Correction of shallow-water electromagnetic data for noise induced by instrument motion
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An unexpected noise source was found in magnetic and sometimes electric field data recorded on the bottom of lakes in the Archean Slave craton (NW Canada) during warm seasons. The noise is due to instrument motion and in some instances direct induction by wind-driven surface gravity waves when the lakes are not ice covered. The noise can be reduced or eliminated by pre-filtering the data with an adaptive correlation noise cancelling filter using instrument tilt records, prior to estimation of magnetotelluric (MT) response functions. Similar effects are to be expected in other shallow water environments, and the adaptive correlation canceller is a suitable method to pre-process MT data to reduce motional noise in the magnetic field. This underscores the importance of ancillary tilt measurements in shallow water MT surveys. In coastal or lake bottom surveys, special efforts to reduce hydrodynamic effects on the instrument should also be pursued.
Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Society of Exploration Geophysicists for personal use, not for redistribution. The definitive version was published in Geophysics 70 (2005): G127–G133, doi:10.1190/1.2080748.