High seismic velocity structures control moderate to strong induced earthquake behaviors by shale gas development

Moderate to strong earthquakes have been induced worldwide by shale gas development, however, it is still unclear what factors control their behaviors. Here we use local seismic networks to reliably determine the source attributes of dozens of M > 3 earthquakes and obtain a high-resolution shear-wave velocity model using ambient noise tomography. These earthquakes are found to occur close to the target shale formations in depth and along high seismic velocity boundaries. The magnitudes and co-seismic slip distributions of the 2018 Xingwen M_L5.7 and 2019 Gongxian M_L5.3 earthquakes are further determined jointly by seismic waveforms and InSAR data, and the co-seismic slips of these two earthquakes correlate with high seismic velocity zones along the fault planes. Thus, the distribution of high velocity zones near the target shale formations, together with the stress state modulated by hydraulic fracturing controls induced earthquake behaviors and is critical for understanding the seismic potentials of hydraulic fracturing.