earthquake ppt as per syllabus

2. Elements of Engineering Seismology, Characterization
of ground motion, Earthquake intensity and
magnitude, Recording instruments and base line
correction, Predominant period and amplification
through soil, Earthquake spectra for elastic and
inelastic systems, Response Spectrum, Indian
Standard Codes on Earthquake Engineering, Seismic
Zoning Map of India.

3.  It is the study and application of seismology for
engineering purposes. It generally applied to the
branch of seismology that deals with the assessment of
the seismic hazard of a
site or region for the purposes of earthquake
engineering
 It is the scientific study of earthquakes and the
propagation of elastic waves through the Earth.

4. 1. Studying earthquake history and tectonics to
assess the earthquakes that could occur in a
region and their characteristics and frequency of
occurrence
2. Studying strong ground motions generated by
earthquakes to assess the expected shaking from
future earthquakes with similar characteristics.
These strong ground motions could either be
observations from accelerometers or
seismometers or those simulated by computers
using various techniques

9. I. EARTHQUAKES

10.  The shaking or trembling caused by the
sudden release of energy
 Usually associated with faulting or breaking
of rocks
 Continuing adjustment of position results in
aftershocks

12.  Foreshock
◦ Foreshocks are relatively smaller earthquakes
that precede the largest earthquake in a series,
which is termed the mainshock. Not all
mainshocks have foreshocks.
 Mainshock
◦ The mainshock is the largest earthquake in a
sequence, sometimes preceded by one or
more foreshocks, and almost always followed by
many aftershocks.
 Aftershock
◦ Aftershocks are earthquakes that follow the
largest shock of an earthquake sequence. They
are smaller than the mainshock. Aftershocks can
continue over a period of weeks, months, or
years.

13.  Largest earthquake in a sequence
 Larger mainshocks strain larger volume of
rock, have more aftershocks
 Foreshocks and aftershocks usually at least 1
magnitude unit smaller than mainshock

14.  Smaller earthquakes that precede
the mainshock
◦ often by just hours
 Few in number
◦ only half of mainshocks have even
one foreshock
 Near mainshock hypocenter
◦ part of the nucleation process

15.  smaller earthquakes following the largest
earthquake of a sequence (the mainshock)
near mainshock rupture zone
◦ follow almost all shallow earthquakes
◦ cover ruptured area
◦ can number in thousands
◦ can last for years or decades
 aftershocks of Northridge M 6.7 are still occurring
◦ The most predictable (and therefore well-
studied) earthquakes

16.  Every time there is an earthquake, the
volume of rock around the rupture is
strained, that is, twisted or squeezed.
 Sometimes, the strained rock breaks.
 Often, it takes a while for it to break, so
the aftershocks may appear seconds to
years after the causative quake.
 But we don’t know for sure why there is a
delay.
◦ Static fatigue
◦ Visco-elastic relaxation
◦ Diffusion processes (fluids?)

18.  Seismic waves are the waves of energy
caused by the sudden breaking of
rock within the earth or an explosion.
They are the energy that travels
through the earth and is recorded on
seismographs

19.  Explains how energy is
stored in rocks
◦ Rocks bend until the
strength of the rock
is exceeded
◦ Rupture occurs and
the rocks quickly
rebound to an
undeformed shape
◦ Energy is released in
waves that radiate
outward from the
fault

20. The Focus and Epicenter of an Earthquake
• The point within Earth
where faulting begins is
the focus, or hypocenter
• The point directly above
the focus on the surface is
the epicenter

21. ~80% of all earthquakes occur in the circum-Pacific belt
◦ most of these result from convergent margin activity
◦ ~15% occur in the Mediterranean-Asiatic belt
◦ remaining 5% occur in the interiors of plates and on spreading
ridge centers
◦ more than 150,000 quakes strong enough to be felt are
recorded each year

22. Seismic waves are caused by the
sudden movement of materials
within the Earth, such as slip
along a fault during an
earthquake. Volcanic eruptions,
explosions, landslides, avalanches,
and even rushing rivers can also
cause seismic waves.

23. Seismic waves are caused by the sudden movement of
materials within the Earth, such as slip along a fault
during an earthquake. Volcanic eruptions, explosions,
landslides, avalanches, and even rushing rivers can also
cause seismic waves.

24.  Compression wave
 Transverse Wave
 Seismic Wave
◦ Body Waves
 Primary or p-wave
 Compression wave
 Secondary or s-wave
 Transverse wave
◦ Surface
 Love wave
 Rayleigh wave

25.  Seismic waves are the waves of energy
caused by the sudden breaking of rock
within the earth or an explosion. They are
the energy that travels through the earth
and is recorded on seismographs.
 There are several different kinds of seismic
waves, and they all move in different ways.
The two main types of waves are body
waves and surface waves.

27.  Body waves
◦ P or primary waves
 fastest waves
 travel through solids,
liquids, or gases
 compressional wave,
material movement is in
the same direction as
wave movement
◦ S or secondary waves
 slower than P waves
 travel through solids
only
 shear waves - move
material perpendicular
to wave movement

28.  P Waves (Compression Wave)
 The first kind of body wave is the P wave or primary wave.
This is the fastest kind of seismic wave. The P wave can move
through solid rock and fluids, like water or the liquid layers of
the earth. It pushes and pulls the rock it moves through just
like sound waves push and pull the air.

29. D. Earthquake Waves
1. Primary Waves or P-Waves
(Compressional Waves)
a. Travel through solids, liquids and gases.
b. They cause rock particles to
vibrate in the same direction as the
wave is traveling.
c. They are the fastest traveling EQ
waves.

30.  S wave (transverse wave)
 The second type of body wave is the S wave or
secondary wave, which is the second wave you feel
in an earthquake. An S wave is slower than a P
wave and can only move through solid rock. This
wave moves rock up and down, or side-to-side.

31. 2. Secondary Waves or S-Waves or Shear Waves
a. Travel through solids, only.
b. They cause rock particles to
vibrate at right angles to the
direction of travel of the wave.
c. They travel slower than P-waves.

32.  Surface Waves
◦ Travel just below or along the ground’s surface
◦ Slower than body waves; rolling and side-to-side
movement
◦ Especially damaging to buildings

33.  Love Waves
 The first kind of surface wave is called a Love wave,
named after A.E.H. Love, a British mathematician
who worked out the mathematical model for this
kind of wave in 1911. It's the fastest surface wave
and moves the ground from side-to-side.

34.  Rayleigh Waves
 The other kind of surface wave is the Rayleigh wave, named for John
William Strutt, Lord Rayleigh, who mathematically predicted the existence
of this kind of wave in 1885. A Rayleigh wave rolls along the ground just
like a wave rolls across a lake or an ocean. Because it rolls, it moves the
ground up and down, and side-to-side in the same direction that the wave is
moving. Most of the shaking felt from an earthquake is due to the Rayleigh
wave, which can be much larger than the other waves.

35. Seismic wave behavior
◦ P waves arrive first, then S waves, then L and R
◦ Average speeds for all these waves is known
◦ After an earthquake, the difference in arrival times at a
seismograph station can be used to calculate the distance
from the seismograph to the epicenter.

37.  Seismographs are instruments used to record
the motion of the ground during an
earthquake. They are installed in the ground
throughout the world and operated as part of
a seismographic network

38. Modern Seismograph
 Seismic waves cause the seismograph’s drum to
vibrate. But the suspended weight with the pen
attached moves very little. Therefore, the pen stays
in place and records the drum’s vibrations.

40. Seismic wave behavior
◦ P waves arrive first, then S waves, then L and R
◦ Average speeds for all these waves is known
◦ After an earthquake, the difference in arrival times at a
seismograph station can be used to calculate the distance
from the seismograph to the epicenter.

41. Seismographs record earthquake events
At convergent boundaries,
focal depth increases
along a dipping seismic
zone called a Benioff
zone

42. Damage in Oakland, CA, 1989
• Building collapse
• Fire
• Tsunami
• Ground failure

43.  Response of material to
the arrival of energy fronts
released by rupture
 Two types:
◦ Body waves
 P and S
◦ Surface waves
 R and L

44. Time-distance graph
showing the average
travel times for P- and S-
waves. The farther away
a seismograph is from
the focus of an
earthquake, the longer
the interval between the
arrivals of the P- and S-
waves

45.  Three seismograph
stations are needed to
locate the epicenter of an
earthquake
 A circle where the radius
equals the distance to the
epicenter is drawn
 The intersection of the
circles locates the
epicenter

46.  Intensity
◦ subjective measure of the kind of damage done and people’s
reactions to it
◦ isoseismal lines identify areas of equal intensity

48. Awaran district, Balochistan
region , Pakistan
Awaran district,
Balochistan region ,
Pakistan

49. • Modified Mercalli
Intensity Map
– 1994
Northridge, CA
earthquake,
magnitude 6.7

50.  A seismograph is the the tool used to
measure the strength of an earthquakes
 The seismograph prints out a seismogram
that scientists read to determine the strength
of the quake.
 The data from the seismogram is translated
into a 1-10 rating on the Richter Scale. Each
step in the scale represents a tenfold increase
in the size of the quake!

51.  Magnitude
◦ Richter scale measures
total amount of energy
released by an
earthquake;
independent of
intensity
◦ Amplitude of the largest
wave produced by an
event is corrected for
distance and assigned
a value on an open-
ended logarithmic scale

52. Earthquake Precursors
 changes in elevation or tilting of land surface,
fluctuations in groundwater levels, magnetic
field, electrical resistance of the ground
 seismic dilatancy model
 seismic gaps

53. Earthquake Prediction Programs
 include laboratory and field studies of rocks before, during,
and after earthquakes
 monitor activity along major faults
 produce risk assessments

54.  Graph showing the
relationship between the
amount of waste injected
into wells per month and
the average number of
Denver earthquakes per
month
 Some have suggested
that pumping fluids into
seismic gaps will cause
small earthquakes while
preventing large ones