Submarine earthquakes can dramatically affect a large number of coastal areas. Europe and its overseas regions are also threatened, as the Mediterranean-Gibraltar-Azores system, the Caribbean, the area surrounding Mayotte and the Andean subduction zones among others host a number of offshore active faults able to produce major earthquakes and tsunamis. Despite their potential impacts, earthquake processes are still not understood, even though significant conceptual progress has been made over the last fifteen years based on the combination of land-based seismological and geodetic data. For instance, the discovery of slow-slip events (SSE) has radically changed our views of stress release at subduction zones and raised the possibility of predictability of large earthquakes. However, because the active processes occur below the ocean floor, further progress is hampered by the lack of appropriate seafloor seismological and geodetic instrumentation. More generally, while most of the seismic energy is released at plate boundaries below the oceans, only an insignificant fraction of the world’s seismicity is recorded by stations deployed on the ocean bottom.
To address the observational gap in the ocean, a number of developed countries have mobilized important financial resources to develop large-scale, fixed, cabled ocean-bottom observatories, like DONET and SNET in Japan; Ocean Networks in Canada; Ocean Observatory Initiative in the USA . In addition, the international community must be ready to collect new data at as many sites as possible, including in Europe and in its oversea regions, with the appropriate offshore instrumentation, autonomous and mobile. One may here refer to the example of the USA, that has developed since 1999 a national pool of marine instrumentation, presently hosted under the umbrella of IRIS.
MARMOR’s ambition is to start developing such a pool for France, under the umbrella of RESIF-EPOS, with the idea of extending this initiative at the European level, in order to get closer to the sources of submarine earthquakes which release most of the seismic energy affecting the Earth.