OR/17/062 Macroseismic observations
| Baptie, B, Ford, G, and Galloway, D. 2017. The Moidart earthquakes of 4 August 2017. British Geological Survey Internal Report, OR/17/062. |
353 members of the public from 121 different postcodes completed our online macroseisemic questionnaire, allowing EMS intensity to be calculated in different locations. A minimum number of five reports from a given 5 km by 5 km square are required to estimate the intensity. Where there are fewer than 5 different observations, we assign an intensity value of ‘Felt’. A maximum intensity of 5 EMS was observed in the villages of Acharacle and Roshven, 10 km from the epicentre. An intensity of 5 EMS was also observed at Tobermory and Mallaig, approximately 20 km from the epicentre. Intensities of 4 EMS were observed at Lochailort (10 km), Strontian (12 km) and Arisaig (12 km). There were too few observations to determine a value for the intensity from most of the other locations close to the epicentre, perhaps as a result of the low population density. Intensities of 4 EMS were observed in Oban and Fort William at distances of 45 km to the southeast and 48 km to the east, respectively. The earthquake was felt at distances of up to 150 km from the epicentre, including Inverness and Invergarry to the northeast and Glasgow to the southeast. Five reports from central Glasgow suggest an intensity of 4 EMS, however, this does not seem consistent with other observations.
Over half of the reports state that people considered the shaking to be moderate in strength, while around one third thought that it was weak. Many people reported hearing a moderate to loud bang or rumble. There were 31 reports of objects falling over but no reports of damage.