Abstract:

According to the China Earthquake Networks Center, an M_S7.9 earthquake(hereafter referred to as the Myanmar earthquake)struck the Mandalay region of Myanmar(21.85°N, 95.95°E)on March 28, 2025, at a focal depth of 30km. The earthquake occurred along the central segment of the Sagaing Fault and was characterized by a right-lateral strike-slip rupture, generating a ~350km-long surface rupture zone with a maximum coseismic horizontal displacement of 6 meters. The event caused extensive damage to buildings and varying degrees of destruction to infrastructure, including roads and bridges.
Situated in a critical tectonic region where the Indian Plate obliquely converges with the Eurasian Plate, the Myanmar earthquake offers valuable insights into plate boundary deformation processes. Detailed analysis of this event enhances our understanding of the deformation mechanisms along the Myanmar plate boundary and provides essential constraints for seismic hazard assessment along the southeastern margin of the Eurasian Plate. This research holds scientific significance for elucidating continental lithospheric deformation in response to oblique plate convergence. The findings contribute to regional early warning strategies and disaster mitigation efforts and offer a valuable reference for seismic risk studies in comparable tectonic settings worldwide.
This study integrates Global Navigation Satellite System(GNSS)data from across the Sagaing Fault region, establishing a comprehensive GNSS velocity field for Myanmar and addressing previous gaps in coverage along the fault’s southern segment. Using multiscale spherical wavelet analysis and GNSS velocity profiles, we examine the deformation characteristics of the region. We calculate the slip rate deficit distribution along the Sagaing Fault and assess postseismic Coulomb stress changes. Combined with historical seismicity data, we investigate the seismogenic structure and stress perturbations in surrounding areas. The key findings are as follows:
(1)The Myanmar M_S7.9 earthquake was a right-lateral strike-slip event along the central Sagaing fault. The region is affected by the northeastward oblique convergence of the Indian Plate and southeastward extrusion of crustal material from the Tibetan plateau, resulting in strong north-south shear and east-west shortening. The Sagaing fault accommodates most of this deformation, with a rapid right-lateral slip rate of approximately 21~22mm/a.
(2)High-resolution GNSS velocity profiles indicate significant fault locking at depths of 15~25km along the Sagaing Fault. The slip rate deficit analysis reveals a high locking ratio across the fault, indicating elevated seismic potential. Notably, the central segment shows lower seismic moment accumulation compared to the northern and southern segments, forming a ~300km-long seismic gap since 1900, capable of generating earthquakes exceeding magnitude 7.5.
(3)Coulomb stress modeling suggests that the earthquake significantly altered the regional stress field. Stress accumulation zones were identified at both ends of the Sagaing fault and in the central Shan Plateau to the east. These regions of increased stress transfer and loading exhibit heightened potential for future large earthquakes, underscoring the need for enhanced seismic monitoring.

Key words: Myanmar M_S7.9 earthquake, Sagaing Fault, strike-slip fault, slip rate deficit, Coulomb stress

摘要：

2025年3月28日缅甸发生 M_S7.9 地震, 为右旋走滑型破裂, 沿实皆断裂形成长约350km的地表破裂带。文中整合GNSS数据、 历史地震和活动断裂资料, 分析了此次地震的发震构造, 并给出了该地震对区域地震危险性的评估结果。研究表明, 该地震处于印度板块NE向斜向俯冲与青藏高原SE向物质挤出的构造背景下, 区域呈显著的SN向右旋剪切和EW向缩短变形, 发震的实皆断裂以21~22mm/a的走滑活动调节区域的剪切应变。GNSS剖面和滑动速率亏损分布显示, 实皆断裂整体处于高闭锁状态, 且在断裂中段形成地震空区, 表明该断裂段具备孕育M7.5以上地震的构造潜力。库仑应力变化模拟结果显示, 震后应力扰动在同震断裂南、 北端和掸邦高原中部形成应力加载区, 应力加载和转变区域未来的强震危险性值得关注。

关键词: 缅甸M_S7.9地震, 实皆断裂, 走滑断裂, 滑动速率亏损, 库仑应力