ALBERT

Description: Public concern about anthropogenic seismic- ity in Italy first arose in the aftermath of the deadly M ≈ 6 earthquakes that hit the Emilia-Romagna region (northern Italy) in May 2012. As these events occurred in a (tectonically active) region of oil and gas production and storage, the question was raised, whether stress perturbations due to underground industrial activities could have induced or triggered the shocks. Following expert recommendations, in 2014, the Italian Oil & Gas Safety Authority (DGS-UNMIG, Ministry of Economic Development) published guidelines (ILG - Indirizzi e linee guida per il monitoraggio della sismicità, delle deformazioni del suolo e delle pressioni di poro nell’ambito delle attività antropiche), describing regula- tions regarding hydrocarbon extraction, waste-water in- jection and gas storage that could also be adapted to other technologies, such as dams, geothermal systems, CO2 storage, and mining. The ILG describe the frame- work for the different actors involved in monitoring activities, their relationship and responsibilities, the procedure to be followed in case of variations of mon- itored parameters, the need for in-depth scientific anal- yses, the definition of different alert levels, their mean- ing and the parameters to be used to activate such alerts. Four alert levels are defined, the transition among which follows a decision to be taken jointly by relevant au- thorities and industrial operator on the basis of evalua- tion of several monitored parameters (micro-seismicity, ground deformation, pore pressure) carried on by a scientific-technical agency. Only in the case of liquid reinjection, the alert levels are automatically activated on the basis of exceedance of thresholds for earthquake magnitude and ground shaking – in what is generally known as a Traffic Light System (TLS). Istituto Nazionale di Geofisica e Vulcanologia has been charged by the Italian oil and gas safety authority (DGS- UNMIG) to apply the ILG in three test cases (two oil extraction and one gas storage plants). The ILG indeed represent a very important and positive innovation, as they constitute official guidelines to coherently regulate monitoring activity on a national scale. While pilot studies are still mostly under way, we may point out merits of the whole framework, and a few possible critical issues, requiring special care in the implementa- tion. Attention areas of adjacent reservoirs, possibly licenced to different operators, may overlap, hence mak- ing the point for joint monitoring, also in view of the possible interaction between stress changes related to the different reservoirs. The prescribed initial blank- level monitoring stage, aimed at assessing background seismicity, may lose significance in case of nearby ac- tive production. Magnitude – a critical parameter used to define a possible step-up in activation levels – has inherent uncertainty and can be evaluated using differ- ent scales. A final comment considers the fact that relevance of TLS, most frequently used in hydraulic fracturing operations, may not be high in case of trig- gered tectonic events.

Description: Published

Description: 1015–1028

Description: 1IT. Reti di monitoraggio e sorveglianza

Description: JCR Journal

Description: In 2014, the Italian Ministry of Economic Development published monitoring guidelines (ILG) describing in detail the governmental regulations for geophysical monitoring in areas interested by exploitation of underground potentials. The ILG prescribe the monitoring of microseismicity, ground deformation and pore pressure near the industrial activities, and direct the application of a four-stage traffic light protocol, depending on the magnitude, peak ground velocity and peak ground acceleration. In case the prescribed threshold values are exceeded, different alert levels have been scheduled, up to the limit of reduction or interruption of industrial operations. In a three-years test phase, the ILG will now be applied in a few areas involved in different exploitation activities, such as gas storage, hydrocarbon extraction and waste water reinjection, geothermal energy production. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has recently been charged to realize multi-parametric monitoring systems in at least three of the aforementioned test areas and to provide indications about the applicability of these guidelines. INGV instituted specifically a Centre for monitoring underground anthropic activities, entrusted with the duties and responsibilities to implement the ILG at the test sites. The presentation gives a general overview about the state of the art, trying to emphasize critical situations as e.g. the problems in the magnitude calculation or the significance of the traffic light thresholds, especially in areas with multiple mining rights.

Description: Published

Description: Montreal (CA)

Description: 3SR TERREMOTI - Attività dei Centri

Description: Grazie ai finanziamenti ottenuti attraverso il bando di ricerca libera proposto all’interno dell’INGV (0865.039 FISR 2016), a partire da Maggio 2018 è operativo nel centro Italia un’array sismico a piccola scala. L’obiettivo è quello di monitorare la microsismicità locale e regionale, inclusa la sequenza sismica del centro Italia 2016-2018 e le aree geotermiche site ad ovest della zona che ospita l’esperimento. L’array, che prende il nome di CISA (Central Italy Seismic Array), ha un’apertura massima di 1000 metri ed è composto da 9 stazioni con sensori velocimetrici a 3 componenti installati ad una distanza reciproca compresa tra 100 e 500 metri. In fase di progettazione di un array in termini di apertura massima e distanza inter-stazione, è bene tenere in mente le caratteristiche del segnale target e studiare il campo d’onda del rumore locale, per ottimizzare il rapporto segnale/rumore. A questo scopo, sono state analizzate le caratteristiche statistiche del segnale e del rumore ambientale in termini di funzioni di autocorrelazione e cross-correlazione per tutte le combinazioni di coppie di stazioni. In questo modo è possibile determinare la distanza inter-stazione più adatta, così che la risposta dell’array, una volta ottimizzato il segnale registrato, possa sopprimere il contributo di energia ascrivibile al campo d’onda del rumore locale. È stata inoltre calcolata la curva di dispersione combinando i risultati dell’analisi di autocorrelazione con quelli ricavati dall’applicazione della tecnica fk sui dati di rumore ambientale. La curva così ottenuta è stata invertita, utilizzando il metodo neighbourhood algorithm per ricavare il profilo di velocità delle onde S del sito fino ad una profondità proporzionale alla configurazione spaziale dell’array

Description: Unpublished

Description: Roma

Description: 8T. Sismologia in tempo reale

Description: The geothermal field of Torre Alfina is located in central Italy at the northern edge of the Vulsini Volcanic District, the northernmost area of the so-called Quaternary Roman Co-Magmatic Province. In the framework of a medium-enthalpy geothermal exploitation project, INGV installed a local seismic network close to the future geothermal production site for monitoring natural local seismicity. In this paper, we show the results of a study of the microseismicity recorded from June 2014 to May 2016 in a small area of about 10 km2 around Torre Alfina. Analyzing seismic signals recorded by a local temporary network of ten short-period stations and by four permanent stations of the INGV national seismic network, we detected 846 local earthquakes. Then, we accurately relocated 799 events using HypoDD code. Our results show that the region of Torre Alfina is characterized by intense microseismicity, with hypocentral depths between 3 and 7 km and with moderate magnitudes between Md = 0.1 and ML = 2.8. Moreover, more than half of the earthquakes are grouped into six main swarm-like clusters each lasting few days. Furthermore, we computed 36 well-constrained fault plane solutions, which show a clear transtensional deformation regime in the whole study area. Three main tectonic directions have been evidenced from the focal mechanisms analysis: E-W, WSW-ENE, and NW-SE. The understanding of the seismogenic structural setting of the Torre Alfina geothermal field, and the study of its background natural seismicity can be of great importance in recognizing any possible future seismicity induced by the exploitation of the field.

Description: Published

Description: 1279–1298

Description: 2T. Deformazione crostale attiva

Description: JCR Journal