## 1 Introduction  
The current main objective of seismic site classification is to assign design response spectra or to define parameters for its establishment according to the non-linear response of the soil foundation to shear waves generated from the bedrock upward to the ground surface by the action of earthquake ground motions.  
Parameters to carry out seismic site classification remain objects of study and analysis. Despite the discrepancies generated by the geological, geomorphological and laws of each country, some consensus has been achieved at an international level, sometimes indirectly, with respect to parameters that must be applied for such seismic classification. An example of the latter is the known parameter Vs30 proposed by [PERSON] and [PERSON] [1] and [PERSON] [2], which incorporates many design codes as the main classification parameter [3]. Although it has been the subject of some debate [4, 5, 6], the Vs30 parameter is accepted internationally. Note that some questions also arise due to the complexity and nature of the variables that intervene in the non-linear seismic response of the ground, which has hindered the definition of absolute or unified criteria at the normative level. Given the uncertainties generated in the analysis, perhaps in the future it could be convenient to incorporate complementary data analysis tools based on the neuro-fuzzy logic technique into design code committees [7].  
On the other hand, the high seismic demand to which the Chilean infrastructure has been subjected because of great earthquakes during the last 100 years, especially recent large-magnitude earthquakes (Mw 8.8, 8.4, 8.3), has demanded that Chilean engineering be able to define ad hoc characterization parameters. This situation has allowed the response of the ground foundation for a structure to be categorized, which is required to establish the seismic demand for its seismic resistance design. Currently, the Chilean seismic resistance design code, named NCh 433, in its most recent modified proposal (version 2018-2021), contains important advances with respect to the methodology of seismic site characterization and would be a pioneering proposal at the international design code level. This position is not unprecedented for Chile, as the country has developed normative regulations for construction according to its investigations and experience and had integrated qualifying factors for almost 90 years before similar developments by other countries, such as the USA, Japan, and New Zealand. The objective has been to make a difference in seismic requirements according to ground conditions and has produced the seismic classification criteria recorded in different proposed design codes.  
In this document, a review and an analysis of the evolution of methodologies for seismic site classification according to Chilean regulations are performed, from their implementation in the 1930s to the most recent proposal in 2018-2021, which considers some limitations of the use of Vs30 as the only dynamic parameter of soil for classification [3; 4; 5]. These methodologies incorporate the fundamental period measured by the H/V spectral ratio method (HVR), T\({}_{\text{g}}\), as a complementary parameter of seismic classification. Having distinct knowledge of the evolution of ruling criteria from their origins is considered an important tool that contributes to understanding, interpreting and applying better criteria for ground classification methodologies contained in a design code.