Ambient Noise Tomography Study In Liaoning And Its Adjacent Areas

The characteristic of terrain is “the horst embed in two graben”,the north section of Tanlu-fault cross through the Bohai and the Liaoning province.meanwhile,there are the Jinzhou fault ?Yalujiang fault ?Taizihe fault in the area.It had occurred many moderate strong earthquakes in history,for example,the magnitude 7.4 earthquake of Bohai in 1969,the magnitude 7.3 earthquake of Haicheng in 1975,seismic activity is also active in recent years.as we all known,pestilent earthquakes usually happened in crust and stress state of crust have correlation with mantle.the study of crust and mantle structure in Liaoning and its adjacent area is beneficial to analyze the seismic tectonic background and mechanism of earthquakepreparation and the work to study of earthquake monitoring and prediction.In this paper,by collecting continuous background noise waveform vertical data recording of 70 broadband seismic stations in Liaoning and its adjacent areas(Hebei,Shandong,Inner Mongolia,Jilin)from January 2012 to December 2012,we get the surface wave group velocity images through ambient noise tomography in study region.we calculated the inter-station Green fuction and extracted the Rayleigh wave group and phase velocity dispersion curves by the method of CPS330 and FTAN.Acorrding to quality control and screening,we pick high SNR 1660 group and phase velocity dispersion curve of Rayleigh wave from 2415 dispersion curves.then,the study area is divided into a grid of 0.25°×0.25° degree grid by adopting Ditmar&Yanovskaya method and obtained the Raileigh wave group and phase velocity maps at periods 10s~40s in the study.the results show that crust and upper mantle structure of Liaoning region present obvious lateral inhomogeneity.group velocity distribution at short period is quite well in agreement with known geological and tectonic features in the study area.at the 10s~15s period,the group velocity distribution characteristics have the good correspondence with basin and mountain uplift,the character of velocity distribution is the “two graben higher,one basin lower”,the result mainly coincide with the geological structure;The lower phase velocity abnormal appear in the Bohai Bay and Liao Dong bay at periods 20 s ~ 25 s.this phenomenon is mainly reflected that it have existed a thick sedimentary layer in the Bohai Bay Basin and Liaohe basin;For the phase velocity maps at longer periods 30s~40s,it is related to the depth of Moho.the distribution characteristics of depth is that the western is thicker than eastern in the study region.The results illustrated the geological structure and physiognomic characteristics in this area,and also have identical views with correlational studies.In the meantime,it also will serve as important references useful to the tectonic background of seismic activity and seismogenic mechanism in Liaoning and its adjacent areas.