| イベント名 |
第１２回地球惑星科学教室談話会 Labquakes! Laboratory constraints on mechanisms of deep earthquakes, from lower crust to top of the lower mantle |
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| イベント種類 | セミナー |
| 講演者(講師) | |
| イベント詳細 | 演者： Prof. Yanbin Wang (GSECARS, University of Chicago) ＜要旨＞ About 90 years ago, Wadati first reported conclusively earthquakes hundred kilometers deep in Japan. These deep earthquakes (DEQs), which occur at depths between ~50 and 700 km, are puzzling geophysicists ever since, because brittle failure is known to be inhibited by high confining pressure. Furthermore, the elevated temperatures at these depths promote creep and plastic flow, suggesting that ductile deformation should occur before the fracture stress is reached. In this seminar I would like to introduce some of the most recent advances in my laboratory in the study of mechanisms of DEQs. Over the past 8 years, we have been developing techniques of deformation with controlled stress or strain rate combined under high pressure. By integrating these techniques with in-situ acoustic emission (AE) monitoring, we are able to generate tiny earthquakes or “labquakes” in samples on the order of 10 cubic millimeters. Such labquakes can now be treated just like earthquakes using state-of-the-art seismological tools and have revealed critical information on how micro-ruptures nucleate, grow, and self-organize into macroscopic faults. With these advances, I will highlight results relevant to DEQs at several depth ranges of subducted lithosphere, including lower crust (60-100 km), middle depths (200-350 km), and deep depth (350-700 km). In all of these locations, we find that complex exothermic phase transformations in rock assemblies play a key role in inducing mechanical instability. These transformations produce nano-sized grains in their high-pressure assemblies, which weaken the rocks around reaction fronts, causing stress redistribution, to allow micro-ruptures to nucleate and grow. Several examples will be presented. Finally, issues concerning scaling from millimeter-sized laboratory samples to hundreds of kilometer field phenomena will be discussed. |
| 対象 | 教職員向け 在学生向け |
| 使用言語 | |
| キーワード | |
| 開催期間 | 2018年10月25日 16:30 〜 17:30 |
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| 定員 | なし |
| 申込み方法 | 事前申込み不要 |
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