Geology

Volcanic Shakeup

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Science  15 Jun 2007:
Vol. 316, Issue 5831, pp. 1542
DOI: 10.1126/science.316.5831.1542b

The powerful Sumatra Andaman earthquakes of 2004 (magnitude 9.3) and a few months later in 2005 (8.7) caused considerable devastation in Indonesia and, as a result of a huge tsunami, the surrounding regions. Walter and Amelung now suggest that these earthquakes may trigger an additional hazard. Such large subduction-zone earthquakes have been followed within a few years by eruptions in the neighboring volcanic arc, in some cases from dormant or rarely erupting volcanoes; examples include eruptions after the major (magnitude 9.0 or higher) earthquakes of Kamchatka in 1952, Chili in 1960, and Alaska in 1964. Two volcanoes (Talang and Barren Island) erupted in Indonesia soon after the nearby 2005 quake. Although the overall incidents are few, the pattern for large quakes is consistent and, according to the authors' analysis, statistically significant. Their numerical modeling shows that generally such large earthquakes in subduction zones, which are produced by large oceanward slip of the overlying plate, induce some extension in the volcanic arc further landward. Such extension can lower the pressure on trapped magma, inducing or hastening eruptions or leading to further melting. The authors recommend a close watch of generally quiet volcanoes in Indonesia over the next few years. — BH

Geology 35, 539 (2007).

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