中文摘要：

选用甘肃嘉峪关、兰州和天水地磁台2011—2013年的观测数据,重点研究地磁垂直向日变化波形下行段的赫斯特指数变化的时序特征。结果表明,在此3年内,嘉峪关台和兰州台地磁垂直向日变化波形下行段的赫斯特指数变化范围分别是0.08和0.06,天水台在2012年存在一个赫斯特指数幅度超过正常变化范围的过程,在此过程完成后的2013年7月22日,在距离天水130km的漳县和岷县交界发生M6.6地震。结合其他学者的研究结果,认为这一赫斯特指数的异常变化过程可能反映了区域性地球深部（下地壳与上地幔）热物质运移变化而引起地球局部居里面变化,也可能是地震孕育过程在地磁日变中的表征。这一发现有益于进一步研究地磁日变异常的机理、震磁关系以及地震预报的探索。

英文摘要：

Diurnal variation is an important part of the geomagnetic field. In this study, observa- tion data was collected from 2011 to 2013 at three stations （JYG, LZH, and TSY） in the Gansu province. The data focused on time series characteristics of the Hurst exponent of geomagnetic Z- component diurnal variation. The results show that the variation range of the Hurst exponent at JYG and LZH stations is 0.08 and 0.06, respectively. This represents a normal change because the low point is in the middle of a year and the peak point is at the end of the year, completing a change cycle within a year. The change is similar between JYG and LZH stations. In 2012, there was a change in the Hurst exponent exceeding the normal range. On July 22, 2013, the Ms6.6 earthquake occurred at the junction of Minxian and Zhangxian in the Gansu province, 130 km from Tianshui city. The abnormal change of the Hurst exponent at the TSY station may be the result of a magnetic field change induced by the transfer of local, deep thermal mass in the earth.In combination with other research, this may provide an early indication of the Minxian Ms6.6 earthquake. This study provides evidence for further study of the mechanism of geomagnetic diur- nal variation anomalies, seismo-magnetic relation, and earthquake prediction.