Role of Weak Materials in Earthquake Rupture Dynamics
Role of Weak Materials in Earthquake Rupture Dynamics
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DOI：
10.1038/s41598-019-43118-5
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发表时间：
2019-04-29
影响因子：
4.6
通讯作者：
Kaneki, Shunya
中科院分区：
文献类型：
--
作者：
Hirono, Tetsuro;Tsuda, Kenichi;Kaneki, Shunya
地震滑动带中的弱材料是地震力学研究的重要内容。例如，2011年东北大地震期间的特大滑动被归因于断裂带中蒙脱石的存在。然而，脆弱的断层岩石不能积累大量的弹性应变，这被认为会抵消它们增强地震破裂的能力。众所周知，如果一个弱断层的渗透率低到足以允许间隙流体的摩擦热增压，断层的强度就会急剧下降。然而，究竟是断层材料的固有弱点，还是热加压更有效地在断层承载弱材料上产生大滑移，目前还没有确定。为了研究弱断裂材料在地震破裂动力学中的作用，我们采用纯蒙脱石和纯石墨作为弱断裂材料，进行了摩擦实验和动态破裂模拟。即使我们假设没有热加压，这两种介质中的模拟断层也能够触发较大的滑移，因为它们极低的摩擦力不足以阻止沿断层传播的破裂惯性运动。我们使用类似的破裂模拟来调查2011年东北- oki地震期间海沟附近巨大滑动的原因，并证明它可以归因于热加压，尽管我们的研究结果表明，在板块边界断层中存在蒙脱石也可能是必要的。
Weak materials in seismic slip zones are important in studies of earthquake mechanics. For instance, the exceptionally large slip during the 2011 Tohoku-Oki earthquake has been attributed to the presence of smectite in the fault zone. However, weak fault rocks cannot accumulate large amounts of elastic strain, which is thought to counter their ability to enhance seismic rupture. It is well known that if the permeability of a weak fault is low enough to allow friction-induced thermal pressurization of interstitial fluid, the fault strength decreases dramatically. However, whether intrinsic weakness of fault material or thermal pressurization more efficiently produces large slip on faults bearing weak materials has not been determined. To investigate the role of weak materials in earthquake rupture dynamics, we conducted friction experiments and dynamic rupture simulations using pure smectite and pure graphite to represent weak fault materials. Even when we assumed no thermal pressurization, simulated faults in both media were able to trigger large slip because their extremely low friction was insufficient to arrest the inertial motion of rupture propagating along the fault. We used similar rupture simulations to investigate the cause of the huge slip near the trench during the 2011 Tohoku-Oki earthquake and demonstrated that it can be attributed to thermal pressurization, although our findings suggest that the presence of smectite in the plate-boundary fault may also be required.