earthquake- engineeringcivil

8/7/2019 earthquake- engineeringcivil

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DEFINITIONDEFINITION

An earthquake is a sudden tremor orAn earthquake is a sudden tremor ormovement in the earths crust whichmovement in the earths crust whichoriginates naturally at or below theoriginates naturally at or below the

surface.surface.


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PLATE TECTONICS THEORYPLATE TECTONICS THEORY

TheThe EpicentresEpicentres of earthquakes are notof earthquakes are not

randomly distributed over the earthsrandomly distributed over the earths

surfacesurface They tend to be concentrated in narrowThey tend to be concentrated in narrow

zones, about 99 % of them beingzones, about 99 % of them being

concentratedconcentrated in inter platein inter plate zones ofzones of

seismic activityseismic activity

Remainder 1 % considered to beRemainder 1 % considered to be AseismicAseismic


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The earth's lithosphere is made up ofThe earth's lithosphere is made up of21 solid tectonic plates21 solid tectonic plates


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About 90 per cent earthquakes result fromAbout 90 per cent earthquakes result from

tectonic plate movementstectonic plate movements

Rest can be related to volcanic activities,Rest can be related to volcanic activities,collapse of sub terranean cavities or mancollapse of sub terranean cavities or man

made effects such as nuclear explosionsmade effects such as nuclear explosions

Tectonic earthquakes are triggered whenTectonic earthquakes are triggered when

accumulated strain exceeds shearingaccumulated strain exceeds shearing

strength of rocksstrength of rocks


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the Narrow zonesthe Narrow zones

Circum pacific ring of fireCircum pacific ring of fire Alpine Himalayan beltAlpine Himalayan belt

World circling ocean ridgesWorld circling ocean ridges


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12 major plates12 major plates

AntarcticaAntarctica

AfricaAfrica

EurasiaEurasia

IndiaIndia

AustraliaAustralia

ArabiaArabia

Philippines

Philippines

N. AmericaN. America

S. AmericaS. America

Pacific

Nazca

Cocos

Minor plates- Scotia, Carribean, Juan de Fuca

etc


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The major tectonic plates


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CONTINENTALDRIFTCONTINENTALDRIFT

Alfred WegenerAlfred Wegener-- 19121912

Initially a single mass known asInitially a single mass known asPANGAEAPANGAEA

Continents separate and start movingContinents separate and start movingawayaway

Now slowly moving to their initial positionsNow slowly moving to their initial positions

on the globeon the globe Crust and upper mantle assumed to beCrust and upper mantle assumed to be

floating on thefloating on the AesthenosphereAesthenosphere (viscous)(viscous)


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Evidences..Evidences..

Repeated reversals of Earths magneticRepeated reversals of Earths magnetic

fieldfield

YouthnessYouthness of the ocean floorof the ocean floor OccuranceOccurance of major seismic zones alongof major seismic zones along

ocean floors and trenches, sub marineocean floors and trenches, sub marine

mountain ranges etc.mountain ranges etc.


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Seismotonics of IndiaSeismotonics of India


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Indian scenarioIndian scenario

Himalayas one of the most tectonicallyHimalayas one of the most tectonicallyactiveactive

Major strain due to collision is distributedMajor strain due to collision is distributedalongalong himalayashimalayas

Rest is distributed northwards in a wideRest is distributed northwards in a widearea from Tibetan plateau toarea from Tibetan plateau to PamirsPamirs

The push from the north Asian sideThe push from the north Asian sideresulted in compression producingresulted in compression producing giganticgiganticthruststhrusts


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4 sub divisions in4 sub divisions in indiaindia

HimalayasHimalayas AndamansAndamans

Kutch regionKutch region

Peninsular IndiaPeninsular India


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Body waves

TYPES OF WAVES

in an

EARTHQUAKE

1.

2.1. 2.


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REIDS

THEORY

OF

ELASTIC

REBOUND


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San Francisco earthquake 1906

270 miles of fault on ground

A maximum relative slip of 21 feet

HF REID interpreted thebehaviour


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Stage 1Stage 1

-- Continuously increasing shear forcesContinuously increasing shear forcesare acting on 2 blocs of an initiallyare acting on 2 blocs of an initially

unstrained blockunstrained block

-- No movement initially because of frictionNo movement initially because of friction


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Stage 2Stage 2

-- No visible release of energy yetNo visible release of energy yet

-- Lines which were originally straightLines which were originally straight

became obliquebecame oblique

-- Continuous storage ofContinuous storage of energy withinenergy within


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Stage 3Stage 3

-- Weakest part of the fault slips suddenlyWeakest part of the fault slips suddenly-- At this point, strain = fault capacityAt this point, strain = fault capacity

-- Blocks on either side jerk into a lessBlocks on either side jerk into a less

strained conditionstrained condition-- Sudden displacement = Elastic ReboundSudden displacement = Elastic Rebound


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StagesStages

ElasticRebound

Obliquity

Straight


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REIDs ANOLOGY OF A STRECHED TIMBER STICK

REIDS ANALOGY OF ALIMBER STICK


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EFFECTSEFFECTS


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Earthquake Resistance inEarthquake Resistance in

Buildings

Buildings


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Level

e frame

Level j

Level j+1

Roof

O rningMoment

Forces Shear forces


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Irregularities in PlanIrregularities in Plan


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Vertical IrregularityVertical Irregularity


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TorsionalTorsional effects are related to Leffects are related to Land U shaped buildingsand U shaped buildings


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Earthquake

Resistant

Building

Design


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Braces constrained

against

Lateral Buckling


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Recording.. Indian perspectiveRecording.. Indian perspective

1976, the planning1976, the planning comissioncomission

recommended measurementrecommended measurement

Recording stations were set upRecording stations were set up

InstumentsInstuments present inpresent in indiaindia areare

1. RESA1. RESA

(( RoorkeeRoorkee earthquake Schoolearthquake SchoolAccelerographAccelerograph ))

2. SRR ( Structural response Recorder )2. SRR ( Structural response Recorder )


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A network of more than 200A network of more than 200

AccelerographsAccelerographs across the country.across the country.

350 SRRs in the Himalayas and sub350 SRRs in the Himalayas and sub

Himalayas.Himalayas.


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CLASSIFICATIONCLASSIFICATION

LocationLocation

InterplateInterplate andand IntraplateIntraplate

Focal DepthFocal DepthShallow(0Shallow(0--71 km),Intermediate(7171 km),Intermediate(71--300 km),300 km),Deep(>300 km)Deep(>300 km)

EpicentralEpicentral distancesdistances

Local, Regional,Local, Regional, TeleseismicTeleseismic


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MagnitudeMagnitude (on Richter scale)(on Richter scale)

Micro 8.0


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18 points of erathquake resistant design of18 points of erathquake resistant design of

buildingsbuildings

http://www.architectjaved.com/equake_resisthttp://www.architectjaved.com/equake_resist

ant.pdfant.pdf


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