Robust processing of magnetotelluric data in the AMT dead band using the continuous wavelet transform

被引:66
作者
Garcia, Xavier [1 ]
Jones, Alan G. [1 ]
机构
[1] Dublin Inst Adv Studies, Dublin 4, Ireland
关键词
geomagnetism; geophysical techniques; ionosphere; wavelet transforms;
D O I
10.1190/1.2987375
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The energy sources for magnetotellurics (MT) at frequencies above 8 Hz are electromagnetic waves generated by distant lightning storms propagating globally within the earth-ionosphere waveguide. The nature of the sources and properties of this waveguide display diurnal and seasonal variations that can cause significant signal amplitude attenuation, especially at 1-5 kHz frequencies - the so-called audiomagnetotelluric (AMT) dead band. This lack of energy results in unreliable MT response estimates; and, given that in crystalline environments ore bodies located at some 500-1000-m depth are sensed initially by AMT data within the dead band, this leads to poor inherent geometric resolution of target structures. We propose a new time-series processing technique that uses localization properties of the wavelet transform to select the most energetic events. Subsequently, two coherence thresholds and a series of robust weights are implemented to obtain the most reliable MT response estimates. Finally, errors are estimated using a nonparametric jackknife algorithm. We applied this algorithm to AMT data collected in northern Canada. These data were processed previously using traditional robust algorithms and using a telluric-telluric magnetotelluric (TTMT) technique. The results show a significant improvement in estimates for the AMT dead band and permit their quantitative interpretation.
引用
收藏
页码:F223 / F234
页数:12
相关论文
共 51 条
[51]   Enhancement of signal-to-noise ratio in natural-source transient magnetotelluric data with wavelet transform [J].
Zhang, YC ;
Paulson, KV .
PURE AND APPLIED GEOPHYSICS, 1997, 149 (02) :405-419