GNGTS 2019 - Atti del 38° Convegno Nazionale

424 GNGTS 2019 S essione 2.2 LOW COST SYSTEM FOR REAL-TIME EARTHQUAKE G. Vitale 1,2 , S. Scudero 1 , A. D’Alessandro 1 1 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Nazionale Terremoti, Italy 2 Università degli studi di Palermo, Italy Introduction. The implementations of systems for Earthquake Observation (EOS) and Structural HealthMonitoring (SHMS) are highly increasing in the last years, when the limitations deriving from the traditional systems have been overcome. Such limitations basically consist in the high costs of the traditional instruments and in the difficulty to maintain, in the long-term, monitoring systems for an adequate time span after their implementation. For these reasons, apart from the country-scale networks usually managed by governmental institutions, EOS and SHMS systems are limited to small-scale or low-density application. The progresses achieved by the technological development in the last twenty years, have led to a great advancement of the instrumentation for seismic and structural monitoring in term of miniaturization, sensitivity, and quality of data. In particular, the reduction of dimensions has been so pushed that seismometer passed from bulky and heavy apparatus, to compact, low weight, and manageable devices. Even in more recent years, the Micro Electro-Mechanical Systems (MEMS) also contributed to the growth of the seismology and its applications, further reducing costs and dimensions but sometimes going inevitably to the detriment of sensing capability. However, large-scale and high-density applications can also overlook this unfavorable aspect. MEMS sensor are especially suitable for applications of Early-Warning Systems either for site-specific earthquake alerts or for the assessment of the critical conditions in structures. In this paper we introduce the realization of several urban-scale, real-time monitoring network designed for EO and SHM. The monitoring systems. A monitoring system based on the combination between EO and SHM can sensibly lower the potential impact of a destructive earthquake in an urban context. When a destructive earthquake hits a vulnerable urban area, the prompt assessment of damage is very critical for search-and-rescue operation, and such monitoring systems are able to provide useful information to the emergency management center addressing timely and targeted actions in the case of emergency. In fact, the shorter the intervention time, the greater will be the opportunity for effective operations minimizing the number of victims. SHM should be considered necessary, at least for public edifices with strategic function, since stress factors acting on the structures lower the resistance properties and induce potential risks in the long- tem. The stress factors acting on the structures can be due to natural or anthropogenic factors: seismic events, atmospheric agents, vibration due traffic flow, applied loads, lowering of the resistance properties which effects are assessed by means of various types of sensors (Moreno- Gomez 2017 for a complete review). The prototypal urban seismic network implemented in relevant public buildings are being installed in historical city center of Messina, Ragusa, Syracuse, Noto, Catania, and Acireale (D’Alessandro 2016, 2018a, b). Eastern Sicily is a high seismic risk area. In fact, the area has been struck by strong earthquakes several time during history: 1169, 1542; 1693; 1818 are the dates of the main events which reached Imax up to X MCS causing diffuse damage, victims, and even almost complete destruction (Rovida 2015). The monitoring station. The design of a monitoring system is focused on the final objective and consequently the hardware components, the sensors, the code, and the sites, have been accurately selected, designed, and planned. Themonitoring stations are based on a suite ofMEMS sensors suitable for earthquake strong motion detection and structural monitoring, namely tri- axial accelerometers with digital output, and analog velocimeter. Several studies indicate the suitability of such devices for earthquake and structural monitoring systems (D’Alessandro 2013,2014a, b; Zou 2014; Saunders 2016; D’Alessandro 2017) when they are characterized by flat noise response to acceleration and resolution (smallest detectable acceleration) in the order of 10 -2 – 10 -3 m/s 2 . (c.f. Scudero 2018). In particular, the accelerometer is the model 1043_0 produced by Phidget. This MEMS sensor integrates a three-axis capacitive accelerometer. The circuit of transduction is internal to the device and is of the digital type, for which the