用GPS数据反演分析海原断裂带分段活动特征

Inversion and Analysis on the Active Characteristics of Subsections of Haiyuan Fault Belt Using GPS Data

摘要:

首先应用1999-2007年的GPS观测资料分析海原断裂带的运动特征,看出期间该断裂带GPS站点运动速度由南向北逐渐衰减,在NWW和NE走向断层两盘的运动差异较为明显,断层的活动以走滑运动为主。然后依据地质、地球物理等资料给出反演参数初值,利用水平形变资料对断裂三段的走滑速率及断层下界深度进行反演。结果为从西到东断裂带各段走滑速率分别为8.25mm/a、5.49 mm/a和5.97 mm/a,断层底部深度依次为22.8 km;13.3 km;11.1 km。综合分析认为毛毛山-老虎山断裂运动速度明显高于海原断裂速度,在速度变化梯度较大的毛毛山断裂存在6级以上地震空区,推测具有发生强震的危险性。

Abstract:

The active characteristics of Haiyuan fault belt are analyzed using GPS data during 1999-2007 firstly.The surveying data show that the movement rates of those GPS sites become decreasing from south to north,especially the rates on two sides of the NWW and NW diration faults have big difference,and the fault movement is mainly strike-slip.Then the initial parameters of inversion are given based on the information of geology and geophysics.The slipping rates and depths of three subsections of Haiyuan fault belt are inversed with constrains of GPS profiles data. The result show that the rates from west to east are 5.49 mm/a, 5. 97 mm/a and 8. 25 mm/a respectively and the depths are 22.8 km,13.3 km and 11.1 km respectively. Through comprehensive analysis on the GPS data and parameters of the fault it is concluded that the movement rate on Maomaoshan--Laohushan fault segment is faster than that on Haiyuan fault segment. Maomaoshan fault has big rate grads where also is earthquake vacancy（ML〉6. 0）, so this region exists risk of strong earthquake.