U S Expedition U S E

Pacific-based earthquake triggers in the spotlight

[Date: 2011-07-18]

An international team of researchers is unearthing the triggering mechanisms behind large, destructive earthquakes like the Tohoku earthquake that hit Japan last March. Led by the University of Florence in Italy, the researchers collected new samples of rock and sediment from the depths of the Pacific Ocean. The team retrieved almost 1 500 metres of core from the ocean floor not far from the coast of Costa Rica in South America. Supported by the scientific drilling vessel JOIDES Resolution during the latest Integrated Ocean Drilling Program (IODP) Costa Rica Seismogenesis Project (CRISP) Expedition, the samples provide key information in relation to 2 million years of tectonic activity along a seismic plate boundary. 'We know that there are different factors that contribute to seismic activity,' says Professor Paola Vannucchi of the University of Florence, who co-led the expedition with Dr Kohtaro Ujiie of the University of Tsukuba in Japan. 'These include rock type and composition, temperature differences, and how water moves within the Earth's crust, but what we don't fully understand is how these factors interact with one another and if one may be more important than another in leading up to different magnitudes of earthquakes. This expedition provided us with crucial samples for answering some of these fundamental questions.' Over three quarters of the planet's earthquakes with a magnitude of 8.0 and above occur along subduction zones. The Pacific Ocean is a hub for such boundaries, what experts call convergent margins. Specifically, they are found along the coasts of the East Pacific from the United States' state of Alaska in the north down to Patagonia, an area between Argentina and Chile in the south, as well as Tonga, Marianas, New Zealand, to Japan and the Aleutians. Researchers are particularly keen to study this area with the triggering mechanisms of big earthquakes. Over the period of one month, the scientists and crew aboard the vessel drilled four sites; they recovered core samples of sand and clay-like sediment and basalt rock. CRISP scientists noted in a preliminary report released in June that they found evidence for a strong subsidence, or sinking, of the Costa Rica margin combined with a large volume of sediment discharged from the continent and accumulated in the last 2 million years. Says Professor Vannucchi: 'For example we now know that fluids from deeper parts of the subduction zone system have percolated up through the layers of sediment. Studying the composition and volume of these fluids, as well as how they have moved through the sediment helps us better understand the relationship between the chemical, thermal, and mass transfer activity in the seafloor and the earthquake-generating, or seismogenic, region of the plate boundary. They may be correlated.' This expedition is one of a kind because the work involved targets the properties of erosional convergent margins, where subduction processes 'eat' the overriding plates. The researchers say these plate boundaries are characterised by trenches with thin sediment cover, less than 400 metres, fast convergence between the plates and abundant seismicity.

'American Emperor' offers a compelling, provocative portrait of ...

In December 1800, Alexander Hamilton warned his fellow Federalists against using a flaw in the Constitution to make Aaron Burr president of the United States.</p><p>&#x93;Sanguine enough to hope everything, daring enough to attempt everything, wicked enough to scruple nothing,&#x94; Hamilton wrote. Burr was not the lesser of two (Democratic) evils: As president, Burr would &#x93;certainly disturb our institutions to secure himself permanent power.&#x94;</p><p>After 36 ballots, the House of Representatives chose Thomas Jefferson as president and Burr as vice president. Already damaged goods, Burr killed Hamilton in a duel in 1804 and was indicted for murder. When Jefferson ran for re-election, Burr was dropped from the ticket. Undaunted and bent on revenge, he identified an alternate route to wealth, power and glory.</p><p>In &#x93;American Empire,&#x94; David O. Stewart, a lawyer practicing in Washington, D.C., and the author of &#x93;The Summer of 1787,&#x94; examines Burr&#x92;s audacious attempt to form a new empire on the shores of the Gulf of Mexico &#x93;that would rival or even dwarf the United States.&#x94;</p><p>A skilled historian and a splendid storyteller, Stewart makes the most of the episode and its compelling cast of characters. Stewart&#x92;s Burr is an American Satan with feet of clay. A rogue and a rake, he &#x93;fouled the punch bowl&#x94; rather than revering the Founding Fathers.</p><p>As an adventurer, he was, in turn, too cautious and too reckless. Gen. James Wilkinson, the governor of Louisiana &#x93;who never won a battle or lost an investigation,&#x94; was a triple-crosser, taking bribes from Spain, scheming with Burr and then betraying him to American authorities. </p><p>John Marshall, the Chief Justice of the Supreme Court, Stewart reveals, used a narrow definition of the term &#x93;levy war&#x94; at Burr&#x92;s trial, over which he presided, to taunt and thwart Jefferson, his cousin and political adversary.</p><p>Acknowledging that existing sources do not permit him to pinpoint Burr&#x92;s plans, Stewart speculates that the former vice president improvised, with his forays resembling &#x93;the path of a pinball through an arcade machine.&#x94;</p><p>Burr approached Spain, France and Britain, as well as American officials, for assistance. He hoped to use a declaration of war by the United States against Spain as a pretext to launch his expedition, but went ahead when there was no war.</p><p>According to Stewart, Burr&#x92;s protestations that he did not intend to precipitate secession by western territories were a &#x93;lawyer&#x92;s dodge.&#x94; Burr was a man with the foresight to realize that if New Orleans, the essential trade route for everyone living in the environs of the Mississippi River, fell into his hands, the pressure to leave the Union would be virtually irresistible.</p><p>Nonetheless, Stewart provocatively argues that, judged by the standards of the day, Burr was not a traitor.</p><p> In 1806, he reminds us, the United States was a fledgling republic, with fluid geographical dimensions (thanks to Jefferson&#x92;s Louisiana Purchase) and British, French and Spanish rivals on its borders.</p><p>Burr was by no means alone in thinking that inhabitants of far-flung parts of the continent might well assert that they could, legitimately, go their own way. Discussed openly, his expedition was less an act of conspiracy than an &#x93;act of buccaneering.&#x94;</p><p>In the end, Burr recruited only about 100 men to his private army. As Thomas Jefferson had guessed, his quixotic venture fizzled without having to be smashed by the iron fist of the federal government.</p><p>For a few decades, until the sin of slavery could no longer be ignored, Stewart concludes, the bonds of the Union remained strong. And for more than two centuries, Aaron Burr became known only by the crimes he had committed.</p><p><strong>American Emperor: Aaron Burr&#x92;s Challenge to Jefferson&#x92;s America</strong>, by David O.

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