Scientific Expedition Studies Geology of Costa Rican Earthquake Fault
Puntarenas, Costa Rica – An international team of scientists has just returned from an ocean drilling expedition on board the JOIDES Resolution,near the Pacific coast of Costa Rica, designed to study the subduction zone where the Cocos tectonic plate dips beneath the Caribbean plate. This fault boundary was responsible for causing two earthquakes earlier this year, on September 5 and October 23. While the epicenter of those quakes was north of the study site, under the Nicoya Peninsula, the samples and data collected offshore will help scientists better understand how earthquakes happen – here in Costa Rica and elsewhere.
Integrated Ocean Drilling Program (IODP) Expedition 344 (Costa Rica Seismogenesis Project A Stage 2), also known as CRISP 2, picked up where Expedition 334 (CRISP 1) left off last year. The study site, near the Osa Peninsula, is of particular interest for two major reasons. First, it is a relatively shallow subduction zone, and such boundaries are responsible for some of the world’s deadliest and most damaging earthquakes and tsunamis. Second, the boundary is an erosive convergent margin, a type that is relatively poorly understood by scientists.
“There are a lot of subduction zones where we could drill – and have drilled – to study earthquake processes. However, the Cocos-Caribbean margin represents a particularly strategic opportunity to learn about shallow, erosive margins,” says co-chief scientist Robert Harris of Oregon State University. “What we learn here could potentially frame new research questions for decades to come.”
In contrast to accretionary convergent margins, which transfer sediments to the overlying plate as the subducting plate travels deeper, erosive margins like the Cocos-Caribbean boundary drag large amounts of sediment into the Earth’s interior. Because this process removes mass from the upper plate, it can cause the overlying ground to subside, potentially generating seismic activity. While accretionary margins have been studied more extensively, scientists still have much to learn about erosive margins. Drilling into these zones is the only way to directly observe the processes responsible for damaging seismic activity.
The expedition left from Panama on October 23 and concluded in Puntarenas on December 11. The team drilled 10 boreholes, each of which penetrated from 25 to 800 meters into the ocean floor. Core samples, as well as data recorded from the borehole walls using sensitive instruments lowered into the holes, will help the team characterize the geophysical and chemical properties of the seismogenic zone. In total, the team recovered more than one and a half kilometers of core.
“Our purpose is to understand the mechanisms of earthquakes and tsunamigenesis,” says co-chief scientist Arito Sakaguchi of the Japan Agency for Marine-Earth Science and Technology. “This is basic science, but the knowledge will contribute to disaster management and will help people in countries like Japan and Costa Rica.”
The science team comprises 34 scientists from 12 IODP member countries, including the first participants from Brazil – the newest nation to join IODP. An educator and a computer graphics animator also joined to share updates from the expedition. The team shared photos, blog entries, and videos with the public using social media tools, and participated in videoconferences with schools from around the world. For more information, see the websites below.
The Integrated Ocean Drilling Program (IODP) is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The JOIDES Resolution is a scientific research vessel managed by the U.S. Implementing Organization of IODP (USIO). Together, Texas A&M University, Lamont-Doherty Earth Observatory of Columbia University, and the Consortium for Ocean Leadership compose the USIO. IODP is supported by two lead agencies: the U.S. National Science Foundation (NSF) and Japan’s Ministry of Education, Culture, Sports, Science, and Technology. Additional program support comes from the European Consortium for Ocean Research Drilling (ECORD), the Australia-New Zealand IODP Consortium (ANZIC), India’s Ministry of Earth Sciences, the People’s Republic of China (Ministry of Science and Technology), the Korea Institute of Geoscience and Mineral Resources, and Brazil’s Ministry of Education (CAPES). For more information, visit www.iodp.org.
For more information about IODP Expedition 344 (Costa Rica Seismogenesis Project A Stage 2), visit http://iodp.tamu.edu/scienceops/expeditions/costa_rica_seismogenesis.html
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Consortium for Ocean Leadership
Washington, D.C. USA
IODP Management International, Inc. (IODP-MI)