The area of land at the surface that contains the wellhead

Caused by human activity. For example, anthropogenic earthquakes are those caused by human actions such as mining or hydraulic fracturing

A layer of rock with sufficient porosity

Chemicals added to the frack fluid to prevent build-up of algae or bacteria in the wellbore

The equipment used during the construction and drilling phase of a well to drill the borehole. This equipment is removed once well construction is complete, which may take several months.

Because of the pressure of the overlying rocks, a proportion of the frack fluid

The mix of water, proppant

The process by which gas is extracted from impermeable shale rocks. Water, proppant

Unplanned releases of gas, predominantly methane, that occur at any stage of the gas production process. This includes leakages from pipelines, abandoned wells, and producing gas wells.

Water contained below the ground surface. In the context of fracking, groundwater usually refers to water stored in aquifers