A persistent radon anomaly signal preceding the destructive 7.7 M_w earthquake in Myanmar on March 28, 2025

On March 28, 2025, a devastating earthquake doublet of moment magnitude 7.7 and 6.7 struck the Sagaing Region of Myanmar, causing extensive damage and significant casualties across Southeast Asia. In the months preceding this seismic event, a continuous radon monitoring system-BhaROSA-installed in Imphal, India, as a part of the Indian Network for Detecting Radon Anomaly signal (INDRA), recorded a pronounced and statistically significant novel radon anomaly signal. The anomaly signal commenced on December 5, 2024, with a gradual buildup, followed by a sharp rise on February 28, 2025. Multiple peak alerts were observed prior to the mainshock (7.7 M_w) on March 28, 2025, after which the signal declined rapidly, returning to baseline levels-suggesting a potential correlation with pre-seismic crustal stress accumulation and release. The anomaly signal exhibited a normalized squared deviation of 35.14 from the baseline value, far exceeding natural variability at the time of main shock. The radon signal, with a build-up period of approximately 109 days and a decay of ~ 96 h, closely matched the spatial and temporal characteristics of the dilatancy-diffusion model. A pooled analysis of radon anomalies from ten earthquake events, including this major event, across multiple Indian observatories of INDRA reveals a robust positive correlation (r = 0.96, R² = 0.93) between radon buildup duration and earthquake magnitude. These findings strongly suggest that radon emissions are sensitive indicators of impending seismic activity and radon build up period can be a good indicator of magnitude of earthquake. The study highlights the potential of continuous radon monitoring in tectonically active regions like Northeast India and Myanmar as a viable component of earthquake precursor research and early warning systems.