3:30 PM - 3:48 PM
[SIT19-07] Teleseismic constraints on the cratonic continental margin beneath the Korean Peninsula: Insights into lithospheric dynamics in Northeast Asia
Keywords:Travel-time Tomography, Cratonic Continental Margin, Lithospheric Dynamics, Anisotropy
It is widely recognized that the subduction of oceanic plates and/or mantle plumes may result in the destruction of cratons. However, the destabilization and modification at cratonic continental margins are less understood and remain an active area of research. Geologically, the Korean Peninsula (KP) is positioned as a bridging position between the North China Craton and the Japan Trench of the western Pacific Plate subduction zone. The detailed lithospheric structure of the KP can contribute to elucidating the tectonic evolution of Northeast Asia.
For anisotropic tomography, we collected teleseismic P-wave data from a remarkably dense seismic network in Korea (140 stations) over five years (2018–2022) and inverted 43,977 rays from 399 events of magnitudes over 5.5. To enhance the quality of the tomographic models, we incorporated hypothetical seismic anisotropy models into the tomographic inversion since seismic anisotropy can manifest as velocity artifacts while also providing insights into mantle flow dynamics. The anisotropy models were constructed based on observations of shear wave splitting and hypotheses regarding regional geological evolution. Extensive resolution and synthetic tests demonstrate that our tomography model robustly resolves velocity structures of 50 km x 50 km for a depth range of 50-300 km. In line with previous studies, our P-wave velocity model shows a clear E-W variation in the upper-mantle structure: a high-velocity structure in the topographically flat western part and a low-velocity structure in the mountainous eastern part of Korea.
The dominant E-W contrast in our anisotropic tomography can be attributed to variations in lithospheric properties. The low-velocity structure may originate from intraplate upwelling; however, the volume of warm mantle might have been overestimated, as the lower part of the low-velocity structure may be due to anisotropy. Meanwhile, the high-velocity structure appears to be unaffected by anisotropy and likely represents cold lithosphere. Our results suggest that the KP is a transition zone with a complicated lithospheric architecture, providing evidence of ongoing modifications to the craton.
For anisotropic tomography, we collected teleseismic P-wave data from a remarkably dense seismic network in Korea (140 stations) over five years (2018–2022) and inverted 43,977 rays from 399 events of magnitudes over 5.5. To enhance the quality of the tomographic models, we incorporated hypothetical seismic anisotropy models into the tomographic inversion since seismic anisotropy can manifest as velocity artifacts while also providing insights into mantle flow dynamics. The anisotropy models were constructed based on observations of shear wave splitting and hypotheses regarding regional geological evolution. Extensive resolution and synthetic tests demonstrate that our tomography model robustly resolves velocity structures of 50 km x 50 km for a depth range of 50-300 km. In line with previous studies, our P-wave velocity model shows a clear E-W variation in the upper-mantle structure: a high-velocity structure in the topographically flat western part and a low-velocity structure in the mountainous eastern part of Korea.
The dominant E-W contrast in our anisotropic tomography can be attributed to variations in lithospheric properties. The low-velocity structure may originate from intraplate upwelling; however, the volume of warm mantle might have been overestimated, as the lower part of the low-velocity structure may be due to anisotropy. Meanwhile, the high-velocity structure appears to be unaffected by anisotropy and likely represents cold lithosphere. Our results suggest that the KP is a transition zone with a complicated lithospheric architecture, providing evidence of ongoing modifications to the craton.