Tsunamis propagate only when earthquakes occur under water and have an up and down component to their motion. Earthquakes where tectonic plate boundaries slide side by side, do not cause tsunamis. Subduction zone earthquakes, those areas where one plate moves beneath another, are prime candidates for tsunami generation, but if the two plates slide smoothly across each other, water is displaced very slowly.
"If a fault is not locked, the two plates just creep along and there is no big upsurge," says Fisher. "However, if they are locked, the bottom plate drags the top plate along until it snaps back and quickly displaces water."
An expedition, organized by the Discovery Channel and BBC-TV, explored the 136-mile area of the fault using seismic reflection, a system where a sound source activates beneath the water and researchers record the time the sound takes to reach the underwater receivers. This process provides a detailed map of the sea bottom and the terrain beneath it. The researchers reported their work in a recent issue of Geology.
The researchers, who included Fisher; David Mosher, Geological Survey of Canada – Atlantic who supplied the seismic reflection equipment; James A. Austin Jr., senior research associate and Sean P.S. Gulick, research associate, University of Texas, Austin; Timothy Masterlark, assistant professor, University of Alabama, and Kathryn Moran, associate professor, University of Rhode Island, found that the shape of the upper plate boundary was unusual.
"The fault line does not look as we assumed it did," says Fisher. "We expected a wedge with one plate going under the other."
The Sumatran plate boundary looked, in many ways, like the cabling on a suspension bridge. The area near the edge did form a wedge, but the central portion was framed by two peaks with a sway or saddle in the middle, with the farthest part then sloped downward. The central swayback portion was also populated by bumps located about 8 miles apart across its length.
"We also found that this is a blind fault, one that is not visible at the surface because it is covered in a deep layer of silt and sediment," says Fisher. "The peaks every 8 miles were caused when an earthquake folded the sediment."
These peaks add to the amount of water displaced when the entire plate edge snaps back. The fold spacing shows that the sediments are from 1 to 3 miles deep. The researchers suggest that the sediment deforms independently from the actual plate boundary.
The researchers conclude that the combination of processes, plate edge movement and snap back and the deformation of the sediment combines to enhance the uplift on a substantial portion of the fault and has important implications for evaluation of the 2004 tsunami and others that occur in this location.
A'ndrea Elyse Messer | EurekAlert!
Algorithm provides early warning system for tracking groundwater contamination
14.08.2018 | DOE/Lawrence Berkeley National Laboratory
Artificial Glaciers in Response to Climate Change?
10.08.2018 | Universität Heidelberg
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur
What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...
The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.
Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...
08.08.2018 | Event News
27.07.2018 | Event News
25.07.2018 | Event News
14.08.2018 | Life Sciences
14.08.2018 | Life Sciences
14.08.2018 | Earth Sciences