Anomalies of astronomical time-latitude residuals of photoelectric astrolabe of Yunnan Observatories with three strong earthquakes in Yunnan in 2014

In 2014 in Yunnan Province occurred three strong earthquakes. The synchronous anomalies greater than 2σ appeared in RT and RL of the photoelectric astrolabe at Yunnan Observatories before the three earthquakes. Besides the three anomalies there were no other anomalies. Before the strong earthquake astronomical time and latitude residuals appearant anomalies, this phenomenon was first discovered by the researchers of Beijing Observatories of the Chinese Academy of Sciences after the Tangshan earthquake in 1976, which was found over 30 years ago. Over 30 years of research and practice for this anomalies shows that this phenomenon is real, and its physical mechanism is relatively clear. The optical astrometric instrument is based on local plumb line as a reference carry out observation. Before earthquake the plumb line changes caused by underground substance motion may be the reasons for this astronomical time and latitude residual anomaly. Therefore, the results reported herein, once again proves that anomalies of astronomical time and latitude residual can provide useful warning sign for strong earthquake prediction around the station. It may be an effective precursor, deserves attention and further study.