Analysis of anomalous environmental responses to the 5.5 earthquake in Pingyuan County, Dezhou in august 2023 based on GNSS

To investigate the abnormal environmental response caused by the magnitude 5.5 earthquake in Pingyuan County, Shandong Province, on August 6th, 2023, this study based on the Global Navigation Satellite System (GNSS) observation data located about 26 km northeast of the epicenter, proposes a moving time-varying frequency method and incorporates the interquartile range (IQR) method to analyze the abnormal environmental responses triggered by the earthquake. The results indicate significant anomalies in the N and E directional coordinate velocity time series at 9 to 10 seconds after the earthquake, with a minor anomaly in the U direction at 16 seconds. Moreover, the sliding time-varying frequency method detects noticeable changes 5 to 10 seconds before the abnormal jump in the velocity time series, demonstrating higher sensitivity. The study also discovered abnormal disturbances in the ionosphere above the epicenter the day before the earthquake, with the anomaly reaching 4 TECU. This research demonstrates the effectiveness of GNSS technology in detecting abnormal environmental responses during earthquakes, offering a new perspective and tools for earthquake monitoring and early warning.