The Geophysical and Seismometric Instrumentation lab
- Written by Marco Cirilli
The Geophysical and Seismometric Instrumentation Laboratory of the INGV National Earthquake Observatory, managed by the personnel of the Seismic Networks and Geophysical Technologies functional unit, was established almost thirty years ago as part of the technical activities of the National Seismic Network.
We asked the manager Sandro Rao, INGV technologist, to tell us something more about the activities of this important laboratory at the Rome headquarters.
Sandro, How the Laboratory was born of Geophysical and Seismometric Instrumentation?
At the beginning of its activity it was the place where the electronic technicians mainly maintained the commercial devices, produced by companies specialized in the sector and used in seismic stations.
How has it evolved over time?
Over time and with the know-how acquired in the field, towards the end of the 90s the personnel belonging to the Lab began to design GAIA, a 24-bit digital data acquisition device, suitable for acquiring velocimetric and accelerometric signals. Within a few years, after the first prototype phase, several hundred were produced at relatively convenient costs compared to similar instruments built by other companies outside the Institute.
What tools do you use for your activities?
A vibrating table has been built in the laboratory for some years to be able to carry out checks and calibrations on the seismic sensors. In practice, the sensor is located on a plane which is able to move with impulses generated by a PC connected to an electronic control box and, parallel to the movements generated, the response signal supplied by the sensor is acquired.
It is easy to identify malfunctioning sensors by comparing them with the responses already collected with perfectly functioning reference sensors. Once the problems have been identified, maintenance interventions are carried out, sometimes even very delicate and difficult given the electromechanical complexity of the sensors in question.
What other activities characterize the work you carry out in the Lab?
In the Laboratory we also perform accurate measurements of various parameters characterizing dataloggers and sensors by setting up suitable measuring benches based on various instruments: digital multimeters, precision power supplies and wattmeters. This is because the use of this instrumentation in a National Monitoring Network cannot ignore the knowledge of some parameters that characterize the sensors themselves and which provide users with a picture of their performance and, therefore, of the accuracy of the measurements of the quantities of interest in the various fields of experimental seismology that they provide.
Among the parameters of greatest interest we mention the power absorbed by the seismic stations and the effective resolution of the data acquisition unit. Accurate knowledge of the first parameter makes it possible to optimize the sizing of the power system based on the photovoltaic panel, in order to guarantee the continuous operation of the remote station regardless of the randomness of the weather conditions. Knowledge of the effective resolution of each type of data logger is, however, indispensable for making accurate measurements of acceleration and velocity, quantities which, when suitably processed, allow seismologists to calculate the magnitude, epicenter and depth of a seismic event.
Finally, routine activities for the Laboratory include technical support for all the instrumentation of the National Seismic Network, from the more purely scientific one (which therefore includes loggers or sensors) to the more specifically technical one (electrical or transmission equipment for sending of the data into realtime to the Monitoring Operations Room of the INGV headquarters in Rome).