SPATIAL DISTRIBUTION OF FELT INTENSITIES FOR PORTUGAL EARTHQUAKES

Abstract

Macroseismic intensity is a parameter of the severity of ground movement evaluated in terms of the effects that earthquakes produce on people, buildings and the environment, constituting an extremely important information source for the seismologist and engineer of structures. In recent studies, the authors of this study published a new map of maximum intensities observed for continental Portugal considering all observations of macro-seismic intensity higher than III relative to earthquakes occurred between 1344 and 2015 (Teves-Costa et al., 2019). In each parish and municipality of the continental part of the country, the maximum values of intensity were defined. A map of maximum intensities produced in this way was essentially controlled by earthquakes of greater intensity, the 1909.04.23 (near-field) and 1755.11.01 (far-field) earthquakes. In the present work, a spatial distribution of the earthquakes presents in the database (classified by their nature - near-field or far-field - intensity, and epoch) are analysed. The spatial structure, which allows the detection of spatial dependence or autocorrelation of intensity values is also explored in this work, in order to identify regions with similar macroseismic characteristics. The combination of the map of maximum intensities and the products generated in this work are essential for the authorities as a base of support in the definition of joint adaptation strategies for the various regions of the territory, as well as contribute to a better management of the emergency system in Portugal.