Earthquakes, Tsunamis and Nuclear Testing
By Lila Rajiva
In the aftermath of a cataclysm like the Asian tsunami, speculation can run wild. Reserving judgment until we really know what happened, here is a list of salient questions and answers that I,ve compiled from news reports, government and other reliable sources.
Q: What set off the gigantic tsunamis that devastated coastal south-east Asia?
A: An undersea earthquake measuring 9.0 on the Richter scale with its epicenter about 160 km from the northern portion of the island of Sumatra in Indonesia on Sunday, December 26.
Q: How soon after the quake did the tsunami hit?
A: The earthquake hit Indonesia at 6:58 a.m; the tsunami arrived as much as 2 1/2 hours later, without warning, suggesting that it might not have been caused directly by the quake but by some other change triggered by the quake.
Q: How large was it?
A: It was the largest since the 9.2 quake in Prince William Sound in Alaska in 1964 and the 4th largest in the century. The quake moved the entire island of Sumatra about 100 feet toward the southwest and even disturbed the Earth’s rotation. It was the first tsunami in the Indian Ocean since 1883. Waves of around 30-40 ft in height and even greater were widely reported.
Q: What caused the undersea earthquake?
A: Compression between the Indian and Burmese tectonic plates. Scientists believe that one plate that comprised the landmass from India to Australia has broken up into two. The initial 8.9 eruption happened near the location of the meeting point of the Australian, Indian and Burmese plates
Q: What made the plates shift?
A: It may have been set off by another quake of about 8.1 on the Richter scale on the other side of the plate about 900 km SE of the coast of Tasmania on Thursday, December 24, which caused no serious damage however. The causal relationship is not proved but the time sequence is striking and some seismologists have considered it quite possible.
Q: Were tsunamis expected from that earlier quake?
A: The U.S. government’s Pacific Tsunami Warning Center said on its Web site that “widely destructive” tsunamis from the quake were possible in the open ocean
Q: Have there been similar earthquakes set off the South East of Tasmania before?
A: Yes, in 1998 a very large earthquake occurred south of Australia and New Zealand, between Macquarie Island and Antarctica on March 25 about 2,300 km south of Hobart in Tasmania, and 500 km north of the Antarctic coast
Q: Did this generate tsunamis?
A: Very large long-period surface waves were recorded in the hour after the earthquake.
Q: What connection if any is there between Tasmania and Antarctica?
A: Its capital Hobart on the South East coast is the base for the administration of Australia’s Antarctic program. The French regularly resupply their Antarctic base at Dumont d’Urville from the port, and American, Chinese, Russian and Italian ice breakers regularly visit.. Through its exploratory, commercial and scientific associations with the sub-antarctic and Antarctic regions, Hobart possibly enjoys a longer continuous Antarctic connection than any other spot on the planet.
Q: What are some other disturbances that can cause tsunamis?
A: Landslides or explosions such as underwater nuclear testing.
Q: Is underwater nuclear testing common?
A: Yes, The United States has conducted 1,054 tests of nuclear devices between July 16, 1945 and September 23, 1992. Before 1962, all the tests were atmospheric (on land or in the Pacific or Atlantic oceans) but overall the majority – 839 – were underground tests. From 1966 to 1990, 167 French nuclear test explosions have been performed on two atolls in French Polynesia, Morurua and Fangataua. Of the 167 tests, 44 were atmospheric. Atmospheric explosions were carried out until 1974, but only underground tests after that. The underground tests have been conducted at the bottom of shafts bored 500-1200 meters into the basalt core of the atoll. Initially these shafts were drilled in the outer rim of the atoll. In 1981, most likely due to the weakening of that rim, the tests with higher yields were shifted to shafts drilled under the lagoon itself.
Full Article: counterpunch.org