GNGTS 2018 - 37° Convegno Nazionale

590 GNGTS 2018 S essione 3.1 The present study represents a Peace River Project integration involving an area of about 19 km by 11 km (Fig. 1, Area 1) within Peace River Project. This study has been developed to obtain different types of geophysical models testing several inversion strategies. The key contribution expected from different inversion models is therefore to better resolve layers boundaries, lateral and vertical extent of resistivity features. How these final models could change the subsequent geological interpretation has been thoroughly investigated. In order to assess the potential and limits of different types of geophysical inversions 4 synthetic models were performed. These models have been carried out considering the general geological structures observed in British Columbia (Jørgensen et al. , 2016). From the SkyTEM data acquired in the Peace Region, many cross sections have been produced. 30% of these cross sections, located in the Area1 (Fig. 1, left panel) has been inverted applying settings analyzed for synthetic models. We have selected one cross-section, located in Figure 1, for presentation. We show different sharp inversions in order to study how working on different sharp settings implies the models complexity evolution. The project goal is to better outline sedimentary units specifically within Quaternary deposits. These features could potentially host groundwater resources. We present a subsequent rough geological interpretation of the cross-section A (Fig. 1) based on sharp Laterally Constrained Inversion (LCI) sharp inversion. In order to improve the final result, the quasi-3D Spatially Constrained Inversion (SCI) have been performed. The strategy. After studying the general geological structures of British Columbia, 4 different synthetic models have been built, using similar geological geometries. For each model 3 different inversion strategies have been carried out: 1) Smooth; 2) Few Layers; 3) Sharp (Vignoli et al. , 2017). The first type of inversion discretizes the half-space with numerous layers having thickness logarithmically increasing with depth. The second type reconstructs petrophysical interfaces using a discretization with a limited number of layers. A relatively new type of inversion is the sharp method that promotes the reconstruction of blocky solutions using a parameterization characterized by many layers (as in the more traditional smooth inversion) (Zhdanov, 2002). Synthetic results. The inversion results of synthetic models have generated an ensemble of hundreds of resistivity models that adequately fit the data given the assigned noise levels. The details of one synthetic model are found in Fig. 2 (left panels). The smooth inversion was parameterized with 30 layers and a homogeneous half-space of 100 Ωm as a starting model. This approach (Fig. 2, model b) is able to resolve qualitatively the bottom of glaciofluvial and glaciolacustrine deposits and the bottom of the Buckinghorse Formation as well, up to a Fig. 2 - Left panels: Synthetic modelling results. a) the true model; b) smooth result; c) few layers result; d) sharp result (below each inversion, also the associated data residuals are presented: solid blue and red line is the data misfit respectively for HM and LM); e) legend of the electrical layers. Right panels: Sharp models with gradually changing complexity. Tight to loose settings from profile 1 to 6. Models are shaded with DOI and shown associated data misfit (red line).