T1-P12 ATTENUATION OF GROUND MOTION IN BANGLADESH · 2013-07-11 · T1-P12 ATTENUATION OF GROUND...

T1-P12 ATTENUATION OF GROUND MOTION IN BANGLADESH

1897 Great Indian Earthquake (M=8.7) Location of Earthquakes 1918 Srimangal Earthquake (M=7.6)

1930 Dubri Earthquake (M=7.1)

Directional Dependence of Attenuation

Directions Affecting Bangladesh

Development of Intensity Attenuation Model

Attenuation law for Intensity is considered to be represented by:

I=a+b*(M)+c*(R)+d*log(R)+σP

Intensity Attenuation Model(Using Epicentral Distance)

I=1.1425+1.4670*(M)-0.0038*(R)-2.4963*log(R)+1.001P.

with standard deviation σ = 1.001

Validation of Attenuation Models with Field Data

Isoseismal Map (Nandy, 2001)

1885 M=7.0 Great Bengal Earthquake (Sirajganj)

1897 M=8.1 Great Indian Earthquake (Shillong)

1918 M=7.6 Srimangal Earthquake (Srimangal)

1930 M=7.1 Dhubri Earthquake (West Assam)

1945 M=6.7 Mikirhills Earthquake (Central Assam)

1964 M=5.5 Medinipur Earthquake (Coast W. Bengal)

1999 M=5.1 Moheshkhali Earthquake (Coast Cox’s Bazar)

Studied Earthquakes 1999 Moheshkhali earthquake (M=5.1)

Cyclone Shelter Column Damage

Isoseismal Data

Development of PGA Attenuation Models for

Rock/Hard Soil

PGA Attenuation Model-1 (using Murphy & O’Brien(1977)

PGA Attenuation Model-1 (using Trifunac and Brady, 1975

PGA Attenuation Model-1 (using Wald et al., 1999)

Attenuation law for Intensity is considered to be represented by:

Log(PGA)= -0.1092+0.5128*(M)-0.0014*(R)-0.8705*log(R)+0.35*P. with standard deviation σ = 0.35

Log(PGA)= 0.40636+0.4396*(M)-0.0012*(R)-0.7462*log(R)+0.301*P. with standard deviation σ = 0.35

Log(PGA)= 0.6858+0.40*(M)-0.0011*(R)-0.679*log(R)+0.2735*P. with standard deviation σ = 0.2735

Log(PGA)=a + b*(M)+c*(R)+d*log(R)+σ*P.. with standard deviation σ

Conclusions Attenuation of earthquake intensity appears to have directional

dependence. Directions affecting Bangladesh appear to show

greater attenuation.

Developed attenuation equations for intensity agree quite well

with field isoseismal data for the different earthquakes except

for Srimangal earthquake which was a very shallow earthquake

with relatively faster attenuation.

PGA based attenuation laws obtained for Bangladesh using Trifunac

and Brady (1975) and Murphy and O’Brien (1977) intensity PGA

relationship appear to be more in agreement with standard

attenuation laws.

Comparison of measured strong motion data for a 26/07/2008

M=4.8 earthquake with developed attenuation relation is presented.

Tahmeed M. Al-Hussaini1 and M. Saiful Islam2

Dept. of Civil Engineering, Bangladesh University of Engineering & Technology, Dhaka.

Tectonic Map of India

Earthquake Bangladesh is located in a

tectonically active region

close to the plate boundaries

of the north moving Indian

plate and the Eurasian

plate to its north and east.

Lack of earthquake awareness

and preparedness may lead to

massive disaster if major

earthquake strikes.

Recent tremors have frequently

shaken the eastern coastal zone

(Chittagong), some have caused

damages.

Comparison of PGA Attenuation Model with

Other Attenuation Laws for Rock /Hard Soil

Comparison of Peak Ground Motion

Acceleration of Earthquake on 26/07/2008

20

21

22

23

24

25

26

27

28

85 87 89 91 93 95

La

titu

de

Longitude

1

2

3

4 5

6 7

1- 1885 Bengal

EQ

2- 1897Great

Asam EQ

3- 1918

Srimangal EQ

4- 1930 Dhubri

EQ

5- 1945 Mikirhills

EQ

6- 1964

Medinipur EQ

7- 1999

Moheshkhali EQ