Passive seismology is the science of real-time recording and analysis of natural seismicity (e.g. earthquakes or ambient noise) or induced seismicity (e.g. due to fluid injection) with surface or borehole sensor arrays. Passive seismic data can be useful to: (1) image/monitor subsurface fluid flow, pressure/stress fronts, rock fracturing, and fault excitation; (2) estimate the insitu stress conditions in the subsurface to constrain model predictions of fault seal and fluid-flow, and (3) serve as an early-warning system to detect small-scale induced seismicity during fluid injection before it triggers a larger high-risk event; for example fluid leakage or the unlikely event of a fluid injection-induced earthquake. Passive seismic monitoring can also provide the ability to determine whether any measured seismicity in the vicinity is natural or caused by man-made fluid injection. Our research focuses on simulating, imaging and inverting 3D passive seismic wavefield and ambient noise data.