19603554 Seismology

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Global Seismicity

(USGS)

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Crust

Mantle

Outer

Core

Inner

Core

Inside the Earth

IITK-BMTPC Earthquake Tips

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Local Convective Currents in the Mantle


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Pangea: Continents 200 million years ago

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Plate tectonic processes

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Mid-Ocean Ridge Spreading

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Major tectonic plates, mid-ocean ridges, trenches

and transform faults

(Bolt, 1993)

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Indo-

Australian

Plate

Pacific

Plate

Eurasian

PlateNorth American

Plate

South

American

Plate

AfricanPlate

Antarctic

Plate

Major Tectonic Plates on the Earth’s surface


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Convergent Boundary

Divergent Boundary

Transform Boundary

Types of Inter-Plate Boundaries


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Dip Slip

Faults

Strike SlipFaults

Type of Faults


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Stage A

Stage C

Slip

Stage B

Elastic Strain Build-Up and Brittle Rupture


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Time

(years)

StrengthEnergy

Build-Up

E l a s t

i c S t r e s s

Energy

Release

C u m u l a t i v e S l i p

C

A

Slip

AB

C

A

B

C

EQ

EQ

Time

(years)

EQ

Elastic Rebound Theory


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EQ

Surface Waves

Fault

Rupture

Body Waves

Structure

Soil

Geologic Strata

Arrival of Seismic Waves at a Site


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Direction of

Energy Transmission

Side to side

Up and down

P-WavesPush and pull

CompressionExtension

S-Waves

Love WavesSideways in horizontal plane

Rayleigh WavesElliptic in vertical plane

Motions caused by Body and Surface Waves


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StringMagnet

Pendulum Bob

Pen

Rotating

Drum

Chart Paper

Support

Direction of

Ground Shaking Recorded

Schematic of Early Seismograph


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Locating Earthquake

(Louie, 1996)

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Epicenter

Focus

Place of

Interest

Epicentral Distance

Fault

Rupture

Focal

Depth

Basic terminology


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Calculation of the Richter Magnitude (ML)of a Local Earthquake

(Bolt, 1993)

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R d i ill i ti ith di t

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Bright

(100 lumens)

Normal

(50 lumens)

Dull

(20 lumens)

Near

Far

100 Watt Bulb

Reducing illumination with distance

from an electric bulb


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IX

VIII

X

VII

Isoseismal Map of the 2001 Bhuj (India)

Earthquake (MSK Intensity)


SEP 1999

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PGA from Intensity Data

• Guttenberg and Richter (1956)

log a = 0.333 I - 0.500

• Neumann (1954)

log a = 0.308 I - 0.041

• Trifunac and Brady (1975)

log a = 0.300 I - 0.014• Trifunac and Brady (1977)

log a = 0.350 I - 0.435

• Neuman (1977)

log a = 0.380 I - 0.560

• Murphy and O'Brien (1977)

log a = 0.250 I + 0.250

SEP-1999

0.010

0.10

1.0

4 5 6 7 8 9 10

G-R (1956)

N (1954)

T-B (1975)

T-B (1977) N (1977)

M-O'B (1977)

P G A

( g )

MMI

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0 10 20 30 40 50 60

0.5g

Time (sec)

1985 Mexico Earthquake (SCT 1A; N90E)

1940 Imperial Valley Earthquake (El Centro; S00E)

1971 San Fernando Earthquake (Pacoima Dam; N76W)

1991 Uttarkashi Earthquake (Uttarkashi, N75E)

Some typical recorded accelerograms


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Ground Motion Records

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Maximum Recorded PGA and PGV

(Martinez-Pereira, 1999)

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Deterministic Hazard Assessment

(Reiter, 1990)

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Probabilistic Hazard Assessment

(Reiter, 1990)

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Attenuation Curves

1979 Imperial Valley M~6.6 Earthquakes

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Preparing Zoning Maps

Source areas

• Historical earthquakes

• Known faults

• Chosen for discrete seismicity andrelated tectonic element

Recurrence Relations

• Extension of N-M from historical data

• Seismic activity of the area

Attenuation Relations

• Effect of eqk. (accn.) at each site due tooccurrence of eqk. in each source area

Probability of Exccedance

• Integrate effect of eqks. of diff. Sizes, atdiff. Sites at diff. probability ofoccurrence

Zoning Map

• Contours of equal intensity for aparticular probability of excceedance

Algermissen

Geographical Layout and

T t i Pl t B d i t I di

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Deccan Shield

Indo-

Gangetic

Plains

Himalayas

Peninsular

India

Bay of Bengal Arabian Sea

Indo-Australian

Plate

Eurasian Plate

Narmada

Plains

Godavari

Plains

MahanadiPlains

Tectonic Plate Boundaries at India


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<5

5<6

6<77<8

>8

Magnitude

2001 Bhuj

1934 Bihar-

Nepal

1905 Kangra

1950 Assam1897 Assam

Some Past Earthquakes


Recent Past Indian Seismic Zone Map

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p

(IS:1893-1984)


Current Indian Seismic Zone Map

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Current Indian Seismic Zone Map

(IS 1893-2001)


Documents

19603554 Seismology