10:45 AM - 11:00 AM
[SSS07-05] Imaging the Ice Sheet Structures with Ambient Noise using F-J method in the Larsemann Hills of East Antarctica
Keywords:Antarctic Ice Sheet, Ambient Noise, F-J method
Introduction
The Antarctic ice sheet, a type of polar continental glacier, is formed by the gradual accumulation of perennial snowfall. The lower layers of snow, under the gravitational force of the upper layers, undergo compaction and recrystallization to form hard ice, preserving a complete stratified structure. The structure of ice sheets is important for accurate modelling the ice dynamics and the icequake locating. The ambient noise imaging can be applied over large areas at a low cost and without direct sampling, and has been used to study ice sheets structure in Antarctica (Z. Zhan et al., 2014). However, conventional ambient noise imaging method are based on fundamental mode dispersion curves. The ice sheet velocity models are quite different from the conventional structure models beyond the polar area and more complex; therefore, the overtones must be used as the an important constrain. The frequency-Bessel transform method (F-J method) is a useful method to extract the dispersion curves of higher modes (Wang et al., 2019), and it has been widely used to imaging the structure under different areas (Li et al., 2022; Li & Chen, 2020; Wu et al., 2020; W. Zhan et al., 2020; Zhang et al., 2021). However, we need a suitable subarray selection to make sure that both the high-quality dispersion curves and a sufficient horizontal resolution are satisfied for imaging. To solve this problem, we introduced the FJ-VoroTomo method (Li et al., 2023), and applied it on the two-dimensional imaging.
In this work, we obtain high-resolution images of the ice sheet and uppermost crustal structure beneath the Larsemann Hills, Prydz Bay, East Antarctica.
Discussion
In the process of extracting overtones, it is crucial to ensure the accuracy of the extraction as much as possible. In some subarray, however, interference of different modes may happen at some frequency points, which is called ‘mode kissing’ phenomenon. This overlap makes it challenging to distinguish the true mode. Mode kissing phenomenon is model dependent and that the existence of strong S-wave velocity contrasts increases the possibility of mode-kissing (Gao et al., 2016).
In the result of the south area, we find smaller Vs than standard ice velocity at lower layer of ice sheet. That may be caused by a strong seismic anisotropy that the lower layer ceiling corresponds approximately to the −30 °C isotherm (Wittlinger & Farra, 2015).
Acknowledgement
This work was supported by the “CUG Scholar” Scientific Research Funds at China University of Geosciences (Wuhan) (Project No.2022132).
The Antarctic ice sheet, a type of polar continental glacier, is formed by the gradual accumulation of perennial snowfall. The lower layers of snow, under the gravitational force of the upper layers, undergo compaction and recrystallization to form hard ice, preserving a complete stratified structure. The structure of ice sheets is important for accurate modelling the ice dynamics and the icequake locating. The ambient noise imaging can be applied over large areas at a low cost and without direct sampling, and has been used to study ice sheets structure in Antarctica (Z. Zhan et al., 2014). However, conventional ambient noise imaging method are based on fundamental mode dispersion curves. The ice sheet velocity models are quite different from the conventional structure models beyond the polar area and more complex; therefore, the overtones must be used as the an important constrain. The frequency-Bessel transform method (F-J method) is a useful method to extract the dispersion curves of higher modes (Wang et al., 2019), and it has been widely used to imaging the structure under different areas (Li et al., 2022; Li & Chen, 2020; Wu et al., 2020; W. Zhan et al., 2020; Zhang et al., 2021). However, we need a suitable subarray selection to make sure that both the high-quality dispersion curves and a sufficient horizontal resolution are satisfied for imaging. To solve this problem, we introduced the FJ-VoroTomo method (Li et al., 2023), and applied it on the two-dimensional imaging.
In this work, we obtain high-resolution images of the ice sheet and uppermost crustal structure beneath the Larsemann Hills, Prydz Bay, East Antarctica.
Discussion
In the process of extracting overtones, it is crucial to ensure the accuracy of the extraction as much as possible. In some subarray, however, interference of different modes may happen at some frequency points, which is called ‘mode kissing’ phenomenon. This overlap makes it challenging to distinguish the true mode. Mode kissing phenomenon is model dependent and that the existence of strong S-wave velocity contrasts increases the possibility of mode-kissing (Gao et al., 2016).
In the result of the south area, we find smaller Vs than standard ice velocity at lower layer of ice sheet. That may be caused by a strong seismic anisotropy that the lower layer ceiling corresponds approximately to the −30 °C isotherm (Wittlinger & Farra, 2015).
Acknowledgement
This work was supported by the “CUG Scholar” Scientific Research Funds at China University of Geosciences (Wuhan) (Project No.2022132).