## 3 The WebGIS System  
The geospatial tools for predicting and mapping the vulnerability of a large area to seismic hazard, and assessing the potential impacts of a possible seismic event, in order to support the response planning have been developed as a Web-GIS subsystem of an earthquake EWS, designed and developed into national SIT_MEW Project framework. The data-processing unit architecture of the developed earthquake EWS integrated several subsystems such as knowledge discovery database (KDD) and data warehouse (DW) subsystems for discovering decision-relevant knowledge from the very large amount of available seismic parameters observations [14]; temporal modeling subsystems for simulating the seismic activities; specialized visualization modules for supporting the operator in the process of deciding whether a warning has to be generated and finally the proposed open source Web-GIS subsystem--geospatial data and models, and collaborative tools--for seismic hazard assessment and emergency management tasks. A task of the operating centre is the acquisition of data from different sources and their integration to provide--via a broadband network--information for executing security measures. Geospatial data and _ad hoc_ tools play a fundamental role in earthquake early warning and post-event emergency management: to this purpose, the proposed GIS subsystem has been integrated into the EWS architecture as geospatial interface of the Operating Center (OC). Consequently, basic spatial information and thematic maps are stored and managed in a geospatial database specifically implemented so that it is possible to display and query the data by means of a map viewer. Figure 4: Example of expected damage scenario. The map is categorized considering six different levels of damage as described below (level representation shown on the left). The geospatial analysis tasks are fairly simplified and suitable for use with regional spatially-distributed data, which can often be incomplete in the amount and type of available information. The proposed Web-GIS subsystem architecture, based on free/open source GIS technology (FOSS) [33] includes several modules (Figure 5) such as:  
1. Geodatabase Module (by using PostgreSQL/PostGIS);
2. GIS Module (by using Quantum GIS);
3. WebGIS Module (by using MapServer). The Geodatabase Module has been designed to manage and integrate geospatial data provided as input to the system, including the alphanumeric data related to seismic events (e.g., magnitude and epicenter, recorded and processed by the operating center) and specific geospatial data related to the area of interest (geology, vulnerability maps, urbanized areas, census, _etc._). The FOSS technologies chosen to implement this module were PostgreSQL/PostGIS ([[http://www.postgresql.org](http://www.postgresql.org)]([http://www.postgresql.org](http://www.postgresql.org)) and [[http://postgis.refractions.net/](http://postgis.refractions.net/)]([http://postgis.refractions.net/](http://postgis.refractions.net/))). Data collected in Geodatabase (UTM-WGS84 reference system) were:  
Figure 5: Geographical Information System (GIS) logical architecture: GIS modules are represented inside the dashed box, to differentiate them from other subsystems developed within the SIT_MEW Project. * Basic GIS Layers (Italian DBPrior10K: Administrative boundaries, road network, railways, hydrograph, _etc._);
* Thematic Maps (hydroology, geomorphology, seismic classification, _etc._);
* 1:25.000 Cartography;
* Census data (ISTAT);
* Digital Terrain Model (DTM, 20 m ground spacing);
* Geographic location and data of ISNet seismic sensors;
* PGA (Peak Ground Acceleration) distribution maps;
* Data from parametric catalogue of damaging earthquakes in Italy (INGV). These spatial data and thematic maps have been used for the spatial analysis tasks carried out through the GIS Module. This module is devoted to process geospatial data collected in Geodatabase.