1. Mar 30, 2011 – Workshop Seafloor geodesy – the need to respond to an imminent challenge Peter La Femina, Dept. of Geosciences, Penn State, USA Christoph Waldmann, Achim Kopf Center of Marine Environmental Sciences, MARUM, Germany

2. Most seismic and volcanic activity on Earth occurs underwater. This includes approximately 60,000 km of mid-ocean spreading ridges, where oceanic plates grow by volcano-tectonic processes, and associated transform faults. The most actively deforming portions of the world’s 55,000 km of subduction zones are covered by water Substantial seafloor deformation is also associated with submarine land-sliding, hydrocarbon extraction, and CO2 injection into submarine reservoirs. The Challenges in Seafloor Geodesy

3. Despite the progress that has been made over the past three decades, seafloor geodesy is only slowly beginning to transition from demonstration projects to comprehensive monitoring systems. We expect that the development of more advanced and lower-cost seafloor geodetic systems will lead to more comprehensive monitoring of a wide range of submarine deformation processes and the hazards and resources they reveal. Bürgmann, Chadwell, Seafloor Geodesy, Annu. Rev. Earth Planet. Sci. 2014. 42:509–34 The Challenges in Seafloor Geodesy

4. GPS-A using kinematic GPS positioning of a ship or buoy to precisely determine the location of a transponder array on the seafloor in a global reference frame. The Challenges in Seafloor Geodesy - Technology Required precision – cm Current precision - ~ m

5. In Europe, Canada, and the USA there are a number of groups active in this field to investigate: Triggering effects of Tsunami events Impact of landslides Impact of human intervention/impacts on the deep sea, i.e., deep sea hydrocarbon extraction and mining activities. A closer exchange between working groups across the Atlantic is needed to target specific regions and make results intercomparable. The transatlantic perspective

6. Develop a transatlantic marine geodesy working group or organize workshops to: Narrow down the requirements on seafloor geodesy based on existing knowledge & technologies Carry out a systematic inter-comparison of methods Explore alternative approaches (laser ranging) Suggest a concept that allows for verification of methods and validation of results Synchronize with terrestrial techniques and projects The suggested approach