Description of monitoring
Permanent seismic instrumentation was installed at the base of the buildings. The ground motion is recorded with accelerometer sensors during significant seismic events.
The aim of permanent monitoring was to record the seismic input at the base of the monitored structure and to assess the impact of the earthquake. Continuous recording allowed to archive the instrumental seismic history of the monitored buildings and construct a database of engineering parameters. These parameters are useful to evaluate the relationship between the ground acceleration and macroseismic intensity, engineering fragility curves and amplification effects.
Temporary seismic analysis consists of three measurements (top, base and outside the building) of ambient seismic noise with velocimetric sensors. Temporary seismic analysis have been performed to obtain an estimate of the vibratory characteristics of the structures through spectral analysis techniques with the aim to identify soil-structure interaction. The measurement at the top of the building was performed with the aim to extrapolate the main dynamical behaviour of the building.
The fundamental frequency of vibration of the building is extracted from the record of this measurement. The measurement at the base of the building near the permanent instrument helps to verify possible coupling between permanent sensor and structure. The fundamental frequency of the soil is evaluated with the last measurement outside the building in free field where it is possible.

Methods, processes, practices and technologies used in monitoring
Each permanent station is equipped with a 24 bit data logger and a MEMS accelerometer with high dynamics, high gain and low instrumental noise. The stations record ground acceleration continuously, with a sampling of 200 sps. The data are sent in real time to the acquisition centre of the Ancona - INGV headquarters and they are also stored locally on a memory card inside the instrument. The accelerometric stations have been installed in basements and sensors were fixed to the ground. At each site the GPS antenna was installed outside the building, for the synchronization of the recorded signal with others stations so they are integrated in the seismic network and they are available for earthquake localization and shake map.
The seismic signals of earthquakes with the local magnitude equal or great than 3.0 are processed to extract accelerometric waveforms of the events from the arrival time of the P and S phases. The semi-automatic procedures are developed to calculate the value of engineering parameters, for example one of the commonly used is peak ground acceleration.
Temporary seismic survey was performed with 24-bit data logger and a velocimetric sensor. Most of the sensors were oriented with their North-South axis parallel to the longitudinal axis of the building and consequently with orientation of the East-West axis along the transverse axis of the building. Such measures lasted at least 30 minutes and up to 2 hours.
A scientific program was used to analyze seismic noise signals. The data processing was performed selecting the windows of three components signal to exclude those that were particularly disturbed by transients of high energy generated from sources very close, such as human activities or the transit of vehicles. Each selected signal window was used to calculate the Power Spectral Density (PSD) and Horizontal to Vertical Spectral Ratio (HVSR). So, to get more information from the spectral analysis, the direction of oscillation at the fundamental frequency was added to the results, obtained by the comparison of the longitudinal and transversal recording of the motion on the building.
Analogously, temporary seismic analysis were performed outside of buildings, in free field, to evaluate the resonance frequencies of soils. These additional measurements allow to investigate the soil-structure interaction. Indeed, if the fundamental frequency of the ground is similar to the natural period of the building it is possible a resonance effect during an earthquake.
During the project seismic surveys were carried out, information on surface geology was collected through thematic and digital maps and morphological characteristics were defined using geospatial analyses performed by Geographical Information System (GIS) technologies. Digital data raster were collected and organized for the characterization of the geological formations of the surface under buildings. Geological cartography was available at 1:10,000 for the most part of the territory. Where the former was not available, the Geological Map of Italy at 1:100,000 scale was used. The information about geological and morphological characteristics allowed to propose a classification of the various categories of the sites according to Eurocode 8 for the subsoil and topographical conditions.

Description of outputs
The activities developed for seismic monitoring are based on the storage of waveforms and the analysis of ground acceleration recorded at the base of all buildings. Parameters chosen to characterize the SPB site (geographical location, geological and morphological information and classification, seismic amplification, characteristics of building and its fundamental frequency and strong motion parameters) are organized in a MySQL database. This database is useful to compile the instrumental seismic history reconstructed by strong-motion parameters.
In this web portal it is possible to select the technical data sheets for each seismic site and the results of temporary surveys by a form or interactive map. Moreover, the data sheet for each site include earthquake list of the events with magnitude equal or great than 3 that have exceeded the acceleration threshold of 0.001 g.
The choice to implement a low cost strategy for the monitoring of SPB allowed to simplify the output of the basic information useful to earthquake engineering. Indeed, the seismic input at the base of SPB and the main characteristics of the structures are minimal information respect to a massive and expensive monitoring with a high number of sensors inside the structures. The low-cost approach reveals the chance to increase a widespread monitoring on the territory with the aim to cover a large number of municipalities.