Towards multiscalar and multiparameter networks for the next century: The French efforts

The design of the future networks cannot be separated from the scientific issues which scientists are faced to, nor from the new technology tools that are to be developed for the next century. The trilogy, science, scientist and instrument must be web balanced in order to make implementation of the network achievable. Since most of the scientific issues are multiscalar for spatial scales as well as for temporal scales, we present the general design of the network which should enable us to address these scientific issues. They must be able to explore different scales of heterogeneities from global scale to local scale. We review in this paper the different technological developments, which are presently explored, and which prefigure what will be the future geophysical networks. The technical developments carried out by various French scientific programs (GEOSCOPE, OPTIMISM, SOFM) will be presented as an illustration. The concept of multiparameter station is defined and it demonstrated the great scientific interest in installing different kinds of sensors at the same place in a seismic station. Every seismic station will have to be transformed into a multiparameter geophysical station. It is also necessary to cover the oceanic desert by a dense network of geophysical observatories which can fulfill the scientific requirements of the whole geoscientist community. The recent progresses made by Japanese, French and US groups show that the technical challenge of installing permanent geophysical ocean bottom observatories (coined GOBOs) is not out of reach. Therefore, the new generation network will have to be composed of multiparameter continental or oceanic stations including at least broadband seismometers, microbarometers, microthermometers, and eventually other sensors (electromagnetic sensors, strainmeters, GPS,...). The design of the complete chain of acquisition, from the sensor to the distribution of data, will imply the integration of all the technical progresses made in micromechanics, electronics, computers, space science, and telecommunication systems. Finally, the new generation of geophysical networks must be able to provide scientific data at all scales, from the global scale to the local scale. The networks at all scales must be coordinated in order to constitute a hierarchical or multiscalar network, which will constitute the basic tool for addressing scientific issues in geosciences. The efforts necessary to achieve such a hierarchical, multiparameter network represent a formidable technological challenge for the next ten years. (C) 1998 Elsevier Science B.V. All rights reserved.