地球与行星物理论评 (Nov 2023)
Contemporary crustal deformation in the borderland region between China and Myanmar revealed based on GPS measurements
Abstract
The region along the border between China and Myanmar is situated at the intersection of the eastern edge of the Myanmar arc, the southeast edge of the Qinghai Tibet Plateau, and the Sunda Plate. This region is characterized by its complex geological structure and strong tectonic activity. To investigate the contemporary pattern of crustal deformation and the tectonics of the border region, the entire regional GNSS network data from 1998 to 2020 in both countries were analyzed. The multi-scale spherical wavelet algorithm was used to estimate the regional strain rate field for the crust deformation and earthquake risk. The following key findings were obtained: (1) The strong compression and subduction of the Indian plate towards the eastern side of the Myanmar block has caused the GPS stations on the Myanmar arc to move towards the Qinghai-Tibet Plateau in the direction of the Indian plate, at a rate of approximately 30 mm/a. The shear strain accumulation is evident in the Myanmar arc region. The primary compressive stress in the Myanmar arc is nearly east-west compression with a vertical tectonic trend on the outer side of the arc and nearly south-north compression with a parallel structure on the inner side of the arc and the Irrawaddy River basin. The Sagaing fault is situated in a region of high principal and shear strain rates, and its subsection activity has been observed. Significant velocity differences exist between the two sides of the northern segment, with significant shear strain accumulation indicating dextral shear movement and shortening. The middle segment of the Sagaing fault moves towards NNW at a rate of approximately 20 mm/a, characterized by dextral strike-slip movement and tension. (2) The Sichuan-Yunnan block rotates clockwise around the eastern Himalayan tectonic belt, with the GPS velocity direction deflecting from the nearly east-west movement on the northern side of the Himalayan tectonic knot towards the Sichuan-Yunnan rhombus block moving southward or southeastward. The pattern of velocity distribution in the southwestern part of Yunnan is dispersed, with the rate gradually decreasing in a southeastward direction. The Xiaojiang fault zone is generally characterized by sinistral strike-slip movement. The middle segment of the Honghe fault has a low strike-slip rate, while the north and south segments have high shear rates. The Dayingjiang fault in southwestern Yunnan exhibits characteristics of east-west extension and an apparent sinistral strike-slip trend. The Longling-Ruili fault is characterized by dextral strike-slip movement and extension. The NE-trending Nantinghe fault, Menglian fault, and Jinghong-Daluo fault are in a low shear state and are dominated by left lateral strike-slip movement. The NW-SE-trending Lancang fault and Wuliangshan fault are characterized by dextral strike-slip movement, while the NW-trending Longling-Lancang fault zone is characterized by dextral strike-slip movement and tension. The magnitude of the strain rate accumulation is related to seismic activity. (3) Based on these findings, it is important to pay attention to the future seismic risk associated with the Sagaing fault, Wanding fault, Nantinghe fault, and the middle part of Wuliangshan fault, all of which are located in the high strain rate area. The results of this study are of great significance for earthquake disaster assessment and furthering our understanding of the tectonic dynamic characteristics of the borderland between China and Myanmar.
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