Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ocean-drilling expedition cites new evidence related to origin and evolution of seismogenic faults

19.08.2009
NanTroSEIZE science party

New research about what triggers earthquakes, authored by Michael Strasser of Bremen University, Germany, with colleagues from the USA, Japan, China, France, and Germany, will appear in the Aug. 16 2009 issue of Nature Geoscience (online version).

The research article, titled "Origin and evolution of a splay-fault in the Nankai accretionary wedge" is drawn from the scientists' participation in the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a long-term scientific ocean-drilling project conducted by the Integrated Ocean Drilling Program (IODP). Since September 2007, rotating teams of scientists have spent months aboard Japan's drilling vessel, CHIKYU, investigating the Nankai Trough, a seismogenic zone located beneath the ocean off the southwest coast of Japan.

Drilling operations, managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) through its Center for Deep Earth Exploration, have resulted in a collection of cored samples from the sea floor, which have provided scientists with deeper insights into the geologic past of the area.

Discussion in the above-noted article focuses on the Nankai Trough, in which the Philippine Sea plate slips below the Eurasian Plate with a velocity of 4 cm per year. This area is one of the most active earthquake zones on the planet. While being subducted, sediments are scraped off the oceanic plate and added to the overriding continental plate. Due to the movement of the plates these so-called accretionary wedges are exposed to enormous stress that form large faults.

The landward wedge in the Nankai Trough is completely intersected by such a prominent fault which extends laterally over more than 120 km. Scientists refer to this structure as "the megasplay." Movements along such megasplay faults during large magnitude earthquakes generated at depth may rupture the ocean floor and generate tsunamis.

"Our knowledge of megasplay faults up till now has been based on seismic or modelling experiments accomplished over the last twenty years," says Michael Strasser of Post-Doc Fellow of the Center for Marine Environmental Sciences (MARUM) at University of Bremen. "For the first time, with cored samples brought onto the CHIKYU, it has become possible to reconstruct the geological history of a fault in great detail." With his associates, Dr. Strasser found that the fault in the Nankai Trough originated about two million years ago. From the information recorded in the cores, the research team can draw conclusions on the mechanics of the accretionary wedge. They also can infer in which geological time periods the fault was most active.

"Our most significant conclusion is that splay fault activity varies through time," Dr. Strasser states. According to Strasser, after an initial period of high activity, the movement along the fault slowed down. Since about 1.55 million years ago, this fault has been reactivated, favoring ongoing megasplay slip along it.

"It is absolutely fascinating to be part of NanTroSEIZE," says Strasser, noting that the expedition series aims to sample and monitor activity at the point where earthquakes originate. "NanTroSEIZE is something completely new and innovative in scientific drilling," Strasser explains. "Ultimately, we hope to detect signals occurring just before an earthquake to get a better understanding of the processes leading to earthquakes and tsunamis."

The Nankai Trough is particularly suited for this experiment because historical records of earthquakes and tsunamis in this area date back into the seventh century. Additionally, the area where earthquakes are generated, the so-called seismogenic zone, is located at a relatively shallow depth of about six kilometers below the seafloor.

In 2007 and 2008, during the first stage of NanTroSEIZE, the deep sea drilling vessel CHIKYU carried out three expeditions. This drilling project consists of four stages in all, and ultimately focuses on "ultra-deep" drilling that can reach the seismogenic zone, where great earthquakes have occurred repeatedly.

During upcoming expeditions, the Nankai Trough boreholes will be equipped with instruments to establish an ocean observatory network. Currently, scientists are making preparations to install monitoring devices for continous measurements of the Nankai Trough. Prof. Gaku Kimura of University of Tokyo, who led an earlier NanTroSEIZE expedition 316 as Co-Chief Scientist says, "Not only do we have new insights about historic fault activities in Nankai Trough, but the data strongly suggests that the megasplay fault may be a key factor in the occurrence of large earthquakes in the future." He adds, "Greater understanding about the processes of earthquake and tsunami generation in the active subduction zone will be a great contribution to society."

The Integrated Ocean Drilling Program (IODP) is an international marine research program dedicated to advancing scientific understanding of Earth by monitoring, sampling, and instrumenting subseafloor environments. Through multiple platforms, preeminent scientists explore the deep biosphere, environmental change, and solid Earth cycles. IODP is funded jointly by the U.S. National Science Foundation and the Japan Ministry of Education, Culture, Sports, Science and Technology, with additional support provided by the European Consortium of Ocean Research Drilling; the People's Republic of China, the Republic of Korea, Australia, India, and New Zealand. Program details and expedition reports are at www.iodp.org.

Detailed information about NanTroSEIZE can be found at www.jamstec.go.jp/chikyu/eng/Expedition/NantroSEIZE/index.html

Contacts:

Albert Gerdes
agerdes@marum.de
MARUM, Bremen University
Toru Nakamura
press@jamstec.go.jp
Manager of Press office, JAMSTEC
Raesah Et'Tawil
rettawil@iodp.org
IODP Management International

Raesah Et'Tawil | EurekAlert!
Further information:
http://www.iodp.org

More articles from Earth Sciences:

nachricht Devils Hole: Ancient Traces of Climate History
24.05.2017 | Universität Innsbruck

nachricht Supercomputing helps researchers understand Earth's interior
23.05.2017 | University of Illinois College of Liberal Arts & Sciences

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>