Cinque anni fa, il Dipartimento di Protezione Civile della Presidenza del Consiglio incaricò una Commissione Internazionale (ICHESE) per investigare se vi fossero state attività umane che potessero avere indotto o innescato il terremoto in Emilia del 2012. La commissione concluse che non poteva essere escluso che la re-iniezione di fluidi nel giacimento petrolifero di Cavone, vicino a Modena, potesse aver innescato la catastrofica sequenza. Oggi alcuni ritengono infondate le conclusioni della Commissione ICHESE. Sinora, nessuno ha mai chiesto l’opinione al Professor Peter Styles, che presiedeva la Commissione. Sapere lo ha fatto.
Cinque anni fa, il Dipartimento di Protezione Civile della Presidenza del Consiglio incaricò una Commissione Internazionale (ICHESE) per investigare se vi fossero state attività umane che potessero avere indotto o innescato il terremoto in Emilia del 2012. La commissione concluse che non poteva essere escluso che la re-iniezione di fluidi nel giacimento petrolifero di Cavone, vicino a Modena, potesse aver innescato la catastrofica sequenza. Oggi alcuni ritengono infondate le conclusioni della Commissione ICHESE. Sinora, nessuno ha mai chiesto l’opinione al Professor Peter Styles, che presiedeva la Commissione. Sapere lo ha fatto.
Potete leggere l’intervista in italiano con il commento del direttore, Nicola Armaroli, sul numero 1/2019 di Sapere che potete acquistare qui. Di seguito l’intervista originale in inglese.
Enrico Bonatti (Columbia University, New York),
in his quality as a member of the Scientific Board of Sapere,
interviews Peter Styles (Keele University, United Kingdom)
Prof. Styles, what are the main anthropogenic activities that may cause earthquakes?
We have grown to realise over the last decade, that it is much easier than might have been expected to generate seismicity, albeit of a variety of magnitudes, often quite small, but sometimes significant, through our human activities. The Earth’s crust in most regions, even those far away for current plate boundaries, has had a complex geological history, with collisions and mountain building, rifting and changes in stress field and this has produced faults which have moved at some time geologically but are now in a variety of states of stability. Investigations in coal mines, from direct underground observations and induced seismicity by my (then) Liverpool research group and the Liverpool Fault Analysis Group showed that there are perhaps thousands of faults present which are not easily recognisable at the Earth’s surface or even on the highest quality seismic investigations and that they have a broad spectrum of stability states. As would be expected in any statistical distribution, some are very stable, others are quite stable, and some are extremely unstable and are capable of being rejuvenated by relatively modest geomechanical or hydrogeological stimuli. I have often in my 40-year career much of which has been spent investigating induced seismicity, asked myself, “Why did this fault actually stop moving and what would it require to start moving again?!”
The triggers may be mechanical; mining (coal and mineral) excavations are good examples, but often are caused by fluid pressure changes, injection of waste-water, extraction of water and hydrocarbons, gas storage and perhaps even by climatic changes such as periods of unusually heavy and persistent rainfall! Sometimes, the causes as in the case of hydraulic fracturing (better known now by the pejorative name “fracking”) combine mechanical deformation with high fluid pressure. Even what we might have surmised were very benign uses of the sub-surface such as Geothermal Energy have caused seismicity, (in Basel for instance) and have led to the projects being abandoned.
Are there unexpected new findings, as knowledge on anthropogenic seismicity advances?
Major spates of significant seismicity perhaps best displayed in the USA – e.g. in Oklahoma where thousands of seismic events have occurred – are clearly associated with the re-injection of waste-water from hydrocarbon activities back into the ground. In the UK the first foray into shale gas exploration through fracking generated seismic events of limited magnitude (2.3ML) but which nevertheless have stimulated major opposition to unconventional gas extraction. It seemed to come as a surprise to the companies but not to me as in the light of experience mining induced seismicity, I predicted that this would be the case! This has been observed in America now as well.
From work which my research group carried out with BP in the 1990s I had become aware that correlated pressure changes had been observed between hydrocarbon wells some 20 km apart, albeit through mechanisms which weren’t then clear and even now are poorly understood. However, recent studies, again mainly in the USA, are reporting induced seismicity many, many kilometres away from the direct injection point, greater than 30 km from the injection point.
What was the genesis of the ICHESE Commission? What kind of information was provided to the Commission, in order to conduct your complex assessment and who delivered it?
I was asked by Professor Paolo Gasparini, at an International meeting on Induced Seismicity held in London whether I would take the chair of a commission, which was being established to examine the relationships, if any, between hydrocarbon extraction activities and the Emilia Romagna Earthquake sequence and I agreed once I knew that the other members were expert, internationally respected academics expert in induced seismicity such as Professors Stanislaw Lasocki (Polish Academy of Science) and Ernst Huenges (Deutsches GeoForschungsZentrum, Germany), in addition to Professors Gasparini and Scandone. As President, I sent a letter (extract below) asking for the following information:
For our first meeting the following information relating to the 2 years preceding the May 20th, 2012, Emilia earthquake, it would be extremely useful, in addition to maps showing the well locations along with particular details such as total depth, complete shutoff of the wells, the current status of wells (open, active, potentially productive but non-operating at present, date of abandonment) if you were able to provide the following information:
- Any new extractive knowledge about fields which are currently operational;
- Details of geophysical exploration activities in the relevant area with descriptions of excitation source and energizing.
- Description of drilling operations;
- Injection pressure and volume data related to any kind of fluid (gas, oil, water) and activities (injection, extraction, storage, etc);
- Microseismicity information from local networks (detailed micro seismicity records).
In order that we do not overlook any extractive activities in different geo-structural contexts, but contiguous to those under investigation, we would kindly ask you to locate and provide, in addition to the information required above, the same information for the area of the concession for natural gas storage in the Minerbio field.
We were presented with a great deal of information on paper as well as a substantial number of presentations from the following companies:
ERS (R. Bencini) – The ERG Rivara Storage
Gas Plus – General overview of the ongoing activities in the considered area
ENI – Local seismic network, data acquired and their analysis
STOGIT – Gas storage in Po Plain
SOCIETÀ PADANA ENERGIA
As Chair of the Commission, do you confirm the conclusions of the ICHESE final report, which states that it cannot be ruled out that the activities carried out in the Mirandola License Area (Cavone Oil Field, Editor’s note) have had a triggering effect on the 2012 Emilia earthquake?
Yes, those were our Commission’s agreed conclusions which we communicated in our final report and I still hold them to be an accurate statement of our findings after a great deal of examination, analysis and synthesis of the information communicated to us.
Since 2014, have there been scientific advances that may further support or negate the controversial hypothesis of the ICHESE Commission?
Various modelling studies have been carried out and published on the Emilia earthquake sequence, which state that it is not possible for the hydrocarbon activities to have acted to influence the faults which failed and gave rise to the catastrophic and devastating seismicity. The Earth, however, does not read these papers or feel bound by their conclusions! Studies in the USA are suggesting that far-reaching poroelastic effects complicate the assessment of distance-based induced seismic hazard and should be included in mitigation strategies as reported by Goebel and Brodsky (Goebel et al., Science 361, 899–904, 2018) and the more we look the more we find evidence of the effect of our anthropogenic activities on the triggering and initiation of new movements on pre-existing faults, especially in areas which are already tectonically complex and inherently unstable.
As reported by Science, shortly after the release of ICHESE there was another report that ruled out any triggering effect on the 2012 earthquake by the Cavone activities. The project was called Monitoring Laboratory of Cavone and was promoted by the Ministry of Economic Development, Regione Emilia Romagna, Padana Energia (the company exploiting the Cavone field), under the sponsorship of Assomineraria (the Italian Petroleum and Mining Industry Association). The conclusions of this study are now officially considered the ultimate verdict on the controversy by the Italian authorities. Was ICHESE informed of this “parallel commission” during its activity and what is your opinion on this procedure and its technical conclusions?
As I describe in some detail below, we were not aware that these studies were being carried out until the final results were communicated to us in December 2013, together with a statement that they ‘proved’ that hydrocarbon activities in the areas could not play any part in the triggering of the seismicity. These studies and further recent published papers are primarily based on numerical modelling of the stresses under certain assumptions, but I do not consider that they alter or would have altered our final conclusions that it cannot be ruled out that the activities carried out in the Mirandola License Area have had a triggering effect on the 2012 catastrophic event.
Your investigation ruled out that other facilities in the area (other than the Cavone field) had triggered the earthquake, namely Spilamberto and Recovato (hydrocarbon exploitation licences in the Modena province), Minerbio (a large natural gas storage reservoir near Bologna) and Casaglia (a geothermal field in Ferrara). Do you think the advancement of knowledge on anthropogenic seismicity or new findings may warrant a reconsideration of these reassuring conclusions?
With the benefit of hindsight, I am not sure that all of the information which might have been relevant to our deliberations was made available to us and so it might be prudent – in the light of the devastating events of 2012, and with an eye to the future – to have another look at these other activities in the context especially of the great deal of careful work which has been carried out, especially in the USA, in the last few years.
Five years later, how do you assess your overall experience as foreign Chairman of the ICHESE Commission?
I was very disappointed with certain aspects of the conduct of this investigation. As President of the ICHESE Commission, we received a request in the first days of December 2013 from two hydrocarbon companies, ENI and Gas Plus (operators in the Mirandola area) to present new analyses that they had carried out on the Mirandola area. This meeting took place on December 13th, 2013 and was attended by two of the Commissioners, Professor Paolo Gasparini and Dr Franco Terlizzese.
I was very concerned to find out that these two companies had independently commissioned two additional reports from external committees, which they presented to the meeting with the stated conclusion that the general academic community was of the opinion that the seismicity was indisputably due to natural tectonic activity. There was also a request (which was refused by the Commissioners present) that the ICHESE Commission did not use terminology such as ‘”non si può escludere che” (it cannot be excluded that)” in our final report. As we had not then reported our conclusions it had to be the case that they had been communicated in advance to the officials by someone who had either been party to our discussion or who had had sight of the minutes.
I considered (and still do consider this) this to be a blatant attempt to interfere in the due process of the considerations of the International Commission and while I cannot speak for the Italian system this would be seen in the UK as an unpardonable breach of protocol and I protested at the time in the strongest possible terms about this and clearly we were not persuaded by the exhortation not to make a certain recommendation.
