Many efforts have been made to face magnetotelluric (MT) static shift. Impedance tensor analyses give insight to the presence of this feature and allow the determination of some parameters described by the MT distortion matrix. A quantitative determination of the full distortion matrix is, however, still difficult and needs additional measurements. In addition to MT, other electric and electromagnetic methods also are effected by static shift. Using direct current resistivity techniques, e.g., we can determine the static-shift factors in a simpler way because the sources can be controlled. Generally, because the distortion matrix has four entries, four additional quantities have to be determined to describe the static shift completely. They can be achieved, e.g., through measuring two orthogonal electric field components for two orthogonal source configurations. The source electrode spacing, however, has to be sufficiently large to resemble horizontal currents and match the MT plane-wave analog. The procedure at hand extracts the static-shift factors from multielectrode measurements after this condition is met. For the sake of simplicity and demonstration purposes, only inline measurements orthogonal to the strike direction of a 2D model are considered so that the vectorial problem reduces to a scalar one. This procedure is applied to a MT field data set in a regional 2D environment that shows only two additional quantities are necessary to determine the static shift.
A method to determine the magnetotelluric static shift from DC resistivity measurements in practice
TRIPALDI S
;SINISCALCHI, AgataSupervision
;
2010-01-01
Abstract
Many efforts have been made to face magnetotelluric (MT) static shift. Impedance tensor analyses give insight to the presence of this feature and allow the determination of some parameters described by the MT distortion matrix. A quantitative determination of the full distortion matrix is, however, still difficult and needs additional measurements. In addition to MT, other electric and electromagnetic methods also are effected by static shift. Using direct current resistivity techniques, e.g., we can determine the static-shift factors in a simpler way because the sources can be controlled. Generally, because the distortion matrix has four entries, four additional quantities have to be determined to describe the static shift completely. They can be achieved, e.g., through measuring two orthogonal electric field components for two orthogonal source configurations. The source electrode spacing, however, has to be sufficiently large to resemble horizontal currents and match the MT plane-wave analog. The procedure at hand extracts the static-shift factors from multielectrode measurements after this condition is met. For the sake of simplicity and demonstration purposes, only inline measurements orthogonal to the strike direction of a 2D model are considered so that the vectorial problem reduces to a scalar one. This procedure is applied to a MT field data set in a regional 2D environment that shows only two additional quantities are necessary to determine the static shift.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
