8.-Ground-rupture.pptx

DRRR

1. Ground rupture Section 4.2

2. objectives Explain how, when and where ground rupture forms Describe the characteristics of ground ruptures Distinguish ground ruptures from other deformation features on the earth surface Analyze the effects of ground ruptures on man-made and natural structures 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. 

5. normal and thrust fault model

6. 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.

7. 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.

8. strike slip fault model

9. 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. 

10. 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)

11. 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.

12. 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.

13. 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 /

14. Mindanao fault map

15. 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

16. Factors affecting the characteristics of ground rupture Type of fault movement The depth and the nature of sedimentary materials Magnitude of the earthquake

17. 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.

18. 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.

19. 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

20. 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.