Tsunami (World of Earth Science)
Tsunami, or seismic sea waves, are a series of very long wavelength ocean waves generated by the sudden displacement of large volumes of water. The generation of tsunami waves is similar to the effect of dropping a solid object, such as a stone, into a pool of water. Waves ripple out from where the stone entered, and thus displaced, the water. In a tsunami, the "stone" comes from underneath the ocean or very close to shore, and the waves, usually only three or four, are spaced about 15 minutes apart.
Tsunami can be caused by underwater (submarine) earthquakes, submarine volcanic eruptions, falling (slumping) of large volumes of ocean sediment, coastal landslides, or even by meteor impacts. All of these events cause some sort of landmass to enter the ocean and the ocean adjusts itself to accommodate this new mass. This adjustment creates the tsunami, which can circle around the world. Tsunami is a Japanese word meaning "large waves in harbors." It can be used in the singular or plural sense. Tsunami are sometimes mistakenly called tidal waves, but scientists avoid using that term since they are not at all related to tides.
Tsunami are classified by oceanographers as shallow water surface waves. Surface waves exist only on the surface of liquids. Shallow water waves are defined as surface waves occurring in water depths that are less than one half their wavelength. Wavelength is the distance between two adjacent crests (tops) or troughs (bottoms) of the wave. Wave height is the vertical distance from the top of a crest to the bottom of the adjacent trough. Tsunami have wave heights that are very small as compared to their wavelengths. In fact, no matter how deep the water, a tsunami will always be a shallow water wave because its wavelength (up to 150 mi [240 km]) is so much greater than its wave height (usually no more than 65 ft [20 m]).
Shallow water waves are different from deep water waves because their speed is controlled only by water depth. In the open ocean, tsunami travel quickly (up to 470 mph [760 kph]), but because of their low height (typically less than 3 ft [1 m]) and long wavelength, ships rarely notice them as they pass underneath. However, when a tsunami moves into shore, its speed and wavelength decrease due to the increasing friction caused by the shallow sea floor.
Wave energy must be redistributed, however, so wave height increases, just as the height of small waves increases as they approach the beach and eventually break. The increasing tsunami wave height produces a "wall" of water that, if high enough, can be incredibly destructive. Some tsunami are reportedly up to 200 ft (65 m) tall. The impact of such a tsunami can range miles inland if the land is relatively flat.
Tsunami may occur along any shoreline and are affected by local conditions such as the coastline shape, ocean floor characteristics, and the nature of the waves and tides already in the area. These local conditions can create substantial differences in the size and impact of the tsunami waves, even in areas that are very close geographically.
Tsunami researchers classify tsunami according to their area of effect. They can be local, regional, or ocean-wide. Local tsunami are often caused by submarine volcanoes, submarine sediment slumping, or coastal landslides. These can often be the most dangerous because there is often little warning between the triggering event and the arrival of the tsunami.
Seventy-five percent of tsunami are considered regional events. Japan, Hawaii, and Alaska are commonly hit by regional tsunami. Hawaii, for example, has been hit repeatedly during this century, about every 50 years. One of the worst was the April 1, 1946, tsunami that destroyed the city of Hilo.
Pacific-wide tsunami are the least common as only 3.5% of tsunami are this large, but they can cause tremendous destruction due to the massive size of the waves. In 1940 and 1960, destructive Pacific-wide tsunami occurred. More recently, there was a Pacific-wide tsunami on October 4, 1994, which caused substantial damage in Japan with 11.5 ft (3.5 m) waves. However, waves of only 6 in (15 cm) over the normal height were recorded in British Columbia.
Tsunami are not only a modern phenomenon. The decline of the Minoan civilization is believed to have been triggered by a powerful tsunami that hit the area in 1480 B.C. and destroyed its coastal settlements. Japan has had 65 destructive tsunami between A.D.684 and 1960. Chile was hit in 1562 and Hawaii has a written history of tsunami since 1821. The Indian and Atlantic Oceans also have long tsunami histories. Researchers are concerned that the impact of future tsunami, as well as hurricanes, will be worse because of intensive development of coastal areas in the last 30 years.
The destructive 1946 tsunami at Hilo, Hawaii, caused researchers to think about the problem of tsunami prediction. It became clear that if scientists could predict when the waves are going to hit, steps could be taken to minimize the impact of the great waves.
In 1965, the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization agreed to expand the United States' existing tsunami warning center at Ewa Beach, Hawaii. This marked the formation of the Pacific Tsunami Warning Center (PTWC), which is now operated under the U.S. Weather Service. The objectives of the PTWC are to "detect and locate major earthquakes in the Pacific basin; determine whether or not tsunami have been generated; and to provide timely and effective information and warnings to minimize tsunami effects."
The PTWC is the administrative center for all the associated centers, committees, and commissions of the International Tsunami Warning System (ITWS). Japan, the Russian Federation, and Canada also have tsunami warning systems and centers and they coordinate with the PTWC. In total, 27 countries now belong to the ITWS.
The ITWS is based on a world-wide network of seismic and tidal data and information dissemination stations, and specially trained people. Seismic stations measure movement of the earth's crust and are the foundation of the system. These stations indicate that some disturbance has occurred that may be powerful enough to generate tsunami. To confirm the tsunami following a seismic event, there are specially trained people called tide observers with monitoring equipment that enables them to detect differences in the wave patterns of the ocean. Pressure gauges deployed on the ocean can detect changes of less than 0.4 in (1 cm) in the height of the ocean, which indicates wave height. Also, there are accelerometers set inside moored buoys that measure the rise and fall of the ocean, which will indicate the wave speed. These data are used together to help researchers confirm that a tsunami has been generated. Tsunami can also be detected by satellite monitoring methods such as radar and photographic images.
The ITWS is activated when earthquakes greater than 6.75 on the Richter scale are detected. The PTWC then collects all the data, determines the magnitude of the quake and its epicenter. Then they wait for the reports from the nearest tide stations and their tide observers. If a tsunami wave is reported, warnings are sent to the information dissemination centers.
The information dissemination centers then coordinate the emergency response plan to minimize the impact of the tsunami. In areas where tsunami frequency is high, such as Japan, the Russian Federation, Alaska, and Hawaii, there are also Regional Warning Systems to coordinate the flow of information. These information dissemination centers then decide whether to issue a "Tsunami Watch," which indicates that a tsunami may occur in the area, or a more serious "Tsunami Warning," which indicates that a tsunami will occur. The entire coastline of a region is broken down into smaller sections at predetermined locations known as "breakpoints" to allow the emergency personnel to customize the warnings to account for local changes in the behavior of the tsunami. The public is kept informed through local radio broadcasts. If the waves have not hit within two hours of the estimated time of arrival, or, the waves arrived but were not damaging, the tsunami threat is assumed to be over and all Watches and Warnings are canceled.
One of the more recent changes in the ITWS is that the Regional Centers will be taking on greater responsibility for tsunami detection and warning procedures. This is being done because there have been occasions when the warning from Hawaii came after the tsunami hit the area. This can occur with local and regional tsunami that tend to be smaller in their area of effect. Some seismically active areas need to have the warning system and equipment closer than Hawaii if they are to protect their citizens. For example, the Aleutian Islands near Alaska have two to three moderate earthquakes per week. As of May 1995, centers such as the Alaska Tsunami Warning Center located in Palmer, Alaska, have assumed a larger role in the management of tsunami warnings.
In terms of basic research, one of the biggest areas of investigation is the calculation of return rates. Return rates, or recurrence intervals, are the predicted frequency with which tsunami will occur in a given area and are useful information, especially for highly sensitive buildings such as nuclear power stations, offshore oil drilling platforms, and hospitals. The 1929 tsunami in Newfoundland has been studied extensively by North American researchers as a model for return rates and there has been some dispute. Columbia University researchers predict a reoccurrence in Newfoundland in 1,0005,000 years. However, some geologists argue that it may reoccur as soon as 100,000 years. These calculations are based on evidence from mild earthquakes and tsunami in the area. They also suggest that the 1929 tsunami left a sedimentary record that is evident in the soil profile, and that such records can be dated and used to calculate return rates. Research is currently ongoing to test this theory.
See also Seismology; Wave motions
Tsunami (Contemporary Musicians)
Alternative rock band
Tsunami is an Arlington, Virginia, based band fronted by the razor-sharp smarts of Jenny Toomey and Kristin Thomson, who also boast musical talent in such excess that they moonlight in other bands. Furthermore, Toomey and Thomson run their own label, Simple Machines, dedicated to providing welcoming business turf for fledgling indie bands. That label is also home of the Tsunami catalog, which includes a staggering number of singles in near-collectible sleeve designs. "Tsunami come across like a kind of teen gang," wrote Melody Maker's Sharon O'Connell. "It's their autonomy, their spirit and their drive, and the way they celebrate the raw and the very ordinary; the way it is when you're very young and every feeling is new each time you feel it."
Tsunami was formed inside the suburban Washington, DC house that Toomey and Thomson shared with John Pamer in the last months of 1990. Toomey had been in a band called Geek, where she met Andrew Webster, and she talked him into moving to the area so they could form a band with Pamer and Thomson; their goal was to play a New Year's Eve 1990 party. Toomey and Thomson were no newcomers to the music scene, having already formed the Simple Machines label with the help of their friend Ian MacKaye, head of the famed DC label Dischord. By February of 1991, they took their fledgling band on the road.
During 1991, Tsunami came into being as a band with some difficult tours and a well-packaged single or two. Touring was a strictly low-budget affair, with the band and gear loaded into a sometimes unreliable Isuzu Trooper, playing college towns across the country. Their worst show ever, Toomey told ViVidzine's Juliette Morris, was at a college in Ohioot at a bar, but at "some really bad fraternity-type of party and it was 'Mom's Night,'which meantthateverywhere we looked, we saw mothers with their arms around their staggering, drunk children." A bad sound system, and a sound man who mistakenly thought Toomey was making fun of him and began lousing up everything during their performance completed the farce. Their first single, released in the spring of 1991, was "Headringer," followed by that summer's "Genius of Crack."
Tsunami recorded and toured with pals Velocity Girl, and also recorded split singles with them, such as 1992's SubPop release "Left Behind." Another track from 1992 sums up the unique attitude with which Toomey and Thomson hurtle through the male-dominated world of indie rock: "Punk Means Cuddle" calis for a nicer, less belligerent attitude among their college-radio bands and fans. Toomey used to be active in the riot-grrl movement, but came to some realizations about what Tsunami cali the "loadhog" phenomenon, and even wrote a song about it. "Loadhogs are people who martyr themselves for the cause," Toomey told Melody Maker's Sally Margaret Joy. "People who would rather do the work for you than teach you how to do it yourself." In the song, Toomey explained, she "was trying to explore the delicate problem of how work is delegated."
In early 1993 a national promoter phoned and asked them if they might be interested in playing on that summer's Lollapalooza tour. Originally, they assumed it was a prank cali. Their six shows on a side stage shared with other acts such as Sebadoh and Thurston Moore dovetailed nicely with the release of their first full-length record, Deep End. Later that year Tsunami recorded their follow-up, The Heart's Tremolo, in Chicago and it was released in 1994. Like ali of their Tsunami issues, the two albums boasted beautifully designed covers; one single, from the previous year, "Diner," featured the menu from their favorite low-budget restaurant.
This irreverence infects much of what Tsunami does. They once undertook a microphone relay race from their office to a club, taped it, and played it live during a show. Yet they also donate money to non-profit organizations and are quite serious about the seemingly insurmountable wall between feminist ideology and alternative music. "I believe that women will never be accepted in punk rock, and that is why Tsunami walks the line between pop and punk," Toomey told Melody Maker. Band members still had their day jobs in 1993: Toomey worked as a bookkeeper for an anti-nuclear Organization, while Thomson worked in a food co-oput continued to run the Simple Machines label. Its office was at their houseso we wake up, put on our clothes, and start work," Thomson told Joy in Melody Maker. "We have no free time at all.... [L]uckily, there are no pubs near where we live."
The members of Tsunami were busy throughout 1993 and 1994. They had a friend in England, John Loder, who owns a studio, and began traversing back and forth to do recordings. They toured with the bands Rodan and Eggs, and, when asked how England responds to Tsunami, Toomey told ViVidzine that the music press there is quite fickleIt's depending on what bands are popular at the moment, you could be everyone's darlings or everyone could hate you. It's such a small country, and they start these weird little trends a lot." Sharon O'Connell reviewed a live show for Melody Maker and lauded it: "They bang and strum, leaving slight spaces before they storm in to mess things up."
Tsunami completed two American tours in 1994 in addition to more dates in England, but time became more unmanageable with Pamer still in college and living elsewhere. During their get-togethers, the band was torced "to write and record real fast, so we're very goal-oriented," Toomey told Melody Maker's Joy. Toomey also explained to ViVidzine that her bandmate "has had a hard time on tour," she said of Thomson, "because she's a good workaholic and it's been hard for her to get in the van, because there's no desk in there."
Though the band has managed to issue a full-length record annually, it is their singles that fuel the Tsunami wave. In 1994 they released "Be Like That," as well as a split CD with Rodan and Eggs from their U.K. tour entitled "Cowed by the Blah Blah." After releasing World Tour and Other Destinations in 1995ontaining 22 singles previously released and difficult to findhe band went on hiatus so Pamer could finish his degree. Toomey and Thomson continued to run the label and work with other bands. Toomey moonlighted in Liquorice, signed to England's 4AD label. Thomson married and began spending time in Philadelphia with her husband, Brian Dilworth, of the band the Gelcaps and head of the Compulsiv record label. Webster began a career as a documentary filmmaker. Yet after Pamer graduated in 1996, he remained in Massachusetts and made clear his intention to live in New York, not Virginia.
The break seemed to have changed everyone. "When we stopped playing, I was exhausted," Toomey told Magnets Cyndi Elliott. "It was because we didn't want to play, l've always thought that a band benefits from not having to be a band ali the time. We always held day jobs and did other things. That's one of the reasons we were able to stay a band for so long. When you are forced to play because you have to pay rent, you lose quality control and a lot of the Joy of it." In a decision made with some trepidation, they hired another drummer, Luther Gray. Formerly an intern at Simple Machines, Gray has a jazz background and brought a new rhythmic dimension to their music. It fit in perfectly with their maturation as a band, with Toomey and Thomson writing more melodie and less strident songs, which was evident on their 1997 release A Brilliant Mistake. Many of Tsunami's friends from the Chicago music scene contributed as well, including members of the Coctails and Poi Dog Pondering, and Rob Christiansen from Liquorice, who played bass on half the record.
Despite her work with Liquorice and Tsunami, Toomey admits to being insecure about her songwriting abilities: "Very rarely l'Il have something I think I should write," she told Magnet. "Excepte-mails and purchase Orders." Both Toomey and Thomson are confident about their business acumen, however. They claim anyone can begin a label, and have even written a booklet on how to do it, "but we don't talk about ambition in it," Toomey told Joy in the Melody Maker interview. Referring to the observation that substance abuse sometimes prevenis creative types from accomplishing things, Toomey noted that "You can't give people energy and enthusiasm." Sometimes other labels or bands cali the Simple Machines offices and ask to have their radio-station mailing list, for instance, and Toomey and Thomson must refuse. Notes Toomey: "The only reason those stations play us is because of our track record with them.... You have to find the addresses of the stations you like and send them nice lettersust like we had to."
Singles; on Simple Machines unless otherwise noted
"Genius of Crack," Homestead, 1991.
"Left Behind" (split single with Velocity Girl; on SubPop), 1992.
"Punk Means Cuddle," C/Z, 1992.
"Beautiful; Arlington VA," 1992.
"Season's Greetings" (split single with Velocity Girl), 1992.
"Be Like That," 1994.
"Cowed by the Blah Blah" (split CD with Rodan and Eggs), 1994.
"She Cracked" (split single with Superchunk; on Huggy Bear Records), 1995.
"Poodle/Old City," 1997.
LPs; on Simple Machines
Deep End, 1993.
(Contributor) The Machines 1990-1993, 1993.
The Heart's Tremolo, 1994.
World Tour and Other Destinations, 1995.
A Brilliant Mistake, 1997.
Melody Maker, January 30, 1993, p. 16; February 20, 1993, pp. 36-37; June 3, 1995, p. 37.
ViVidzine, December 1994.