Three-dimensional crustal velocity structure and tectonic implication of the Haiyuan-Liupan Mountain area based on ambient noise tomography
The Haiyuan-Liupan Mountain region,located on the northeastern edge of the Tibetan Plateau,is the frontal zone of the northeastern compression of the Tibetan block,characterized by active geological structures.Historically,this region has experienced several earthquakes with magnitudes exceeding 7.However,there have been no strong earthquakes of magnitude 6 or higher in many years in this area,making it a seismic gap with potential risks of strong earthquakes.Detailed velocity structures of the Haiyuan-Liupan Mountain region can help to understanding regional tectonic activity and seismic hazard.This study performed ambient noise tomography to obtain high-resolution three-dimensional crustal shear wave velocity structure,based on the continuous data from 50 temporary and 38 permanent seismic stations deployed in the study region.Combined with the precise earthquake relocation results from 2010 to 2023,several insights were obtained.(1)The study area,divided by the Haiyuan-Liupan Mountain fault,exhibits notable structural differences between its eastern and western sides.The eastern side,part of the Ordos Block,primarily consists of large area low-velocity sedimentary layers associated with lower seismic activity;whereas,the western side is featured by prominent high-velocity anomalies and higher seismic activity.(2)Precisely relocated earthquakes indicate that most earthquakes occur along the boundaries of high and low-velocity anomalies,with their distribution showing good consistency with surface tectonic units.(3)Near the northern margin of the Western Qinling fault zone,the Liupan Mountain and western edge of the Ordos display distinct high-velocity anomalies,suggesting that this area is part of the Qilian orogenic belt with dense crystalline basement at depth.(4)The crustal thickness in the Haiyuan-Liupan Mountain region gradually decreases from the southwest to the northeast,and no low-velocity"channels"were observed in the middle to lower crust within the study area.
Northeastern margin of the Tibetan PlateauAmbient noise tomographyCrustHaiyuan-Liupan Mountain Fault ZoneSeismicity
万方数据
维普
