# Seismic Exploration Methods for Structural Studies and for Active Fault Characterization: A Review
## 1 Introduction  
Seismic exploration methods have long been used in geophysical studies to investigate the subsurface structure and the properties of geological formations. Seismic methods provide key subsurface information for structural geologists and have become highly effective in imaging even complex geological settings. Among seismic methods, reflection seismology, that has revolutionized our understanding of the earth's subsurface, is certainly the main tool of seismic imaging and the primary technique used in energy exploration: it was initially developed in the 1920s for the petroleum industry. Over the years, this method has undergone continuous improvements in data acquisition, signal enhancement, and geological interpretation, resulting in significant advances [1]. As documented by [PERSON] and [PERSON] [2], originally, the reflection technique involved detonating a dynamite charge in the ground and recording the seismic waves reflected from subsurface interfaces using a linear array of geophones, consisting of several dozen units. The seismograms were initially stored on photographic paper. In regions where conditions were favorable, geophysicists could track the same reflected phase over an extended distance beyond what the receiver spread covered for a single record. In such instances, they aligned the records adjacent to each other to analyze the subsurface. However, in numerous regions, particularly those underwater, the noise generated by the source (e.g., reverberations and multiple reflections) dominated the primary reflections, making visual identification difficult. To address the challenge of removing source-generated noise, the major oil and geophysical companies of the time provided sponsorship to the MIT Geophysical Analysis Group for the development of digital-processing techniques [3; 4; 5; 6]. This was the first-ever effort to convert an industry from analog to digital, and exploration geophysics was at the forefront of this transformation. Geophysicists coined the term\"digital revolution\" to describe this shift [6]. Such was the rapid pace of advancements that, by the close of the 1950s, the seismic reflection method had become the oil industry's primary geophysical methodology, providing detailed images of sedimentary basins and faults. The development of three-dimensional (3D) methods in the late 1970s began to resolve the interpretation ambiguities inherent in interpolating between seismic profiles and provided significant noise reduction [2]. Early 3D surveys revealed so much structural and stratigraphic detail that the method started growing very rapidly. Among all geophysical methods available today, reflection seismology certainly provides the highest resolution, making it a valuable tool for a wide range of applications. However, processing seismic reflection data is a computationally intensive process. The high cost associated with acquiring and processing seismic reflection data, especially for 3D imaging, has traditionally limited its use to the oil industry. Nevertheless, advances in microelectronics in the early 1980s enabled the development of cost-effective seismographs and microcomputers, opening new possibilities for reflection seismology in a range of fields, from deep crustal exploration to civil engineering site investigations [7]. As a result, this technique is now used successfully in various fields, including deep crustal exploration, groundwater resource assessment, and civil engineering site investigations [8]. The interpretation of seismic reflection data is a fundamental step to infer the subsurface characteristics of sedimentary basins in terms of stratigraphy and structures [9; 10; 11]. Three-dimensional (3D) seismic data provide a means for structural geologists to examine structural styles across the studied volume and to map structures in detail, facilitating the development of hypotheses about the factors controlling them [12].