The fine-scale structures of lithosphere discontinuities contain important information on the dynamics of lithosphere formation, development, transformation, and destruction. In this paper, a new seismic daylight imag...The fine-scale structures of lithosphere discontinuities contain important information on the dynamics of lithosphere formation, development, transformation, and destruction. In this paper, a new seismic daylight imaging method is developed to explore the small-scale structures of lithosphere discontinuities. This method makes use of the P-wave first arrival and coda in the 0.5–4 Hz high frequency band of teleseismic events, and reaches a resolution of 2 km for lithosphere discontinuities. This method rests on the basic principle that the autocorrelation of the vertically incident transmission response below the seismic station is equivalent to the reflection response with the source and station both on the free surface. The transmission responses include the first-arrival P-waves below the station traversing the discontinuities to reach the free surface, and the multiple reflections between the free surface and the discontinuities. In this study, the normal incidence requirement of the method is further extended to include dip incidence illumination, which expands its applicability. The accuracy and feasibility of the seismic daylight imaging (SDI) theory are verified by synthesized theoretical seismograms, and the factors affecting the imaging results are discussed. The data processing steps and the interpretation criteria for the method are also given. The fine-scale lithosphere structure of two permanent stations at the eastern North China Craton is determined by the method described here, as well as instantaneous frequency. Clear discontinuities are found in the lithospheric mantle at 52 and 75 km below the two stations, respectively. Seismic daylight imaging and the receiver function reveal a more consistent lithosphere structure beneath the MBWA permanent station of the West Australia Craton, with the unmistakable presence of the lithosphere discontinuities.High-frequency SDI can be used to detect the fine-scale lithospheric structures. As its waveform is more complex, and hence appropriate reference to existing seismological information, such as from tomographic velocity inversion and the receiver function, is recommended.展开更多
Recent seismic studies reveal a sharp velocity drop mostly at^70–100 km depth within the thick mantle keel beneath cratons, termed the mid-lithosphere discontinuity(MLD). The common presence of the MLD in cratonic re...Recent seismic studies reveal a sharp velocity drop mostly at^70–100 km depth within the thick mantle keel beneath cratons, termed the mid-lithosphere discontinuity(MLD). The common presence of the MLD in cratonic regions indicates structural and property layering of the subcontinental lithospheric mantle(SCLM). The nature and origin of the MLD, and many issues associated with the layering of the SCLM are essential to understand the formation and evolution of continents, and have become frontier subjects in the Earth sciences.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 41720104006, 41774060)Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2017094)
文摘The fine-scale structures of lithosphere discontinuities contain important information on the dynamics of lithosphere formation, development, transformation, and destruction. In this paper, a new seismic daylight imaging method is developed to explore the small-scale structures of lithosphere discontinuities. This method makes use of the P-wave first arrival and coda in the 0.5–4 Hz high frequency band of teleseismic events, and reaches a resolution of 2 km for lithosphere discontinuities. This method rests on the basic principle that the autocorrelation of the vertically incident transmission response below the seismic station is equivalent to the reflection response with the source and station both on the free surface. The transmission responses include the first-arrival P-waves below the station traversing the discontinuities to reach the free surface, and the multiple reflections between the free surface and the discontinuities. In this study, the normal incidence requirement of the method is further extended to include dip incidence illumination, which expands its applicability. The accuracy and feasibility of the seismic daylight imaging (SDI) theory are verified by synthesized theoretical seismograms, and the factors affecting the imaging results are discussed. The data processing steps and the interpretation criteria for the method are also given. The fine-scale lithosphere structure of two permanent stations at the eastern North China Craton is determined by the method described here, as well as instantaneous frequency. Clear discontinuities are found in the lithospheric mantle at 52 and 75 km below the two stations, respectively. Seismic daylight imaging and the receiver function reveal a more consistent lithosphere structure beneath the MBWA permanent station of the West Australia Craton, with the unmistakable presence of the lithosphere discontinuities.High-frequency SDI can be used to detect the fine-scale lithospheric structures. As its waveform is more complex, and hence appropriate reference to existing seismological information, such as from tomographic velocity inversion and the receiver function, is recommended.
基金supported by the National Natural Science Foundation of China (41225016, 41688103, 91414301)Chinese Academy of Sciences
文摘Recent seismic studies reveal a sharp velocity drop mostly at^70–100 km depth within the thick mantle keel beneath cratons, termed the mid-lithosphere discontinuity(MLD). The common presence of the MLD in cratonic regions indicates structural and property layering of the subcontinental lithospheric mantle(SCLM). The nature and origin of the MLD, and many issues associated with the layering of the SCLM are essential to understand the formation and evolution of continents, and have become frontier subjects in the Earth sciences.
