Earthquake Engineering 2012 Lecture 0103 Measures of Earthquakes

EARTHQUAKE
ENGINEERING
1.3. Waves & Measures

1.3.1. Seismic Waves

1.3.2. Earthquake Measures


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


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


Body and Surface 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



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.



Illustration (Body & Surface Waves)

Rayleigh Waves Love 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



Illustration (Surface Waves)

Love wave

Rayleigh wave

Rayleigh Waves Love Waves


Propagation of 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

Wave Recording
g


Wave Velocity
y
Velocity of P wave

Velocity of S wave

K - Bulk Modulus

- Soil Rigidity

 - Density


Wave Velocity
y
P Waves
1-14 (8)

S Waves
1-8 (4)

Love W
L Waves
2-6

Releigh Waves
1-5


Focal Distance
Arrival Times

d- Focal Distance

Common



 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

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


Frequency & Energy
q y gy


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


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


Huge Events
g


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


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.


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.


PGD – PGV - PGA
El Centro 1940

San Fernando 1971

North Bridge 1994


Earthquake Engineering 2012 Lecture 0103 Measures of Earthquakes

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