Seismic Refraction Tomography (SRT); Multi-Channel Surface Wave Analysis (MASW); Refraction Microtremor (REMI)

Seismic Refraction Tomography (SRT)

Multi-Channel Surface Wave Analysis (MASW)

Refraction Microtremor (ReMi)

The seismic method is based on the principle of recording—as a function of time—the reflections and refractions of acoustic waves (generated by a source and transmitted into the subsurface) that occur at the interfaces between various geological formations. By analyzing the resulting variations in seismic velocities, it becomes possible to determine or image the velocity distribution within the medium. Acoustic waves—produced by any energy source (such as an impact, weight drop, explosion, or vibration)—propagate through the subsurface in various phases. Consequently, the seismic method enables the characterization of a wide range of environments, from layers near the Earth’s surface to deep-seated geological structures. Since the method aims to determine seismic velocities, it allows for the detection of both lateral and vertical discontinuities. When applied tomographically, it can reveal a detailed model of the subsurface. A significant advantage of this method is its applicability in both terrestrial and marine environments. Its utility and widespread use, particularly in hydrocarbon exploration, have facilitated the rapid development of the technique.

Seismic refraction tomography (SRT) is an investigation technique that has come into widespread use over the last few decades for addressing geological and geotechnical problems. The method enables the creation of a two-dimensional model of the subsurface based on seismic P-wave velocities.

Multichannel analysis of surface waves (MASW)—a method developed by Park et al. (1999)—is another seismic technique currently used extensively, particularly in geotechnical and microzonation studies. Through MASW surveys, surface waves are recorded to determine the shear-wave velocities (Vs) of subsurface layers; these data are then used to calculate the elastic parameters of the subsurface for geotechnical purposes.

Refraction Microtremor (ReMi) is a significant technique used for the geotechnical characterization of the subsurface by utilizing shear waves. The ReMi method is conducted using the same geophone array employed for seismic refraction (Vp) surveys. The ReMi technique records ambient background noise (microtremors), and the data is subsequently analyzed using methods similar to those applied in MASW.