近日，智利康塞普西翁大学Tassara Andrs及其课题组的最新研究报道了速度衰减断层屏障的多种滑动行为。这一研究成果于2023年11月9日发表在国际顶尖学术期刊《自然—地球科学》上。
研究人员通过沿一个由摩擦特性和正应力的横向变化分割的速度减弱的巨型断层，进行地震周期模拟来研究速度减弱屏障的可能性。研究表明，速度减弱断层段表现出广泛的行为，包括永久障碍行为。它们可以在很长一段时间内被锁定，并通过地震或抗震方式释放滑动缺陷。研究人员量化了速度减弱屏障在阻止破裂方面的效率，这是基于断裂力学理论的一个无量纲参数，该参数可以受到自然断层观测的约束。他们的结果提供了一个理论框架，可以改进基于物理的地震危险性评估。
研究人员表示，地震屏障是断层的一部分，它促进了地震破裂的阻止和断层分割。尽管它们在控制地震的最大震级方面起着基本作用，但地震屏障的性质仍然不确定。一种常见的解释是，屏障具有速度增强的摩擦——随着滑动速度的增加而增加的稳态摩擦——仅仅部分地与实验中观察到的摩擦的热控制相一致，这意味着俯冲通道中的大多数相关物质在发震深度都是速度减弱的。
附：英文原文
Title: Diverse slip behaviour of velocity-weakening fault barriers
Author: Molina-Ormazabal, Diego, Ampuero, Jean-Paul, Tassara, Andrs
Issue&Volume: 2023-11-09
Abstract: Seismic barriers are fault portions that promote earthquake rupture arrest and fault segmentation. Despite their fundamental role in controlling the maximum magnitude of earthquakes, the nature of seismic barriers is still uncertain. A common interpretation of barriers as having velocity-strengthening friction—steady-state friction that increases with increasing slip velocity—is only partially consistent with the thermal control of friction observed in laboratory experiments, which implies that most relevant materials in subduction channels are velocity-weakening at seismogenic depths. Here we examine the possibility of velocity-weakening barriers by conducting earthquake cycle simulations along a velocity-weakening megathrust segmented by lateral variations of frictional properties and normal stress. We show that velocity-weakening fault segments display a wide range of behaviours, including permanent barrier behaviour. They can be locked during long periods and release their slip deficit either seismically or aseismically. We quantify the efficiency of velocity-weakening barriers in arresting ruptures using a non-dimensional parameter based on fracture mechanics theory that can be constrained by observations on natural faults. Our results provide a theoretical framework that could improve physics-based seismic hazard assessment.
DOI: 10.1038/s41561-023-01312-1
Source: https://www.nature.com/articles/s41561-023-01312-1