Transcript Magnitude 3.2 & 3.5 Oakham, Rutland, UK Thursday, 17 April, 2014

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
A magnitude 3.2 earthquake occurred in Oakham, Rutland, in the UK’s East
Midlands region on 17th April 2014. 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 Oakham, Rutland, UK
Thursday, 17 April, 2014 at 06:27:14 UTC
Friday, 18 April, 2014 at 06:50:52 UTC
Where was the earthquake felt?
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 17/04
M3.5 earthquake 18/04
Location of shaking reports (image courtesy BGS)
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.
Modified Mercalli Intensity Scale
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
Past earthquakes in the region
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).
M5.2 Market Rasen
earthquake, 2008
Possible
mininginduced
earthquakes
M4.1 Melton Mowbray
earthquake, 2001
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
What caused these earthquakes to occur?
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.
N. American
plate
Mid-Atlantic
Ridge
Eurasian plate
Alpine –
Pyrenees
mountain belt
Africa – Eurasia
collision zone
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
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.
Seismic recordings of the 17 April M3.2 earthquake
P-wave
S-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
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.
Seismic recordings of the 18 April M3.5 earthquake
P-wave
S-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
Find out more …
•
BGS webpages for these earthquakes
http://earthquakes.bgs.ac.uk/earthquakes/recent_events/20140417060453.html and
http://earthquakes.bgs.ac.uk/earthquakes/recent_events/20140418065001.html
•
BGS (British Geological Survey) – seismology and earthquakes – frequently asked questions
http://www.earthquakes.bgs.ac.uk/education/faqs/faq_index.html
•
IRIS (Incorporated Research Institutions for Seismology) – learning about earthquakes
http://www.iris.edu/hq/programs/education_and_outreach/students
•
UK School Seismology Project – classroom activities, videos and support documents
http://www.bgs.ac.uk/schoolseismology/home.html
•
USGS (United States Geological Survey) – FAQs, glossary, posters, animations
http://earthquake.usgs.gov/learn/
•
EMSC (European Mediterranean Seismological Centre)
http://www.emsc-csem.org/