Download Mw 7.8, Muisne, Ecuador Fri, 16 April 2016 at 23:58:37 UTC USGS

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.

Cocos
plate
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.

Nazca
plate
South American
plate
M 7.8
2016/04/16
Image courtesy of Google Earth.
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
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
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
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
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
Ecuador


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
M 7.8
generated by the Mw ~8.8, 1906 M 7.0
2016/04/16
2016/04/15
earthquake
Peru
Image extracted from Bilek et al, 2009. 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
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
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

Above: Corresponding focal mechanism for the Ecuador ear
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)
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.
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!
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