Numerical simulation of ground‐penetrating radar data for studying the geometry of fault zone

Abstract

Palaeoseismology studies the footprints of ancient earthquakes to improve the knowledge about the modern seismicity of the territory. A ground-penetrating radar (GPR), among other geophysical methods, is used for quick determination of shallow stratigraphy -displaced, oblique layers within the fault zone. GPR data interpretation from diverse and complex reflection patterns of the fault zone heavily depends on the interpreter's experience. The range of different fault zone parameters in which this method can be successfully applied has not yet been investigated. We used a numerical simulation of GPR data to determine how GPR images the elements of faults (fault plane, hanging wall, footwall) in comparison with other reflections. Furthermore, we studied which parameters have the most significant impact on GPR wave patterns. We performed a series of numerical models of a fault, changing its geometry with increasing complexity from elementary models to realistic ones. The resulting synthetic profiles allowed finding specific GPR signatures from the fault plane, the hanging wall and the footwall. We collected field GPR data from two different fault zones and examined them for verification.

Influence of the rock massif physical properties variability on the localization of its disturbances with GPR

“…New research methods, including computer modeling of induced electromagnetic fields and the generation of synthetic radar grams, provide additional opportunities for analyzing wave patterns and resolving ambiguities in data interpretation [5,9,[11][12]. The use of modeling the electromagnetic field induced by ground penetrating radar sounding made it possible to significantly reduce the uncertainty in the interpretation of the data obtained by understanding the mechanism of formation of the wave characteristics and comparing synthetic data with natural ones.…”

“…The use of the GPR method made it possible not only to identify the locations of faults, but also to determine their thickness and angles of incidence [4]. Much attention is paid to the use of computer modeling of GPR operation in the interpretation of vertical faults in South Korea [5]. Using numerical modeling of the GPR operation, the features of the wave pattern in the fault zone were identified, and the issues of interpreting GPR data based on various models in the fault zone were considered, where it was noted that the identification of such structures is extremely difficult [6].…”

Geophysical investigation of the 2022 Cianjur earthquake: Uncovering a new active fault

“…The fault is located at a depth of 4 m at a track position of 27 m and a depth of 4.2 m at a track position of 32 m. This can be seen because the indication of a fault is characterized by a low dielectric value due to an increase in the air fraction compared to earth material and there is the same lithology but is experiencing damage or deformation [18]. There is a curved line forming a green parabola starting at a depth of 6.6 m at a track position of 12 m which is a change in the propagation of electromagnetic wave signals in the layer near the surface which is expressed in the curvature of the layer boundary [19].…”

Ground-penetrating radar signature of Quaternary faulting: a study from the Mt. Pollino region, southern Apennines, Italy

“…A review of the near-surface GPR faulting studies suggests some reflection characteristics as possible indicators for the detection of subsurface fractures and faults (e.g., Smith and Jol, 1995;Liner and Liner, 1997;Reiss et al, 2003;Gross et al, 2004;McClymont et al, 2008and Bubeck et al, 2015. Among these, sharp lateral reflectivity variations, interruptions of the reflections, and the presence of hyperbolic diffractions are considered convincing evidence, as shown also by numerical simulations (Ercoli et al, 2013a;Bricheva et al, 2021). In addition, we have accounted for additional GPR indicators identified for Quaternary faulting in similar environments (Ercoli et al, 2013a, b;, which are linked to the geometry of stratigraphic deposits across fault zones: (i) reflections of abrupt truncating and offsetting along sub-vertical discontinuities (especially in the case of a normal fault); (ii) reflection packages thickening as they approach the fault strands; (iii) abrupt lateral dip variation of the reflections; (iv) peculiar reflection package geometries, with contorted reflection patterns resembling "colluvial wedges", which McCalpin (2009) defines as deposit due to "subsidence and sedimentation of the hanging wall and erosion of the morphological scarp in the footwall"; (v) localized strong GPR signal attenuation due to the presence of conductive media within the main fault zone.…”