by
Francois Nadeau
Francois Nadeau
- Abstract:
This report describes some of the methods used by Tsunami Warning Systems (TWS) Information Systems (IS) to detect and warn coastal population of threats caused by Tsunamis. The report concludes that TWS have high detection capabilities.
| Table of Content |
| Chapter 1: Introduction |
| Chapter 2: Background |
| Chapter 3: Discussion |
| Chapter 4: Conclusion |
| Chpater 5: Recommendations |
| Bibliography |
Introduction
This report describes some of the Information Systems (IS) used for detecting tsunamis, and warning coastal populations. Its purpose is to better understand the characteristics of tsunami Warning Systems (TWS) IS.
Tsunamis are large waves generated in oceans or lakes when a large amount of water is suddenly displaced. Common causes for this phenomenon are "earthquakes, landslides, volcanic eruptions and large meteorite impacts"[1].
Tsunamis create three challenges for coastal communities. The first challenge is the survival of the tsunami waves. For instance, it has been reported that 174,452 persons died during the 2004 Indian Ocean tsunami[2]. The second challenge is the economical difficulties created by the destruction. This includes financial difficulties such as the cost of rebuilding commercial companies, social infrastructures, individual homes, and feeding and sheltering the survivors. The third challenge is of an ecological nature. It includes the damage to vegetation and forest due to the force of the tsunami, chemical contamination due to commercial leakage, and salt contamination of farm land by sea water displaced during the tsunami. In the case of the 2004 Indian Ocean tsunami, it is expected that these challenges will take years to solve, and that the local inhabitants will have to endure a great deal of hardship[2].
To eliminate the first threat caused by tsunamis, several governments have established TWS to warn coastal populations[3][4]. Due to the nature of tsunamis, there currently exist very few methods to prevent economic and ecological damages. The methods used by TWS to warn the population are further explored in the discussion section of this paper.
Background
Approximately 85% of tsunamis occur in the Pacific Ocean[5]. These tsunamis are most often caused by the "Ring of Fire", which is a circle-like array of active volcanoes in the Pacific ocean. Other coastal areas in the world which have been affected in the past include East Europe, Eastern Canada, South America, and the Mediterranean[1].
Although tsunamis can be devastating, they are not a common natural disaster. The National Geophysical Data Center has a tsunami Event Database which lists all recorded tsunamis from 2000 BC to the present day. As of the writing of this paper, this database system has 2399 entries for the entire world[6]. This represents an average of 0.6 Tsunami per year in the world since 2000 BC.
Prior to the development of TWS, tsunami detection relied on the observation of symptoms, and the ability of the observer to properly evaluate the risk. Such symptoms included earthquakes, receding water, and frothing bubbles on the water's horizon[2]. However, there have been occurrences when the symptoms where either not detectable, or left uninterpreted by the coastal population. For example, Alaska's Aleutian Earthquake of April 1, 1946, occurred too far away to be felt by the population of Hawaii, though a tsunami caused by it devastated its coastal community.
The 1946 Aleutian tsunami, mentioned above, forced the authorities to reevaluate the means used to detect tsunamis. From this initiative, the Pacific tsunami Warning Center (PTWC) was born in 1949 in Hawaii[7], and the West Coast/Alaska tsunami Warning Center (WC/ATWC) was established in 1967 in Alaska[8]. Both of these TWS have had success in warning the Pacific population of tsunami threats.
Up to now, the establishment and maintenance of TWS have been a governmental responsibility. Although some commercial companies produce products for TWS, this writer was unable to find instances of privately owned TWS.
Discussion – Tsunami Warning System Information Systems
Two different difficulties exist for a TWS to warn a coastal population of an approaching tsunami. The first is the detection of the tsunami, and the second is the communication or broadcasting of the approaching danger. Although these two challenges are not related to each other, both have to be accomplished quickly in order for the TWS to help the population. For example, the PTWC detected the earthquake which caused the 2004 Indian Ocean tsunami, and issued a communication 15 minutes later stating that there was no tsunami threat in the Pacific region, but that a tsunami near the epicenter of the earthquake was expected. Since the PTWC did not have an established communication channel to send this information to the affected countries,
warnings where not sent to the soon-to-be-affected coastal populations[9].
IIIA. Detection mechanisms
TWSs detect and monitor earthquakes with seismic devices to predict tsunamis. By recording the location and strength of earthquakes, experts at TWSs are able to evaluate the possibility of a threat caused by such events. For example, the PTWC issues a tsunami warning for earthquakes with a magnitude of 7.5 (Richter
scale) or greater within the Pacific basin region[7]. Instruments to detect tsunamis are used to evaluate threats from earthquakes which may not have been noticed, and to confirm predictions which were made with seismic devices. The most common methods are the Tide Gauges, Satellites, and the Deep-ocean Assessment and Reporting of Tsunamis (DART) system[10].
• The Tide Gauge is a device used to measure the height of the sea-surface. This device functions by sending a sound pulse inside a tube which has been inserted into the water. By measuring the time required for the sound pulse to return to it's originating location, scientist can monitor the height of a body of water within a 1mm accuracy.[10]
• Satellites can also be used to measure the height of the sea-surface. By sending electro-magnetic pulses down to earth from a satellite, and measuring the amount of time required for the pulse to return to the satellite, scientists can calculate an ocean's water height. Once this calculation has been completed, it is compared with pre-recorded ocean height. For example, during the 2004 Indian Ocean tsunami, the Jason satellite recorded water level variations between -40 cm to +50cm of their normal levels. However, the use of satellites in this manner has a major drawback, as a satellite needs to be located above a tsunami while it is occurring, which is not very common. For instance, the Jason satellite pases over the Indian Ocean approximately once a month[10].
• The DART system consists of an underwater pressure recorder, and a surface buoy. The pressure recorder is attached to the seabed, and communicates to the buoy by sonar. The buoy sends the information received by the pressure recorder to a TWS via satellite. Thanks to this mechanism,tsunamis can be detected and measured through the calculation of changes in water pressure reported by the system. Currently the buoy and pressure recorder are replaced once a year and every two years, respectively[10]. Each DART unit costs approximately 300,000 USD per month to operate[11].
TWS ISs merge the data received from each devices, and create information such as the areas which will be affected, the strength of the tsunami at each of the locations, and the amount of time before the waves reach the areas.
IIIB. Warning mechanisms
Once the TWS has evaluated a tsunami threat, various methods are used to notify the areas which will be affected. These methods include radio, commercial television, the Internet, National Guards, and telephone systems[7]. The TWS IS can facilitate the notification mechanism for each of the broadcasting methods. For example, the PTWC has an on-line web-page used to display the latest warning information.
IIIC. Current TWS IS
A TWS is a linked network of detection stations. For instance, the PTWC has over 150 seismic stations and about 100 sea-level analyzing devices throughout the world[12]. The IS connecting these stations and the main control center uses various communication mechanisms such as satellite communication and radio waves[10].
IIID. Special requirements for TWS IS
This writer was not able to find any information specifying the requiremnets of TWS ISs. However, he feels that, due to the devastating nature of tsunamis, TWS ISs need to have a level of reliability which would allow them to function even during natural disasters. Furthermore, TWS ISs need to function year-round,
since tsunamis may occur at any time.
IIIE. Similarity between TWS ISs and commercial ISs
Ironically, unlike many commercial ISs, TWS IS do not need to be outfitted with the latest and most powerful computer systems. While calculating the specific information about a tsunami is a task which needs to be completed quickly, the bottleneck for the calculation is the detection devices, not the computers. Therefore, having computers which run faster does not provide any additional value to the IS.
Companies such as Japan Radio Co. offer products for the Japanese market for broadcasting emergency messages such as tsunamis[13]. These products are sold to towns or regions who want a greater level of security for their citizens. Although these ISs serve the same purpose as TWSs, their role is only to broadcast messages, not evaluate threats. These products complete this task by retrieving weather information from the Geostationary Meteorological Satellite, which is a series of government-sponsored satellites used to monitor the earth's weather[14].
IV Conclusions
Various devices for preventing the loss of death caused by tsunamis are now being used by coastal regions throughout the world. However, as it was seen in 2004, areas such as the Indian ocean are still lacking adequate TWSs. Although reasons such as tsunami infrequency in that region have been used to explain such a deficit, this maybe one effect of the economical difference between thirdworld and developed countries.
Further research on the possibility of integrating all of the TWS with coastal communities in the third world should be carried out.
V Recommendation(s)
Future TWSs should be constructed in cooperation with TWSs that have already been constructed, and communication channels should be created between these. This would allow each additional TWS to share its findings with the rest of the network, and would thereby increase its operational capabilities.
An international standard for communicating tsunami warnings should be developed, and the current TWSs should broadcast all known information with this standard. For instance, it may be possible to create Internet client programs capable of warning coastal communities of a tsunami threat.
Bibliography
[1] Wikipedia, "Tsunami", [Online document], Available at HTTP:
http://en.wikipedia.org/wiki/Tsunami
[2] Wikipedia, "2004 Indian Ocean earthquake", [Online document], Available at HTTP:
http://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake
[3] P. Anderson, and G.Gow, "Tsunamis and Coastal Communities in British Columbia," pp.iii, 2004.
[4] "Tsunamis", [Online document], Available at HTTP: http://www.noaa.gov/tsunamis.html
[5] J. Perce, "Tsunami warning systems", [Online document], Available at HTTP:
http://www.oceansatlas.org/servlet/CDSServlet?status=ND0xMjc2MC4xODIwOSY2PWVuJjMzPXdlYi1zaXRlcyYzNz1pbmZv
[6] "NGDC Tsunami Event Database", [Online document], Available at HTTP:
http://www.ngdc.noaa.gov/seg/hazard/tsevsrch_idb.shtml
[7] "About The Pacific Tsunami Warning Center", [Online document], Available at HTTP:
http://www.prh.noaa.gov/ptwc/aboutptwc.htm
[8] "History of the WC/ATWC", [Online document], Available at HTTP:
http://wcatwc.arh.noaa.gov/thewcatwc/history.htm
[9] "Scientific Background on the Indian Ocean Earthquake and Tsunami", [Online document],
Available at HTTP: http://iri.columbia.edu/~lareef/tsunami/
[10] "Tsunami Information", [Online document], Available at HTTP:
http://www.bom.gov.au/info/tsunami/tsunami_info.html
[11] "Indonesia concerned about cost of tsunami warning system", [Online document], Available at
HTTP: http://english.people.com.cn/200503/19/eng20050319_177471.html
[12] "Pacific Tsunami Warning Center", [Online document], Available at HTTP:
http://ioc3.unesco.org/itic/categories.php?category_no=192
[13] "EARTHQUAKE and TSUNAMI INFORMATION RECEIVING and WARNING SYSTEM",
[Online document], Available at HTTP: http://www.jrc.co.jp/eng/product/system/tsunami.html
[14] "Geostationary Meteorological Satellite Program Platform Document", [Online document],
Available at HTTP: http://ghrc.msfc.nasa.gov:5721/source_documents//gms_source.html
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