Over 300 microtremors hit the northern area of Valencia and southern Catalonia the first week of October. The quakes could be related to the recent injection of natural gas by the Castor Project  [es], a submarine natural gas company found along the Mediterranean coasts of those areas.
The injection is meant to convert an empty oil reserve into a gas storage facility. The Spanish government has stopped  [es] the gas injection, which began a few weeks ago, until technical reports clarify the matter. The company denies the injection caused the tremors, but ecological and political sectors view a direct relationship, and local online movements have begun to speak out against the project using the hashtag #projectecastor  [ca] (Castor Project) on Twitter. The protests connect  [ca] the injection practices with the globally controversial technique of fracking .
The Castor Project boasts  [es] an oil well 1,750 meters (approximately 1.1 miles) deep that stores enough gas to serve up to a third of the Spanish demand. The project, which cost 1.3 billion euros (1.762 billion US dollars), was granted approval by a joint venture with the canadian CLP (30 percent) and the Spanish ACS (70 percent), a construction company supervised by Florentino Pérez, who also oversees the football club Real Madrid.
Even though the movement against the project emerged strongly after these possibly related quakes, some ecologists and politicians have already been warning against these same sorts of threats for some time. On his blog, European parliament member and ecologist Raül Romeva noted  [ca] that the concern over this gas company should not come as unexpected:
Potser hi ha qui s’ha sorprès amb les recents notícies relacionades amb els moviments sísmics que han tingut lloc a la costa, davant de Vinaròs, relacionats amb la planta d'emmagatzematge de gas, més coneguda com a Projecte Castor. No obstant, cal recordar que fa molt de temps que molta gent ens ve advertint dels riscos vinculats a aquesta mena d’explotacions, i que han fet arribar a les diferents institucions les seves preocupacions.
Perhaps there are some who have been surprised by the recent news related to the seismic movements that took place on the coast, in front of Vinaròs, related to the oil plant, better know as the Castor Project. Nevertheless, we must remember that a long time ago, many people warned us about the risks linked to this kind of cultivation, and that their concerns were sent to the different institutions.
On Twitter, Juan López de Uralde, member of the political and social movement EQUO  [es], warned of the consequences that a project like Castor could create and criticizes the Spanish energy policy:
Regarding #Castor on the Mediterranean coast. It shows the absurd Spanish energy policy: support for gas and punishment for renewables.
The mayors of some of the towns affected by the tremors have come out against the project, as announced in this tweet from the Platform in Defense of the Lands of Sénia  [ca/es], located in the town of Sénia on the Catalan border near Valencia:
Marcelino Domingo, alcalde del PP de Benicarló, anuncia al seu perfil de FB q demanarà la paralització i desmantellament del #ProjecteCastor — Plataforma pel Sénia (@plataformasenia) October 1, 2013 
Marcelino Domingo, head of the People's Party  [es] in Benicarló, announces on his FB profile that he'll order the cessation and dismantling of #ProjecteCastor
In an interview with the leading Catalan online periodical, VilaWeb  [ca], Lluc Ulldemolins, of the same Sénia Platform, shows the fears of uncertainty about the origin of the earthquakes, which continue even though the Spanish government assures that the gas injection has stopped:
—Sí, l'empresa diu que ja no injecta gas, però els terratrèmols han agafat més intensitat. I això encara és més preocupant. Si sabéssim que hi ha terratrèmols perquè s'injecta gas, tindríem la causa controlada. Però si és cert que l'empresa ho ha aturat, i amb tot i això els terratrèmols continuen, és que la situació és més complicada que no ens podíem imaginar. A qui ens hem de creure? Realment preferiríem que fos l'empresa que mentís, no per donar-li la culpa, sinó perquè almenys sabríem la raó dels moviments sísmics.
—Yes, the company says they no longer inject gas, but the earthquakes have gained force. And that's even more worrisome. If we knew that there were tremors because gas has been injected, we would have the cause controlled. But if it's true that the company has stopped injecting, and yet the quakes still continue, the situation is more complicated than we could ever imagine. Who are we to believe? We'd really prefer that the company lie, not to put them at fault, but rather to, at least, know the reason behind the seismic movements.
While the indignation and fear grow within the population, the natural gas company, according to some press reports  [es], has begun to make arrangements to get rid of the grant and charge a compensation. The company has the right to reverse the grant to the state and receive the net value as compensation, since the project was promoted by Ministry of Industry.