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Keywords searched: 1998 Interview with Dr. Frank Gonzalez

  1. What is the current tool used to detect tsunamis?
  2. Is it possible for a tsunami to hit the East Coast? Has it ever happened?
  3. Are tsunamis measured on a scale similar to those of tornadoes and hurricanes?
  4. Do tsunamis lose speed as they approach land?
  5. What type of force is needed to allow a tsunami to travel a long distance?
  6. Could the effects of atomic bombs tested in the Pacific enhance force of waves and tsunamis?
  7. How do you think the new warnings systems will help people in Hawaii, California, Oregon, Washington, and Alaska be better prepared for tsunamis?
  8. What was the reason you started doing research on tsunami patterns? What do you hope to accomplish with this tsunami research and how long will it take? How far do you think you are from your goal?
  9. Are tsunamis more (or less) dangerous on islands or on normal coasts? Is Hawaii hit so often because it's an island or because it's "in the way" of most tsunamis in the Pacific?
  10. Why does the amplitude of the wave rise when the tsunami reaches a beach?
  11. Was the Bourbon tube invented just for the BPR, or is it a commonly used device in physics?
  12. Could you give me a figure of the average slip during an landslide (Is it 1 mm, or more like 10 cm ?...)
  13. What's the cost of a BPR installation?

  1. What is the current tool used to detect tsunamis?

    Tsunamis are detected by open-ocean tsunami buoys and by coastal tide gages. These instruments report their information in real-time to tsunami warning centers (one center in Alaska, another in Hawaii, and a third to be installed soon in Puerto Rico).

    Besides the direct observations, the amplitudes of tsunamis are also estimated from the size and type of earthquake that may have generated them. The warning centers receive earthquake (seismic) data from many sites as well as analyses of this information from earthquake centers. Since seismic waves travel much faster than tsunamis, the earthquake information is often available hours before the tsunamis are able to travel across the ocean. This is much help for people near the earthquake, however, since the local tsunami is there often within minutes. It is that easy to estimate the strength of a tsunami from the character of an earthquake. Hence, there are false alarms. It is hoped that the direct tsunami observations will reduce the number of these.

    Local tsunamis are also generated by underwater landslides and volcanoes. There is some research being done to better understand these types of tsunamis and to develop early detection methods for them.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

    References and more info: DART Tsunami Buoys

  2. Is it possible for a tsunami to hit the East Coast? Has it ever happened?

    In principle, dangerous tsunamis could strike the East Coast. However, there aren't the large number of marine earthquakes in the Atlantic as compared with the Pacific Ocean.Mo

    The two reported tsunamis in the Atlantic are the 1755 Lisbon tsunami (which killed 60,000 people) and the smaller 1929 Grand Banks tsunami that struck eastern Canada (which killed 27). There is also evidence of a prehistoric tsunami in northern Europe that was caused by a gigantic submarine landslide off Norway.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  3. Are tsunamis measured on a scale similar to those of tornadoes and hurricanes?

    There is a tsunami intensity scale, although it is not used much anymore. Nowadays, tsunamis are usually described by their heights at the shore and the maximum runup of the tsunami waves on the land.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  4. Do tsunamis lose speed as they approach land?

    Tsunamis do slow down as they approach land because the water is shallower there. As they slow down, conservation of energy requires that the amplitudes of the waves grow larger.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  5. What type of force is needed to allow a tsunami to travel a long distance?

    Tsunamis are what are called long gravity waves. There are two interacting processes that allow these waves to propagate. The first is the slope of the sea surface caused by the waves, which creates a horizontal pressure force. The second is the piling up (or lowering of sea surface) as water moves with different speeds in the direction that wave form is moving. When these two processes have the right relationship in time, they create propagating waves.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  6. Could the effects of atomic bombs tested in the Pacific enhance force of waves and tsunamis?

    There is no widely-held belief along scientists that atomic bomb testing has done so. Basically, the energy associated with large earthquakes is many times that released by an atomic bomb. During the Cold War, however, a number of studies were done on the types of local tsunamis that would be generated if a bomb were detonated in the water near cities.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  7. How do you think the new warnings systems will help people in Hawaii, California, Oregon, Washington, and Alaska be better prepared for tsunamis?

    I'm assuming you refer to the new DART buoys we're developing. These will help make the tsunami warnings faster and more accurate. Right now, the warning centers depend on earthquake data and on tide gage data to assess the danger. The earthquake data tells you how big the earthquake was, and the location of the epicenter.

    If the location is:

    1. in a region that has generated tsunamis in the past -- basically, very seismically active regions of the "Ring of Fire" around the Pacific Rim, where plate tectonics drives the Pacific plate under various continental plates, and
    2. if the earthquake is big enough, i.e., about a magnitude 7 or greater, then it is considered a possible tsunami hazard.

    But the warning center still doesn't know if a tsunami was generated, because it doesn't have a way to measure it, until the tsunami propagates into a nearby harbor and registers on the tide gage.

    That may take a while, and:

    1. it's too late to warn the folks in that particular harbor and
    2. you may have lost a lot of time waiting for the tsunami to register on the tide gage.

    So DART systems are being place close to the potential tsunamigenic zones, offshore in deep water. That way, if a tsunami is generated by the earthquake, you get the measurement right away. Not only that, but you know that it is headed out to sea and you can warn communities across the ocean that a tsunami is heading toward them.

    See also:



    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  8. What was the reason you started doing research on tsunami patterns? What do you hope to accomplish with this tsunami research and how long will it take? How far do you think you are from your goal?

    Understanding tsunami patterns is very important, because the DART buoys are very expensive to build, deploy and then maintain, so we can't put as many of them out in the ocean as we would like to. That means that when a tsunami is generated, we might only get one or two measurements of the tsunami. So we'll have an incomplete picture of what's going on in other parts of the ocean.

    For example, the DART buoy might be in a part of the ocean where the tsunami is small, but there may be other parts of the ocean without a DART buoy where the tsunami is very big. So we don't get a measurement of the big part of the tsunami. But if we understand tsunami patterns for a whole lot of different earthquake sizes and locations, then we can compare these patterns with the DART measurements we have, and find the pattern that agrees best with the measurements. If we find one that agrees well with the DART measurements, then we have some confidence in using the pattern to predict the wave height in places that we don't have measurements.

    So the numerical model that generates the patterns can be thought of as a tool to "fill in the gaps" that exist in the measurements. However, the tsunami problem is very difficult and complex, so our models, even though they are accurate enough to give us useful guidance, are not perfect. So we have to develop this warning tool as carefully as we can, because peoples lives are at stake, and that takes time. We hope to finish our tsunami pattern development for Hawaii in about 3 years, and we hope to have a network of six DART buoys in about 2 years.

    Authority: Dr. Frank Gonzalez, interviews in 1998, NOAA Center for Tsunami Research

  9. Are tsunamis more (or less) dangerous on islands or on normal coasts? Is Hawaii hit so often because it's an island or because it's "in the way" of most tsunamis in the Pacific?

    I read somewhere that the most dangerous tsunamis for Hawaii are those generated by local earthquakes (on the islands itself). I don't understand: wouldn't the tsunami flee the island if it's generated by it? The article seemed to suggest that an earthquake under one of the islands implied a violent tsunami on hawaiian beaches shortly after.

    Because Hawaii is in the middle of the North Pacific and because this ocean is surrounded by a many earthquake/tsunami generating regions, Hawaii tends to receive many trans-oceanic tsunamis. Also, volcanic islands tend to have steep, unstable slopes where landslides can occur. The southeastern coast of the Island of Hawaii (with active volcanoes and ground movement) has had two major landslides in the past 150 years that have generated dangerous tsunamis.

    While most of the tsunami energy does radiate out to sea, some remains near the coast. There are two reasons for this. The first is that tsunami waves tend to turn toward shallow water and can be trapped near the coast in the form of 'edge waves'; these can propagate right around an island. The second is the reflection of tsunami waves that occurs when the wave encounter the sharp change in water depth between the shallow areas just off the coast and the deep ocean water farther away from the island.

    The reason that the landslide tsunamis reach the beach so quickly is that they have only a short distance to propagate away from the landslide area before they reach the beach.

    Authority: Dr. Frank Gonzalez, interviews in 1998, NOAA Center for Tsunami Research

  10. Why does the amplitude of the wave rise when the tsunami reaches a beach?

    I read that it was because the wave's energy, proportional to (amplitude)2, remained constant. I don't see how this explains anything. What's more, isn't there a kinetic term in the wave's energy?

    What remains constant as a tsunami wave propagates is the energy flux, which is the product of the wave energy density times the group velocity of the wave. One way to understand why the flux is conserved is to imagine a box-shaped area in the ocean through which tsunami waves propagate. Unless the same amount of energy propagates out of the box that propagated in, same wave energy must remain inside the box. However, this is not possible with an open box.

    If one side of the box is in deep water H_0 and the opposite side is in shallow water H_1 , then the group velocity c = (gH)^1/2 is less on the shallow side. Since the flux is proportional to c A^2 , the amplitude must increase as the waves move into shallower water.

    The issue of conservation of energy is subtle when it comes to waves. Actually, when a group of waves enters an area that was previously still, the background water level drops (releasing potential energy) while the wave group propagates through the area and rises back to its original level (regaining potential energy) after the wave group has passed. This is a different process than what goes on to conserve energy flux.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  11. Was the Bourbon tube invented just for the BPR, or is it a commonly used device in physics?

    The Bourbon tube is a commonly used device in physics that was adapted for use in ocean pressure measurements. It is used to convert changes in pressure into some other quantities, such as an angle of rotation for a mirror or a frequency of oscillation of a crystal, that can be recorded. Note: BPR is bottom pressure recorder, used in measuring the height of a tsunami wave in the open water.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  12. Could you give me a figure of the average slip during an landslide (Is it 1 mm, or more like 10 cm ?...)

    Landslides slips are typically hundreds to thousands of meters. This is in contrast to earthquake slips which are tens of centimeters (not causing dangerous tsunamis) to several meters.

    Authority: Dr. Frank Gonzalez, NOAA Center for Tsunami Research

  13. What's the cost of a BPR installation?

    The cost of a DART/BPR (Bottom Pressure Recorder) installation to obtain data in real-time is $100,000-200,000, plus the cost of periodically replacing the equipment. Self-recording systems for use in research are cheaper Note: BPR means bottom pressure recorder, used to measure the height of a tsunami in the ocean.

    Authority: Dr. Frank Gonzalez, interviews in 1998, NOAA Center for Tsunami Research

    References and more info: DART buoy