Signals of Surface Deformation Areas in Central Chile, Related to Seismic Activity--Using the Persistent Scatterer Method and GIS  
[PERSON]  
1 Facultd de Ciencias Ambientales, Universidad de Concepcion, Concepcion 4070386, Chile; [EMAIL_ADDRESS] (M.I.A. ); [EMAIL_ADDRESS] (L.G.-R.)  
[PERSON]  
2 Departamento de Ciencias Geodesics y Geometac, Campus Los Angeles, Universidad de Concepcion, Los Angeles 4451032, Chile; [PERSON]DRESS]  
[PERSON]  
1 Facultd de Ciencias Ambientales, Universidad de Concepcion, Concepcion 4070386, Chile; [EMAIL_ADDRESS] (M.I.A. ); [EMAIL_ADDRESS] (L.G.-R.)  
[PERSON]S] (L.G.-R.)  
sedimentation of the coastal mountain range [22]. The importance of post-seismic deformation on the inertia perturbation due to seismic sources has been emphasized for its effects on the displacement of the axis of rotation. Deformations can be identified as the effects of uplift or subsidence of a given terrain [14; 23; 24]. The Central Chile area experienced several major earthquakes in the past. In 2010, an earthquake occurred in the Chilean sea, and its epicenter occurred off the coast of the then Biobio region (now Nuble region) with a magnitude of Mw 8.8 that was felt over a wide area and caused damage to structures located more than 600 km away. This earthquake is considered the second strongest in the history of the country and the eighth strongest recorded by mankind. One of the most serious consequences of this earthquake was the loss of human lives, with 525 people dead and 23 missing according to official reports in January 2011 [25]. However, it is estimated that the number of fatalities could have been much higher, as the earthquake and tsunami affected the most populated areas of Chile [22]. In seismic countries, the daily seismic activity is recorded in which energy is released in a short period. Scientific work has a major focus on studying earthquakes that release more energy over a longer period [9; 18; 26; 27]. In Chile [14], it was found that in the period (1886 and 2010) between the two earthquakes, Santa Maria Island sank approximately 1.4 m. They used nautical surveys conducted in 1804, after the 1835 earthquake, and in 1886, along with modern echo sounder surveys and GPS (global positioning system), measurements were taken immediately before and after the 2010 earthquake to quantify the vertical deformation over the entire seismic cycle. These changes occurred under a great discharge of energy due to the earthquake. However, after a major seismic event, there may be a possibility that the energy released in a short period may also generate deformation [28]. However, what would happen to the land surface in coastal areas under scenarios of low- and medium-intensity earthquakes? Is it possible to identify deformation zones for urban planning and/or safety assessment? The quantitative assessment of ground displacements that may affect infrastructures is traditionally based on ground instrumentation. However, with the evolution of technology, alternative solutions have emerged that can be fully assimilated to ground monitoring generally quantified through the expected peak ground acceleration and the spectral accelerations [29]. Among the alternative methods for the protection of buildings against earthquakes, we can find the geotechnical seismic isolation [30; 31]. Additionally, GPS/GNSS (global navigation satellite system) positioning is a commonly used method for measuring deformation [32; 33]. However, there are few GNSS stations for continuous monitoring in Central Chile. This is where the interferometric synthetic aperture radar (InSAR) method can be an alternative [34] because in Chile, the information coming from the receivers is not free or easy to access. The InSAR method is relatively new and is currently not fully exploited [27; 35; 36; 37; 38]. It has a large amount of available data, high accuracy, and low cost, making it an attractive source of information. The technology is based on the comparison of multiple radar (SAR) image pairs [39].