The Yilan crater represents the second confirmed meteorite impact crater discovered in China,with an estimated diameter of about 1850 meters.Previous research in the Yilan crater region focused primarily on evidence associated with impact metamorphism.Drill core data revealed the true depth of the crater's impact structure.Nevertheless,the three-dimensional characteristics of this structure require further constraint through geophysical exploration techniques.In this study,a total of 220 nodal seismographs were deployed across the Yilan crater area,collecting continuous data over a one-month period.Applying the Horizontal to Vertical Spectral Ratio(HVSR)method based on ambient noise,the peak frequency of the study area was determined.Subsequently,Monte Carlo inversion was utilized to derive the shallow velocity structure and sediment layer thickness within the study area.The findings show that the peak frequency in the Yilan crater region increased radially from the center toward the periphery,ranging between 0.3 Hz and 10 Hz.The sediment layer thickness of the Yilan crater gradually decreases from approximately 100 m at the center to about 20 m near the rim.The sediment layer thickness adjacent to the drill hole aligns with the drill core data,confirming a depth of 100 m.An additional interface was identified at 200 m below the surface,potentially corresponding to the boundary between medium-coarse-grained granite and fine-grained granite near the drill hole.This study provides crucial foundational data regarding the site effects and the three-dimensional shallow velocity structure of the impact structure beneath the Yilan crater,which are essential for advancing scientific research and promoting regional educational initiatives.
维普
万方数据