DRRR

1. Ground rupture
Section 4.2

2. objectives
1. Explain how, when and where ground rupture forms
2. Describe the characteristics of ground ruptures
3. Distinguish ground ruptures from other deformation
features on the earth surface
4. Analyze the effects of ground ruptures on man-made and
natural structures
5. List ways to minimize or avoid the damage ground rupture
may cause

3. Ground deformation vs Ground rupture
•Magmatic - Volcano deformation may occur
through the migration, accumulation, degassing,
cooling and crystallization of magma.
•Hydrothermal - Hydrothermal volcano
deformation results from the flow of fluids in a
hydrothermal reservoir, surf -ace processes
associated with hydrothermal features (e.g., hot
springs and fumaroles), or from the extraction of
geothermal fluids.

4. Ground deformation vs Ground rupture
• Surface deposits – Volcanoes are built of poorly
consolidated rock at much faster rates than they erode,
making them inherently unstable. Consequently, shallow
processes acting on a volcanic edifice can result in
measurable ground deformation.
• Faulting / tectonics - The re-activation of tectonic faults
or fractures during volcanic unrest may lead to observed
volcano deformation. Features such as caldera ring-
faults, eruptive fissures and intra-caldera faults can all
become active.

6. normal and thrust fault model

7. normal fault
• Normal faults generally occur in places where the lithosphere is
being stretched. This is a geologic fault in which the hanging wall
has moved downward relative to the footwall. Normal faults occur
where two blocks of rock are pulled apart, as by tension.

8. thrust fault
• A thrust fault is a type of fault, or break in the Earth's
crust across which there has been relative movement, in
which rocks of lower stratigraphic position are pushed up
and over higher strata. They are often recognized
because they place older rocks above younger.

9. strike slip fault model

10. Strike-slip faults
• Strike-slip faults are vertical (or nearly
vertical) fractures where the blocks have
mostly moved horizontally.
• If the block opposite an observer looking
across the fault moves to the right, the slip
style is termed right lateral; if the block
moves to the left, the motion is termed left
lateral.

11. Ground rupture
• Surface rupture occurs when
movement on a fault breaks through to
the surface.
• Rupture may occur suddenly during an
earthquake or slowly in the form of
fault creep.
• Fault rupture almost always follows
preexisting faults, which are zones of
weakness.
The crack stretches for several
kilometers through farmland.(Japan)

12. How ground rupture forms?
• The lithosphere breaks when its strength is
overcome by a large amount of stress applied.
The breaking happened when in much the same
way a piece of rock does when struck hard
enough with a hammer
• An earthquake is generated when faults moves, as
its frictional resistance could not match the large
amount of accumulated stress related to the
plate motion.

13. blind thrust fault
• blind thrust fault. A thrust
fault that does not rupture
all the way up to the
surface so there is no
evidence of it on the
ground. It is "buried" under
the uppermost layers of
rock in the crust.

14. fault map in the Philippines
SOUNDS ALARM BUTTON ON 2 NEW FAULTS IN DAVAO
CITY
PHIVOLCS WARNS OF DAVAO ‘KILLER QUAKE
two new active faults in Davao City were
discovered by geologists as Philvolcs updated its
10-year old fault map.
She said Phivolcs is conducting further studies to
establish the actual location of the two new faults.
https://durianburgdavao.wordpress.com/2015/06/19/phivolcs-warns-of-
davao-killer-quake/

15. Mindanao fault map

16. Active Faulting
• The activity of a fault is generally
defined by the way it cumulates
displacement over geologic time. An
active fault is one that cumulated some
displacement in the recent past (see
diagrams below) so that we can
speculate it is very likely that the fault
will be offset again in the near future.
• An active fault is a fault that is likely to
become the source of another earthquake
sometime in the future.
• Geologists commonly consider faults to
be active if there has been movement
observed or evidence of seismic activity
during the last 10,000 years

17. Factors affecting the characteristics of
ground rupture
1. Type of fault movement
2. The depth and the nature of sedimentary materials
3. Magnitude of the earthquake

18. Can we predict when will an earthquake occur?
•Scientists have tried lots of different
ways of predicting earthquakes, but
none have been successful.
•They have an idea of where an
earthquake is most likely to hit, but
they still can't tell exactly when it will
happen.

19. Can we predict when will an earthquake occur?
So far, scientists haven't been able to find
a signal for earthquakes - there is no
obvious sign to say that an earthquake is
coming very soon.
Vibrations can be detected just before an
earthquake occurs, but this doesn't give
enough time for people to escape.

20. Measures to minimize ground
ruptures
• The best measure is avoidance of
active fault traces and
deformation zones when planning
any construction.
• It is important to find out which
active faults are located near your
community
• You can access this information
from PHIVOLCS that can minimize
the effects of ground ruptures
https://tinyurl.com/6r3uvkuf

21. How far from fault is safe from rupturing?
•Setback refers to the distance from the fault trace
that is considered safe from the effects of ground
rupture
• Setback varies depends on the fault characteristics in a
locality obtained from detailed and site-specific studies.
Example: valley fault system(VFS) assigned 5 meters setback on
both sides along the fault on the eastern part of Metro Manila.
Thus 10 meter danger zone is off-limits to construction
activities.