Study The Depth Variation Of Moho In Northeast China From Ambient Noise Autocorrelations

In recent years,the research on seismic ambient noise has developed rapidly.Because it is not limited by the time-space distribution of the earthquakes,and the geological structure information under the stations can be obtained only by deploying seismic stations,which makes this method become one of the most popular research directions in the field of seismology.At present,most these researches use the surface wave signal extracted from the ambient noise.In fact,through appropriate data processing methods,the body wave signal can also be extracted from the ambient noise.In this study,the continuous observation data of 94 portable stations in Northeast China from September 2009 to August 2011 are collected,and the reflection signal of Moho Surface P wave is extracted by ambient noise autocorrelation method,and then the Moho surface depth change and its geological significance in this area are studied.In the data processing,the phase autocorrelation method is used to calculate the ambient noise autocorrelation,and the time-frequency domain phase weighted stacking method is used to stack the autocorrelation waveforms to obtain high-quality noise autocorrelation stacked waveforms of each station.The novel method of maximum value of the second derivative of the waveform envelope is used to quantitatively estimate the travel time of the P wave reflection of the Moho surface,and then the time-depth conversion is used to obtain the depth of the Moho surface below each station in the study area.We evaluated the reliability of the results by various methods,and compared with the Moho depth results obtained by the receiver function method in the study area,and found that the two have good consistency.We believe that the method of extracting the P wave reflection response of the Moho surface from noise autocorrelation is feasible.The results of this study show that the Moho surface in the Greater Xing' an Mountains area is deeper,with an average of 36.7 km.The depth of the Moho surface in the Songliao Basin gradually decreases from west to east,with an average of about 31.6 km.There is a steep change zone of Moho depth of about 5 km between Daxinganling and Songliao Basin.The steep change zone is basically consistent with the distribution direction of the Daxinganling-Taihang Mountain gravity linement.It may be that the western boundary of Songliao Basin is affected by the impact of Pacific subduction;the overall Moho depth of the Songliao Basin gradually deepened from southeast to northwest,possibly due to the upwelling of mantle thermal material caused by Mesozoic and Cenozoic volcanic movements.In addition,the depth of the Moho in the north of the Songliao Basin is higher than that in the south,which may be related to the more developed sediments in the northern part of the post-rift period.