Transcript Magnitude 7.5, NORTHERN AFGHANISTAN Monday, 26 October

Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Earthquake location & overview
AFGHANISTAN
PAKISTAN
INDIA
A magnitude 7.5 earthquake struck in North East
Afghanistan; the epicentre was centered about 48.0
km (≈ 30.0 miles) SSW of Jurm. The depth has been
estimated to be about 220 km (~135 miles).
At least 40 people have been killed in Pakistan and
20 in Afghanistan and more than 100 have been
reported to be injured as a result of the earthquake.
Reports say shaking was sustained for about one
minute. Mass panic ensued as a result of the
shaking and it has caused significant damage to
building and infrastructure.
Shaking has been felt as far as Delhi, India.
Pakistan
KABUL
Images courtesy of Google Earth.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Strong (VI) into rather strong (VII) shaking was felt inside about a 200 km
radius from the epicentre. Moderate (IV) shaking was experienced
through most of the surrounding region.
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.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Orange alert level for shaking-related fatalities. Significant casualties are likely and the
disaster is potentially widespread. Past events with this alert level have required a
regional or national level response. Yellow alert level for economic losses. Some
damage is possible. Estimated economic losses are less than 1% of GDP of Afghanistan.
USGS PAGER
Map with MMI contour overlay.
Images courtesy of the US Geological Survey.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Right: A Peak Ground Acceleration (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 within a 20
km radius at ≥ 0.42 g (≈ 4.12 ms-2).
Image courtesy of US Geological Survey.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Earthquake slip models
Top right: A preliminary slip model
generated by the USGS from
seismic data.
Bottom right: A cross section of the
preliminary slip model generated
by the USGS from seismic data.
Above: A graph displaying total energy release over time
for the rupture. The most energy release occurred
approximately 15 seconds after the start of the earthquake.
Images courtesy of US Geological Survey.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Historical seismicity
Himalayas is one of the most
tectonically active areas in the
world. There are a lot of large
earthquakes that have
occurred in this area. In last
century there have been nearly
160 earthquakes with
magnitude greater than 6 in Interferogra
this area. This includes seven m from
earthquakes with a magnitudeinsarap.org
of greater than 7.0.
M 7.4
2002/03/03
M 7.5
2015/10/26
M 7.6
2005/10/08
In March 2002 just 20 km from this event, there was a magnitude 7.4
earthquake. The event in 2002 at a similar depth was also a thrust fault
earthquake. The 2002 event caused over 150 fatalities and the damage or
destruction of over 400 houses in relation to an associated landslide.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Earthquake mechanism
The depth of this earthquake is 220 km, which
is known as an intermediate-depth earthquake.
The focal mechanism shows that this
earthquake has a thrust mechanism.
This is unusually deep for a thrust earthquake,
which usually occur on the boundary between
two plates. This cannot be the case for this
intermediate depth earthquake. The potential
causes of this earthquake are discussed on the
next slide.
Left: Diagram showing the
mechanism of a thrust fault
Left: Focal mechanism
of the earthquake
showing reverse faulting
(from the USGS)
Below: A map of the extent of the slip
along the deep thrust fault.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Tectonic setting
In this area, the India plate under moving
northward beneath the Eurasia plate at
about 38-45 milometers a year.
The friction between these two plates can
cause large earthquakes like the recent
Nepal earthquake, but this is not what
caused this earthquake.
This event occurred much deeper,
probably in ancient oceanic crust that was
subducted before the Indian plate collided
with Eurasia. This thrusting earthquake is
likely due to the stresses between the
subducted continental crust, and much
older subducted oceanic crust.
Above: Map showing the location of the
collision plate boundary fault and the
earthquake
Left: A schematic diagram showing the
subduction of oceanic crust, followed be
thicker continental crust
Indian
plate
Eurasian
plate
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Seismic waves recorded in the UK
P-waves
S-waves
Surface waves
• Even though the earthquake occurred more that 6,000 km (~3800 miles) from the UK, the
seismic waves emitted by this earthquake can still be measured.
• The plot above shows the horizontal (East-West) 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 left hand side of the slide.
• The P-wave and S-wave arrivals can be clearly seen, but the surface wave arrivals have
a lower amplitude than other earthquakes, as the source is so deep in this case.
Magnitude 7.5, NORTHERN AFGHANISTAN
Monday, 26 October, 2015 at 09:09:32 UTC
Find out more….
• University of Liverpool ‘Viewpoint’ article on the earthquake
http://news.liv.ac.uk/2015/10/27/viewpoint-deep-thrust-earthquake-in-northern-afghanistan/
• 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/
• USGS summary of the earthquake
http://earthquake.usgs.gov/earthquakes/eventpage/us10003re5#general_summary
10