A SIMPLE-MODEL FOR THE FAULT-GENERATED MORPHOLOGY OF SLOW-SPREADING MIDOCEANIC RIDGES
A SIMPLE-MODEL FOR THE FAULT-GENERATED MORPHOLOGY OF SLOW-SPREADING MIDOCEANIC RIDGES
复制标题
DOI：
10.1029/94jb02593
复制
发表时间：
1995-01-10
影响因子：
3.9
通讯作者：
HILL, DP
中科院分区：
文献类型：
--
作者：
THATCHER, W;HILL, DP
我们推测，大洋中脊岩浆活动的波动扰乱了横跨裂谷边界的正断层的水平最小主应力，导致岩浆吸积和构造伸展的交替阶段，从而增加山谷宽度，从而导致内裂谷墙地形的发育。精细水深测量和地震断层面解表明，缓慢扩展海脊的活动正断层在整个孕震海洋岩石圈呈中等倾角(约45度)平面特征。一个简单的定量模型，包括一个10公里厚的弹性板在45度倾斜的正断层上滑动而产生的弯曲变形，可以匹配几个缓慢展开的山脊段的水深剖面。对大洋中脊、海沟-外隆区和大陆上正断层地震倾角分布的比较表明，这三种构造环境下的大多数地震都是在倾角接近45度时开始的，这引发了有关断层形成的力学条件的悬而未决的问题。
We postulate that fluctuations in magmatic activity at mid-oceanic ridges perturb the horizontal least principal stress across rift-bounding normal faults, leading to alternating phases of magmatic accretion, which increases valley width, and tectonic extension, which results in the growth of inner rift wall topography. Fine-scale bathymetric surveys and earthquake fault plane solutions show that active normal faults at slow-spreading ridges are moderately dipping (approximately 45 degrees) planar features throughout the seismogenic oceanic lithosphere. A simple quantitative model that includes flexural deformation of a 10-km-thick elastic plate by slippage on 45 degrees dipping normal faults can match the bathymetric profiles across several slow-spreading ridge segments. Comparison among dip distributions of normal-faulting earthquakes at mid-ocean ridges, in the trench-outer rise region, and on continents suggests that most events from these three tectonic environments initiated at dips close to 45 degrees, raising unanswered questions about the mechanical conditions under which the faults originated.