FAQs

1:What is an earthquake and why they occur?

A: An earthquake occurs because of a sudden slip on a fault. Stress in the earth's outer layer pushes the sides of the fault together. Stress builds up and the rocks slip suddenly, releasing energy in waves that travel through the earth's crust and cause the shaking. An EQ occurs when plates grind and scrape against each other. 

2: What is plate tectonics?
A: Plate tectonics is the continual slow movement of the tectonic plates, the outermost part of the earth. This motion causes earthquakes and volcanoes.

3: What is a fault?

A: A fault is a fracture between two blocks of rock. Faults move the blocks relative to each other. This movement may occur rapidly, in the form of an earthquake - or may occur slowly, in the form of creep. Faults may range in length from a few millimeters to thousands of kilometers. Most faults produce repeated displacements over geologic time. During an earthquake, the rock on one side of the fault suddenly slips with respect to the other. The fault surface can be horizontal or vertical or some arbitrary angle in between.

4: What are different types of faults?

A: Earth scientists use the angle of the fault with respect to the surface (known as the dip) and the direction of slip along the fault to classify faults. Faults which move along the direction of the dip plane are dip-slip faults and described as either normal or reverse, depending on their motion. Faults which move horizontally are known as strike-slip faults and are classified as either right-lateral or left-lateral. Faults which show both dip-slip and strike-slip motion are known as oblique-slip faults.

normal fault is a dip-slip fault in which the block above the fault has moved downward relative to the block below. This type of faulting occurs in response to extension and is often observed in the Western United States Basin and Range Province and along oceanic ridge systems.

thrust fault is also a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. This type of faulting is common in areas of compression, such as regions where one plate is being subducted under another as in Japan. When the dip angle is shallow, a reverse fault is often described as a thrust fault.

strike-slip fault is a fault on which the two blocks slide past one another. 

A left-lateral strike-slip fault is one on which the displacement of the far block is to the left when viewed from either side.

A right-lateral strike-slip fault is one on which the displacement of the far block is to the right when viewed from either side

5: Foreshocks? - what's the difference?

A: Foreshocks are earthquakes which precede larger earthquakes in the same location. 

6: Aftershocks ?

A:Aftershocks are smaller earthquakes which occur in the same general area during the days to years following a larger event or "mainshock", defined as within 1-2 fault lengths away and during the period of time before the background seismicity level has resumed.Aftershocks represent minor readjustments along the portion of a fault that slipped at the time of the main shock.The frequency of these aftershocks decreases with time. Historically, deep earthquakes (>30km) are much less likely to be followed by aftershocks than shallow earthquakes

7:Where did the biggest earthquake occur?

A:The earthquake in Chile on May 22, 1960, is the biggest in the World with magnitude 9.5 Mw.

8: What is magnitude ?

A:Magnitude measures the energy released at the source of the earthquake. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded on a seismogram at a certain period. 

9: What is intensity ?

A:Intensity measures the strength of shaking produced by the earthquake at a certain location. Intensity is determined from effects on people, human structures, and the natural environment. Intensity does not have a mathematical basis, but is based on observed effects.

10: How can I know the magnitude of an EQ?

A:A ritcher scale.It is a mathematical formula. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded on a seismogram at a certain period


11: How long an EQ lasts?

A:Two to three minutes.

12: What is liquefaction (of soil)?

A:Process of soil and sand behaving like dense fluid rather than a wet solid mass during an earthquake

13: Can earthquakes be predicted?

A:No, It is almost impossible to predict an EQ.There is a myth that 
animals can predict EQs.

14: Where is the safest place to be in an earthquake?

A:Open places are safe when earthquakes occur because northing can fall
on You.Run for an open place as soon as posiible.If you are inside a building get under astrong piece of furniture.

15: How do we know a fault exists?

A:If the EQ left surface evidence, such as surface ruptures or fault scarps (cliffs made by EQs);
If a large EQ has broken the fault since we began instrumental recordings in 1932;
If the faults produces small EQs that we can record with the denser seimographic network established in the 1970s

16: What is the Continental Drift Theory?

A:The Continental Drift Theory is the belief that all seven contintental plates were connected millions of years ago to form a super-continent: Pangea, and that they are still moving today. 

17: What are the most active earthquake zones?

A:The most active earthquake zone is below the pacific and usually along fault lines. 

18: Does a small earthquake mean that a larger earthquake is coming?

A:No, except for very rare cases. Only a very tiny minority of these precede a larger earthquake. Although a large earthquake may be preceded by a foreshock, the occurrence of a small earthquake is not in itself a typical sign. 
A small earthquake, however, provides an ideal opportunity to offer reminders about safety measures to take before, during and after an earthquake

19: What is a Scrap

A:Sometimes called an escarpment, a scarp is any roughly linear slope or cliff. Any fault which produces some vertical offset will typically produce a scarp. While we will focus on scarps formed by the action of faults, they can also be formed by erosion, or other means. When fault-formed, scarps can be obvious markers of surface traces.

20: Is there no way to recognize a foreshock before the mainshock strikes?
A:Recognizing foreshocks in advance of the mainshock has, quite naturally, been a prize goal of seismologists ever since foreshocks were first recognized. The reality of the situation, however, is that we still have no consistent method with which to make such identifications.

21: What are Earthquake Swarms

A:Earthquake swarms are clusters of earthquakes -- sometimes hundreds or thousands of them -- with no definitive mainshock; the largest events in a swarm are all of roughly the same magnitude. Swarms occur in a limited area, and vary greatly in duration. Some die off within a day, others can persist for months at a time