of pavement were tilted in circular areas 1 to 1.5 meters (3 to 5 feet) 

 across, apparently as a result of hydraulic pressure from water penetrat- 

 ing into the sand under the pavement when the tsunami flooded the area. 

 The higher pressure under the pavement has not been explained, but could 

 have resulted from water trapped in the sand during a rapid withdrawal 

 of the tsunami . 



f. Other Hazards . When considering the total effects of a tsunami 

 surge, additional hazards should be considered in addition to the actual 

 forces of the surge. Some of these are listed below: 



(a) Contamination from debris carried in the surging water; 



(b) effects of flooding, including spoilage of goods and 

 materials, shorting of electrical lines and transformers, and 

 contamination of water supplies with saltwater; 



(c) fire and explosion from the impact and rupturing of 

 petroleum tanks or containers of chemicals (see Fig. 72); and 



(d) release of poisonous gas or toxic materials from ruptured 

 containers. 



VIII. TSUNAMI WARNING SYSTEM AND INSTRUMENTATION 



Cox (1964) discusses the development of the tsunami warning system 

 in Japan. Local, informal warning systems operated sporadically for 

 centuries, and a formal tsunami warning system was recommended as early 

 as the late 19th century. The Japan Meteorological Agency organized the 

 present Japanese system in 1941. 



Spaeth and Berkman (1972) discuss the early history of the seismic 

 sea wave (tsunami) warning system in the United States. The need for a 

 warning system in the United States was recognized following the 1 April 

 1946 tsunami generated in the Aleutian Islands. That tsunami caused 

 heavy damage and resulted in the loss of many lives in Hawaii, particu- 

 larly at Hilo. 



The present tsunami warning system was organized by the former U.S. 

 Coast and Geodetic Survey (now the National Ocean Survey, National Oceanic 

 and Atmospheric Administration - NOAA) . Tsunami detectors were designed 

 and installed at tide stations to alert personnel of forthcoming tsunamis. 

 The first detector was installed at Honolulu in 1947. Meetings to discuss 

 implementation of the warning system throughout the Pacific coastal areas 

 were held in 1948. The tentative communication plan for the warning 

 system was approved in 1948. Initially, the warning system supplied 

 information to civil authorities in Hawaii and to military bases through- 

 out the Pacific. In 1953, Civil Defense Agencies of California, Oregon, 

 and Washington were added to the agencies receiving tsunami warning 

 information, and the system has expanded since that time. 



193 



