Multiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocks

Abstract

Abstract. The multiscale analysis of lineament patterns helps define the geometric scaling laws and the relationships between outcrop- and regional-scale structures in a fracture network. Here, we present a novel analytical and statistical workflow to analyze the geometrical and spatial organization properties of the Rolvsnes granodiorite lineament (fracture) network in the crystalline basement of southwestern Norway (Bømlo Island). The network shows a scale-invariant spatial distribution described by a fractal dimension D≈1.51, with lineament lengths distributed following a general scaling power law (exponent α=1.88). However, orientation-dependent analyses show that the identified sets vary their relative abundance and spatial organization and occupancy with scale, defining a hierarchical network. Lineament length, density, and intensity distributions of each set follow power-law scaling laws characterized by their own exponents. Thus, our multiscale, orientation-dependent statistical approach can aid in the identification of the hierarchical structure of the fracture network, quantifying the spatial heterogeneity of lineament sets and their related regional- vs. local-scale relevance. These results, integrated with field petrophysical analyses of fracture lineaments, can effectively improve the detail and accuracy of permeability prediction of heterogeneously fractured media. Our results also show how the geological and geometrical properties of the fracture network and analytical biases affect the results of multiscale analyses and how they must be critically assessed before extrapolating the conclusions to any other similar case study of fractured crystalline basement blocks.

Detailed investigation of multi-scale fracture networks in glacially abraded crystalline bedrock at Åland Islands, Finland

“…The possibility of using normalisation methods other than area-normalisation should also be simultaneously investigated (Bonnet et al, 2001) and the use of the probability density function in place of the complementary cumulative number might have more merit when analysing multi-scale length data (Bour et al, 2002). The occurrence of partly scale-independent azimuth sets (Figure 5; Table 4) within our data might be indicators of hierarchical organisation of the fracture network where the different sets cause differences in the scaling laws between scales of observation, similar to a study by Ceccato et al (2022) where this option was discussed for their multi-scale fracture and lineament dataset with scale-variant azimuth sets.…”

“…Using multi-scale azimuth sets determined from a visual inspection of rose plots of the scales of observation, we could further investigate the possibility of fitting multi-scale power-law trends to multi-scale length data that is categorised by azimuth set. The approach has the potential to reveal differences between length distributions of fractures and lineaments in different azimuths (E.g., Skyttä et al, 2021;Ceccato et al, 2022). Of particular interest is whether the effect of glacial erosion has caused differences in the length distributions of features in different azimuths.…”

Aerogeophysics and light detecting and ranging (LiDAR)-based lineament interpretation of Finland at the scale of 1:500 000

“…Furthermore, when large-scale airborne geophysical measurement survey campaigns were initiated approximately fifty years ago, the resulting datasets could be used to complement the interpretation previously based 25 almost solely on topography. Today, lineament interpretations are primarily based on photographic, topographical and geophysical source raster datasets (Tirén, 1991;Middleton et al, 2015;Yeomans et al, 2019;Ahmadi and Pekkan, 2021;Ceccato et al, 2022). These are, for example, aerial photos, elevation data, multi-spectral sensing, laser, radar and airborne geophysical data comprising magnetic and electromagnetic radiation measurements, and gravimetric measurements.…”

“…During recent years, a higher demand for groundwater, geothermal solutions, and increased use of underground rock 40 volumes in construction projects has led to higher requirements for the understanding of subsurface brittle bedrock structures, e.g., fractures and faults (Ledésert et al, 1993;Berkowitz, 2002;Geiger and Emmanuel, 2010;Ceccato et al, 2022). Consequently, this has resulted in the need for a new and improved lineament interpretation for identifying brittle structures reaching the surface.…”

Introduction: Faults and fractures in rocks: mechanics, occurrence, dating, stress history and fluid flow

“…Bistacchi et al 2015;Bisdom et al 2017;Corradetti et al 2018), and multiscalar fracture network attributes retrieved from the analysis of 2D satellite and aerial images (e.g. Palamakumbura et al 2020;Ceccato et al 2022) are nowadays routinely used to generate DFN (e.g. Healy et al 2017).…”