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A magnitude 3.2 earthquake occurred in Oakham, Rutland, in the UK’s East Midlands region on 17 th April 2014. This earthquake was followed by another,

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Presentation on theme: "A magnitude 3.2 earthquake occurred in Oakham, Rutland, in the UK’s East Midlands region on 17 th April 2014. This earthquake was followed by another,"— Presentation transcript:

1 A magnitude 3.2 earthquake occurred in Oakham, Rutland, in the UK’s East Midlands region on 17 th April This earthquake was followed by another, slightly stronger, magnitude 3.5 quake 24 hours later. The earthquakes occurred at a depth of 2-3 km (~1 mile). Shaking was felt by people living in surrounding towns and villages. The earthquakes were felt up to 55 km away from their epicentres. The UK typically experiences around 3 earthquakes of this size every year. Magnitude 3.2 & 3.5 earthquakes Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC

2 Modified Mercalli Intensity Scale I. Instrumental Not felt by many people unless in favourable conditions. II. Weak Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing. III. Slight Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many to do not recognise it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated. IV. Moderate Felt indoors by many people, outdoors by a few people during the day. At night, some awakened. V. Rather Strong Felt outside by most, may not be felt by some people in non-favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like train passing close to house. VI. Strong Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight. VII. Very Strong Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars. VIII. Destructive Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved. IX. Violent General panic; damage considerable in poorly designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. X. Intense Some well build wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent. XI. Extreme Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly. XII. Cataclysmic Total destruction – everything is destroyed. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock move position. Landscape altered, or leveled by several meters. In some cases, even the routes of rivers are changed. Location of shaking reports (image courtesy BGS) Where was the earthquake felt? Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC Most shaking was felt within a 30 km radius of the earthquakes’ epicentre. The furthest felt reports came from Mansfield to the northwest and Wellingborough to the south (45 – 55 km away). The strongest recorded felt intensity was IV (moderate shaking). The M3.5 earthquake on 18/04 had more felt reports than the 3.2 quake, especially north of the epicentre. This is probably due to the second earthquake’s slightly larger magnitude. M3.2 earthquake 17/04M3.5 earthquake 18/04

3 Small earthquakes in this part of the UK are not unusual. The largest recorded earthquake in this region of was a magnitude 4.1 event that occurred near Melton Mowbray in October 2001 (20km NW of the 2014 quakes). The largest recorded earthquake in the East Midlands region was a magnitude 5.2 earthquake near Market Rasen on February 2008 (80 km NW of the 2014 quakes). Historic seismicity (since 1970) recorded in the region. The earthquake epicentre is indicated by the red star. Earthquake locations from the BGS catalogue. Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC M4.1 Melton Mowbray earthquake, 2001 M5.2 Market Rasen earthquake, 2008 Possible mining- induced earthquakes Past earthquakes in the region

4 The UK does not lie on an active tectonic plate boundary (one of its nearest plate boundaries is the Mid-Atlantic Ridge – located some 2000 km to the west). However, the stresses from these plate boundaries can be transferred to the middle of the plates. This stress is sometimes released along pre-existing faults within the crust of the Eurasian tectonic plate. Earthquakes in the UK can also be caused by gradual uplift of the crust since the last ice age. Many of the UK’s ancient faults are not seen on the surface – these are known as‘blind faults’. The lack of earthquakes in the UK also means we are unable to identify every fault in the UK that could cause an earthquake. Africa – Eurasia collision zone Mid-Atlantic Ridge Alpine – Pyrenees mountain belt Map of major tectonic boundaries in Western Europe Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC Eurasian plate N. American plate What caused these earthquakes to occur?

5 Recordings of the earthquake from the British Geological Survey seismometer network By finding the difference in arrival times between the P- and S-wave arrivals at different seismic stations, we can calculate the distance of the earthquake from each receiver (circles). If we do this for several stations (triangles), we can determine the approximate epicentre of the earthquake (red star) by finding the common intersection point of these circles. P-waveS-wave Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC Seismic recordings of the 17 April M3.2 earthquake

6 Recordings of the earthquake from the British Geological Survey seismometer network By finding the difference in arrival times between the P- and S-wave arrivals at different seismic stations, we can calculate the distance of the earthquake from each receiver (circles). If we do this for several stations (triangles), we can determine the approximate epicentre of the earthquake (red star) by finding the common intersection point of these circles. P-waveS-wave Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC Seismic recordings of the 18 April M3.5 earthquake

7 BGS webpages for these earthquakes and BGS (British Geological Survey) – seismology and earthquakes – frequently asked questions IRIS (Incorporated Research Institutions for Seismology) – learning about earthquakes UK School Seismology Project – classroom activities, videos and support documents USGS (United States Geological Survey) – FAQs, glossary, posters, animations EMSC (European Mediterranean Seismological Centre) Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014 at 06:27:14 UTC Friday, 18 April, 2014 at 06:50:52 UTC Find out more …


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