Scientific Ocean Drilling in the Early 21 Century and Seismic Survey Requirements

Abstract

Abstract The global earth sciences community is currently planning a new scientific drilling program, following and building upon the successes of the Deep Sea Drilling Project (1968–1983) and Ocean Drilling Program (1985–2003). International in scope, the new Integrated Ocean Drilling Program (IODP) will combine multiple drilling platforms, new approaches, and new technologies in addressing major, outstanding Earth system problems. These problems involve both the solid earth and our environment, and include such topics as the earthquake generation zone at convergent plate boundaries, the deep biosphere, gas hydrates, rapid climate change, extreme climates, continental breakup and sedimentary basin formation, large igneous provinces (LIPs), and oceanic crust. Three types of drilling platforms are planned:a deep water, riser-equipped drill ship;a deep water, non-riser drilling vessel; andalternate (fit-to-mission) drilling facilities. All drill sites will require seismic surveys, and the need for sophisticated seismic investigations is especially highlighted in the deep targets planned for the riser vessel. Industrial seismic acquisition and processing have advanced far beyond academic and governmental capabilities in the past decades, but the new scientific drilling program will be state-of-the-art, with continuous coring, downhole logging, and analytical laboratory facilities. Thus, opportunities for industry to cooperate with academia and government in the new era of scientific ocean drilling are highly promising. Introduction In recent decades, scientific ocean drilling has revealed much about the dynamic nature of Planet Earth and the importance of interactions among complex biological systems (including humankind) and the equally complex physical environment though time. Processes operating at all time scales have important scientific and societal impact. For example, over millions of years (Myr) continents are rifted apart, ocean basins open and close, and new mountain ranges form where continents collide. These large-scale plate tectonic interactions cause such short-lived phenomena as large, destructive earthquakes at subduction zones (e.g., Japan trench) or along continental transforms (e.g., San Andreas fault in California), and explosive volcanism in island arcs (e.g., Mt. Pinatubo in the Philippines). These planetary tectonic processes, and accompanying changes in ocean circulation and climate, have profoundly affected both biological evolution and biogeochemical cycling. On intermediate time scales, variations in the Earth's orbital parameters have led to periodic variations in climate, the most dramatic of which is the late Cenozoic alternating expansion and contraction of global ice volume. These more gradual, evolutionary or cyclic changes have been punctuated by as yet unexplained abrupt shifts in climate, by very short-term oscillations in the Earth's climate system, and by catastrophic events such as the impact of large extraterrestrial bodies. As the impact of humankind on the physical world grows, it becomes increasingly urgent to understand the processes which control or influence Earth systems, their natural variability, and the interactions among these systems and with the biological world. With continued growth of the Earth's population, the need to accurately assess global natural resources and understand natural hazards such as earthquakes, volcanoes, and rising sea level is also increasing.