# Destructive M6.2 Petrinja Earthquake (Croatia) in 2020--Preliminary Multidisciplinary Research
## 6 Earthquake Performance of Buildings
Such buildings belonged to vulnerability classes C and D in compliance with the EMS-98 scale [43]:  
Medium earthquake resistance was realised by building code regulations in the period between 1982 and 1998, when the Ordinance on Technical Standards for the Construction of High-Rise Buildings in Seismic Areas [38] was introduced (in the aftermath of the M7.1 1979 Montenegro earthquake). However, this resulted in poor performance of buildings with 30-50% of the required earthquake resistance realised, as defined by [34]. Masonry infilled RC frame structures were frequently used for medium- and high-rise buildings (infill walls were considered to be non-structural partition walls). Such buildings belonged to vulnerability classes C and D in compliance with the EMS-98 scale [43]:  
In the years between 1999 and 2012, building codes ENV 1998-1:1:1994 [39] were introduced, which resulted in 70-100% of the required building earthquake resistance [34]. They were superseded by contemporary building codes EN1998-1:2004 [34] in 2013 (100% of the required building earthquake resistance). Such buildings belonged to vulnerability classes D and E in compliance with the EMS-98 scale [43]. In any case, buildings possess an initial resistance that depends on the structural system and the construction method, which can be increased via retrofitting techniques, e.g., [44; 45]. In Tables S1 and S2 (see Supplementary Materials), the building code requirements on masonry buildings with respect to the building code era (e.g., on materials, wall and opening measures and confining elements) are summarised. Detailed information on the building code requirements of masonry and reinforced concrete buildings for earthquake-prone regions is available in [34; 35; 36; 37; 38; 39; 40; 41]. In the seismic intensity maps for the period of building code provisions from 1965 to 1981 [37], from 1982 to 1998 [38] and from 1998 to 2012 [39; 40; 41], intensities of VII (very strong) to VIII (severe) MCS were assigned for Sisak-Moslavina County. They correspond to intensities of VII (damaging) and VIII (heavily damaging) EMS, respectively. By considering the relationship between _PGA_ and the intensities according to the EMS-98 [43] and MCS [46] (subjective) intensity scales, e.g., as shown in Figure 9[47], a mean _PGA_ values of 0.3 g could be related to intensity IX (violent) MCS or EMS scale. Furthermore, mean _PGA_ values of 0.1 g could be related to an intensity of VIII MCS or EMS scale, and a _PGA_ of 0.07 g to an intensity of VII MCS or EMS scale. The two intensity scales, namely EMS-98 and MCS, correlate in a straightforward manner with the earthquake M6.2 event with a _PGA_ of 0.25 g that struck Sisak-Moslavina County in 2020 at intensities of VIII (heavily damaging, severe) to IX (destructive, violent) MCS/EMS. In a survey of damage to buildings in Sisak-Moslavina County after the M6.2 Petrinja 2020 earthquake that was conducted by structural engineers in the field, vulnerability classes and damage grades were defined in compliance with the EMS-98 scale. The damage grades (qualitative measures of vulnerability) are described as follows: Grade 1 (DG 1): negligible to slight damage; Grade 2 (DG 2): moderate damage; Grade 3 (DG 3): substantial to heavy damage; Grade 4 (DG 4): very heavy damage and Grade 5 (DG 5): destruction. The damage grades describe the degree of damage to the buildings (which range from 1 to 5) and could be regarded as a function of earthquake intensity. They provide a detailed description of building damage that results from an earthquake by differentiating building structural systems or elements (structural and non-structural). Therefore, they are the most suitable tool for the assessment of building conditions after earthquakes. As reported by [48], on 1 February 2021, a total of 34,056 damaged buildings were reported, of which 22,966 were examined.