Do Clues to Japan Earthquake Lie Under Costa Rican Seafloor?
Roca Bruja, Northern Pacific coast of Costa Rica
Excerpts; By OurAmazingPlanet
Pieces of rock and seafloor from deep in the Pacific Ocean near Costa Rica may help explain why Japan’s deadly magnitude 9.0 quake and consecutive tsunami were so large.
Nearly one mile of sediment cores (cylinders of earth drilled out from the ground) collected from the ocean floor off the coast of Costa Rica reveal detailed records of some two million years of tectonic activity along a nearby seismic plate boundary, where one tectonic plate dives beneath another, called a subduction zone. It was the rupture of a subduction zone that generated the Japan temblor.
The scientific drilling vessel JOIDES Resolution retrieved the samples during a recent monthlong expedition called the Costa Rica Seismogenesis Project (CRISP). Participating scientists aim to use the samples to better understand the processes that control the triggering of large earthquakes at subduction zones.
More than 80 percent of global earthquakes above magnitude 8.0 occur along subduction zones.
“It’s critical to understand how subduction zone earthquakes and tsunamis originate, especially in light of recent events in Japan,” said Rodey Batiza of the National Science Foundation’s Division of Ocean Sciences. …
