Exploring new drilling prospects in the southwest Pacific

A major International Ocean Discovery Program (IODP) workshop covering scientific ocean drilling in the southwest Pacific Ocean was held in Sydney, Australia, in late 2012. The workshop covered all fields of geoscience, and drilling targets in the area from the Equator to Antarctica. High-quality contributions and a positive and cooperative atmosphere ensured its success. The four science themes of the new IODP science plan were addressed. An additional resource-oriented theme considered possible co-investment opportunities involving IODP vessels. As a result of the workshop, existing proposals were revised and new ones written for the April 2013 deadline. Many of the proposals are broad and multidisciplinary in nature, hence broadening the scientific knowledge that can be produced by using the IODP infrastructure. This report briefly outlines the workshop and the related drilling plans

A review of the 2011 Tohoku-Oki earthquake (Mw 9.0): Large-scale rupture across heterogeneous plate coupling

The 2011 Tohoku-Oki earthquake ruptured a large source region, which included areas with a range of past M 7 to M 8 earthquakes, varying stress accumulation, and different structural features. This megathrust event was substantially larger than anticipated in this region, though there were indications that the sequences of events in recent times were insufficient to relieve the full accumulated strain in the relatively rapid subduction of the Pacific plate. The source process time of about 150. s included rupture of an area of very large slip (30 to 60. m) on the shallow portion of the megathrust, updip of the hypocenter. The area of large slip produced large amplitude low-frequency radiation, while the dominant high-frequency radiation was generated from deeper sources down-dip of the hypocenter. Real-time information systems in Japan were able to issue timely warnings of the strong shaking and tsunami, but the complicated pattern of rupture growth led to an underestimate in the initial estimates of magnitude and tsunami threat. Variations in the plate coupling and heterogeneities of physical properties in the megathrust zone characterize the different source areas that ruptured together during the earthquake. Tomographic images of shear-wave and bulk-sound speeds show subtle changes of physical properties that may be associated with coupling condition and present clues for understanding the rupture process of this Mw 9 earthquake, which combined the source areas of many past earthquakes

Drilling Reveals Climatic Consequences of Tasmanian Gateway Opening

One of the great stories of geoscience is how Gondwana broke up and the other southern continents drifted northward from Antarctica, which led to major changes in global climate. The recent drilling of Ocean Drilling Project (ODP) Leg 189 addressed in detail what happened as Australia drifted away from Antarctica and the Tasmanian Gateway opened. The drifting contributed to the change in global climate, from relatively warm early Cenozoic “greenhouse” conditions to late Cenozoic “icehouse” conditions. It isolated Antarctica from warm gyral surface currents from the north and provided the critical deepwater conduits that eventually led to ocean conveyor circulation between the Atlantic and Pacific Oceans