Aftershock Evolution Characteristics of the 28 March 2025 Mw7.7 Myanmar Earthquake Sequence

Abstract

On March 28, 2025, a strong earthquake of MW7.7 struck central Myanmar, occurring on the Meiktila segment of the Sagaing Fault, which had been locked for 186 years. This event validated previous predictions that this segment could produce an earthquake of MW7.8–7.9. This study analyzes the aftershock sequence characteristics using the catalog recorded by the Thailand Meteorological Department’s Seismic Monitoring Center (TMD). The results show that the minimum magnitude of completeness for the sequence is 3.2. The sequence decayed rapidly, with 62.5% of M≥5.5 aftershocks occurring within the first three days after the mainshock. The ETAS model indicates the α-value of 2.02, suggesting that the aftershocks were primarily triggered by the mainshock and had a strong ability to induce secondary aftershocks. The p-value of 1.47 indicates that the aftershock decay rate was faster than the original Omori’s law. The magnitude difference between the largest aftershock and the mainshock is 1.0, consistent with regional historical patterns. The spatial fractal dimension reveals a non-uniform stress state along the fault. The aftershock distribution is controlled by the Sagaing Fault, exhibiting a north-south alignment and closely correlating with historical earthquake ruptures. After this MW7.7 earthquake, most segments of the central and southern Sagaing Fault—except for the Bago segment—have ruptured, making another MW7.7 earthquake unlikely in the near future. However, the northern end of the Bago segment still poses a risk of an MW7.0-class earthquake.

Keywords: MW7.7 Myanmar earthquake sequence, Sagaing Fault, aftershock characteristics, earthquake rupture characteristics