Tsunami alert causes anxiety among some travelers

The possibility of a tsunami Friday gave the Costa Rican emergency system a test.

The national emergency commission issued a low-level alert at 3 a.m. Friday. By that time scientists had calculated that any serious tsunami effect would touch northern México and not Central America.

The tsunami originated with the 8.9 earthquake off the eastern shore of Japan. Although there were reports of secondary effects of the earthquake and the aftershock on the Pacific beaches, the Comisión Nacional de Prevención de Riesgos y Atención de Emergencias lifted the alert Saturday and said that there were no effects of consequence here.

The Canadian, U.S. and British embassies issued alerts to their citizens based on the emergency commission report. Each embassy has its own network of persons who registered their presence here.

The concern about tsunamis caused anxiety among Costa Ricans Friday. Some delayed planned trips to Jacó and other Pacific locations because of tsunami concerns. México got the strongest waves in Latin America, as had been predicted shortly after the quake. The highest was about 70 centimeters, about 27.5 inches.

Costa Rica got much less. The first wave arrived here about 4 p.m.

In the United States hardest hit were Oregon and California, where authorities estimate the more than two-meter (6.5-foot) tsunami caused millions of dollars in damages, according to the A.M. Costa Rica news services. One man was washed out to sea while taking photographs of the wave and is missing and feared drowned, a news service report said.

The tsunami first hit the United States when it washed up on the shores of Hawaii early Friday. Residents and visitors had been warned hours before the two-meter wave arrived.

Residents of the Pacific coast reported continued movement of the sea much of Saturday due to secondary waves, according to Guillermo Quirós Alvarez, a Costa Rican oceanographer. He noted that some of the bays on the Pacific trapped the energy of the waves, which resulted in greater effect at the shoreline.

Japan is experiencing more than 100 aftershocks, with a handful in the 6.2 to 6.9 magnitude range. The bulk are below 5.0 magnitude. Some of these are generating ocean waves.

Costa Rica pays close attention to earthquakes elsewhere because the country is vulnerable to such events. There have been six felt quakes in Costa Rica already in March with the strongest being 5.0 magnitude.

Costa Ricans also know that there is a high probability that a strong quake will take place in the Gulf of Nicoya. There have been 11 major quakes in and around the Nicoya Peninsula since 1827.

Costa Rica is one of the most earthquake-prone and volcanically active countries in the world, according to the University of California at Santa Cruz, which has studied the area extensively. Just off the west coast is the Middle America Trench, where a section of the sea floor called the Cocos Plate dives beneath Central America, generating powerful earthquakes and feeding a string of active volcanoes, said researchers.

This type of boundary between two converging plates of the earth’s crust is called a subduction zone ― and such zones are notorious for generating the most powerful and destructive earthquakes.

The National emergency commission has the job of responding to quakes and attempting to mitigate their effect by prior planning. The most recent event was a killer quake Jan. 8, 2009, in Cinchona north of Heredia and Alajuela.

That quake did not involve the Nicoya fault.  Some 25 persons died as a result of the quake, mostly due to landslides.

In addition to the Nicoya peninsula, the entire central Pacific coast south to Panamá is an earthquake-prone area.

Had the quake Thursday been off the Costa Rican shore, there would have been no warning of a tsunami. The first emergency commission warning came at 3 a.m., more than three hours after the Japanese quake. The wave would have made it to shore first.

The major concern now among Costa Rica officials is the possibility that damaged nuclear rectors in Japan will give off radioactive clouds. A hydrogen explosion rocked one of the damaged plants Sunday.

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