# Assessing Seismic Vulnerability and Pollution Risks of Wastewater Treatment Plants
## 2 Methodology
The country is divided into 13 regions, as shown in Figure 1.  
The layers in QGIS include the coastline of the Greek territory, the location of WWTPs, the ISV, the ISV-REF, and their deviations from the average values. Additionally, a raster of the three zones from the SHM is incorporated into the GIS platform. All the layers for the above parameters are in SHP format and have been transformed from Excel database files. These are integrated into the program as either point layers or area layers. The Greek Geodetic Reference System EGSA '87, established in 1987, was used for the georeferencing of the maps. The scale of each map is depicted through a line scale in kilometers. Consequently, the paper utilized a variety of sources for the data used, including the following:  
1. The SHM according to the Greek Official Gazette 1154/vol.B/12.8.2003 and from the published paper by [PERSON] et al. [47];
2. The coastline layer of Greece from the link: Geodata.gov.gr/en/ [48];
3. The WWTP layer from the General Secretariat of Water Resources/Ministry of Environment and Energy [8];
4. The region layer of Greece from Geodata.gov.gr [48];
5. A collection of data from the statistical database that exploits the findings from previous scientific papers, including the ISV, ISV-REF, and their deviations [29]. The definition and visualization of the class scores or the zonation of the SHM were categorized as follows: (a) low seismicity values (expected acceleration = 0.16 g) are represented in blue, (b) medium seismicity values (acceleration = 0.24 g) are shown in green, and (c) high seismicity values (acceleration = 0.36 g) are depicted in red, according to the probabilistic model and Greek Laws. The map, which has been in force since 2003, specifies a 10% probability of exceedance of the Peak Ground Acceleration (PGA) values for shallow seismicity and intermediate soil conditions over an exposure time of 50 years. Figure S1 in the SM presents the WWTPs within the statistical population (Figure S1a in the SM) and the statistical sample (Figure S1b in the SM). The statistical sample consisted of 38 Units from Zone I and 78 Units from Zone II out of 116 WWTPs. Combinations of the above layers were used to extract the paper's outcomes, employing qualitatively cross-referencing to estimate potentially seismic and vulnerable WWTPs or regions. The categorization of the distinct section of regions was introduced using data provided by the link: geodata.gov.gr/en/dataset (accessed on 20 September 2024) (Figure 1). The categories emerged as percentages, with 20-40% representing a low WWTP ISV per region and 40-60% representing a high ISV per region (Figure 2) after merging partial data. The range of the ISV-REF was divided into classes of 0-20%, 20-40%, 40-60%, and 60-80%, with the SHM as the background. According to the class percentages, a circle with a varying diameter was designed progressively (Figure S2a in the SM). The paper suggests that seismic vulnerability values under 40% indicate a low class, values between 40 and  
Figure 1: Map of WWTPs’ seismic vulnerability (ISV) per region. 60% indicate a medium class, and values over 60% indicate a high class for the units. The categories were also merged into percentages of 20-40% for a low WWTP ISV-REF per region and 40-60% for a medium ISV-REF per region (Figure S2b in the SM). Subsequently, the average values for the ISV and ISV-REF were calculated using Excel, and all the corresponding values of the WWTPs were compared with these average values to determine whether they exceeded the above mentioned classes. A comparison was introduced into the QGIS program in SHP format as a point layer. A red rhombus represented the graduation for negative values of exceeding, while positive values were represented by a green rhombus. According to the class of the percentages (ranging from the \(-20\%\) to over 100%), the rhombuses were designed progressively (Figure S3 in the SM). A background of the SHM could also depict the hazard of an area and lead to combining the results.