In the last two weeks, more than 50 small earthquakes hit the villages of the foothills of the Sierra de El Perdón in Navarra. It is another seismic swarm like the one experienced in 2007, at that time longer, about two months and more than 60 tremors, or like the one in 1982, then more violent and with scenes of panic in that capital, Pamplona, which already sheltered 175,000 people; the epicentral zone is only about 10 km from the city.

A seismic swarm is not something extraordinary, they have occurred before and will continue to do so in the future, but the key issues to pay attention to are:

1. Are there known potentially dangerous entity failures?

2. Are there precedents of intense impacts in the study of historical seismicity?

As for the area of El Perdón to the south of the capital of Navarra, where today more than 350,000 people live, maintaining a certain calm is not so easy, people ask for information and today it is easy to find. Unlike what has been observed for example in similar episodes such as those of Jaen, the source of the tremors can be associated directly or indirectly to the so-called fault of Pamplona or Estella, this has a known seismogenic character, although even the programs of study on what could come to originate are quite scarce; It is very likely that this episode is due to a segment of the same fault or to an associated fault reactivated by an increase in fluid pressure due to historically unprecedented rainfall; January exceeded 310 liters, something not seen since 1880, and February, still unfinished, has no equal. A year's worth of rainfall, close to 500 liters, has already fallen in two months.

The historical precedents of 1982 with earthquakes between 4.5 and 5 in that same district, should mean that this area and nearby areas should have been considered for years as special risk areas for urbanization, construction, etc. Undoubtedly a pending subject of the people of Navarre.

The geologist Esteban Faci, from department de Fomento, has considered that "it is most likely that these seismic movements are due to the high rainfall recorded in the area in January and February". (ABC 26-II-2013). It would be a new episode of natural hydroseismicity, and is that the geography of Navarre after more than 300% of rainfall with respect to the known average , suffers everywhere landslides, liquefactions, hillsides that move, cuts in roads, breaks in the water supply, evacuations and earthquakes. It is sad to think that the best programs of study in this regard could have been made in Spain, but Germany, Brazil, India, France, Italy or USA document and report these phenomena for years in congresses and specialized media, we still do not have any, despite the popular wisdom that we carry in our Genetics, Granada or Navarra coincide in popular sayings: "year of rains, year of tremors".

The construction sector earned money in abundance in the last years of bonanza, but did not care the least to ensure its future through investment in research and development+i, today they could have had some pioneering programs of study dedicated to the object of its activity: the territory, thus ensuring part of its future; but neither was driven from the administrations such challenge, although experts have been proclaiming for years the need to face the urban XXI century in the least vulnerable way.

It is very likely that the 1903 Pamplona earthquake had an origin linked to this seismogenetic source , then 30,000 people lived in the Pamplona Basin, it seems that it was a multiple earthquake and at the same time faults were activated in several areas of Navarra, even the impact was very violent in San Sebastian.

We should not alarm the population, but today's reality is what it is and the historical reality is what we have inherited. Perhaps we as human beings with little report have underestimated the seismic danger and we only remember Santa Barbara when it thunders. However, we must remember: several towns included in the Pyrenean seismic area , have been hit in the past by destructive earthquakes; at least four major earthquakes with magnitudes of 6 to 7 and intensities VIII to X during the last 650 years; even so, no special plans of urban planning or technical inspection of buildings have been developed according to this natural reality, especially in towns with more than 10,000 inhabitants in Navarra, Guipúzcoa or Álava. 

Pamplona was the epicenter and the scene in 1903 of that earthquake that reached a Degree of intensity VI and affected some 30,000 people. It seems appropriate and necessary to face the 21st century with this reality in mind in the future growth plans of the metropolitan area of one of the most modern but also most vulnerable cities in Spain. We have to think about it as soon as possible and plan accordingly. We can no longer assume that no damage will result from our changes in the water table, thinking in this way to continue without taking measures to be included in the urban planning and building regulations.

I hope that in time governments will recognize that the damage may become a reality; and worse if we continue to avoid contributing funds from research that we should be devoting to understanding this fragile interface, between the atmosphere and the hydrosphere, in which we live.