Ambient Noise Tomography of the Tanlu Fault, Eastern China Using Local Dense Seismic Array

Session: Waveform Cross-Correlation-Based Methods in Observational Seismology [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Ambient noise tomography (ANT) has been used successfully to image earth structures at different scales. It is capable of turning seismic ‘‘noise’’ into useful signals to retrieve surface waves between stations based on cross-correlation and stacking analysis of ambient noise. The retrieved surface waves can then be used to invert high-resolution images of structures at multiple scales. For the fault zone imaging, many studies have been conducted to image detailed structures using local dense seismic array.

To image high-resolution structure for the Tanlu fault in eastern China, one of the longest strike slip faults in the world, we deployed two local arrays for its southern segment. One array consists of 53 stations with station interval of ~5 km and is located to the north of Chao lake, one of the 5 largest lakes in China. The other array consists of 240 stations with station interval ranging from ~300 m to 3 km and is located in Suqian, Jiangsu province of China. Both arrays continuously recorded data for over one month. Standard ambient noise processing procedure of Bensen et al. (2007) is adopted and Rayleigh waves can be clearly seen from cross-correlation functions. To expedite the processing procedure, we have developed an automatic dispersion curve extraction algorithm based on the convolutional neural network (CNN). The data quality from automatic process is comparable to the data picked manually.

Using denser stations around the fault zone, we were also able to identify reflected surface waves from the fault zone. The ANT results show that the Tanlu fault is clearly associated with high velocity anomalies. This suggests that Tanlu fault may act as a channel for hot mantle materials arising from deeper zone to the upper crust in the past. After hot materials cooled down in the upper crust, they have higher velocities compared to the surrounding crustal rocks. This finding is importance to assess the fault zone activity.

Presenting Author: Haijiang Zhang

Authors