河北唐山丰南4.5级地震前重力变化

利用首都圈地区2017~2019年流动重力观测资料，分析2019-12-05河北唐山丰南4.5级地震前不同时间尺度的重力场变化。结果表明：1）0.5 a尺度重力场变化图像可较好地反映此次地震“震前1 a重力场持续出现上升（正）变化-震前局部反向（负）变化-在重力变化梯度带零等值线附近发震”的演化过程；2）震前0.5 a、1 a和2 a尺度重力场均显示，地震发生在重力变化零等值线附近；3）地震前观测到的重力变化可能由深部热物质上涌引起。

Gravity Changes before the Fengnan M4.5 Earthquake in Tangshan,Hebei Province

Based on the observation data of flowing gravity in the capital area from 2017 to 2019, we analyze the gravity changes at different time scales before the M4.5 earthquake in Tangshan, Hebei province, on December 5, 2019. The results show:1) The image of the variation of the 0.5 a scale gravity field well reflects the evolution process of the earthquake: “in 1 a before the earthquake, the gravity field continued to rise(positive) change-the local reverse(negative) change before the earthquake-the earthquake occurred near the zero contour line of the gravity gradient zone”; 2) The 0.5 a, 1 a and 2 a scale gravity fields before the earthquake, show that the earthquake occurred near the zero contour line of gravity change; 3) The change of gravity observed before the earthquake may be caused by the upwelling process of deep thermal materials.