High-Resolution 3D Ambient Noise Tomography via Compressive Sensing-Based NCF Reconstruction: Application to the Yarlung Tsangpo Suture Zone Using a Short-Period Dense Array

Among the various ambient noise inversion techniques, shallow crust inversion methods are of particular interest due to their capacity to address the growing need for high-resolution subsurface characterization. A critical aspect of the research lies in identifying the most relevant observables or processed data, selecting the most effective inversion approach, and determining the optimal set of model parameters to adjust in order to obtain the best solution. To resolve the fine-scale shallow crustal structure beneath the Yarlung Tsangpo Suture Zone (YTSZ) using a short-period dense array, this study introduces a high-resolution three-dimensional ambient noise tomography (3D ANT) framework that incorporates compressive sensing-based reconstruction of ambient noise cross-correlation functions (NCFs). This approach enables the retrieval of high-frequency ambient noise signals from dense array data and significantly enhances the resolution of shallow crustal imaging under low signal-to-noise ratio conditions. Our results reveal that the shallow crust within the YTSZ is predominantly composed of Quaternary unconsolidated sediments and fractured fault zones, indicative of a pervasive weak layer that facilitates strain accommodation. The identified high-velocity anomalies likely correspond to obducted ophiolitic fragments or well-cemented conglomeratic strata. In conjunction with the widespread distribution of dismembered ophiolites and mélanges—signatures of intense tectonic reworking—these findings provide critical constraints on the emplacement of ophiolitic fragments through subduction-obduction processes. Furthermore, the delineated coupling between deep-seated ductile flow and shallow brittle rupture offers new insights into strain partitioning within the eastern Himalayan syntaxis and its implications for regional seismic hazard assessment.