Digging Deep at Plate Boundary

Sunday, May 27, 2012 Vessel drills deep in 3/11 quake area Kyodo SENDAI — A deep-sea drilling vessel has collected rock samples from 820 meters below the seabed near the epicenter of the Great East Japan Earthquake, the Japan Agency for Marine-Earth Science and Technology said. The maritime research agency said Friday the samples could be from an area forming part of the fault that triggered the magnitude 9.0 earthquake, and that analyzing them could help predict future major quakes off the Pacific coast. An international research team led by Kyoto University conducted the drilling aboard the Chikyu deep-sea exploration vessel in an area 200 km from the Oshika Peninsula in Miyagi Prefecture, the agency said. The samples are the first taken from below the seabed at the boundary of two plates in the Japan Trench, which lies off the Tohoku region, it said.

Viva the Northwest Passage

How many centuries have explorers waited for this to become possible? Thursday, May 24, 2012 Ministry panel to study new Arctic Ocean trade route Jiji The transport ministry plans to set up a panel of experts to study the potential new trade route to Europe via the Arctic Ocean, sources said Wednesday. The envisioned northern sea route would be around 40 percent shorter than traditional routes to Europe via the Strait of Malacca, the Indian Ocean and the Suez Canal, and would thus also help to cut fuel costs and carbon dioxide emissions. The route has attracted mounting global attention in recent years, as the decreasing volume of Arctic sea ice due to global warming has increased its viability.

What about rising sea levels?

One of the questions concerning the submerged ruins off Yonaguni island is this: did they submerge slowly or suddenly? No one knows for sure, but the question matters to today's coastal dwellers. As for today's rising sea levels, global warming accounts for part of it. Water expands as it warms, and the volume of the sea increases as glaciers melt. A new report says there is more to it than those two factors. Tuesday, May 22, 2012 Riddle of rising sea levels said solved AFP-Jiji PARIS — Massive extraction of groundwater can resolve the puzzle over rising sea levels seen in past decades, Japanese scientists said Sunday. Global sea levels rose an average of 1.8 mm per year from 1961 to 2003, according to data from tide gauges. But the big question is how much of this can be pinned on global warming? In its landmark 2007 report, the U.N.'s Nobel Prize-winning Intergovernmental Panel on Climate Change ascribed 1.1 mm per year to thermal expansion of the oceans — water expands when it is heated — and to meltwater from glaciers, icecaps and the Greenland and Antarctica icecaps. That left 0.7 mm per year unaccounted for, a mystery that left many scientists wondering if the data were correct or if there were sources that eluded them. In a study published in the journal Nature Geoscience, a team led by Yadu Pokhrel of the University of Tokyo says the answer lies in water that is extracted from underground aquifers, rivers and lakes for human development but is never replenished. The water eventually makes its way to the sea via rivers and evaporation in the soil, they noted. Groundwater extraction is the main component of additions that account for the mystery gap, according to their paper, which was based on computer modeling. "Together, unsustainable groundwater use, artificial reservoir water impoundment, climate-driven change in terrestrial water storage and the loss of water from closed basins have contributed a sea-level rise of 0.77 mm per year between 1961 and 2003, about 42 percent of the observed sea-level rise," the paper said. The probe sought to fill one of the knowledge gaps in the complex science of climate change.

What's Happening Underneath Mout Fuji (2)

Here is more from The Japan Times online about the fault line running directly under Mt. Fuji: Saturday, May 12, 2012 New Mount Fuji fault seen as threat to Gotemba AFP-Jiji Parts of Mount Fuji could collapse if a newly discovered fault line underneath it shifts, a government-commissioned report warns. The three-year seismological study turned up an active fault underneath the volcano 100 km west of Tokyo that poses a theoretical threat to a city nearby. "It's possible that (parts of) the mountain could collapse, sending mudslides flowing into Gotemba," which is situated between the mountain and the Pacific, said Yasuhiro Yoshida, director for earthquake investigation at the science ministry. Researchers led by academics from the University of Tokyo fired simulated seismic waves at the mountain that revealed a fault theoretically capable of generating a magnitude 7 quake. The team believes the fault has shifted some time within the past million years, although it is not certain exactly when. Yoshida said the local geography shows that Mount Fuji experienced major mudslides nearly 3,000 years ago, but more studies are required to determine how the fault could affect potential volcanic activity, and vice versa.

What's Happening Underneath Mt. Fuji?

The results of a geological survey were reported in The Japan Times online. Friday, May 11, 2012 Active fault may lie directly beneath Mount Fuji: researchers Kyodo An active fault as long as 30 km may lie directly beneath Mount Fuji, a team of researchers has said in a recent survey report. The possible fault was detected through a simulated earthquake conducted during a crustal survey over a distance of around 34 km from Fujiyoshida in Yamanashi Prefecture to Susono in Shizuoka Prefecture, said Hiroshi Sato, professor at the Earthquake Research Institute at the University of Tokyo. "More studies are needed to determine the depth and other details of the fault," Sato added. While faults have been confirmed around Mount Fuji, little is known about the seismic structure beneath Japan's highest mountain due to mudflows caused by a huge landslide that occurred around 2,600 to 2,900 years ago, as well as thick layers of volcanic ash.

What's Happening Under the Sea?

Tuesday, May 8, 2012 Extremely slow quakes confirmed Jiji Extremely slow earthquakes occurred at the Nankai Trough, south of Japan, in March 2009, Japanese researchers have reported. Crustal ruptures in the earthquakes took 30 to 100 seconds, compared with some 1 to 2 seconds in ordinary quakes with magnitude of around 4, said the researchers, including members of the Japan Agency for Marine-Earth Science and Technology, or JAMSTEC. The findings were published in the latest online edition of the British journal Nature Geoscience. The low-frequency earthquakes took place in unexpectedly shallow areas of the plate boundary, suggesting such areas may be a source of so-called tsunami earthquakes that cause disproportionately large tsunami for their seismic energy, the researchers said. By setting up broadband seismometers off the coast of Tanabe, in Wakayama Prefecture, they observed the earthquakes for 10 days from March 22, 2009. "Our research could lead to understanding the mechanism of tsunami quakes, which could cause severe damage, and it is necessary to continue the research for the long run," said Hiroko Sugioka, a JAMSTEC researcher. (from The Japan Times online, May 8, 2012)