A study on the mechanisms of strong earthquake occurrence in the North China Basin
A study on the mechanisms of strong earthquake occurrence in the North China Basin
复制标题
华北盆地强震发生机制研究
DOI：
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发表时间：
2010
影响因子：
1.4
通讯作者：
Shi Yao-Lin
中科院分区：
文献类型：
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作者：
Zhu Shou-Biao;Zhang Pei-Zhen;Shi Yao-Lin
强震常发生在地表变形大的地区。而在华北盆地形变较小的地区，破坏性事件频发。本文用有限元法对华北盆地可能的地震速度异常区域进行了力学分析。计算结果表明，在水平构造应力作用下，高低速异常体中应力和能量都会聚集。综合本文和前人的研究成果，华北盆地强震发生的物理机制如下：华北克拉通在岩石圈减薄裂解过程中，岩浆侵入体或上涌的地幔物质在中下地壳演化为低速异常体（LVB）。在水平构造应力作用下，发震断层下方的LVB上方应力和应变能的积累速度要快于其他区域。当应力达到破坏极限时，LVB以上的材料将发生破裂，然后释放能量。一些能量将被转移到发震断层。同时，发震断层上的锁定区域也会缩小。在构造应力的作用下，一旦发震断层内的应力达到临界点，断层就会发生滑动，从而发生强震。结果还表明，LVB在强震中起着重要的刺激作用。此外，本文的分析表明，研究华北盆地地壳的精细速度结构对地震预报具有重要意义。
Strong earthquakes often occur in the regions where the surface deformation is large. But destructive events took place frequently in the North China Basin in which the deformation is small.In the paper,we made a mechanical analysis of the possible region with seismic velocity anomaly in the North China Basin with finite element method.The calculated result shows that stresses and energy will accumulate both in the high and low-velocity anomaly bodies under the horizontal tectonic stresses.Based upon the results of this paper and previous workers,the physical mechanisms of strong earthquake occurrence in the North China Basin are as follows.In the process of break-up of the North China Craton through lithospheric thinning,the magmatic intrusions or the upwelling mantle material will evolve into low-velocity anomaly body (LVB) in the lower and middle crust.The stresses and strain energy will accumulate more quickly above the LVB underlain the seismogenic fault than in other regions under the horizontal tectonic stresses.The material above the LVB will rupture when stresses reach the failure limit,then the energy will be released.Some of the energy will be transferred to the seismogenic fault.At the same time,the locking area on the seismogenic fault will be reduced.With the loading of tectonic stresses,once the stresses in the seismogenic fault reach critical point,the fault slips,and a strong earthquake occurs.Also the result shows that the LVB plays an important role in stimulating strong earthquakes.Moreover,the analysis in the paper suggests that it is important to study the fine velocity structure in the crust in the North China Basin for earthquake prediction.