The use of the D+ solution in magnetotelluric interpretation

Abstract

The MT interpretation procedure begins with a set of sounding data in the frequency domain. The overall quality of these data can be variable both as a function of frequency and location. Many simple interpretation procedures, such as the assessment of static distortion, act directly on the sounding data. A number of response characteristics, such as the location (in frequency) and number of turning points, are important to the interpretation. Localised scatter (noise) in the response estimates can produce false gradients which degrade the quality of the inferences made from the data.This study considers how the D+ solution can be used to process the raw sounding data to provide a number of interpretational advantages. Although the D+ solution has strict formal roots in I D inverse theory, it is used here simply to enhance those data attributes, particularly that of physical validity, which lead to a more meaningful assessment of data characteristics. The data considered are 84 broadband array soundings from the Parana basin, Brazil. The advantages provided by the D+ processed data set are demonstrated by using the raw and processed data in two main interpretational procedures. The first procedure concerns the ability of the data to provide quantitative assessments of the influence of static distortion. The second procedure concerns the application of transform methods which attempt to recover a resistivity I depth or reflectivity profile directly from the sounding data.

Exploration and assessment of the geothermal resources in the Hammam Faraun hot spring, Sinai Peninsula, Egypt

“…However, the Occam inversion minimizes the combination of the roughness and data fitting that leads to a simple model containing the essential properties of all possible models fitting the MT data (Constable et al, 1987). We used D + smoothing techniques to smooth the resistivity and phase curves instead of other numerical smoothing techniques; this technique specifically relates the apparent resistivity and phase of the same component through a D + function (Beamish and Travassos, 1992). In essence, this method finds the 1D earth that best fits both parameters.…”

Deep Resistivity Structure of Basalt‐Covered Central Part of Paraná Basin, Brazil, From Joint 3‐D MT and GDS Data Imaging

“…For up to 5 km depth from sea level, model features are consistent with the information from the three wells (E, C, and D) as shown in Figure . Similar agreement was seen between 1‐D MT inversion model and well log data at another location further south by Beamish and Travassos (). This borehole validation of our result at shallow depth, and the demonstrated correspondence of our gross crustal model with seismological crustal layering in Figure a, would suggest that 3‐D MT imaging can provide reliable constraints for understanding the deep crustal and upper mantle structure beneath Paraná basin.…”

Preliminary magnetotelluric results across Dalma Volcanics, Eastern India: Inferences on metallogeny

“…The consistency of acquired MT data has been reconfirmed by the D+ smoothing (Fig. 2) (Beamish and Travassos, 1992). The D+ algorithm relates apparent resistivity and phase of the same component (xy or yx) through a D+ function.…”

“…The apparent resistivity and phase error are 10% for estimating the D + smoothing MT curves. It is valid for most 2D data and for some 3D cases and provides a much improved, homogenous and consistent data set for most of the cases (Beamish and Travassos, 1992).…”