川滇地区地壳均衡状态及其与区域强震的关系

首先利用CRUST1.0模型分析川滇地区上地壳厚度和Moho起伏的主要结构特征,然后基于Airy地壳均衡理论计算区域均衡Moho深度,并利用其与实际Moho值的差异分析区域地壳均衡状态。将川滇地区上地壳厚度图和区域地震深度分布图对比可知,地震主要发生在上地壳脆性层内。区域地壳均衡状态显示,四川盆地地壳处于均衡状态,而龙门山断裂带为均衡差异最显著的地区,其北侧为正均衡状态(+6km),南侧为负均衡状态(-6km),西南侧为正均衡状态(+6km),揭示龙门山断裂带附近为地壳深部物质重新分异、调整和能量强烈交换的地带。

The Crustal Isostatic State of Sichuan-Yunnan Region and Its Relationship with Regional Earthquakes

Using the model CRUST 1.0, we analyze the structure of upper crust thickness and the moho discontinuity in Sichuan-Yunnan region. Then we calculate the regional isostatic moho discontinuity based on the Airy isostatic theory. With the difference between the isostatic and the real moho discontinuity, we study the state of crustal equalization in the Sichuan-Yunnan region. Comparing the map of upper crust thickness with the depth distribution diagram of regional earthquakes, we found that regional earthquakes mainly occurred in the upper brittleness crust. The crustal isostatic apparently shows that the Sichuan basin is in an isostatic state. However, the Longmen mountain’s fault zone poses a state which is out of the isostatic, and represents the most remarkable disequilibrium area in Sichuan-Yunnan region, whose north side presents positive equilibrium (+6 km), south side presents negative equilibrium (-6 km) and southwest side presents positive equilibrium (+6 km). All of this possibly reflects that the deep crust material beneath Longmen Mountain’s fault zone is undergoing a dramatic differentiation, adjustment and intense exchange of energy.