Shallow 3-D velocity structure and its implications for seismogenic structure in the Xunwu(Jiangxi)region and its adjacent areas
Situated within the Shaowu-Heyuan fault zone,the Xunwu area has experienced several moderate earthquakes,notably the M6 earthquake in 1806,the M～5.75 earthquake in 1941,and a swarm of M～5.5 earthquakes in 1987.It is one of the seismically active regions along the Shaowu-Heyuan fault zone,and also one of the key areas for earthquake prevention and mitigation in Jiangxi province.The shallow subsurface velocity structures in this area help improve the accuracy of earthquake location and seismogram calculation.However,the sparse seismic network in the region,coupled with the complex development of NW and NE-trending faults,has posed significant challenges to studying the seismogenic environment.In this study,based on continuous waveforms observed by a dense array across Xunwu and its neighboring areas,we computed noise cross-correlation between station pairs and extracted Rayleigh wave(0.5～6 s).The surface wave tomography method was applied to invert the velocity structure up to 6 km depth of the study area.Both phase velocity and S-wave velocity reveal the shallow spatial characteristics of faults,graben basins,and lithological structure.The shallow low-velocity zone approximately 3 km deep reveals the distribution of graben basins such as Huichang and Xunwu and exhibits a strong correspondence with the'S'-shaped sharp turn of the Shaowu-Heyuan fault zone near Zhoutian,which highlights the influence of regional fault zones on the evolution of the basin.Earthquakes in the region predominantly occur in the transition zone between high and low-velocity structures.Variations of S-wave velocity demonstrate the spatial distribution of NW-trending faults,suggesting that NW-oriented faults are the primary contributors to the seismicity in the study area.
Xunwu areaAmbient noise tomographyDense arrayShallow velocity structureShaowu-Heyuan fault zone
万方数据
维普
