for the frequency range from 3.4 Hz to 250 Hz. At frequencies below 3.4 Hz, however, the result of cascade decimation was not satisfactory because a sufficient number of stacks could not be obtained due to high local noise and limited measurement time.

Processing of noisy magnetotelluric time series from Koyna-Warna seismic region, India: a systematic approach

“…With the growth of the modern civilization it becomes difficult to get a site which is not contaminated by cultural noise. Many researchers [Kao and Rankin 1977, Gamble et al 1979, Fontes et al 1988, Egbert 1997, Yamane and Takasugi 1997, Nagata et al 2012 have addressed this issue by developing innovative processing techniques to suppress the cultural noise. In the present study area, many of the MT stations were close to the high tension distribution power lines from Koyna and Warna hydroelectric power projects along with wind mills and were affected by other cultural noise such as wind , vehicle etc.…”