## 1 Introduction  
Chile is located along the Pacific Ring of Fire, which experiences large earthquakes on a frequently recurring basis. The deep subduction zone earthquake that occurred on 27 February 2010, exhibited a remarkably high magnitude of Mw 8.8 and lasted approximately 3 min. This event affected at least one-third of the nation, the longest country in the world, and released an energy equivalent to 11,780 Hiroshima bombs. Therefore, news of this event spread worldwide. The earthquake generated relatively few cases of structural failure. A study conducted by the Chilean Structural Engineers Association concluded that 11% of the infrastructure in the country's capital city required major repairs to nonstructural elements; 33% presented minor or medium failures in the structure that could be repaired, and a mere 0.4% corresponded to severely damaged or collapsed structures that had to be demolished [1]. The low level of damage suffered by Chilean buildings in the face of such a strong earthquake, in comparison with that of structures in Christchurch, New Zealand, following the 2010 Canterbury earthquake or in Manabi, Ecuador, in response to the 2016 Ecuador earthquake, has intrigued the earthquake engineering community around the world. Eleven years after the 2010 event, research on its effects on built civil infrastructure is still of great relevance, with studies being continuously performed to improve current structural design codes and thus ensure satisfactory structural performance [2; 3]. In particular,Chile is seen as a natural laboratory that provides the national and international earthquake engineering communities with the opportunity to calibrate structural design standards and serves as a reference in the earthquake-resistant construction industry. The earthquake-resistant design aims to ensure that structures can adequately resist seismic forces, limiting the seismic risk and guaranteeing peoples' well-being. To this end, standards committees continue to propose design models or methodologies based on experiences such as those of Chile in 2010. Therefore, it is imperative to develop techniques that increase our knowledge and to evaluate the adequacy of proposed design methods through measurements. In this regard, monitoring large structures such as bridges, buildings, and dams is critical for calibrating the existing design methodologies and assessing their safety and health. Typical monitoring approaches for such structures are based on the analysis of either static strain or displacement data or discrete and continuous dynamic acceleration data gathered at specified points in the structures [4; 5; 6; 7; 8]. To obtain dynamically measured data, the proper monitoring of a structural system necessitates the collection of vast volumes of data over specified periods, from which mode shapes or other dynamic properties of the structures can be derived. Modal parameter changes in structures provide helpful information about the state of health of structural systems, provided that the dynamic features predicted in the design stage are affected by construction processes as well as seismic phenomena. The dynamic characteristics of structures can be derived either passively from ambient conditions [9] or actively by force excitations [10; 11]. Then, modal parameters such as natural frequencies, damping factors, and mode shapes can be obtained based on response data. Thus, the structural properties can be estimated, and the performance and integrity of a structure can be assessed [12; 13]. Modal analysis approaches yield essential information on the overall health of buildings. The process of determining the modal parameters of structures typically entails the deployment of accelerometers, gathering vibration data and using one of many analytic techniques. The accuracy of the data is based on not only the number, measurement sites, and resolution of the accelerometers but also the choice of a suitable analytic approach. In particular, the number and positions of sensors significantly impact the outcome.