In the late 1960s the BGS installed a network of eight seismometers around Edinburgh, with data transmitted to the recording site in Edinburgh by radio. Over the next thirty years our monitoring network grew to 146 stations, stretching from Jersey to the Faroes, and giving UK wide coverage for onshore earthquakes with magnitudes of 2.5 ML and above. Most of the stations consist of single, vertical component, short-period Willmore MK-III seismometers, although there are also a number of three-component Willmore MK-III seismometers, three component, strong motion accelerometers and broadband seismometers. The primary aim of the network is to develop a national database of seismic activity in the UK for seismic hazard assessment and to provide a response to felt earthquakes. In addition, data are available to the academic community both within the UK and overseas for investigations of crustal and upper mantle structure and processes. The network is being upgraded with the deployment of more broadband seismometers and high dynamic range recording to improve the scientific value of the data. Currently we have nineteen broadband stations. Over the next few years we intend to increase this number to 40-50.

On average, the network locates around 200 local earthquakes per year and is capable of detecting all events greater than 1.5 ML (Richter local magnitude) in mainland Britain. In a typical year, 40 events will have magnitudes greater than 2.0 ML and about 20 are felt by local residents. Seismologists are able to discriminate between earthquakes and the large number of other signals (such as quarry blasts, explosions, sonic booms and collapses ) which are recorded in addition to earthquakes.

Above: Seismogram from the Dumfries Earthquake, 13 May 2001, 08:26 UTC, 2.9 ML.

Background earthquake monitoring is required to refine our understanding of the level of seismic risk in the UK. Although seismic hazard/risk is low by world standards it is by no means negligible, particularly with respect to potentially hazardous installations and sensitive structures. The results help in assessment of the level of precautionary measures which should be taken to prevent damage and disruption to new buildings, constructions and installations which otherwise could prove hazardous to the population. In addition, seismic events cause public concern and there is a need for objective information as soon as possible in order to allay any unnecessary concerns. Most seismic events occur naturally but some are triggered by human activities such as mining, and other tremors (eg. sonic booms and explosions) are often mistaken for earthquakes.