earth 2011-lec-02

EARTHQUAKEEARTHQUAKEEARTHQUAKEEARTHQUAKEENGINEERINGENGINEERING11..33. Waves & Measures. Waves & Measures

11..33..11. Seismic Waves. Seismic Waves

11..33..22. Earthquake Measures. Earthquake Measures

1.3.1. Seismic Waves

DefinitionDefinition

"seismic wavesseismic waves" are the vibrations resulting as a result

DefinitionDefinition

gof the energy released from the earthquake

These waves travel outward from the source of the earthquake along the surface and through the Earth atearthquake 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


ClassificationClassificationClassificationClassification

Body WavesBody Waves Primary (P)Primary (P)

Secondary (S)Secondary (S) SVSV

SHSH

Surface WavesSurface Waves Love (LQ)Love (LQ)

RelieghReliegh (LR)(LR)

Successive Successive (Torsion)(Torsion)

Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr


Body and Surface WavesBody and Surface WavesBody and Surface WavesBody and Surface Waves



Body Waves (Primary Waves)Body Waves (Primary Waves)

The faster of the seismic

Body Waves (Primary Waves)Body Waves (Primary Waves)

waves

The P waves are able to travelthrough solid rock, liquidmaterial, such as volcanic magmaor the water of the oceans.

Its motion is the same asthat of a sound wave in afluidfluid

In most earthquakes, the P wavesare felt first



Body Waves (Secondary Waves)Body Waves (Secondary Waves)

The slower wave throughthe body of rock is called

Body Waves (Secondary Waves)Body Waves (Secondary Waves)

the body of rock is calledthe secondary or S wave.

At right angles to thedirection of travel

The S waves cannot propagate in the liquid parts of theearth, such as the oceans, and their amplitude issignificantly reduced in liquefied soil.



Surface WavesSurface Waves

Love wave moves theground side to side in a

Surface WavesSurface Waves

ground side to side in ahorizontal plane parallel tothe earth’s surface

Ra leigh a e like rollingRayleigh wave like rollingocean wave, the pieces ofrock distributed by a

It ti i t i t d t Rayleigh wave move bothvertically and horizontallyin a vertical plane

Its motion is restricted tonear the ground surface.

in a vertical plane



Propagation of WavesPropagation of WavesPropagation of WavesPropagation of Waves



Earths StructureEarths StructureEarth Diameter about 12756 Km

Crustal Earthquakes Up to 30 Km

Shallow Earthquakes 5-20 Km

M d t E th k 20 50 KModerate Earthquakes 20-50 Km

Deep Earthquakes 300-700

Prof.Dr. Osman Shaalan Earthquake Engineering Dr. Tharwat Sakr


Wave VelocityWave Velocity

Velocity of P wave

yy

Velocity of S wave

K - Bulk Modulus

- Soil Rigidity

Density


- Density


Wave VelocityWave Velocityyy

P Waves1-14 (8)

S Waves1-8 (4)

L WLove Waves2-6

Releigh Waves1-5



Focal DistanceFocal Distance

Arrival Times

d- Focal Distance

Common



ProblemProblem


1.3.2. Earthquake Measures

Modified Mercally Scale

Magnitude

Modified Mercally Scale (1 to 12 Points concerning Earthquake Effects

Peak Ground Acceleration (PGA) Peak Ground Acceleration (PGA)(from Earthquake Acceleration Record )

Peak Ground Velocity (PGV)

Peak Ground Displacement (PGD)

Peak Ground Velocity (PGV)(from Earthquake Velocity Record )

Peak Ground Displacement (PGD)(from Earthquake Displacement Record )

Duration of Ground motion and Frequency content


MagnitudeMagnitude

Measured for the Amount of Strain Energy Released

gg

Logarithm (Base 10) of maximum amplitude measured in micrometers of

measured in micrometers of the earth record obtained from Wood-Anderson seismograph corrected toseismograph corrected to distance of 100 km

Less than 5 No structural damage is expected



Frequency & EnergyFrequency & Energyq y gyq y gy



Frequency & DescriptionFrequency & Descriptionq y pq y pRichter

M Desc. Earthquake effects Frequency of occurrence

< 2 0 Micro Micro earthquakes not felt [6] 8 000 per day< 2.0 Micro Micro earthquakes, not felt. 8,000 per day2.0–2.9 Minor Generally not felt, but recorded. 1,000 per day3.0–3.9 Often felt, but rarely causes damage. 49,000 per year

4.0–4.9 Light Noticeable shaking of indoor items, rattling noises. Si ifi d lik l 6,200 per year4.0 4.9 Light Significant damage unlikely. 6,200 per year

5.0–5.9 ModerateCan cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.

800 per yearg g

6.0–6.9 Strong Can be destructive in areas up to about 160 kilometres(100 mi) across in populated areas. 120 per year

7.0–7.9 Major Can cause serious damage over larger areas. 18 per yearC i d i l h d d8.0–8.9 GreatCan cause serious damage in areas several hundred miles across. 1 per year

9.0–9.9 Devastating in areas several thousand miles across. 1 per 20 years

10 0+ Massive Never recorded; see below for equivalent seismic Extremely rare


10.0+ Massive qenergy yield.

y(Unknown


Frequency & DescriptionFrequency & Descriptionq y pq y pRichterApp. M

TNT forSeismic Energy

Joule equivalent

Example

0 0 15 0 g (0 529 oz) 63 1 kJ0.0 15.0 g (0.529 oz) 63.1 kJ1.5 2.67 kg (5.88 lb) 11.2 MJ World War II conventional bombs3.5 2.67 metric tons 11.2 GJ Chernobyl nuclear disaster, 19864.0 15.0 metric tons 63.1 GJ Small atomic bomb4.5 84.4 metric tons 355 GJ Tajikistan earthquake, 20066.0 15.0 kilotons 62.7 TJ Double Spring Flat earthquake (Nevada, USA), 19946.5 84.4 kilotons 355 TJ Eureka earthquake (California, USA), 20106 6 119 kilotons 501 TJ San Fernando earthquake (California USA) 19716.6 119 kilotons 501 TJ San Fernando earthquake (California, USA), 19716.7 168 kilotons 708 TJ Northridge earthquake (California, USA), 19947.5 2.67 megatons 11.2 PJ Kashmir earthquake (Pakistan), 20058.1 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 tested8.8 238 megatons 1.00 EJ Chile earthquake, 20109.0 474 megatons 2.00 EJ Sendai earthquake and tsunami (Japan), 20119 5 2 67 gigatons 11 2 EJ Valdivia earthquake (Chile) 1960


9.5 2.67 gigatons 11.2 EJ Valdivia earthquake (Chile), 196010.0 15.0 gigatons 63.1 EJ Never recorded


Huge EventsHuge Eventsgg



The Modified The Modified MercalliMercalli intensity intensity yyI. Instrumental (2) Not felt by many people unless in favourable conditions.

II. Feeble (2) Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing.

III. Slight (3)

Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration i il t th i f t k D ti ti t dsimilar to the passing of a truck. Duration estimated.

Felt indoors by many people, outdoors by few people during h d A i h k d Di h i d d

IV. Moderate (4)the day. At night, some awakened. Dishes, windows, doors 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.


The Modified The Modified MercalliMercalli intensity intensity yyV. Rather Strong (4)

Felt outside by most, may not be felt by some outside in non-favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to house.g g p g

VI. Strong (5)

Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen

Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in

( ) y ;plaster. Damage slight.

VII. Very Strong (5-6)

building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars.

VIII. Destructive (6)

Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks,

y p p g


(6) g p y y , y ,columns, monuments, walls. Heavy furniture moved.


The Modified The Modified MercalliMercalli intensity intensity yy

IX. Ruinous (7)

General panic; damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse.

X Di (7) Some well built wooden structures destroyed; most masonry and

g g g , p pBuildings shifted off foundations.

XI Very Few if any masonry structures remain standing Bridges

X. Disastrous (7) Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent.

Total damage Everything is destroyed Total destruction Lines

XI. Very Disastrous (8+)

Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.

XII. Catastrophic (8+)

Total damage - Everything is destroyed. Total destruction. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock move position.


position.


PGD PGD –– PGV PGV -- PGAPGA

El Centro 1940

San Fernando 1971

North Bridge 1994



0.05

0.10

ion

(g)

0.0 4.0 8.0 12.0 16.0 20.0 24.0 28.0 32.0Time (second)

-0.10

-0.05

0.00

Acc

eler

ati

El-Akaba Earthquake (November, 22, 1995)

0.10

g)

-0.10

-0.05

0.00

0.05

Acc

eler

atio

n (g

El-Centro Earthquake (May, 18, 1940)

0.0 4.0 8.0 12.0 16.0Time (second)

earth 2011-lec-02

Education

tharwat sakr

seismic wavesproblemprof

seismic waves1

releigh waves

waves measures1

rayleigh wave

rollingocean wave

sound wave