Typical anomalies of underground fluid before the 2019 Tangshan M4.5 earthquake feature analysis

This paper analyzes the typical abnormal characteristics of underground fluid within 200km before the M4.5 earthquake in Tangshan, Hebei Province on December 5, 2019. The results show that the anomaly pattern is consistent with that of the previous cases, and has obvious repeatability. The anomaly time process includes three stages: medium-term anomaly, short-term anomaly and impending earthquake anomaly. Spatially, the anomaly is mainly distributed within 100 km of epicenter distance, and has a certain relationship with fault distribution. The comprehensive analysis shows that the seismogenic process of Tangshan earthquake is mainly affected by regional stress field and local tectonic activity.