​The 1980 eruption of Mount St. Helens taught a very powerful lesson — that one natural hazard can trigger another. For example, eruptions of Vesuvius appear to trigger earthquakes in the Appenines, earthquakes in Papua New Guinea appear to trigger landslides, and the Luzon earthquake may have triggered the eruption of Mount Pinatubo. If we can better understand the mechanical coupling underlying the temporal and spatial correlation of such events, we will improve our assessments of the hazards they pose. Here we propose to study couplings between three classes of natural hazards: earthquakes (EQ), landslides (LS), and volcanoes (VO).

These three phenomena are linked to and by the stress field in the crust. If the stress field changes enough, the material will fail catastrophically. For example, magma injection beneath a volcano can trigger an earthquake by increasing stress on a fault. Increasing shear stress on unconsolidated materials on steep slopes can trigger landslides. Such stress change triggers may also be tectonic (from plate driving forces), hydrological (from heavy rain), or volcanic (magmatic injection). Any of these events can disturb the stress field enough to trigger another event. Indeed, stress changes as small as 0.1 bar (0.01 MPa) suffice to trigger an earthquake. This change increases the Coulomb stress beyond the failure threshold, breaking the material. This quantity is the primary means we will use for describing mechanical coupling. The observational evidence of the stress changes is the surface deformation field.

The objective of RETINA is to use new space geodetic observational techniques for precisely monitoring surface deformation to determine the source of that deformation, and then calculate the Coulomb failure stress generated by that source to quantify the likelihood of triggering further events.

The long term goal of the RETINA project is to improve integrated hazard assessment and support decision making systems through the application of these new models and technologies for understanding the coupling and temporal interactions between earthquakes, volcanoes, and landslides. In three areas of Europe where these linked phenomena are prevalent, the Alps, Iceland, and the Azores, we will exploit existing observational networks and incorporate innovative satellite geodetic techniques that permit centimeter-level monitoring of crustal deformation: Synthetic Aperture Radar interferometry (INSAR) and continuous Global Positioning System (CGPS). Viable technologies will drive new automatic monitoring systems, and the results will be delivered to specifically identified European users with responsibility for risk management.​​​