This talk will focus on recent development of data processing of continuous seismic monitoring data. I’ll start to review the status of seismic time-lapse seismic monitoring. Then I will show the research progress my group made of advancing time-lapse waveform data processing algorithms to quantify the CO2 plume from a single indicator to full 3D image. A single indicator is referred to seismic wave attenuation that is shown to, combining velocity, be useful to estimate CO2 saturation. Then, time-shifts from coda wave interferometry are likely indicators of total CO2 volume in the pores. To achieve full 3D geological image, I will show a newly developed time-lapse full waveform inversion using hierarchical matrix powered extended Kalman filter (HiEKF) for estimating seismic velocity and attenuation, and their uncertainty. The accuracy of the inverted model is increasing over time by assimilating more time-lapse data while the standard deviation is decreasing over lapsed time. Finally, I will discuss possible future topics of real-time seismic monitoring for continuously imaging the distribution of subsurface gas and fluids in the future large-scale CO₂ sequestration experiments and reservoir management.