Detection Statistics
Larger earthquakes occur less frequently than smaller ones. The relationship is exponential, ie there are ten times as many magnitude 4 or larger earthquakes in a given time period than magnitude 5 or larger earthquakes. This can be expressed by the Gutenberg-Richter formula
where N is the number of earthquakes per year exceeding a given magnitude M. The constant a reflects the absolute level of seismicity in an area, and the value of b has generally been found to be consistently close to 1.0.
The graph shows the relationship for the UK. A least-squares regression to this data gives the relationship
Also shown is an alternative doubly-truncated exponential model which gives a curved fit ot the data at the higher magnitude end.
On average, the UK may expect:
- an earthquake of 3.7 ML or larger every 1 year
- an earthquake of 4.7 ML or larger every 10 years
- an earthquake of 5.6 ML or larger every 100 years.
- Magnitude 3.9 ML Earthquake Grimsby 09/06/2018
- Magnitude 4.6 ML Earthquake South Wales 17/02/2018
- The magnitude 4.6 ML Earthquake South Wales on 17/02/2018 recorded on the Vale of Pickering sesimic network
- M7.1 PUEBLA, MEXICO 19/09/2017
- M8.1 CHIAPAS PROVINCE, MEXICO 08/09/2017
- North Korea Nuclear Test 03/09/2017
- Baseline Monitoring in the Vale of Pickering
- Are yesterday's earthquakes tomorrow's disasters?
- Monitoring earthquakes: PlanetEarth podcast
