2. 1.3.1. Seismic Waves
Definition
"seismic waves
seismic waves" are the vibrations resulting as a result
g
of the energy released from the earthquake
These waves travel outward from the source of the
earthquake along the surface and through the Earth at
earthquake along the surface and through the Earth at
varying speeds depending on the material through
which they move.
Prof. Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
3. 1.3.1. Seismic Waves
Classification
Body Waves Primary (P)
Secondary (S) SV
SH
Surface Waves Love (LQ)
Reliegh (LR)
Successive
(Torsion)
Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
4. 1.3.1. Seismic Waves
Body and Surface Waves
Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
5. 1.3.1. Seismic Waves
Body Waves (Primary Waves)
The faster of the seismic
waves
The P waves are able to travel
through solid rock, liquid
Its motion is the same as material, such as volcanic magma
that of a sound wave in a or the water of the oceans.
fluid
In most earthquakes, the P waves
are felt first
Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
6. 1.3.1. Seismic Waves
Body Waves (Secondary Waves)
The slower wave through
the body of rock is called
the secondary or S wave.
At right angles to the
direction of travel
The S waves cannot propagate in the liquid parts of the
earth, such as the oceans, and their amplitude is
significantly reduced in liquefied soil.
Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
7. 1.3.1. Seismic Waves
Surface Waves
Love wave moves the
ground side to side in a
horizontal plane parallel to
the earth’s surface
Rayleigh a e
Ra leigh wave like rolling
ocean wave, the pieces of
rock distributed by a
Its
It motion i restricted t
ti is t i t d to Rayleigh wave move both
near the ground surface. vertically and horizontally
in a vertical plane
Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
9. 1.3.1. Seismic Waves
Earths Structure
Earth Diameter about 12756 Km
Crustal Earthquakes Up to 30 Km
Shallow Earthquakes 5-20 Km
Moderate E th
M d t Earthquakes 20 50 K
k 20-50 Km
Deep Earthquakes 300-700
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
10. 1.3.1. Seismic Waves
Wave Velocity
y
Velocity of P wave
Velocity of S wave
K - Bulk Modulus
- Soil Rigidity
- Density
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
11. 1.3.1. Seismic Waves
Wave Velocity
y
P Waves
1-14 (8)
S Waves
1-8 (4)
Love W
L Waves
2-6
Releigh Waves
1-5
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
12. 1.3.1. Seismic Waves
Focal Distance
Arrival Times
d- Focal Distance
Common
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
14. 1.3.2. Earthquake Measures
Magnitude
Modified Mercally Scale
(1 to 12 Points concerning Earthquake Effects
Peak Ground Acceleration (PGA)
(from Earthquake Acceleration Record )
Peak Ground Velocity (PGV)
(from Earthquake Velocity Record )
Peak Ground Displacement (PGD)
(from Earthquake Displacement Record )
Duration of Ground motion and Frequency content
15. 1.3.2. Earthquake Measures
Magnitude
g
Measured for the Amount of Strain Energy Released
Logarithm (Base 10) of
maximum amplitude
measured in micrometers of
the earth record obtained
from Wood-Anderson
seismograph corrected to
distance of 100 km
Less than 5 No structural
damage is expected
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
16. 1.3.2. Earthquake Measures
Frequency & Energy
q y gy
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
17. 1.3.2. Earthquake Measures
Frequency & Description
q y p
Richter Frequency of
Desc. Earthquake effects
M occurrence
<20
2.0 Micro Micro earthquakes not felt [6]
earthquakes, felt. 8,000
8 000 per day
2.0–2.9 Generally not felt, but recorded. 1,000 per day
Minor
3.0–3.9 Often felt, but rarely causes damage. 49,000 per year
Noticeable shaking of indoor items, rattling noises.
4.0 4.9
4.0–4.9 Light 6,200 per year
Significant d
Si ifi damage unlikely.
lik l
Can cause major damage to poorly constructed
5.0–5.9 Moderate buildings over small regions. At most slight damage to 800 per year
well-designed buildings.
g g
Can be destructive in areas up to about 160 kilometres
6.0–6.9 Strong 120 per year
(100 mi) across in populated areas.
7.0–7.9 Major Can cause serious damage over larger areas. 18 per year
Can
C cause serious damage in areas several hundred
i d i lh d d
8.0–8.9 1 per year
Great miles across.
9.0–9.9 Devastating in areas several thousand miles across. 1 per 20 years
Never recorded; see below for equivalent seismic
q Extremely rare
y
10.0+
10 0+ Massive
energy yield. (Unknown
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
18. 1.3.2. Earthquake Measures
Frequency & Description
q y p
Richter TNT for Joule
Example
App. M Seismic Energy equivalent
0.0
00 15.0 (0.529
15 0 g (0 529 oz) 63.1
63 1 kJ
1.5 2.67 kg (5.88 lb) 11.2 MJ World War II conventional bombs
3.5 2.67 metric tons 11.2 GJ Chernobyl nuclear disaster, 1986
4.0 15.0 metric tons 63.1 GJ Small atomic bomb
4.5 84.4 metric tons 355 GJ Tajikistan earthquake, 2006
6.0 15.0 kilotons 62.7 TJ Double Spring Flat earthquake (Nevada, USA), 1994
6.5 84.4 kilotons 355 TJ Eureka earthquake (California, USA), 2010
6.6
66 119 kilotons 501 TJ San Fernando earthquake (California USA), 1971
(California, USA)
6.7 168 kilotons 708 TJ Northridge earthquake (California, USA), 1994
7.5 2.67 megatons 11.2 PJ Kashmir earthquake (Pakistan), 2005
8.1 21.2 megatons 89.1 PJ Guam earthquake, August 8, 1993[12]
8.35 (app.) 50 megatons 210 PJ Tsar a - Largest thermonuclear weapon ever tested
8.8 238 megatons 1.00 EJ Chile earthquake, 2010
9.0 474 megatons 2.00 EJ Sendai earthquake and tsunami (Japan), 2011
9.5
95 2.67
2 67 gigatons 11.2
11 2 EJ Valdivia earthquake (Chile), 1960
(Chile)
10.0 15.0 gigatons 63.1 EJ Never recorded
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
20. 1.3.2. Earthquake Measures
The Modified Mercalli intensity
y
I. Instrumental
Not felt by many people unless in favourable conditions.
(2)
Felt only by a few people at best, especially on the upper floors
II. Feeble (2)
of buildings. Delicately suspended objects may swing.
Felt quite noticeably by people indoors, especially on the
upper floors of buildings. Many do not recognize it as an
III. Slight (3)
earthquake. Standing motor cars may rock slightly. Vibration
similar to the passing of a truck. Duration estimated.
i il t th i f t k D ti ti t d
Felt indoors by many people, outdoors by few people during
h d A i h k d Di h i d d
the day. At night, some awakened. Dishes, windows, doors
IV. Moderate (4) disturbed; walls make cracking sound. Sensation like heavy
truck striking building. Standing motor cars rock noticeably.
Dishes and windows rattle alarmingly.
Dishes and windows rattle alarmingly
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
21. 1.3.2. Earthquake Measures
The Modified Mercalli intensity
y
Felt outside by most, may not be felt by some outside in non-
V. Rather
favourable conditions. Dishes and windows may break and large
Strong (4)
bells will ring. Vibrations like large train passing close to house.
g g p g
Felt by all; many frightened and run outdoors, walk unsteadily.
VI. Strong Windows, dishes, glassware broken; books fall off shelves; some
( )
(5) heavy furniture moved or overturned; a few instances of fallen
y ;
plaster. Damage slight.
Difficult to stand; furniture broken; damage negligible in
building of good design and construction; slight to moderate in
VII. Very
well-built ordinary structures; considerable damage in poorly
Strong (5-6)
built or badly designed structures; some chimneys broken.
Noticed by people driving motor cars.
yp p g
Damage slight in specially designed structures; considerable in
VIII.
ordinary substantial buildings with partial collapse. Damage
Destructive
g
great in p
poorly built structures. Fall of chimneys, factory stacks,
y y, y ,
(6)
columns, monuments, walls. Heavy furniture moved.
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
22. 1.3.2. Earthquake Measures
The Modified Mercalli intensity
y
General panic; damage considerable in specially designed
structures, well designed frame structures thrown out of plumb.
IX. Ruinous (7)
Damage great in substantial buildings, with p
g g g, partial collapse.
p
Buildings shifted off foundations.
Some well built wooden structures destroyed; most masonry and
X. Disastrous (7)
X Di
frame structures destroyed with foundation. Rails bent.
XI.
XI Very Few,
Few if any masonry structures remain standing. Bridges
standing
Disastrous (8+) destroyed. Rails bent greatly.
Total damage - Everything is destroyed Total destruction Lines
destroyed. destruction.
XII. Catastrophic of sight and level distorted. Objects thrown into the air. The
(8+) ground moves in waves or ripples. Large amounts of rock move
position.
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
23. 1.3.2. Earthquake Measures
PGD – PGV - PGA
El Centro 1940
San Fernando 1971
North Bridge 1994
Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr
