断裂带震源机制节面聚类确定断裂带产状方法及在2021年漾濞地震序列中的应用

Method of active fault geometry determination by clustering nodal planes of focal mechanisms occurred on the fault belt and its application to the 2021 Yangbi earthquake sequence

一条断裂带上发生地震的破裂面通常与断裂带形状接近,同一地震破裂带上大量震源机制节面中应该有集中于断层面形状的一个集合,求出此集合的节面中心就可以得到断裂带的几何形状.根据这个原理,本研究给出了震源机制节面之间距离的方法,将带有噪声、基于密度的空间聚类方法(DBSCAN)应用于震源机制的节面聚类分析,并应用于2021年云南漾濞地震序列的震源机制数据中,得到两簇节面中心与地震序列的空间密度线性分布较为一致的分支断层,两个分支断裂的走向分别为317.41°和119.42°,置信区间为312.26°~322.55°和118.79°~120.05°,倾角为87.04°和85.73°,置信区间为83.19°~89.55°和80.16°~89.01°.该研究提供了独立于地震波资料、大地测量资料、地质资料等之外的确定断裂带形状分布的方法.

The fault plane of an earthquake on a fault belt is usually close to the shape of the fault belt.A large number of nodal planes of focal mechanisms on the same seismic fault belt should concentrated on the shape of seismic fault belt,and the center of the clustered nodal planes can represent the geometry of the seismic fault belt.On this principle,I provide the quantitatively difference of two nodal planes of focal mechanisms,and introduce Density-Based Spatial Clustering of Application with Noise(DBSCAN)to nodal planes of focal mechanisms on the same seismic fault belt.The method is applied to the nodal planes of focal mechanisms in the 2021 Yangbi earthquake sequence.Two obtained centers of the clustered nodal planes are corresponding to the two brunches of the spatial densely distributed earthquake hypocenters of the Yangbi earthquake sequence.The azimuths and their confidence intervals of the two brunches are 317.41°and 119.42°,312.26°~322.55°and 118.79°~120.05°,respectively.The dip angles and their confidence intervals of the two brunches are 87.04°and 85.73°,83.19°~89.55°and 80.16°~89.01°,respectively.I provide a method for determining the shape of seismic fault belt independent of seismic wave data,geodetic data and geological data,etc.