## 1 Introduction
The lack of detailed characterization of dune deposits in the country, which have specific geomorphological conditions, along with the growing urban development, underscores the need for a microregional seismic response analysis of the city. Figure 1: Location and characteristics of the study area, Conč, Chile. (**a**) View of Chilean territory; (**b**) Aerial view of the city of Conč, Chile; (**c**) View of real estate development in Conč in 2004; (**d**) View of increased real estate development in Conč in 2024. Images taken from Google Earth. Image data © 2004 and 2024 Google, © 2004 and 2024 TerraMetrics. The selection of the microzonation parameter is an aspect that is conditioned by its potential application. For the purpose of providing complementary information for the evaluation of structural response, the microzonation parameter may be linked to the seismic site classification criteria according to the seismic design code of the country where the study area is located. Additionally, a particularly useful aspect of this selection is that the parameter should preferably be easy to measure, so that the microzonation can achieve a measurement point density that ensures an adequate characterization of the area. The fundamental vibration period of the soil, T, is a parameter that allows the identification of the vibration period at which greater amplification of the seismic response of the terrain can be expected [24]. For this reason, different seismic design codes consider the period T, either directly or indirectly, as one of the parameters for defining design response spectra [25; 26; 27]. In particular, the Chilean Seismic Design Code, NCh 433, in its most recent proposal, still pending official approval, has incorporated the period T as one of the complementary parameters for seismic site classification. Additionally, it mandates that the measurement of this period must be conducted through field measurements, specifically recommending the use of the Horizontal-to-Vertical Spectral Ratio (HVSR) method [28; 29]. Considering this, for the present study, the selected parameter was T, recorded using the HVSR method. As previously indicated, it is of practical interest to expand the application and use of the microzonation map that is obtained. While such a map is undoubtedly of great practical utility for analyzing the potential seismic response in the study area, a significant application that adds value lies in identifying how this information can be complemented with other methods. To this end, an approach is proposed that integrates the microzonation process with the geomorphological and geotechnical background of the study area, along with the generation of a three-dimensional finite element model (3D FEM), to evaluate the seismic response of a city; in this case, Concon, Chile. The combined analysis of microzonation and FEM 3D modeling allows for a preliminary identification of potential localized seismic response effects that may require special attention in future studies and structural designs. [PERSON] and [PERSON] [30] emphasized the need for more specific studies in areas with complex morphologies, such as dunes and coastal terraces, to better understand how these geological influences affect seismic response. By addressing these characteristics in Concon, this study makes a significant contribution by providing data and models that can be used to improve construction regulations and mitigation strategies in similar terrains.