1. Mw 7.8, Muisne, Ecuador Fri, 16 April 2016 at 23:58:37 UTC
Earthquake overview
Caribbean
plate
A moment magnitude Mw 7.8 earthquake was registered offshore of the west coast of northern Ecuador
Epicentre was located 170km (105.6mi) north west of the capital city Quito.
Last earthquake in the same region occurred on May 14th, 1942 (Mw 7.8)
Until now over 400 fatalities and thousands injuries has been reported.
Cocos
plate
Nazca
plate
South American plate
M 7.8
2016/04/16
Image courtesy of Google Earth. 1

2. Shaking Intensity – Modified Mercalli Intensity Scale (MMI)
Mw 7.8, Muisne, Ecuador
Fri, 16 April 2016 at 23:58:37 UTC
Earthquake hazard map
Localized regions of Strong shaking can be seen in various regions to the south of the epicentre
Shaking Intensity – Modified Mercalli Intensity Scale (MMI)
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.
Image courtesy of US Geological Survey 2

3. Map with MMI contour overlay.
Mw 7.8, Muisne, Ecuador
Fri, 16 April 2016 at 23:58:37 UTC
Earthquake hazard map
Orange alert level for shaking-related fatalities and economic losses
Estimated economic losses are < 1% of GDP of Ecuador
USGS PAGER
Map with MMI contour overlay.
Images courtesy of the US Geological Survey

4. Peak Ground Acceleration (PGA)
Mw 7.8, Muisne, Ecuador
Fri, 16 April 2016 at 23:58:37 UTC
Peak Ground Acceleration (PGA)
PGA map produced by the USGS
Each contour represents the acceleration of the ground as a percentage of g (≈ 9.81 ms-2)
The most intense shaking was experienced around to 35% of g value which corresponds to approximately 3.43 ms-2
Image courtesy of US Geological Survey

5. Mw 7.8, Muisne, Ecuador Fri, 16 April 2016 at 23:58:37 UTC
Earthquake slip model
N/S transform faults
Above: Graph displaying the total energy release over time for the rupture. Most of the energy was released after 20 seconds of the beginning of the earthquake
Right: Cross section of the preliminary slip model generated by the USGS from seismic data using the ruptured plotted on the map
Images courtesy of US Geological Survey

6. Historical seismicity
Mw 7.8, Muisne, Ecuador
Fri, 16 April 2016 at 23:58:37 UTC
Historical seismicity
Colombia
In the northern segment of the South American margin, few large events are present in catalogues
Since 1906, after a Mw ~8.8 earthquake, few events with lower magnitudes (Mw 7.8, 1942; Mw 8.1, 1979) occurred in the affected area
The Mw 7.8, 2016 earthquake is located at the southern end of the ruptured generated by the Mw ~8.8, 1906 earthquake
Ecuador
Plates Convergence zone
Peru
M 7.8
2016/04/16
M 7.0
2016/04/15
Image extracted from Bilek et al, Seismicity along the South American subduction zone: Review of large earthquakes, tsunamis, and subduction zone complexity. Red dot indicate the epicentre of the 2016 Ecuador earthquake 6

7. Mw 7.8, Muisne, Ecuador Fri, 16 April 2016 at 23:58:37 UTC
Tectonic setting
This earthquake occurred offshore of the west coast of northern Ecuador, as a result of a thrust faulting near the plate boundary between the Nazca and South American plates
At the location of the earthquake, Nazca plate subducts eastward beneath the South American plate at a relative velocity of 61 mm/yr
Subduction process led to the uplift of the Andes mountain and presence of active volcanic chain along the deformation front
Occurrence of large thrust earthquakes is common in this convergent region
Map showing the location of the plate boundary, subduction zone and the epicentre of the Ecuador Mw 7.8 earthquake 2016 7

8. Earthquake focal mechanism
Mw 7.8, Muisne, Ecuador
Fri, 16 April 2016 at 23:58:37 UTC
Earthquake focal mechanism
The depth of this earthquake is 24 km, which can be associated to a plate interface earthquake
The focal mechanism shows that the earthquake has a reverse mechanism in agreement with the tectonic setting of the region
Cocos Plate
Nazca Plate
South American Plate
Above: Corresponding focal mechanism for the Ecuador earthquake (obtained from USGS)
Above: Rupture of a reverse fault showing the convergence of two blocks indicated by arrows, displacement is indicated by thin black arrows
Below: Location of the earthquake (yellow star) 8

9. Seismic waves recorded in the UK
Mw 7.8, Muisne, Ecuador
Fri, 16 April 2016 at 23:58:37 UTC
Seismic waves recorded in the UK P S
Even though the earthquake occurred more that 9000 km (~5600 miles) from the UK, the seismic waves emitted by this earthquake can still be measured.
The plot above shows the vertical component of the seismic waves measured at seismic stations across the UK. The colour of the line corresponds to the station at which it was recorded, shown on the map on the right hand side of the slide. 9

10. Mw 7.8, Muisne, Ecuador Fri, 16 April 2016 at 23:58:37 UTC Find more
BGS (British Geological Survey) – seismology and earthquakes – frequently asked questions GO!
IRIS (Incorporated Research Institutions for Seismology) – learning about earthquakes GO!
UK School Seismology Project – classroom activities, videos and support documents GO!
USGS (United States Geological Survey) – FAQs, glossary, posters, animations GO!
USGS summary of the earthquake GO! 10

11. @seismologyUoL