JAMSTEC: Japan deep sea drilling boat Chikyu casts off to find Earthquakes

Japan's deep-sea drilling vessel Chikyu is anchored at Shimizu port, Shizuoka prefecture on September 11, 2013. 

A Japan-led team of seismologists set off Friday on a mission to drill deep beneath the seabed in a search for the origin of earthquakes.

A Japan-led team of seismologists set off Friday on a mission to drill deep beneath the seabed in a search for the origin of earthquakes.

The scientists weighed anchor on Japan's deep-sea drilling vessel Chikyu, heading for a spot in the ocean off the Kii peninsula, southwestern Japan, and a fracture in the Earth's crust known as the Nankai Trough.

Experts have warned the trough, which marks the place where the Philippine Sea plate slides under the Eurasian plate, is the likely source of a monster earthquake sometime in the near future.

Tamano Omata

Japan's government last year unveiled a worst-case scenario, warning a big quake in the area could kill over 320,000 people, dwarfing the March 11, 2011, quake-tsunami disaster.

In its four-month mission, the latest stage of a multi-year project that began in 2007, the team plans to drill 3,600 metres (2.2 miles) down and take samples from the crust.

They will also be readying for another trip next year in which they hope to get 5,200 metres down, to the spot where the action actually happens.

"It would be unprecedented to drill directly into a seismogenic zone, the area believed to release great energy and cause crusts to slide along fault lines and trigger tsunami," said Tamano Omata, a researcher for the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).

Scientists want to plant sensors—such as seismometers, deformation-measuring devices and thermometers—in the zone, that will form part of a system called Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET), which is linked directly to onshore monitors.

"We expect to become able to monitor how the crusts move immediately before a quake hits," Omata said.

Shinichi Kuramoto

Shinichi Kuramoto, deputy director of JAMSTEC's Center for Deep Earth Exploration, said recent research has shown mild earthquakes, in which the two crusts slip gently past each other, have occurred frequently over stretches of the Nankai Trough in the past five years.

He said it was possible these were precursors to a mega-quake.

"Directly drilling into and observing the place that may release a big quake would be a big step towards understanding the seismological mechanism," he said.

The 56,752-ton Chikyu—"Earth" in Japanese—has been anchored in central Shimizu port, and was open to foreign press this week ahead of the mission.

The vessel, built in 2005 at a cost of $500 million, is equipped with a 121-metre (400-foot) drill tower that can descend 7,000 metres below the seabed, nearly three times as deep as its predecessors.

It depends on satellite location systems with pinpoint accuracy that allow its captain to know exactly where the ship is in relation to the Earth's crust.

Seismically-active Japan experiences 20 percent of the world's major earthquakes every year.

Building standards are high and its people are well-practised at taking cover when quakes strike, meaning damage and death tolls are often much lower than in other parts of the world.

But its proximity to major tectonic faults means the risk is ever-present.

DONET is a submarine cabled real-time seafloor observation infrastructure which was designed to realize precise earthquakes and tsunamis monitoring on seafloor in the long period of time. 

It consists of an approximately 300km length of backbone cable system, 5 science nodes, and 20 observatories. 

Its installation on 20 stations at Kumanonada started in 2006 and has been completed in July 2011.

Research Shows Buildings can Amplify Tsunami Waves

Scientists have re-created an entire city in miniature to model the way a tsunami crashes onshore, and have found that buildings can exacerbate the oncoming rush of water.

The findings, presented Monday at the annual meeting of the American Geophysical Union, show that even if a city overall tolerates the force of a massive tsunami well, certain buildings and alleyways may concentrate the rushing wave, generating 80 to 100 times the speed of waves without buildings.

"When we think about designing structures or planning for city layouts, understanding the real, detailed tsunami flow through the built environment is very, very important," said study co-author Patrick Lynett, a civil engineer at the University of Southern California.

In the 2004 Indian Ocean tsunami and the 2011 Japanese tsunami, building engineers routinely noticed that there were often two buildings standing, while one located in the middle behind it was completely washed away.

Lynett and his colleagues wanted to understand why that occurred. Such an understanding is particularly important given studies showing that the West Coast is more vulnerable to tsunamis than previously thought.

To understand how a tsunami affects a coastal city, Lynett and his team created a 1:50 scale replica of the entire town of Seaside, Ore. They then flooded it with a simulated tsunami 7.9 inches (20 centimeters) high and 5 seconds long that mimicked the relative height and duration of a 200-year tsunami, Lynett reported.

As water broke over the tiny buildings, the team noticed that certain hotspots concentrated the effects of the waves. A U-shaped hotel on the coast seemed to focus the impact of the tsunami, Lynett said. "We call it the tsunami-catcher because it really amplifies the speed," he said.

Buildings arranged in a T, with two buildings in front of the wave and another building behind them, also seemed to emphasise the wave's impact.

Overall, some parts of the city experienced 80 to 100 times the maximum speed and momentum that would occur without any buildings in the landscape, Lynett added. In addition to T-shaped building layouts, narrow alleyways could lead to much higher speeds of rushing water.

The findings suggest that engineers designing seaside buildings should use some of the same modeling approaches used to assess wind forces on skyscrapers, Lynett said.

"This is an argument here that, when we're trying to understand the fluid flow through a city, shadowing and concentration of fluid flow through the built environment becomes very important."

NASA Messenger: Mercury's tectonic plates and pie crust surfaces

NASA MESSENGER has discovered assemblages of tectonic landforms unlike any previously found on Mercury or elsewhere in the Solar System.

The findings are reported in a paper led by Smithsonian scientist Thomas Watters, "Extension and contraction within volcanically buried impact craters and basins on Mercury," published in the December issue of the journal Geology.

The surface of Mercury is covered with deformational landforms that formed by faulting in response to horizontal contraction or shortening as the planet's interior cooled and surface area shrank, causing blocks of crustal material to be pushed together.

Contraction from cooling of Mercury's interior has been so dominant that extensional landforms caused by fault formation in response to horizontal stretching and pulling apart of crustal material had not been previously documented outside of the interiors of a few large impact basins.

ESA ENVISAT Image: Bali, Lombok, and Sumbawa: Where Worlds Collide

This image from the Envisat satellite is dominated by the Indonesian islands of Bali, Lombok and Sumbawa.

All three are part of the volcanic Sunda Arc along the submarine Java trench, where two tectonic plates are moving towards one another, and one slides under the other.

This tectonic deformation along the Java trench caused the 2004 Indian Ocean earthquake and subsequent tsunami.

To the west is Bali, one of Indonesia's main tourist destinations. The island's central mountains include peaks that reach over 3000 m, including an active volcano visible on the right side of the island.

Strong reflections of the radar signal used to produce this image appear like specks of light. They are mainly detectable in the southern part of the island, and are particularly concentrated around the provincial capital city of Denpasar.

This is the typical appearance of built-up areas in radar images, owing to the multiple reflection of the radar beam by buildings and especially metal constructions.

In the centre of the image is Lombok. Similar to Bali, we can see multiple reflections concentrated around the city of Mataram.

Varying colours stretch across the island's lowlands, which are highly cultivated, depicting changes in the land.

Sumbawa island lies to the east, dominated by mountainous terrain. This is also home to Mount Tambora, an active volcano.

In 1815, its massive eruption caused heavy ash falls that ruined local agriculture and even affected much of the Northern Hemisphere.

The deaths of over 70 000 people are attributed to this event. This image is a compilation of three passes by Envisat's radar on 20 June, 19 August and 17 December 2011.

Each is assigned a colour (red, green and blue) and combined to produce this representation. The colours reveal changes in the surface between Envisat's passes.

Seafloor Mountain Expedition Studied Crust's Deepest Layer

A topographical map of the Atlantis Massif, which also shows the location of its Lost City hydrothermal vents.

CREDIT: NOAA.

Scientists recently returned from an expedition to an unusual seafloor mountain, where they conducted what may be the first-ever on-site study of a type of rock that makes up a huge amount of our planet, but is largely out of reach.

Researchers aboard the research vessel JOIDES Resolution sent instruments to the Atlantis Massif, a seamount that lies near the Mid-Atlantic Ridge, a long volcanic rift bisecting the Atlantic Ocean, where two tectonic plates are being slowly shoved apart and fresh oceanic crust is created.

Seamounts are essentially a mountain that doesn't rise above the ocean's surface.

Unlike most seamounts, which are typically made of volcanic rock, geological forces essentially yanked the Atlantis Massif from the Earth's gabbroic layer — the deepest layer of the Earth's crust, which rests directly on the planet's ever-shifting mantle.

High-Res Show Crust-Mantle Boundary - Moho, Where Is Earth's Mantle?

This map shows the global Mohorovičić discontinuity, better known as Moho, based on data from the GOCE satellite.

CREDIT: GEMMA project

Beneath the Earth's crust, the outermost hard shell that makes up just 1 percent of the volume of the planet, lies a hot, viscous layer of rock called the mantle.

Together, the crust and upper portion of the mantle. called the lithosphere, are where most important geological processes occur, such as mountain-building, earthquakes and the source of volcanoes.

The slow churning and overturning of the mantle is what drives the movements of Earth's tectonic plates.

New methods of observation using satellites are helping scientists learn more about this important layer of the Earth's inner and outer layers and where it begins under different regions of the planet.

Andrija Mohorovičić
Until just a century ago, we didn’t know Earth has a crust. In 1909, Croatian seismologist Andrija Mohorovičić found that at about 50 km underground there is a sudden change in seismic speed.

Ever since, that boundary between Earth’s crust and underlying mantle has been known as the Mohorovičić discontinuity, or Moho.

Even today, almost all we know about Earth’s deep layers comes from two methods: seismic and gravimetric.

Seismic methods are based on observing changes in the propagation velocity of seismic waves between the crust and mantle.

Gravimetry looks at the gravitational effect due to the density difference caused by the changing composition of crust and mantle.

But the Moho models based on seismic or gravity data are usually limited by poor data coverage or data being only available along single profiles.

GEMMA Project

GEMMA’s Moho map is based on the inversion of homogenous well-distributed gravimetric data.

For the first time, it is possible to estimate the Moho depth worldwide with unprecedented resolution, as well as in areas where ground data are not available.

This will offer new clues for understanding the dynamics of Earth’s interior, unmasking the gravitational signal produced by unknown and irregular subsurface density distribution.

GEMMA is being carried out by Italian scientist Daniele Sampietro and is funded by the Politecnico di Milano and ESA’s Support To Science Element under the Changing Earth Science Network initiative.

This initiative supports young scientists at post-doctoral level in ESA Member States to advance our knowledge in Earth system science by exploiting the observational capacity of ESA missions

Read more at the ESA Goce website

Mars tectonics

Dents in Earth's gravitational field due to plumes - physics-math

Ancient pieces of continental crust that are falling to the bottom of the Earth's mantle could explain mysterious dents in our planet's gravitational field.

Sail towards the centre of the Indian Ocean and you will find yourself losing weight because the Earth's gravitational field is weaker in this region. Similar dents in field strength are found in the north-east Pacific Ocean and the Ross Sea.

These weaknesses are believed to be created by "slab graveyards" – ancient pieces of crust and sediment that were pushed down into the Earth when plates collided and are now falling through the mantle. The slabs are denser than the surrounding mantle, so they have a stronger gravitational pull. As they fall, however, their effect on the gravitational field at the Earth's surface decreases.

But surrounding these areas are even weaker, unexplained dents in the field. Now Sonja Spasojevic from the California Institute of Technology in Pasadena and colleagues say this could be because the movement of the slabs through the mantle forces plumes of less dense material to rise towards the surface. The distribution of the unexplained weak spots simply reflects the pattern of these plumes, they say.

However, there are other ways the slabs may be creating density changes in the mantle, including chemical reactions that may occur between the slab and the mantle. "The new explanation is plausible but there are other possibilities too," says Norm Sleep a geophysicist at Stanford University in California.

Journal reference: Nature Geoscience, DOI: 10.1038/ngeo855

Tectonic Plate Line runs through Haiti

The sharp diagonal line exactly at the image center is the Enriquillo fault. Port-au-Prince is immediately to the left (north) at the mountain front and shoreline.

A magnitude 7.0 earthquake occurred on January 12, 2010, at Port-au-Prince, Haiti, with major impact to the region and its citizens.

This perspective view of the pre-quake topography of the area clearly shows the fault that is apparently responsible for the earthquake as a prominent linear landform immediately adjacent to the city.

Elevation is color coded from dark green at low elevations to white at high elevations, and the topography is shaded with illumination from the left. The topography in this image is exaggerated by a factor of two.

The sharp diagonal line exactly at the image center is the Enriquillo fault. Port-au-Prince is immediately to the left (north) at the mountain front and shoreline.

The Enriquillo fault generally moves left-laterally (horizontally, with features across the fault shifting to the left when the fault breaks in an earthquake), but vertical movements occur along the fault where irregularities in the fault line cause local compression or extension of the earth.

Meanwhile, movements of the topography at the Earth's surface can falsely appear to be vertical where mountain slopes are cut and misaligned by horizontal shifts of the fault.

Additionally, differing erosion rates on the two sides of the fault, due to the juxtapositioning of differing rock types by the fault, can give the appearance of vertical offsets of the current topographic surface.

All of these real and apparent horizontal and vertical offsets of the topographic surface may (and likely do) occur here, making the fault easily observed in the topographic data.

The elevation data used in this image were produced by the Shuttle Radar Topography Mission (SRTM), flown aboard Space Shuttle Endeavour in February 2000. SRTM acquired elevation measurements for nearly all of Earth's landmass between 60 degrees North and 56 degrees South latitudes.

For many areas of the world, SRTM data provide the first detailed three dimensional observation of landforms at regional scales.

Hip! Hip! USArray

Probably the most ambitious seismological project ever conducted is taking place in the heartland of America. Its name is USArray and its aim is to run what amounts to an ultrasound scan over the 48 contiguous states of the US. Through the seismic shudders and murmurs that rack Earth's innards, it will build up an unprecedented 3D picture of what lies beneath North America.

It is a mammoth undertaking, during which USArray's scanner - a set of 400 transportable seismometers - will sweep all the way from the Pacific to the Atlantic. Having started off in California in 2004, it is now just east of the Rockies, covering a north-south swathe stretching from Montana's border with Canada down past El Paso on the Texas-Mexico border. By 2013, it should have reached the north-east coast, and its mission end.

Though not yet at the halfway stage, the project is already bringing the rocky underbelly of the US into unprecedented focus. Geologists are using this rich source of information to gain new understanding of the continent's tumultuous past - and what its future holds.