Antoine Solene L, Shrestha Rajani, Milliner Chris, Im Kyungjae, Rollins Chris, Wang Kang, Chen Kejie, Avouac Jean-Philippe
Geological and Planetary Science Division, California Institute of Technology, Pasadena 91125, CA.
Earth Sciences New Zealand, Lower Hutt 5011, New Zealand.
Proc Natl Acad Sci U S A. 2025 Aug 19;122(33):e2514378122. doi: 10.1073/pnas.2514378122. Epub 2025 Aug 11.
We use remote sensing observations to document surface deformation caused by the 2025 M7.7 Mandalay earthquake. This event is a unique case of an extremely long (510 km) and sustained supershear rupture probably favored by the rather smooth and continuous geometry of this section of the structurally mature Sagaing Fault. The seismic rupture involved the locked portion of the fault over its entire depth extent (0 to 13 km) with a remarkably uniform slip distribution that averages 3.3 m, and an average stress drop of 4.7 MPa. No shallow-slip deficit is observed. The rupture extent challenges usual scaling laws relating earthquake magnitude, fault length, and slip. The fault ruptured along a known seismic gap that last ruptured in 1839 and tailed off into sections that ruptured during large earthquakes in 1930 and 1946. The amplitude and spatial distribution of fault slip in the 2025 event conform only approximatively to the slip-predictable model and the segmentation inferred from the fault geometry and past ruptures. Plausible sequences of earthquakes with variable magnitude, segmentation, and return periods, including events similar to the 2025 earthquake are produced in quasidynamic simulations using a simplified but nonplanar fault geometry. Based on this simulation, M>7.5 events return irregularly with an interevent time of ~141 y on average and a SD of ~40 y. The simulation is consistent with the historical seismicity and with the maximum magnitude ~M7.9 and return period (250 y) derived from moment conservation. Data assimilation into such simulations could provide a way for time-dependent hazard assessment in the future.
我们利用遥感观测记录了2025年曼德勒7.7级地震引发的地表变形。此次地震是一个独特的案例，其破裂异常长（约510公里）且持续出现超剪切破裂，这可能得益于结构成熟的实皆断裂带这一区域相当平滑且连续的几何形态。地震破裂涉及该断层在其整个深度范围（0至13公里）内的闭锁部分，具有显著均匀的滑动分布，平均滑动量为3.3米，平均应力降为4.7兆帕。未观测到浅部滑动亏损。破裂范围对通常将地震震级、断层长度和滑动相关联的标度律提出了挑战。该断层沿着一条已知的地震空区破裂，该地震空区上次在1839年破裂，然后延伸至在1930年和1946年大地震期间破裂的区域。2025年事件中断层滑动的幅度和空间分布仅大致符合滑动可预测模型以及根据断层几何形态和过去破裂推断出的分段情况。使用简化但非平面的断层几何形态进行的准动态模拟产生了震级、分段和复发周期可变的合理地震序列，包括类似于2025年地震的事件。基于此模拟，震级大于7.5级的事件平均以约141年的事件间隔不规则复发，标准差约为40年。该模拟与历史地震活动性以及根据矩守恒得出的最大震级约7.9级和复发周期（约250年）相一致。将数据同化到此类模拟中可为未来随时间变化的灾害评估提供一种方法。
