中文摘要：

研究了高台地震台和兰州地震台在2008年5月12日汶川8．0级、2009年8月28日青海海西6．4级、2009年9月30日撒摩亚群岛8．1级地震前重力记录资料脉动幅度及频谱变化，总结了重力地脉动在时问域和频率域上的临震前兆异常特征，发现有与宽带地震仪低频波异常对应的异常信息，即震前时域脉动曲线出现纺锤型或喇叭口形态，0．1～0．14Hz的频幅最大值在震前几天加速增大直到发震。跟踪地脉动异常变化可以为地震短l临预报提供有用信息。

英文摘要：

Analyzing the variation of microtremor-amplitude and frequency spectrum of the gravity data recorded by Gaotai Station and Lanzhou Station before the Wenchuan Ms8.0 earthquake on May 12, 2008, the Haixi, Qinghai, Ms6. 4 earthquake on August 28, 2009, and the Samoa Islands Ms8. 1 earthquake on September 30, 2009, we summarized the characteristics of impending precursors of the gravity data in the time domain and frequency domain. Then we discovered that before the earthquakes, the microtremor curve in the time domain appeared to be spindlelike or bellmouthed. Further, the amplitude-frequency value in 0. 1 Hz -0. 14 Hz acceleratedly rose a few days before the earthquakes. Tracking the abnormal variation of the gravity microtremor, we may find the useful information for the short-term earthauake prediction.