利用GPS数据研究缅甸实皆断裂形变特征

doi:10.12196/j.issn.1000-3274.2025.03.001

摘要/Abstract

摘要： 实皆断裂位于缅甸境内, 其作为缅甸微板块与巽他板块的右旋走滑边界, 是调节印度板块巽他板块斜向汇聚的核心构造, 其运动学特征对地震潜势的判定十分重要。基于1998—2024年缅甸及邻区密集GPS观测数据, 通过高精度解算与ITRF框架统一校准, 构建了以巽他板块为基准的水平速度场, 并结合VISR方法反演区域应变率场, 揭示了实皆断裂的形变特征。结果表明: ① 实皆断裂整体呈现右旋走滑特征, 西侧块体以10~40 mm/a向西北运动, 东侧块体以<10 mm/a向西运动, 形成显著速度梯度带, 曼德勒附近(约22°N)速度突变达8~10 mm/a, 指示该位置深部闭锁, 为应变累积与强震孕育的关键区段。 ② 应变率场分析显示, 断裂北段(21°N以北)以剪切-挤压复合变形为主, 最大压缩应变率达-90×10^-9 /a, 与历史强震群集高度耦合; 中段(18°N~21°N)局部发育次级应变集中区, 如内比都附近(21°N, 97°E)的椭圆状异常, 揭示断裂系统内部应变分配的复杂性; 南段(21°N以南)受安达曼海扩张调节, 面应变率(-30×10^-9 /a~10×10^-9 /a)与地震活动性反映出其稳态走滑特征。 ③ 最大剪切应变率(>120×10^-9 /a)沿断裂走向呈带状分布, 与历史强震(2012年塔贝钦M_W6.8地震、 2025年曼德勒M_S7.9地震)空间位置高度吻合, 印证高应变梯度带对孕震的控制作用。 ④ 实皆断裂带变形特征揭示了印度板块巽他板块斜向汇聚背景下缅甸微板块西向逃逸与边界阻挡作用的动态平衡。位于北段的速度梯度突变区与历史地震空区的空间耦合性为识别闭锁段及潜在地震危险区提供了关键运动学约束。未来需重点关注北段闭锁区(实皆段与梅固蒂拉段)应变累积速率及中段次级断裂的发震潜势。

关键词: GPS, 实皆断裂, 速度场, 地壳形变

Abstract: The Sagaing fault, situated within Myanmar, serves as the right-lateral strike-slip boundary between the Burma microplate and the Sunda plate. As a major structure accommodating the oblique convergence between India and Sunda, its kinematic characteristics are critical for seismic potential analysis. This study utilizes dense GPS observations from Myanmar and adjacent regions (1998—2024) to construct a horizontal velocity field referenced to the Sunda Plate through high-precision processing and ITRF framework alignment. Integrated with strain rate inversion via the VISR method, we systematically reveal the deformation characteristics and dynamic mechanisms of the Sagaing fault. The key findings include: ① The fault exhibits dominantly right-lateral strike-slip motion. The western block moves northwestward at 10~40 mm/a, while the eastern block shifts westward at <10 mm/a, forming a prominent velocity gradient zone. A velocity jump of 8~10 mm/a near Mandalay (~22°N) indicates deep fault locking, marking a critical segment for strain accumulation and major earthquake preparation. ② The strain rate analysis demonstrates that the northern segment (>21°N) undergoes shear-compression composite deformation, with a maximum compressive strain rate of -90×10^-9 /a, correlating with historical seismic clusters. The central segment (18°N~21°N) hosts localized secondary strain concentration zones (e.g., an elliptical anomaly at 21°N, 97°E), reflecting complex internal strain partitioning. The southern segment (<21°N) exhibits steady strike characteristics, evidenced by dilatational strain rates (-30×10^-9 /a~10×10^-9 /a) and seismicity, modulated by Andaman Sea expansion. ③ Maximum shear strain rates (>120×10^-9 /a) align spatially with historical large earthquakes (e.g., the 2012 Thabeikkyin M_W6.8 earthquake and the 2025 Mandalay M_S7.9 earthquake), confirming the control of high-strain gradients on seismogenesis. ④ The deformation patterns of the Sagaing Fault reveal the dynamic equilibrium between westward extrusion of the Burma microplate and boundary confinement under oblique Indian-Sunda plate convergence. The spatial correlation between velocity gradient discontinuities in the northern segment and historical seismic gaps establishes critical kinematic constraints for identifying both locked segments and regions of elevated seismic risk. Future research should prioritize quantifying strain accumulation rates within the northern locked segments (particularly the Sagaing and Meiktila segments) while systematically evaluating the seismic potential of secondary fault systems in the central segment.

Key words: GPS, Sagaing Fault, Velocity field, Crustal deformation

中图分类号:

P315.7

王宇凡, 孟国杰, 吴伟伟. 利用GPS数据研究缅甸实皆断裂形变特征[J]. 地震, 2025, 45(3): 1-12.

WANG Yu-fan, MENG Guo-jie, WU Wei-wei. Deformation Characteristics of the Sagaing Fault in Myanmar Revealed by GPS Observations[J]. EARTHQUAKE, 2025, 45(3): 1-12.

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