太原和灵石地震前后的重力场变化及其成因初探

研究了１９９３年６月２６日和１９９４年４月２６日相继在太原和灵石发生的Ｍｓ４．３级和Ｍｓ４．４级地震前后的重力场变化。结果表明，距震中越近，重力点值变化越大；震前重力场呈下降变化，震后短时间内仍维持下降，尔后，重力场逐渐回升。导致重力场变化的原因，在地质上表现为断层蠕动；而在深部构造的脆弱部位，水平梯度大，温差热应力高，差异活动明显，是推动断层蠕动，促进重力场变化和地震孕育发生的重要力源之一

PRELIMINARY RESEARCH ON THE GRAVITY FIELD VARIATION BEFORE AND AFTER TAIYUAN AND LINGSHI EARTHQUAKES AND THEIR CAUSE

The variations of gravity field before and after both earthquakes,the Taiyuan M s 4.3 on June 26, 1993 and Lingshi M s 4.4 on Apr.28,1994,are studied.The results show that the closer observational position is to the epicenters,the more obvious variation in gravity value will become.The gravity values drop before the events and it continues temporarily after earthquake, then retrieve upward progressively.The causes for variation of gravity field appear to be fault creep geologically.The large horizontal-gradient,the high heatstress by temperature difference and the obvious differential activity in the brittle-weak positions in deep structure are one of the important forces promoting fault creep,gravity field change,earthquake preparation and occurrence.