Study On Q_c Value Characteristics Of Coda In Hexi Corridor Based On The Single Backscattering Model

Quality factor Q is a dimensionless parameter that reflects the attenuation of wave amplitude and energy during seismic wave propagation.Coda Q_Cvalue,also known as one of the quality factors of underground media,is a comprehensive reflection of media heterogeneity and inelasticity.It has important applications in seismic wave propagation,structural imaging,seismic prediction and engineering seismic research.With the improvement of seismic observation system and more and more digital seismic records,the solution of coda Q_Cvalue has a more solid data foundation.The data in this paper are selected from 82 seismic stations in Hexi Corridor Area（37°-41°N,97°-103°E）,which received 14883 seismic rays with a epicentral distance of less than 100 km and 5948 earthquakes;The starting and ending time of seismic records is from June 2000 to December 2020.The python program developed based on the single backscattering model is used to process and analyze the seismic data in the study area.The main conclusions of this paper are as follows:1.Analysis of the influence of different parameter selection,magnitude and epicenter distance,station type and other factors on coda Q_Cvalue.The parameters that affect the Q_Cvalue of coda mainly include filter and filter bands,lapse time window（LTW）,coda window start time,minimum signal-to-noise ratio and maximum correlation coefficient.The selection of maximum correlation coefficient and mini-mum signal-to-noise ratio has little influence on the coda Q_Cvalue.In order to ensure that the seismic records involved in the calculation have a long coda length and sufficient data volume,finally,the maximum correlation coefficient is-0.6 and the minimum signal-to-noise ratio is 3;The epicenter distance is positively correlated with the coda Q₀value,and is correlated with theηValue is inversely correlated;Station type and earthquake magnitude have little influence on coda Q_Cvalue.2.Q_Cvalue of coda wave in Hexi Corrid or Area:under 20-s LTW,Q_C（f）=（115?16）f^{（0.89?0.05）};Under 30-s LTW:Q_C（f）=（156±22）f^{（0.8±0.04）};Under 40-s LTW,Q_C（f）=（185?25）f^{（0.75?0.05）}.The Q₀value in Hexi Corridor is 115～185,Theηvalue is0.75～0.89,which indicates that the Q₀value in this area is low and relatively highηValue characteristic tectonic active area.3.According to the main active faults in the Hexi Corridor Area,it is divided into four sub regions:region I includes the fault zone on the northern edge of Qilian Mountain,region II includes the fault zone on the southern and northern edge of Longshou Mountain,region III includes the faults on the northern and Eastern edges of Yumu Mountain,and region IV includes the Changma-OBO fault.The coda Q_Cvalue is obtained for four sub regions,and the results under 30-s LTW are compared:in region I,Q_C（f）=（166?26）f^{（0.77?0.05）};Region II,Q_C（f）=（163?20）f^{（0.81?0.04）};Region III,Q_C（f）=（155?24）f^{（0.80?0.05）};Region IV,Q_C（f）=（158?24）f^{（0.78?0.05）}.The results show that there is little difference between Q₀value andηvalue in the above four regions,and it is considered that the tectonic activity level of the four regions is similar.4.The coda attenuation characteristics of Hexi Corridor and different regions at home and abroad are compared and analyzed.The coda attenuation characteristics of Hexi Corridor Area and Shanxi rift zone area are generally similar,showing low Q₀value and highηvalue.They are all tectonic active areas and their seismic activities are relatively frequent.