PrESENCE

Very dense seismic networks, consisting of thousands of geophones, are common in the subsurface exploration industry. They allow very detailed imaging of the underground through active or passive seismic methods and have been used to monitor and optimize the development of reservoirs in particular in the oil-and-gas industry through the recording of micro/nano seismicity induced during fluid injections. However, these seismic networks are designed to be installed for a limited amount of time, from a few days to a few weeks, and represent a major investment that is generally unaffordable outside the oil-and-gas industry. By contrast, permanent/long-term monitoring networks are usually restricted to a very few numbers of sensors. This limits, or even precludes, the complete characterization of seismic events (precise location, focal mechanism, source time function, etc.), detailed analysis of repeating events (a signature of aseismic deformation), and 4D imaging from micro-seismicity or ambient seismic noise. These networks are not adequate for reservoir management, which requires detailed information about reservoir structure and dynamics. The PrESENCE project presents and tests a new paradigm of collaborative monitoring of geohazards in urban environments: we will obtain seismological observations using a large number of low cost internet-connected equipment together with strong involvement of local public authorities and citizens. The PrESENCE project focuses on seismic hazards induced by deep geothermal operations and their associated societal perception. This topic is becoming a major issue in the development of renewable energies that involve the subsurface as seismic hazards are of significant public concern and can have major socio-economic impacts. The PrESENCE project is based on our rich experience from the recent seismic crisis in Strasbourg, which culminated in the paroxysmal Dec 4, 2020 M3.6 earthquake that led to the closure of the deep geothermal energy Geoven site (Fonroche-Geothermie company). The breakthrough strategy at the heart of the PrESENCE project relies on the deployment of Dense Semi-permanent Seismic Networks (DSSN) using low-cost seismic stations installed in internet-connected buildings and operated by non-seismologists. This new network concept goes beyond the historical choice between sparse permanent networks and very dense but temporary networks that cannot facilitate long-term monitoring. DSSNs represent an opportunity for traditional seismic network operators (public research institutes or private companies) to benefit from a vast amount of complementary data. The PrESENCE project will characterize the impacts of this new network concept on operational seismic monitoring, subsurface imaging, temporal monitoring of subsurface properties, warning systems, and the estimation of sociological impacts on the perception of seismic risk. The main questions we will tackle are: What are the intrinsic technical performance, limitations and complexity of these low-cost systems in terms of scientific requirements? How do such systems compare to classic and emerging seismic wave field measurement technologies? What scientific contributions can we expect from local or regional-scale DSSN in terms of knowledge of sub-surface reservoirs, their dynamics and the assessment of related hazards? How can DSSN data and products be integrated and used to improve the efficiency of reservoir monitoring? What are the impacts of public commitment in scientific research through the operation of a seismic station, on the public perception and representation of seismology and related scientific and industrial activities?