Feasibility evaluation of an early warning system in the Lombardy region (northern Italy)

Student: Paola Traversa
Supervisors: Prof. Carlo Lai, Dr. Claudio Luciano Strobbia

ABSTRACT

Lombardy (northern Italy), being considered one of the engines of Italian economy, is one of the most important regions in Europe. It is therefore evident the relevance of a matter as security and preservation of existing sensitive structures, such as the large number of hospitals serving the area.

Lombardy results to be a low-seismicity area, the security of constructions against earthquakes, therefore, should be more oriented at preserving sensitive equipment and safety of people than dedicated to prevention of structure collapsing.

This work illustrates a feasibility study of an Earthquake Early Warning System (EEWS) in this Region. The aim is to issue the hospitals with a warning which have to be transmitted sufficiently ahead before the arrival of damaging ground shaking in order to allow the medical staff to start the shut-down operations of medical equipments and all the necessary security operations.

Simulating earthquake scenarios represented by occurred events in northern Italy, the EEWS could be able to issue a warning time of few to tens of seconds in Lombardy, depending on the distance of the urban area from the seismic source. Once the earthquake's size has been determined in real time from P-waves characteristics, the warning time is function of the temporal separation between first arrival of P- and S-waves at the observation point. Most of the major centres are therefore likely to be alarmed sufficiently ahead. Being affected by medium-low magnitudes events, in Lombardy the effectiveness of an EEWS is strongly reduced: towns located at a distance allowing for relevant warning times would not be struck by damaging ground motion due to ground motion attenuation with distance, while struck by strong ground motion due to the proximity to the source, would not be alerted sufficiently ahead.

Synthetic velocigrams are compared with real recordings of the event being simulated at seismic stations and attenuation of synthetic ground motion with distance is compared with suitable attenuation laws coming from literature. Nearly linear relationship can be defined between temporal separation of first arrival of P- and S-waves and epicentral distance

The possibility of simplifying all the procedure by considering a geometrical model is considered too simplistic to reproduce properly the developing ground motion. Such a simplified model, however, allows for sensitivity analysis of the parameters.

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