GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 425 outputs are already in a digital format. The characteristics of the accelerometer are: measure range of ±2 g; resolution of 76.3 µg, and white noise of 280 µg and is able to measure both static and dynamic accelerations. Velocimeter 4.5Hz can integrated with a dedicated board for enhance the bandwidth and out-put data in a digital format (Vitale 2018). Combining together the accelerometer with an Inertial Movement Unit (IMU) for angular rate measurements, and broadband velocimeter will be possible to reconstruct the full form of all the components of the shaking and explore a larger frequency band. The working scheme of the station is shown in Fig. 1a. The code automatically runs when the SBC boots, and runs the sampling thread from the digital sensor (or from the ADC). The exact absolute time, retrieved from the GPS or NTP server (Network Time Protocol), is associated to the first datum of each file, while the time for the following data is calculated on the basis of the sampling frequency. The synchronization of the signals between the various stations is fundamental for the determination of the relative position of the earthquake epicenter. In fact, earthquake localization is essentially based on the travel time readings of the seismic phases. The waveform files, one for all component, are written in miniSEED format. This is short version of the SEED format, primarily intended for the archival and exchange of seismological time series data (Ahern 2007). The reading of the incoming data from the sensor, and the writing of mSEED data files require proper Python API libraries. The data transmission exploits the ring-server conceived by the Incorporated Research Institutions for Seismology (IRIS) for the trans-mission of mSEED data; it is widely tested and used in the scientific community. The role of the ring server is to connect the sample loop with the software that manages the record seismic tracks (Fig. 1a). Fig. 1 - Low cost systems: a) Scheme of the monitoring station; b) Scheme of the monitoring network. See the text for further details.