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-Hussaini 1 and M. Saiful Islam 2 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 Latitude 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
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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
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