关键词: 陆丰ML4.3级地震, 流动重力测量, 地震重力异常, 地沉降重力异常

Abstract: On September 24th, 2015, before the Lufeng ML4.3 earthquake, Gravity anomalies occurred at Lufeng, Bomei, Nantang, Jiazi, Xixi and other points in the Guangdong Shantou Mobile Gravity Measurement Network. It was named Lufeng gravity anomaly area, where the accumulated changes of gravity in two years was greater than three times of the observation errors, and Lufeng gravity anomaly area with medium-term decline and reverse turning rise was appeared. Meanwhile, The Measurement points of Chendian and Heping also appear gravity anomalies, It was named Chendian gravity anomaly area，where the Chendian and Heping stations also presented with the continuous monotonic increasing in the Chendian gravity anomaly area, The two gravity anomaly areas were adjacent to each other, forming an oval positive gravity anomaly spatial distribution in east-west direction. The East-West major axis was about 90 km, while the South-North minor axis was about 45 km, there existed significant gravity anomaly areas, but the property of the gravity anomalies was not fully understood, where there might be seismic gravity anomalies and ground subsidence gravity anomalies. In order to analyze the development trend of later-earthquakes, the property of gravity anomaly need to be determined. The method of data analysis and field verification can be used to distinguish the property of gravity changes in each gravity anomaly area. The results showed that Lufeng gravity anomaly area was seismic gravity anomaly area, while Chendian gravity anomaly area was ground subsidence gravity anomaly area, Therefore, the evolution characteristics of seismic gravity field in the process of the Lufeng ML4.3 earthquake are better studied, and the seismic trend after the earthquake is determined.

Key words: Lufeng ML4.3 earthquake, mobile gravity Measurement, seismic gravity anomaly, ground subsidence gravity anomaly