Tides, Earth's rotation among sources of giant underwater waves

Scientists at the University of Rhode Island are gaining new insight into the mechanisms that generate huge, steep underwater waves that occur between layers of warm and cold water in coastal regions of the world's oceans.David Farmer, a physical oceanographer and dean of the URI Graduate School of Oceanography, together with student Qiang Li, said that large amplitude, nonlinear internal waves can reach heights of 150 meters or more in the South China Sea, and the effects they have on surface wave fields ensure that they are readily observable from space.Farmer and Li will report results of their research at the Ocean Sciences Meeting of the American Geophysical Union in Portland, Ore., on February 25."The large waves in the South China Sea have attracted a fair bit of attention in recent years," Farmer said, "but much of this has been directed at the interaction of the waves with the sloping continental shelf of mainland China where they break, overturn and produce intense mixing. Our focus is on the way in which they are generated in Luzon Strait, between Taiwan and the Philippines, and the way they evolve as they propagate westwards across the deep ocean basin of the South China Sea."Farmer and Li studied the evolution of large internal waves occurring at tidal periods generated by currents traversing submarine ridges in Luzon Strait. As these waves travel west through the South China Sea, they steepen and evolve into packets of steep, energetic waves occurring at periods of 20-30 minutes. It is these energetic short period waves that modulate the ocean surface roughness, making their presence observable from satellites in space.The URI scientists' observations showed that the Earth's rotation modifies internal waves as they travel cross the deep basin. This effect mainly influences the internal waves that form on the 24-hour period of diurnal tides, dispersing the energy and inhibiting the steepening process. Internal waves that form on the semi-diurnal tides are not affected in this way, are more readily steepened and then break into the energetic, short period waves.Farmer and Li studied internal waves in the South China Sea using pressure equipped inverted echo-sounders, instruments developed by scientists at the University of Rhode Island. From the seafloor, the device transmits an acoustic pulse and then listens for the echo from the sea surface. Sound travels faster through warm water than it does through cold water, so changes in the echo delay allow measurement of the thickness of the warm surface layer, enabling the shape and size of passing internal waves to be recorded.According to Farmer, nonlinear internal waves impact the ocean in many ways: stirring up sediment on the sea floor, creating hazards to offshore engineering structures, interfering with submarine navigation, and greatly affecting propagation of underwater sound. Internal waves also appear to have significant, if not fully understood, biological impacts, and in shallow water environments they can mix water masses and modify coastal circulation. University of Rhode Island

Maximum Height of Extreme Waves Up Dramatically in Pacific Northwest

A major increase in maximum ocean wave heights off the Pacific Northwest in recent decades has forced scientists to re-evaluate how high a "100-year event" might be, and the new findings raise special concerns for flooding, coastal erosion and structural damage.

The new assessment concludes that the highest waves may be as much as 46 feet, up from estimates of only 33 feet that were made as recently as 1996, and a 40 percent increase. December and January are the months such waves are most likely to occur, although summer waves are also significantly higher.

In a study just published online in the journal Coastal Engineering, scientists from Oregon State University and the Oregon Department of Geology and Mineral Industries report that the cause of these dramatically higher waves is not completely certain, but "likely due to Earth's changing climate."

Using more sophisticated techniques that account for the "non-stationarity" in the wave height record, researchers say the 100-year wave height could actually exceed 55 feet, with impacts that would dwarf those expected from sea level rise in coming decades. Increased coastal erosion, flooding, damage to ocean or coastal structures and changing shorelines are all possible, scientists say.

"The rates of erosion and frequency of coastal flooding have increased over the last couple of decades and will almost certainly increase in the future," said Peter Ruggiero, an assistant professor in the OSU Department of Geosciences. "The Pacific Northwest has one of the strongest wave climates in the world, and the data clearly show that it's getting even bigger.

"Possible causes might be changes in storm tracks, higher winds, more intense winter storms, or other factors," Ruggiero said. "These probably are related to global warming, but could also be involved with periodic climate fluctuations such as the Pacific Decadal Oscillation, and our wave records are sufficiently short that we can't be certain yet. But what is clear is the waves are getting larger."

In the early 1990s, Ruggiero said, a fairly typical winter might have an offshore wave maximum of a little more than 25 feet. It was believed then -- based primarily on data from two offshore buoys -- that 10 meters, or 33 feet, would be about as large as waves would ever get, even in a massive "100-year" storm.

But then a major El Nino -- which tends to bring larger waves, higher water levels and increased erosion -- happened in 1997-98 and led to a string of "100-year" wave events of around and above 33 feet. Researchers went back to the drawing board, continued to study data and storm events, and now believe that the maximum waves the region may face could approach or even exceed 50 feet.

Increasing wave heights, they said, have had double or triple the impact in terms of erosion, flooding and damage as sea level rise over the last few decades. If wave heights continue to increase, they may continue to dominate over the acceleration in sea level that's anticipated over the next couple of decades. The prior concern about what sea level rise could do, in other words, is already a reality. If sea levels do increase significantly in future decades and centuries, that will only add to the damage already being done by higher waves.

Exactly what impacts this will have in terms of beach erosion and shifting shorelines is difficult to predict, scientists say, because currents and sand move in complex ways, creating both "winners and losers" in terms of beach stability. But some effects are already visible, Ruggiero said.

"Neskowin is already having problems with high water levels and coastal erosion," Ruggiero said. "Some commercial structures there occasionally lose the use of their lower levels.

"Going to the future, communities are going to have to plan for heavier wave impacts and erosion, and decide what amounts of risk they are willing to take, how coastal growth should be managed and what criteria to use for structures," he said.

Hampering the research effort is the fact that two of the major buoys used for these studies, which are some distance off the Pacific Northwest coast and measure waves in deep water, were only installed in the 1970s. Even at that they provide two of the longest high-quality wave height records in the world. OSU researchers are studying historical records through climate data, old newspaper records and other information to try to recreate what wave heights and storm events were like going further back in time.

The largest wave height increases, scientists say, have occurred off the Washington coast and northern Oregon, with less increase in southern Oregon and nothing of significance south of central California. The study also noted that similar increases in wave heights have occurred in the North Atlantic Ocean, as well as the seasonal total power generated by hurricanes.

These issues do not consider the potential drop in land level that is expected to occur in this region with a subduction zone earthquake at some point in the future. Ruggiero noted that he did some research in Sumatra following the huge 2004 earthquake there -- an area with geology very similar to that of the Pacific Northwest -- and some of the shoreline had dropped from 1.5 to five feet. If and when that occurs, the impacts on shorelines could be enormous.

This research was supported by the Sectoral Application Research Program, a part of the Climate Program Office at the National Oceanic and Atmospheric Administration.

Samoan Tsunami wave was 46 feet high

The tsunami that killed more than 200 people in the Samoan islands and Tonga earlier this year towered up to 46 feet (14 meters) high - more then twice as tall as most of the buildings it slammed into, scientists said Friday.New Zealand scientists studying the size, power and reach of the tsunami as part of efforts to guard against future disasters said they found up to three destructive waves were caused by the magnitude 8.0 undersea earthquake in September.The massive waves that struck Samoa, American Samoa and Tonga totally destroyed traditional wooden buildings, many of them singly story, along the coast while reinforced concrete buildings sustained only minor damage, said Stefan Reese, a risk engineer with New Zealand's National Institute of Water and Atmospheric Research.The waves were up to 46 feet (14 meters) high, Reese told The Associated Press. The scientists measured watermarks on buildings and trees to help confirm the height of the waves."In some areas there was virtually nothing left" after the waves reached up to 765 yards (700 meters) inland, Reese said.Wide reefs saved some villages by helping to reduce the waves' height to about 10 feet (3 meters), Reese said.The Samoan quake created a sea floor fault up to 190 miles (300 kilometers) long and 23 feet (7 meters) deep.The Sept. 29 tsunami killed 34 people in American Samoa, 183 in Samoa and nine in Tonga.

Tsunami Waves Reasonably Likely To Strike Israel, Geo-archaeological Research Suggests

"There is a likely chance of tsunami waves reaching the shores of Israel," says Dr. Beverly Goodman of the Leon H. Charney School of Marine Sciences at the University of Haifa following an encompassing geo-archaeological study at the port of Caesarea. "Tsunami events in the Mediterranean do occur less frequently than in the Pacific Ocean, but our findings reveal a moderate rate of recurrence," she says.

Dr. Goodman, an expert geo-archaeologist, exposed geological evidence of this by chance. Her original intentions in Caesarea were to assist in research at the ancient port and at offshore shipwrecks.
"We expected to find the remains of ships, but were surprised to reveal unusual geological layers the likes of which we had never seen in the region before. We began underwater drilling assuming that these are simply local layers related to the construction of the port. However, we discovered that they are spread along the entire area and realized that we had found something major," she explains.
Geological drilling -- in areas of 1-3 meters in length and at various depths -- enabled Dr. Goodman to date the underwater layers using two methods: carbon-14 dating and OSL (optically stimulated luminescence). She found evidence of four tsunami events at Caesarea: in 1500 BC, 100-200 CE, 500-600 CE, and 1100-1200 CE.
In an article published by the Geological Society of America, Dr. Goodman explains that the earliest of these tsunamis resulted from the eruption of the Santorini volcano, which affected the entire Mediterranean region. The later, more local tsunami waves, Dr. Goodman assumes, were generated by underwater landslides caused by earthquakes. "'Local' does not necessarily imply 'small'. These could have been waves reaching 5 meters high and as far as 2 km onshore. Coastal communities within this range would have undoubtedly been severely damaged from such a tsunami. While communities onshore clear the ground after such an event and return to civilization, tsunami evidence is preserved under the water," she explains.
Journal reference:
Beverly N. Goodman-Tchernov, Hendrik W. Dey, Eduard G. Reinhardt, Floyd McCoy, and Yossi Mart. Tsunami waves generated by the Santorini eruption reached Eastern Mediterranean shores. Geology, 2009; 37 (10): 943 DOI: 10.1130/G25704A.1
Adapted from materials provided by University of Haifa.

Coral springs back from tsunami

Divers have been helping restore Indonesia's coral reefs Scientists have reported a rapid recovery in some of the coral reefs that were damaged by the Indian Ocean tsunami four years ago. It had been feared that some of the reefs off the coast of Indonesia could take a decade to recover. The New York-based Wildlife Conservation Society (WCS) found evidence of rapid growth of young corals in badly-hit areas. A spokesman said reefs damaged before the tsunami were also recovering. Some communities were abandoning destructive fishing techniques and even transplanting corals into damaged areas, the WCS said. "This is a great story of ecosystem resilience and recovery," said Stuart Campbell, co-ordinator of the WCS's Indonesia Marine Program. "These findings provide new insights into coral recovery processes that can help us manage coral reefs in the face of climate change." Ove Hoegh-Guldberg, a reef expert from the University of Queensland in Australia who did not take part in the study, said the findings were not surprising since corals typically recovered if not affected by fishing and coastal development. "We are seeing similar things around the southern Great Barrier Reef where reefs that experience major catastrophe can bounce back quite quickly," the scientist told the Associated Press. Countries across the Indian Ocean have been remembering the 2004 disaster, which claimed some 230,000 lives. Prayers were said in Indonesia, Thailand and India on Friday, while Sri Lanka declared a two-minute silence in memory of the dead. BBC News

Giant waves break up Caribbean coral

Unusually large waves churned by an Atlantic storm system have littered the beaches of Barbados with broken coral in what could be a sign of damage to reefs across the region, a scientist said Sunday. The amount of rubble on the island's west coast suggests the coral took a heavy pounding, said Leo Brewster, director of Barbados' Coastal Zone Management Unit, who was organizing dives later this week to survey the damage."We think it's going to be pretty extensive," Brewster said. "I think we're going to see it across the Caribbean."The waves, reaching as high as an estimated 30 feet, lashed coastlines from Guyana to the Dominican Republic last week as a large low-pressure system idled off the northeastern United States.At their peak on Thursday morning, a buoy north of the U.S. Virgin Islands recorded swells of 15 feet — the highest since 1991, said Shawn Rossi, a meteorologist with the U.S. National Weather Service in San Juan. Several countries reported flooding in coastal areas.In Barbados, the white coral washed up in chunks as heavy as seven pounds, generally healthy but with their polyps rubbed away by the rough surf, Brewster said.Reef-building coral provide a habitat for thousands of marine creatures but have been dying off across the Caribbean due to coastal pollution, overfishing and disease blamed on rising sea temperatures.

Status Quo Of The Tsunami Early Warning System For The Indian Ocean

The German-Indonesian Tsunami Early Warning System for the Indian Ocean (GITEWS) runs on track। Main milestones like the development of the automatic data processing software SeisComP3, as well as the underwater communication for the transmission of the pressure data from the ocean floor to a warning centre are already finalised. Furthermore the calculations of the ocean modelling including the source modelling were completed and are available in a data base so that the system can be set into operation at the end of 2008. This positive conclusion is drawn by the GITEWS consortium consisting of different German geo and marine scientists on the occasion of the third anniversary of the tsunami catastrophe on December 26, 2004.

After the severe earthquake, where almost a quarter of a million people lost their lives, the German government requested the Helmholtz Association of National Research Centres, represented by the GeoForschungsZentrum Potsdam (GFZ, Germany's National Lab for Geosciences) to develop a tsunami early warning system. Already three weeks after the natural disaster a task group headed by the GFZ submitted a concept for GITEWS to the German government. This concept is based on different kinds of sensor systems on land and on the ocean and goes along with an intensive education and training programme. "The GFZ is working in Southeast Asia since 1992 so these broad geoscientific results could flow into the proposal in a quick reaction" explains Professor Reinhard Hüttl, chair of the executive board of the GFZ. "We would also like to establish this warning system in other endangered regions, such as in the Mediterranean and in the Atlantic."
The tsunami early warning system is financed with 45 Mio. Euros by the Federal German Ministry for Science and Education and come from the 500 Mio. Euro budget of the German Federal Government for reconstruction activities in the tsunami region.
Seismological components
In 90% a tsunami is caused by a submarine earthquake. The quake in December 2004 had magnitude of 9.3, the second largest ever detected rupture in the earth crust. A fast and correct seismological recording and evaluation is therefore essential for the warning system. The biggest challenge is the failure-free recording and the exact quantification of strong quakes close to the epicentre. With the seismic sensors installed so far in Indonesia and with the GFZ developed software system SeisComP3 which was launched in May 2007, there is now for the first time a tool to quickly register and evaluate even strong earthquakes.
Its capacity and functionality has been demonstrated several times: the magnitude of 8.0 and the location of the Bengkulu quake in the southern part of Sumatra on September 12, 2007 could be determined within four minutes. Based on that information the Geophysical Survey in Jakarta (BMG) released a tsunami warning based on these data for the first time.
Meanwhile SeisComP3 is established as standard in several states bordering the Indian Ocean such as in the Indian tsunami warning centre. The tsunami warning centre for the Mediterranean and the North Atlantic will also go into service in 2008 with this software. "With the software technical and methodical development within GITEWS we set new standards not only specifically for earthquake monitoring but also for the tsunami warning" said Dr. Winfried Hanka, project leader for the GITEWS earthquake monitoring at the GFZ.
Oceanographic components
Based only on seismological measurements it is impossible to decide whether a tsunami has arisen or not. Therefore the detection of a tsunami is carried out directly on the ocean floor using oceanographic instruments. These measurements are also important to give the all-clear, because not every earthquake generates a tsunami. This additional information is very important for Indonesia, because earthquakes are easily sensible at the coast and could give rise to panic reactions. So a warning and an all-clear warning respectively need to be given very fast. To meet these expectations different components are established in the GITEWS concept.
Buoy systems
The final system will consist of 10 buoys, which will be deployed along the Sunda arch off the Indonesian coast. The buoys have two functions: they work as a relay station for the data of the underwater pressure sensors (OBU - ocean bottom unit) transmitting their data from the sea floor to a modem close to the water surface and from there via the satellite connection of the buoy to a warning centre. Furthermore the buoy has different sensors to determine meteo data and the sea swell. But the pioneering aspect of the buoys is the GPS functionality: through GPS measurements it is also possible to detect a tsunami independent of the measuring instruments on the ocean floor.
This is an important progress compared to other buoy systems used for example in the Pacific Ocean। The combination of underwater and surface measurements guarantees a higher availability and less breakdowns. Dr Tilo Schöne, GFZ Potsdam, leader of the GPS buoy working group as well as of the tide gauges working group announced: "Based on the experiences made with two test systems in Indonesia eight more systems will be prepared and deployed in summer 2008 along the coastline of Sumatra and Java. These buoys will be important components for the early warning system."

Ocean bottom units (OBUs)
To recognise water pressure changes caused by tsunami waves, ocean bottom units are installed on the ocean floor. In addition to this standard measuring method GITEWS uses specific seismometers to detect an earthquake directly on the sea floor. The challenge is not only the measurement but also the transmission of the data through the 4 km large water column. The first tests with commercial modems did not fulfill the technical requirements because transmitting the signal in thermally and salinary layered ocean water through more than four kilometres is not trivial. In co-operation with small and midsize enterprises it was possible to develop a new transmission technology.
"The so-called PACT bottom pressure system (Pressure based acoustically coupled Tsunami detector) is used for the real-time detection of sea level changes in the deep ocean. In November 2007, the PACT system successfully passed a deep-sea test close to the Canaries" emphasises Dr. Olaf Boebel, PACT project leader from the Alfred-Wegener Institute for Marine and Polar Sciences.
Tide gauge measurements
In deep water a tsunami propagates with the same speed as an aircraft. But in shallow water the tsunami wave looses its speed and gains height - up to 30 meters - close to the coastline. Therefore, it is important to register a tsunami in suitable regions e.g. offshore islands. Meanwhile seven GITEWS tide gauges have been installed in the Indian Ocean, not only in Indonesia, but also in riparian states. Reliable tide gauges data are available from South Africa (Marian Island), Yemen (Aden) and Iran (Chabahar). "Tide gauges measurements allow for a reliable prognosis if a tsunami wave is expected and in which dimension. So it is possible to receive detailed information of the inundation, which is especially of importance for densely populated areas such as Padang" explains Tilo Schöne Simulations.
Tsunami-simulations are of particular importance for the whole warning process. Based on a few measured data an overall picture has to be calculated. A couple of minutes after the earthquake the modelling results will give an estimation on the wave height, the time of arrival and the inundation areas. Combined with the information on the settlement structure in affected coastal stretches this is valuable information for the authorities and the population. Since warning times in Indonesia are extremely short, thousands of different scenarios are pre-calculated. According to measured event data the best-fit scenarios are selected from this data base which compriseall the necessary data like arrival time, wave height and risk evaluation. This assessment of the situation will be continuously improved taking more and more measured data into consideration.
The data gained from this simulation also provides the basis for the alarm of remote areas threatended by the tsunami such as India, Sri Lanka or East Africa. "The concurrent utilisation and analysis of all available data allows - for the first time - a precise prediction of the inundation in the influenced regions in an extremely short time scale. TsunAWI, the new tsunami simulation software based upon calculations on unstructured triangle grids which was developed at AWI and the innovated GFZ modelling of the earth crust deformation/movement, are the basis for this new achievement" underlines Dr. Jörn Behrens coordinator of the GITEWS simulation group.
The Warning Centre
The core of the early warning system is the warning centre. All sensor data converge here, from here all the instruments are controlled, and here the synthesis of all data and the pre-calculated simulations is done and the alarm is given. These different activities are integrated in a decision support centre (DSS), which provides the responsible officer with an overview of the available data, an assessment of the situation and proposals for decision.This system, seen from the viewpoint of conceptual design and complexity, is unique worldwide. The development of the DSS is done by the German Aerospace Centre (DLR) and is in good progress. At the beginning of 2008 the first prototype will be installed in Indonesia.
Civil defence, Education and Training programme
The fastest warning is useless as long as the gap to the so called "last mile to the beach" is not closed. The population in the threatened area needs to be informed in time, but they also need to be trained how to react properly. The people need to be informed about evacuation plans and how to behave in the case of emergency. Japan carries out this kind of training in schools, plants and companies on a regular basis. The establishment of such an education programme in the areas bordering the Indian Ocean has only just started.
In addition, there is an academic education and training programme with regular training courses for different sensor groups or risk modelling for experts and scientists.
Furthermore the "Gesellschaft für Technische Zusammenarbeit" (GTZ) in three pilot regions enhances civil defence activities which aim in particular to the development of necessary institutional and organisational capacities. Members of the German Federal Agency for Gesciences and Ressources (BGR) continue with this consulting on the national level.
Also, a PhD and post doc programme is carried out by the United Nations University (UNU) to guarantee the operation and future upgradingof the GITEWS from the scientific point of view. "Offering this variety of education possibilities makes an important contribution to the early warning system for Indonesia and other bordering states of the Indian Ocean", says Prof. Torsten Schlurmann, Director of the Franzius Institute for Hydraulic and Civil Engineering at the Leibniz University in Hannover. Prof. Schlurmann leads the Capacity Building programme on behalf of the UNU together with colleagues from the GTZ.
A Look into the Future
"The technical system of GITEWS will be established till the end of 2008, on the condition that no unpredictable events occur such as the natural disaster in December 2004 . At the beginning of 2009 we will operate the system together with our Indonesian colleagues. In 2010 the system will be handed over completely to the Indonesian partners", explains the project co-ordinator Dr. Jörn Lauterjung of the GFZ.
Vulnerability analyses, carried out in Indonesia within the GITEWS project, indicate that it is essential but also possible to be prepared. However, complete protection will ever be impossible, even with a technically perfect warning system. Natural hazards such as earthquakes clearly demonstrate the elemental forces of our planet . "Our aim is to minimize the number of victims", says Dr. Lauterjung and explains: "Even more than eight hours after the severe earthquake in 2004 and more than 6000 of kilometres away from the epicentre, over 300 of people were killed. Natural catastrophes of such a size will always claim many lifes. But this huge number of victims could have been reduced very much with an Early Warning System."
Adapted from materials provided by Helmholtz Association of German Research Centres.

Engineering Students Design A Better Surf Board

Surfers in Hawaii had better beware। Four Virginia Tech engineering science and mechanics (ESM) students have completed "Surf Green" for their senior design project, and conclude that they can technically improve the surfboard's performance.

The Beach Boys may have sung about surfing but this team of ESM students decided to "quantify the feel of surfing," something only engineers would try to do.
Michael Porter and Stephanie Salmons, both of Virginia Beach, Va., Matthew Dunham of Pleasantville, N.Y., and Nandan Shah of Midlothain, Va., worked with their faculty adviser, Jack Lesko, professor of ESM, for a year, submitting a final report at the end of 2007.
"Mike Porter lead the effort and completed most of the work this summer while living out of his van and driving up and down the east coast this summer in search of waves," Lesko smiled. He added that the project lasted beyond the spring semester because the surfboards were in his lab in Norris Hall and inaccessible to the students for weeks after the Virginia Tech tragedy last April.
"So, beyond the very good technical work, there is a good bit of character and fortitude exhibited by these students that I would like to acknowledge. I am just honored to be a small part of the lives of these talented students," he added.
The students focused on three different surfboard constructions of the same shape and size to compare the affects of material composition on the mechanical performance of surfboards. For the comparison, the team said they followed "a theory of surfboard mechanics (that is) analogous to the beam theory of solid mechanics."
They attached strain gages to the surface of each surfboard to determine the response or material deformation of each board while testing in and out of the water -- surfing each board to establish feel, while static testing to verify mechanical properties.
The students decided it was a particularly appropriate time to study the composition of surfboards because Clark Foam, a California based manufacturer and distributor of nearly 90 percent of the world's materials for surfboards, ceased its production. "As a result, traditional polyurethane foam surfboards became scarce and new technologies began to emerge," the students said.
A wide variety of new eco-friendly surfboard constructions appeared on the marketplace, and consequently, surfers, manufacturers, and retailers are beginning to experience the pros and cons of the various material compositions.
"However, without numerical evidence to clarify the mechanical performance of these new materials, the future of the surfboard industry is reliant solely on word-of-mouth and marketing strategies," they added.
"We want to assist surf culture, providing the knowledge necessary for board selection and design," the engineering students said।

In their testing, they named the different surfboards Gnarly, Tubular, and Righteous. Porter conducted various field tests with the equipment, "all in the interest of finding engineering solutions," his adviser Lesko joked. Each board "had" to be tested for roughly one hour to ensure at least two similar waves were caught.
With Porter riding the boards, he then developed plots of converted strain while he was surfing, duckdiving (the primary means used to pass through a crashing wave), and paddling. Although the latter is "not a very exciting part of surfing, anywhere from 50 to 90 percent of surfing is paddling. Paddling, especially in strong currents, big waves, or rough weather, is most responsible for depleting a surfer's energy," the team said. Thus, a board that enables a smooth, easy paddle is more beneficial.
The students also developed data for the jump from tensile strain to compressive strain. They learned which board experienced the most shearing strain or torsion when surfing.
Based on their mechanical response findings, the students justified in their findings why each board may ride with more or less speed, stability, and response. They also predicted which boards are ideal for what types of waves and riding.
Gnarly performed best of the three in choppy and bumpy conditions because of its stability. Gnarly was the king of speeding through fast racy sections.
Tubular, on the other hand, managed steep drops better than the other boards. The students believed this was probably related to its superior longitudinal flex properties, since it is able to deform to fit the shape of the wave face. However, once the initial drop was made and the board was turned down the line, board Tubular lost speed.
The students concluded that Righteous performed fairly consistently in all surf conditions. It did not tend to bounce in messy surf; although, it would wobble from side-to-side some. Righteous did not tend to pearl or nose dive on steep waves; although, this could be related to its increased rocker. And, it did not seem to lose speed while pumping; probably because it flexes less lengthwise than board Tubular.
However, the major flaw of board Righteous, they added, was related to its poor torsional stiffness properties. When making turns, especially the first bottom turn, Righteous tended to lose its edge and "slide out" from under the surfer.
As with most research, the students left open the idea that "more is needed" including the internal geometry, and they may have to ride a few more waves before they are completely finished with this project.
Adapted from materials provided by Virginia Tech.

Data Transfer For Tsunami Early Warning System Successfully Tested

In order to extend alert times and avoid false alarms, a new seafloor pressure recording system has been designed to detect tsunamis shortly after their development in the open ocean।

The project is directed by scientists of the working group 'Marine Observation Systems' at the Alfred Wegener Institute for Polar and Marine Research, part of the Helmholtz Association. Successful testing of the recording system off the Canary Islands in November 2007 means that a new mile stone for the development of the Indian Ocean Tsunami Early Warning System (GITEWS) has been reached.
The GITEWS project is supervised by the German National Research Centre for Geosciences (GFZ) in Postdam. Scientists of the Alfred Wegener Institute, in collaboration with companies Optimare and develogic, and with the Zentrum für Marine Umweltwissenschaften (MARUM) and the University of Rhode Island, are developing part of the simulation component and the so-called pressure-based acoustically coupled tsunami detector (PACT) for real-time detection of sea level rises in the deep ocean.
The German tsunami early warning system is unique in that it processes a multitude of information as the basis for a comprehensive and accurate evaluation of every particular situation. Within just few minutes, measurements of the vibrations and horizontal seafloor movements off the coast of Indonesia provide a clear picture of the location and intensity of a seaquake, which, at the warning centre, facilitate the appropriate selection of a previously calculated tsunami propagation model.
However, not every seafloor quake causes a tsunami. "There is only one way to be clear about this and avoid nerve-wrecking and costly false alarms: we must measure sea level directly", says PACT-project leader Dr Olaf Boebel of the Alfred Wegener Institute.
For this purpose, sea level recordings must take place off the coast, in the deep ocean. At water depths of thousands of meters, a tsunami wave travels at several hundred km/hr, but is only some tens of centimetres high, and approximately one hundred kilometres long. Not before it reaches the coast or shallower waters, does a tsunami wave develop into a massive wall of water several meters high.
Being able to detect the very slight sea level rise in the deep ocean reliably and precisely requires the use of bottom pressure sensors. These instruments are installed on the seafloor where they measure any sea level changes in the water column above. In this process, the weight of any additional water leads to minute pressure increases at the seafloor which are, nevertheless, reliably recorded by the PACT bottom units, precision instruments built by Optimare in Bremerhaven.
How is it possible then to send the potentially life-saving information about such pressure changes at the seafloor to the warning centre? Representing one of the greatest challenges of the PACT project, this problem was addressed by the Stuttgart-based company develogic through use of highly modern technology: Similar to a fax machine, an acoustic modem uses a sequence of sounds -- the so-called telegram -- to transmit information to a second modem which is connected to a buoy near the surface, sending the data via satellite to the warning centre.
Within the overarching GITEWS project, the primary PACT objective consists of the new development of a reliable, compact and highly energy efficient system which will record and analyse seafloor pressure every 15 seconds, and which will transmit the information to the surface modem if a tsunami event is detected. After approximately two years of development work on PACT, an important milestone was reached recently, when in-situ tests of the system were completed successfully north of the Canary Islands, using a trial fixture supplied by MARUM (Zentrum für Marine Umweltwissenschaften in Bremen).
From depths below 3100 metres and over periods of several days, pressure data were transmitted repeatedly to the surface modem। The most important result: none of the data telegrams were lost, a crucial requirement for the reliable functioning of the warning system.

Having been tested successfully, the new system will now be integrated into the GFZ-developed surface buoy and the entire early warning system. Further tests, scheduled for early next year in the Mediterranean, will investigate the transmission reliability under various weather conditions. "Surely, the upcoming winter storms will give us the opportunity to discover the limits of the system", suggests Boebel.
PACT system description
The PACT system consists of a bottom unit (white sphere) and a surface unit (pressure casing on frame). The battery-driven bottom unit contains pressure sensors, an acoustic transmission modem, as well as a release unit and a relocation device, the latter facilitating post-operation instrument recovery. The surface unit contains the acoustic reception modem. Attached to the underside of the surface buoy, a cable connection enables data transmission to the warning centre.
Adapted from materials provided by Alfred Wegener Institute for Polar and Marine Research.

Estimating local Tsunami wave height from Great Earthquakes

The massive 9.2-magnitude Sumatra-Andaman earthquake on 26 December 2004 generated a tsunami that propagated throughout the Indian Ocean, killing more than 250,000 people.
By contrast, the nearby 8.7-magnitude Simeulue-Nias earthquake on 28 March 2005 generated a small tsunami that caused only a few casualties. Though these earthquakes occurred in similar tectonic settings, their tsunami were markedly different, highlighting the need for reliably determining tsunami hazards from earthquake geometry.
Using geodetic and stress accumulation studies, McCloskey et al. model about 100 different complex earthquake ruptures in this area and calculate their sea-floor displacements and resulting tsunami wave heights. They find that, for locations close to the earthquake source, the timing of tsunami inundation is independent of the earthquake magnitude and slip distribution.
However, the maximum tsunami wave height is directly proportional to the vertical displacement of the rupture. Because stress field studies indicate that the Sumatra-Andaman region is overdue for another great earthquake, the authors note that a single estimate of vertical displacement during an earthquake might provide a reliable short-term forecast of tsunami wave height.
Title: Near-field propagation of tsunamis from megathrust earthquakes
Authors: John McCloskey, Andrea Antonioli, Sandy Steacy, Suleyman S. Nalbant, JianDong Huang, and Paul Dunlop: Geophysics Research Group, School of Environmental Sciences, University of Ulster, Coleraine, Northern Ireland, U.K.; Alessio Piatanesi, Massimo Cocco, and Carlo Giunchi: Seismology and Tectonophysics Department, Istituto Nazionale de Geofisica e Vulcanologia, Rome, Italy; Kerry Sieh: Tectonics Observatory, California Institute of Technology, Pasadena, California, U.S.A.
Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030494, 2007