Activity Rate: a function of the total number of earthquakes in a given region of space and time that expresses how seismically active that region is.
Anthropogenic: relating to, or resulting from the influence of human beings.
Borehole Breakouts: enlargements or elongations in the cross-section of a wellbore in a direction parallel to the minimum (least) horizontal stress.
Earthquake: shaking of the ground surface caused by the sudden movement along faults within the Earth which releases energy in the form of seismic waves that propagate through the Earth. Such movement on the faults is generally a response to long term deformation and build-up of stress, caused by processes such as plate tectonics.
Earthquake Magnitude: a measure of the amount of energy released during an earthquake. This depends on both the area of the fault that ruptures and also the amount of slip or displacement on the rupture plane.
Earthquake Triggering: the promotion of the occurrence of future earthquakes due to stress perturbations in the Earth's crust.
Enhanced Geothermal System: a geothermal system uses heat from deep in the ground to generate energy. An enhanced geothermal system is one where the natural connectivity does not permit sufficient flow and additional stimulation is required.
Fault: a fracture in the Earth's crust across which the rocks have been displaced relative to each other.
Fold: a bend in planar structures such as rock strata or bedding planes.
Hydraulic fracturing ("fracking"): a process used to increase the permeability of a rock through the creation of networks of interconnected fractures by the injection of pressurised fluids.
Induced Seismicity: seismic activity resulting from changes in the state of stress in the Earth caused by anthropogenic (human) activities. Activities such as underground mining, deep artificial water reservoirs, oil and gas extraction, geothermal power generation and waste disposal can all result in induced seismicity.
Joints: a fracture, or potential fracture, in a rock adjacent to which there has been no displacement.
Lithology: the character of a rock expressed in terms of its mineral composition, structure, grain size and arrangement of its constituents.
Microseismicity: earthquakes with magnitudes of less than 2.0 and too small to be felt.
Permeability: a measure of the ability of a rock to allow fluids to pass through it.
Sedimentary Rock: a rock formed in one of three main ways: by the deposition of the weathered remains of other rocks; by the deposition of the results of biogenic activity; and by precipitation from solution.
Seismic Hazard: a property of an earthquake that can cause damage and loss, like ground shaking. Often expressed as a probability that a given level of ground shaking level being exceeded within a period of time.
Shale: a fine grained sedimentary rock.
Shale Gas: a natural gas found in shale (can also be referred to as unconventional gas).
Stratigraphy: the definition and description of the stratified rocks of the Earth's crust.
Stress: force applied over a given area and resulting in the deformation of the rock mass.
Traffic Light System: a system for mitigating earthquake risk that uses real-time monitoring of seismic activity. Operations continue (green), proceed with caution (amber) or stop (red) depending on the observed level of seismic activity.
Waste Water Disposal: the disposal of waste water from the hydrocarbon and other industries into deep wells. This process often involves large volume of fluid that is injected over long periods of time.
Well Integrity: the ability of the well to prevent hydrocarbons or operational fluids leaking into the surrounding environment.