## 2 Materials and Methods  
### Area of Study and Main Characteristics of Lorca, 2011 Earthquake  
The Lorca earthquake on May 11, 2011, had a magnitude of 5.1 on the moment magnitude scale. It was preceded two hours earlier by a premonitory earthquake of 4.5 M\({}_{\rm w}\). The earthquake was also felt in neighboring regions and other parts of the country, but at very low intensity levels (Figure 1). Multiple aftershocks occurred in the hours following the shock at 16:47, with that of the largest magnitude occurring at 22:37 local time, measured at 3.9 on the moment magnitude scale.  
The southeastern region where Lorca lies is theoretically one of the most active seismic zones in Spain. Nevertheless, the Lorca urban area basic acceleration (parameter defined in the Spanish seismic standard NCSE-02 as the characteristic value of the horizontal ground acceleration, with 10% exceedance probability in 50 years) of 0.12 g in the Spanish standard [17] is not among the most dangerous areas (Figure 2).  
Figure 1: Scope of action of the earthquake in Spain (**a**) and in the Region of Murcia (**b**). Location of the city of Lorca and epicenter of the earthquake (**c**).  
Figure 2: Map of seismic hazard in Spain (source: NCSE-02 [17], city of Lorca marked in yellow).  
The main earthquake occurred on land approximately 2 km northeast of the town of Lorca. Its hypocenter was quite shallow (about 1000 m depth). The area is located on the plate boundary between the Eurasian plate and the African plate. However, most of the earthquakes in the region do not often reach perceptible magnitudes, and therefore are not usually felt. It has been estimated that the earthquake was a direct result of a strike-slip fault close to another major fault, the \"Alhama de Murcia\" one. This fault is a very shallow line, which extends from 40 to 50 km, of which local specialists noted the presence of rupture surfaces in the vicinity [18].  
The earthquake in Lorca aroused the interest of many regional and national experts in the field and the entire local technical staff who came as volunteers to carry out damage assessment, supervision of buildings, realization of public and private reports, etc. This allowed a detailed and reliable multidisciplinary technical database to be obtained on a large scale, with geolocated information and homogeneous analysis codes, thanks to the coordination of public administrations. The geostatistical analysis has the ideal boundary conditions to be applied here, since it will take advantage of the large amount of technical geolocated information available and the existence of various previous studies from different fields of knowledge.  
Despite its low intensity and its short duration (\(t=2\) s), the consequences of the earthquake were controversial due to the high number of fatalities (9 dead and 324 injured) and material damage (more than 1000 houses demolished and \(\upxi 1.2\) billion estimated for complete reconstruction of the city [6]). This aspect has generated numerous theories (some of which have appeared in scientific articles) in recent years on what the main causes of the earthquake damage were and which priority measures should be adopted. Several theories pointed to the importance of the age of the buildings, due to the lack of adaptation of their structures to the current seismic regulations, while others emphasized the erroneous architectural configuration of many of them in the face of an earthquake [15; 18]. Some more recent studies have underlined the effect of the urban configuration of the city [9; 19]; one article even assures that this variable, added to the geologic configuration of the ground and other seismological variables, generated a phenomenon of directivity that remarkably increased the damage [20]. All these analyses have been taken as the basis to configure the following GIS indicators.