During the past decade, there have been spectacular advances in imaging and inversion of temporal variations in subsurface physical properties across a wide range of fundamental and applied seismology. This session brings together a diverse group of scientists that share a focus on Time-Lapse Seismology. Seismic data types may include active/controlled source, natural and induced earthquakes and seismicity, and ambient seismic noise. Research topics (sorted by depth) may include the atmosphere (infrasound-elastic coupled waves, nuclear monitoring, storms...); the critical zone -100m to +100m depth (vadose zone, soil moisture, groundwater, agriculture, cryosphere, volcanoes...), aquifers and reservoirs 100m to 10km depth (CO2 sequestration, geothermal, volcanoes, groundwater, waste water injection...); tectonics, subduction zones and earthquakes 10-100 km depth (Large-N sensor arrays both onshore and offshore, the SZ4D initiatives...). We invite contributions from seismology, tectonics, infrasound, cryosphere, near-surface geophysics, hazards, volcanology, soil sciences, hydrology and related fields.