10:45 AM - 12:15 PM
[SSS05-P06] 3D high-density ambient noise imaging technology for high-resolution detection of three-dimensional structural features of urban buried active faults
Keywords:urban buried active faults, 3D high-density ambient noise imaging technology, prevention and reduction of natural disasters
High-precision three-dimensional detection and model construction of hidden activities in urban faults are of great significance for evaluating seismic and geological hazard risks, and effectively improving the risk awareness and management level of urban faults. The Nankou-Sunhe Fault (NSF) is located in the northern part of Beijing, crossing densely populated urban areas along the northwest-southeast direction. Previous studies have conducted extensive work on its spatial distribution and seismic activity, but there is still a gap in its fine three-dimensional characterization, especially the coupling relationship between the activity of the Ma Chikou Depression and the boundary faults of the NSF and the sedimentary evolution, which requires further in-depth research in a three-dimensional spatial structure.
Active source detection in super mega cities is hindered by complex urban environmental noise and dense housing facilities, and its detection accuracy and effective depth are greatly constrained. To address this issue, we carried out a 3D high-density ambient seismic detection experiment covering an area of approximately 40 square kilometers in the NSF distribution area. In order to shorten the acquisition time and balance the noise impact near the main roads of the city, we added long-term active source excitation locally. The entire observation system used 1000 Smartsolo node seismometers with a main frequency of 5Hz, a design point distance of 200m, and a line distance of 200m for reception, with a collection time of 17-20 days. With the help of noise information generated by the main roads and active source excitation, high-quality observation data was obtained. Cross-correlation calculation was performed using a cloud computing platform to obtain high-quality surface wave records. Then, multi-channel analysis of passive surface waves (MAPS) technology was used to extract the dispersion curves of surface waves and invert for the shear wave velocity, resulting in a high-resolution three-dimensional shear wave velocity structure model with a depth of more than 1000m. The three-dimensional shear wave velocity structure is in good agreement with the two-dimensional active source reflection seismic results. Based on the velocity information, a reliable three-dimensional velocity structure model of the NSF fault was established, revealing a north-east-southwest trending normal fault with a dip angle of 50°-60° in the study area. The experimental results show that combining large-scale high-density three-dimensional ambient noise detection with active source excitation can achieve high-resolution three-dimensional imaging of hidden fault structures in thick sedimentary areas. This experimental exploration provides a reliable research foundation from the perspectives of observation parameter design, data recording, and high-precision data processing, and proposes feasible technical methods and routes for larger-scale super mega cities.
Active source detection in super mega cities is hindered by complex urban environmental noise and dense housing facilities, and its detection accuracy and effective depth are greatly constrained. To address this issue, we carried out a 3D high-density ambient seismic detection experiment covering an area of approximately 40 square kilometers in the NSF distribution area. In order to shorten the acquisition time and balance the noise impact near the main roads of the city, we added long-term active source excitation locally. The entire observation system used 1000 Smartsolo node seismometers with a main frequency of 5Hz, a design point distance of 200m, and a line distance of 200m for reception, with a collection time of 17-20 days. With the help of noise information generated by the main roads and active source excitation, high-quality observation data was obtained. Cross-correlation calculation was performed using a cloud computing platform to obtain high-quality surface wave records. Then, multi-channel analysis of passive surface waves (MAPS) technology was used to extract the dispersion curves of surface waves and invert for the shear wave velocity, resulting in a high-resolution three-dimensional shear wave velocity structure model with a depth of more than 1000m. The three-dimensional shear wave velocity structure is in good agreement with the two-dimensional active source reflection seismic results. Based on the velocity information, a reliable three-dimensional velocity structure model of the NSF fault was established, revealing a north-east-southwest trending normal fault with a dip angle of 50°-60° in the study area. The experimental results show that combining large-scale high-density three-dimensional ambient noise detection with active source excitation can achieve high-resolution three-dimensional imaging of hidden fault structures in thick sedimentary areas. This experimental exploration provides a reliable research foundation from the perspectives of observation parameter design, data recording, and high-precision data processing, and proposes feasible technical methods and routes for larger-scale super mega cities.