A two degree-of-freedom earthquake model with static/dynamic friction
A two degree-of-freedom earthquake model with static/dynamic friction
复制标题
具有静/动摩擦力的二自由度地震模型
DOI：
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发表时间：
1987
期刊：
影响因子：
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通讯作者：
A. Ruina
中科院分区：
文献类型：
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作者：
J. Nussbaum;A. Ruina
一个简单的完全对称的多块弹簧模型能对断层行为做出有趣的预测吗？我们的模型由一个对称的、缓慢驱动的、具有静/动态摩擦的两自由度块弹簧系统组成。简单的摩擦定律和缓慢的驱动速度使得这个四阶系统的状态可以用一个单一的变量来描述，即驱动弹簧拉伸的差异。这一拉伸差测量的是锁定应力，与断层应力不均匀密切相关，一般不能观察到平滑。空间均匀的应力状态几乎总是不稳定的，因为在多次滑移事件之后，系统趋向于非均匀状态。该系统要么演化为两种类型地震之间交替的周期，要么演化为重复但相同的不对称地震的周期。一种交变地震解在结构上是不稳定的，这意味着它对模型扰动非常敏感。对于这个简单的模型，尽管模型中存在对称性，但空间不对称是必然发生的，这表明地震活动模式中的空间结构可能是地震动力学的结果，而不仅仅是断层的非均质性。
Can a simple multi-block-spring model with total symmetry make interesting predictions for fault behaviour? Our model consists of a symmetric, slowly driven, two degree-of-freedom block-spring system with static/dynamic friction. The simple friction law and slow driving rate allow the state of this fourth order system to be described between slip events by a single variable, the difference in the stretch of the driving springs. This stretch difference measures the locked-in stress and is closely related to fault stress inhomogeneity.In general,smoothing is not observed. A spatially homogeneous stress state is found to almost always be unstable, in that the system tends toward an inhomogeneous state after many slip events. The system evolves either to a cycle that alternates between two types of earthquakes, or to a cycle with repeating but identical asymmetric earthquakes. One type of alternating earthquake solution is structurally unstable, which implies a great sensitivity to model perturbations.For this simple model, spatial asymmetry necessarily occurs, despite the symmetry in the model, thus suggesting that spatial structure in seismicity patterns may be a consequence of earthquake dynamics, not just fault heterogeneity.