## 1 Introduction  
Most guidelines for post-earthquake damage evaluation and traditional damage assessment methodologies rely essentially on expert-conducted on-site visual inspections. Some examples of guidelines developed for different countries are [1; 2; 3; 4; 5; 6; 7]. However, visual inspections are subjective and generally slow in addition to not being feasible for use in severely damaged structures, where the safety of inspectors is compromised. Further, the lack of specialists that are available right after an earthquake requires the participation of non-expert building safety inspectors, which might generate a systematic conservatism due to the lack of experience and personal and safety concerns. As a result, buildings can remain unoccupied for long periods until a final decision regarding their structural safety can be properly made. Any increment of the time between an earthquake and the occupancy allowance of buildings decreases the resilience of cities, thus increasing the need for provisional housing and the loss of services and business opportunities. Structural health monitoring (SHM) has positioned itself as an objective solution to take rapid post-earthquake decisions regarding structural safety. For this reason, in the past decade, the use of SHM has become a common practice in important buildings and increase the structural safety and to reduce maintenance cost, as well as economic and human loses [8; 9]. At the same time, the technological advances of the sensors used for SHM (e.g., accelerometers and displacement or velocity transducers) allow for improvements in the accuracy of the structural monitoring, achieving significant developments in vibration-based damage detection (VBDD). These high-precision sensors have proven to be accurate enough for assessing the dynamic response of structures to strong and weak motions through continuous monitoring [8; 10]. However, permanent monitoring requires costly installations and continuous maintenance; hence, this type of monitoring is carried out in a few cases and, generally, in new high-rise buildings, where the owners or the administrations consider it necessary. In addition, contact devices for SHM must be positioned inside the structure. This can not only be problematic, due to accessibility restriction and installation requirements, but also dangerous after an earthquake. When the structure has symptoms of damage and the risk of collapse as well as likely events such as aftershocks, gas leaks, chemical hazard, exposed electrical wiring and falling non-structural objects is unknown, entrance to the structures should remain restricted. This makes it impossible to install and manipulate any device inside the structure as well as enabling visual inspection. Therefore, the use of non-invasive or remote sensing techniques emerges as a reliable, safer and faster alternative, especially in, but not limited to, post-earthquake scenarios. In the same way, the idea of punctual or non-continuous monitoring is proposed to evaluate the structure only at specific times, for example, after the construction, in order to identify the dynamic properties in the healthy state, and after a seismic event to estimate whether the structure has been damaged. Remote sensing not only reduces the cost of monitoring significantly, but it can be carried out safely without the need to enter a structure. These advantages are of the utmost importance, so that periodic monitoring can be implemented in a large number of buildings, and this is of great interest to the government as it has a direct impact on the resilience of the cities and the costs involved in the assessment and retrofitting of damaged buildings. The use of a real-aperture radar (RAR) interferometer is proposed as a good candidate to perform this punctual monitoring. The RAR is a high-sensitivity remote sensing device with a maximum sampling frequency of up to 200 Hz. These types of sensors have exhibited good performance in urban environments under different atmospheric, meteorological and lighting conditions.