Publication Date:
2013-09-21
Description:
Phase transformations of metastable olivine might trigger deep-focus earthquakes (400 to 700 kilometers) in cold subducting lithosphere. To explore the feasibility of this mechanism, we performed laboratory deformation experiments on germanium olivine (Mg2GeO4) under differential stress at high pressure (P = 2 to 5 gigapascals) and within a narrow temperature range (T = 1000 to 1250 kelvin). We found that fractures nucleate at the onset of the olivine-to-spinel transition. These fractures propagate dynamically (at a nonnegligible fraction of the shear wave velocity) so that intense acoustic emissions are generated. Similar to deep-focus earthquakes, these acoustic emissions arise from pure shear sources and obey the Gutenberg-Richter law without following Omori's law. Microstructural observations prove that dynamic weakening likely involves superplasticity of the nanocrystalline spinel reaction product at seismic strain rates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schubnel, Alexandre -- Brunet, Fabrice -- Hilairet, Nadege -- Gasc, Julien -- Wang, Yanbin -- Green, Harry W 2nd -- New York, N.Y. -- Science. 2013 Sep 20;341(6152):1377-80. doi: 10.1126/science.1240206.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Geologie, CNRS UMR 8538, Ecole Normale Superieure, 75005 Paris, France. aschubnel@geologie.ens.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24052305" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
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Chemistry and Pharmacology
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Computer Science
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Medicine
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Natural Sciences in General
,
Physics
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