Addressing Geologic Hazards through International Ocean Drilling Program Workshop

The Illinois State Geological Survey contributes to the International Ocean Drilling Geo Hazard Program (IODP) by developing the Coastal Zone Geo Hazard Geophysical Observation System based on off shore drilling platforms. As was dramatically shown by the Sumatra earthquake and associated tsunami of late 2004, the oceans are the source of some of the most severe geologic hazards. Large tsunamigenic earthquakes tend to occur several times per century, commonly near coastal areas, with devastating impacts on communities and coastlines both near to and far from the source. Smaller earthquakes also can generate significant tsunamis, often much larger than predicted by the earthquake magnitudes. Global examples are well known and include seismically active plate boundaries of all types. Oceanic hazards are generated in many other settings as well. These settings include passive margins in which rapid sedimentation, fluid overpressure, or gas hydrate dissociation can cause slope failure. Explosive eruptions and sudden flank deformation on coastal or island volcanoes can induce sector collapse and catastrophic landslides and have the potential to generate devastating tsunami and related coastal damage.

The mechanisms and controls on tsunamigenic deformation are still incompletely understood, as are their distribution in time and space. Because of their oceanic setting, tsunamigenic events are often preserved in the marine sedimentary record. Thus, ocean drilling provides several new opportunities to extract and read this geologic record and to monitor physical and chemical processes and changes in material properties associated with dangerous geologic phenomena. Developing a sound scientific understanding of the geological and physical processes underlying these hazards is crucial to efforts to evaluate their distributions, to produce predictive models, and to mitigate their risks. Presently, the characterization and understanding of the causes and consequences of oceanic geologic hazards is an under realized element of the IODP Initial Science Plan.

The workshop, which convened in Portland, Oregon, August 26 to 30, 2007, was designed to establish the current state of community knowledge and activity in the area of submarine geologic hazards and to address a series of focused questions. In particular, investigations of geologic hazards through scientific ocean drilling still face many obstacles. The understanding of the necessary conditions and triggers for catastrophic geologic events (e.g., landslides, earthquakes, and tsunami) is incomplete, and instruments for making in situ or remote measurements of the geotechnical and other material properties of the rocks and sediments involved are limited. Moreover, there is a need to define tractable scientific questions and to design realistic science and engineering plans that can actually answer them. Key goals of the workshop were to define outstanding research questions that can be addressed through scientific ocean drilling, establish scientific priorities, identify potential drilling targets, evaluate existing technologies and scientific approaches, and formulate strategies to overcome anticipated scientific and engineering challenges. The workshop enhanced international collaborations and stimulated teams of proponents who are expected to develop competitive IODP proposals addressing oceanic geologic hazards.