• GIS BASED SEISMIC DAMAGE ASSESS:MENT: A CASE STIJDY • ON RAJSHAHI CITY
By
!vIOHAMMAD JOBAIR
A thesis submilled /0 the Department of Urban and Regional Planning.
Bangladnh University of EnpneU/flK and Technology, BUF.! In partialfulfillmem of/hi: n:qlllrememsjor the degree
Of
MASTER OF URBAN AND REGIONAL PLANNTl\"G
• I --. -,~- -- • January 2006
, The thesis titled GIS Based Seismie Damage Assessment: A Case Study on Rajshahi City, Submitted by Mohammad Jobair, Roll No 040315019F, Session April 2003 has been aecepted as satisfactory in partial fulfillment of the requirement for the degree of Master of Urban and Regional Planning on January 2006.
BOARD OF EXAMINEERS
-li ,"""" .~~~ V'=n~ (Dr K. M. Maniruzzaman) ::J-(O/ ItJ7., Chairman Professor (Supervisor) Department of Urban and Regional Planning BD"ET, Dhaka 1000 272.LJ 4 ..J A.v.., (Dr. Mehedi Ahmed Ansarv) Member Associate Professor (Co-sllpervisor) Department of Civil Engineering BVEI, Dhaka 1000
":U,.-..;) ~~~
(Dr K M. Maniruzzaman) Member H,od (Ex-Officio) Department of Urban and Regional Planning Bl'ET, Dhaka 1000
~) Member Professor Department ofUman and Regional Planning BDET, Dhaka 1000
Ms Iwat Islam Member Assistant Professor Department ofUman and Regional Planning BVEI, Dhaka 1000
~1Ii'k Member Senior Structural Engineer (Eldemal) 304 Concord ManOT,HOllOO48,Road 15A Dhanmondi RIA, Dhaka 1209
II ,
CANDIDATES DECLARATION
Il is hereby declared that this thesis or any part of it has not been submitted elsewhere for the award of any degree Of, diploma.
Mohammad Jobair
ill ACKNOWLEDGEMENTS
All praises to Allah, the merciful and the kind.
The author expresses his heartiest appreciation to his supervisor, Dr. K. M. Maniruzarnan, Professor and Head, Department of Urban and Regional Planning, BVET. and co-supervisor Dr. Mdll,Ji Ahmed Ansary, Associate Profcssor. Department of Civil Engineering, RliET I()r theIr eontinlling encouragement and guidance in the study. Their valuable suggestions and advice ,,,,rked 3.', key to open the path of the study.
The author is also grateful to Prof. Dr. Samar Jahan, AssL Prof. Ms. lshrat [slam and Engr. Dr. Ali Akbar MolJik for their valuable suggestions and recommendations on the board.
The author is privileged to express his sincere grntitude to Mr. Gholam Mustafa. Soil Scientist, Expert Soil Engineers Ltd. and Mr. Ashraf Ali Bishwas, Managing Director of Structural Engineers and Planners, Ltd for their inspiration and co-opcration in collecting secondary information.
The author expresses his grateful thanks to CASR, BUET for fimding this research and to scveral individuals and friends, to the memben; of different Government and Non-govenunent organizations specially Geological Swvey of Bangladesh, Rajshahi City Corporation, Rajshahi Developmcnt Authority for giving valuablc advice throughout the development of this research.
IV 'ABSTRACT
For accomplishing comprehensive regional seismic damage assessment, Geographical Information System (GIS) provides a perfect environment, GIS has the capability to store, manipulate, analyze and display the large amount of required spatial and tabular data. This study intends to carry out regional seismIc damage assessment for the Rajshahi City using geographic Information system. where reflection of ground shaking and the secondary site attnbutes of soil amplificalion and liquefaclion are the salient features The melhod to combine the different hazards is based on a weighted average applORch A soil database from 50 boreholes was used to develop site amplification and soil liquefaction potential maps ufthe study area. Bolh of these site effects are integrated in Geographical Information System platfonn for combined hazard assessment, Three past historical earthquakes were assessed as scenario events namely the 1885 ~engal earthquake, the 1897 Greallndian earthquake and the 1930 Dhubri earthquake, Intensily value obtained for these events is' calibrated against attenuation laws to check the applicability ofthe laws for the study. Finally, the Great Indian Earthquake of 1897, with the attenuation law of McGuire (1978) was chosen as the scenario earthquake. as it shows highest bed lOck PGA (0,06340) PGA value is converted into },ill] values to integrate the effect of site amplification as well as liquefaction and then combined hazard map is proposed for this study area, Only for ground shaking, approximately II percent buildings are ~1;imated to be damaged, Again for ground shaking and liquefaction, approximately 15 percent buildings are estimated to be damaged Some major critical facilities are idelllified that are the most vulnerable as they fall under VIIl-MM]! EMS Intensity hazard zone. Based on soil (natural) frequency some zones are suggested for building height restrictions using thumb rules, According to soil liquefaction analysis particular zones are identified where groL1ndimprovementis suggested,
• v Table of Contents Page No.
List of Tables X List of Figures XII List of Appendiccs IX Acknowledgement IV Abstract V
Chapl"r One; Introduction
1,1 Rackground
1,2 Objectives with Specific AIm and Possible Outcome 3 1.3 Conceptualization 4 1.4 Outline oflhe Methodolob'Y 4 1.5 The Study Area' Rajshahi City Corporation 5
1.5,1 The groMh of the city 5
1.5,2 Demographic Changc 6 1.53 Geology and Soil 7
1.5 4 General Topography, Natural Drainage 9 and Natural Fault
1,5.5 Land use pattern 9
I 5.6 Climate 10 1.6 GIS and Seismic Damage Assessment 10
1.6 1 Understanding GIS II
1.6.2 Tools for Analysis and Modeling 12 1.6,3 Function of GIS in this study 13
1,7 -,Organization of the Study l4 ._.. ~~ 1,8 J .-43a'Sic Assumptions and Limitations 16
Chapter Two; Literature Review , .' 2.1 EarthqtJ~e'FtJlldamentals IS 2.2 Principal types of seismic wav"s 18 2.3 Regional Tectonics 21
2.4 Seisrno-tectonic Setup 22
VI , 2.5 Major Seismic Sources 2.6 Historical Earthquakes Fell in Rajshahi City 27 2.6.1 The Bengal Earthquake 1885 27 2.6.2 The Great Indian Earthquake 1897 27 2.6.3 The Dhubri Earthquake 1930 28
2,7 Seismic Zoning Map :l.S Relationship Bdv>een Sh~ar Wave Vdocity (V,l 'lnd 31 sp r (N) value ., 2.9 Ancnuation Law or P"ak Gwund Acceleration '- 2.10 Soil Amplification 33 2.10.1 Research ElTortson Soil Amplification 33 2.10.2 Analysis Method for Amplification 34 2.11 Sod Liquefaction 37 2.11.1 Causes of Liquefaction 37 2.11.2 Liquefaction Potential Based on N-valucs 38 2.12 Damage Distribution 44 2.12.1 Definition of Damage 44
2.12.2 Fragility Cun'es for Bangladesh: MOUOll" 45 Damage Relationship
Chapter Three: BlUic Data Colledion 3.1 Updated Administrative Boundary ofRCC Area 47 3,2 RCC Buill-UP Areas 47 3.3 Poor Housing Areas 48 3.4 Buildmg Types Based on Construction 49 3.5 Building inventory 50 3.6 Forecasting of Building Types According to EMS 53 3.7 Soil Data (SPT-!I') from Primary & Secondary 54 Sources 3.8 GroUlld Water Data 54
Ch.pter Four: Seillmle Hazard Analysis 4.1 EstimationofBedrockLevelPGA " vn '". 4.2 Site Amplification Analysis 60 4.3 Liquefaction Analysis 68
Chapter Five: Seismic Hazard Integration 5 1 Hazard and Integration 73 5.2 Integration of Site Effects in GIS Environment 73
Chapler Si~; Seismic Damagl."Assessment 6 I Fundamentab of Damage Assessment R7 62 Damage Assessment for BlIiJdings 87 6.2 1 Damage Estimation Based on Analysis I 89 (lv/1Yilo,,) 62.2 Damage ESllmation Based on Analysis 2 90 (AfM!F)
Chapter ~en: Urban Development and Seismic Risk. 7, I Introduction 104 72 Existing Land use Under Risk 104 7.3 Evaluation of RMDP (2004-2024) ",jth Respect to 105 Seismic Risk 7.4 Suggested Zones of Building Height Restrictions 105 7.5 Zones where Ground Improvement is Suggested 106 7,6 Other Recommendations for Risk Mitigation 107
Chapter Eight: Conclusion
8. j Overview of the Research 113 8.2 Recommendations 114 8.3 Scope for Further Research II 5
References 116
VIlI List of Appendices Page No. AppendiI-A Eanhquake Chronology of Bangladesh 12] AppendiI-B Building Inventory Format 126 AppendiI-C European Macro Seismic Scale 127 AppendiI-D Modifled Marcelli Scale offell lntensily 134 AppendiI-E Building Typologies of Rajshahi City 136 AppcndiI-F Borehole Data 13 7
IX List of Tables Page No.
Table 1.1 Urban growth in the Rajshahi Region 7 Table 1.2 Existing Land use ofRajshahi City Corporation area 10 Table 2.1 Great historical earthquakes In and around Bang[adesh 23 Table 2.2 Significant SeJSmlC sources and maximum likely 26 eanhquake magnitude in Bangladesh (Bolt. (987)
Table 2.3 Operational basis earthquake, maximum crcdiblc 26 Earthquakc and depth offocus of earthquakes for different seismic sources (after Ali and Chowdhury, [992) Table 2.4 Magnitude, EMS Intensities and distances of some major 26 historical earthquakcs around Rajshahi City (after Ansary, 2001) Table-2.5 Empirical Relations Correlating SPI N-value and Shear- 29 wave Velocity Table 2.6 Published Attenuation Laws ]0 Table3.l Housing Type Changes Within the RCC area, 198 [- I991 49 Table 3.2 Wall and RoofMateria[s ofRCC Area, 1991 49 Table 3.3 Housing Types of RCC Area According to ReofMaterials, 50 [991 (after Is[am, 2005) Table 3.4 Definition of building typologies III Rajshahi City 51 Corporation Table 3.5 Building distribution pattern according to EMS in Rajshahi 53 City, 2005 Table 3.6 UpaziJlawise record of water level at specified WDB 54 wells, 1982 (GSB, 1991) Table 4.1 Some historical earthquakes with their intensities, 57 epicentral distance and focal depth at Rajshahi City (Sabri, 2001) Table 4.2 Shear Wave Velocities at different locations of Rajshahi 58 City Table 4.3 PGA values ("10 of g) at Rajshahi City bedrock level from 60 different attenuation laws for different scenario event
x Tabk 4.4 Results of Amplification factor and corresponding 64 predominant frequency at different locations of Rajshahi City Table 4.S Liquefaction Potential of different locations of Rajshahi 69 City Table 4.6 Summary of the LiquefactIon Potential Index 70 Table S.I Quantification rules for seismic hazard 78 Table 5.2 Combination of po>sible hazards due to scenario 78 earthquake 1R97 in Rajshahi City Table 6.1 Calculated Motion-Damage Ratio lor this study retrieved 88 from Fragility curve by Arya (2000) Table 6.2 Ward wise damaged bUlldings based on Analysi, 1 89 (MM1os) of Rajshahi City Table 6.3 Ward wise damaged buildings based on Analysis 2 91 (M.'-WF)ofRajshahi City
Xl List of Figures Page No. Figure 1.1 Location of Rajshahi City Corporation with respect to 8 Bangladesh (Banglapedea, 2004) Figure 1.2 The information systems composing a fully integrated 12 goographic information system (after Frost et ai, 1992) Figure 1.3 The mapping process for regional hazard seismic loss 15 estimation through GIS (Map1nfo) Figure 2.1 Physical Clues for Predicting Earthquake (Britannica 20 2003) Figure 2.2 India's northward-drift by last 70 million years (Molnar 21 and Tapponneir, 1975) Figure 2.3 Estimated Slip potential along the Himalaya (Bilham et al.. 22 2001) Figure 2.4 Tectonic map of Bangladesh and adjoining areas 24 (Banglapedea, 2004) Figure 2.5 Distribution of Faults and Lineaments III Bangladesh ' 25 (Banglapedea. 2004) Figure 2.6 lsoseismal map of 1897 Great Indian Earthquake (Sabri, 28 2001) )<'igure2.7 Seismic Zoning Map ofBangJadesh (after BNBC, 1993) 31 Figure 2.8 Updaled Seismic zoning map of Bangladesh (Sharfuddin, 32 2000) Figure 2.9 Schematic reprcsemation of procedure for computing 35 effects of local soil conditions on ground motions (Schanbel et aI., 197\) Figu~ 2.10 One dimensional wave propagation system (Sehanbel et 36 at, 1971) Figure 2.11 Cyclic shear stresses on a soil element during ground 39 shaking (Iwasaki, 1982) Figure 2.12 Procedure for determining maximum shear stress (Seed et 40 al. 1983)
XII Figure 2.13 Range of Values of'd for different soil profiles (Seed et 40 aI., 1983) Figure 2.14 Time history of shear stresses during earthquake (Seed et 42 al,,1983) Figure 2.15 Correlation between field liquefaction behaviour of silty 42 sands under level ground conditions and standard penetration re,istance (Seed et al. 1983) Figure 2.16 Recommended curve for determination of r,' (;\1urthy. 46 1991) Figure 2.17 Vulnerability functions based on peak ground acceleratiun 51 (after Arya, 2000) Figure 3.1 Map Showing wards of Rajshahi City Corporation 49 Figure 3.2 Distribution of building type according to construction 52 year, storeys and noar area Figure 3.3 Map Showing Borehole locations used for this study 55 I,'igure 4.1 Flowchart for earthquake Analysis 56 Figure 4.2 Distance versus PGA values for historical earthquakes at 59 Rajshahi CIty Figure 4.3a Amplification factor and corresponding predominanl 61 frequency Figure 4.3b Amplification factor and corresponding predominant 62 frequency Figure 4.3c Amplification factor and corresponding predominant 63 frequency Figure 4.4 Map Showing Fundamental Frequencies of Rajshahi City 65 Soil Figure 4.5 Map Showing Amplification Factors ofRajshahi City Soil 66 :Figure 4.6 Map Showing Amplification Factor in simplified form for 67 Rajshahi Cily Soil Figure 4.7 Flowchart ofLiquefaetion Analysis 68 Figure 4.8 Map Showing Microzonation based on Liquefaction 71 Potential Index for Rajshahi City
XIII Figure 4.9 Map Showing Regional distribution of liquefied areas of n Rajshahi City Figure 5.1 Flowchart for Combined Seismic Hazard Mapping 74 Figure 5.2 Map showing regional distribution of surface level Peak 75 Ground Acceleration (PGA) in Rajshahi City Figure 5.3 Map showing regional distribution of ground shaking 76 hazard (MMI",,) in Rajshahi City Figure 5Aa Map ShOWlllgunly I J times Amplification only 79 "'igure 5.4b Map showmg only I 8 times Amplification only 80 Figure 5.4e Map showing only 1.3 times Amplification with High 81 Liquefaction Areas Figure 5.4d Map shu",ing only I :> times Amplification with Moderate 82 Liquefaction Areas Figure 5.4c Map showing only I 8 times Amplification with High 83 Liquefaction Areas Figure SAf Map showing only 1.8 times Amplification with Moderate 84 Liquefaction Areas Figure 5.5 Map showing regional distribution of combined SClsmlC 85 Peak Ground Acceleration in Rajshahi City Figure 5.6 Map showing regional distribution of combined seismiC 86 hazard (MMlp) in Rajshahi City Egure 6.1 Flowchart of damage estimation methodology for a given 88 lutensity Figure 6.2a Map showing distribution of damaged EMSA type 92 building based on Analysis I in Rajshahi City Figure 6.2b Map showing distribution of damaged EMSB Itype 93 building based on Analysis I in Rajshahi City Figure 6.2e Map showing distribution of damaged EMSB2 type 94 building based on Analysis I in Rajshahi City Figure 6.2d Map showing distribution of damaged EMSC type 95 building based on Analysis I in Rajshahi City Figure 6.3 Map showing distribution of total damaged building based 96 on Analysis I in Rajshahi City
XIV , Figure 6.4a Map showing distribution of damaged EMSA type 97 building based on Analysis 2 in Rajshahi City Figure 6.4b Map showing distribution of damaged EMSB1 type 98 building based on Analysis 2 in Rajshahi City Figure 6.4c Map showing distribution of damaged EMSB2 type 99
building based 0[\ Analy,;, 2 in Rajshahi City Figure 6.4d Map showing di~tribution of damaged E\1SC type 100 building based on Analysis:2 in Rajshahi elly Figure 6.4e Map showing distribution of damaged EMSF lype building 101 based on Analysis 2 in Rajshahi eny
Figure 6.5 Map showing distribution of total damaged bllJlding based 102
on -'''-nalysi, 2 in Rajshahi City Figure 6.6 Comparison of Building Damage In Rajshahi City 103 Corporation based on Analysis I and 2 Figure 7.1 Existing Land use ofRCC area under the risk of combined 109
seismic hazard (}vfMIF) Figure 7.2 RMDP (2004-2024) proposed land use undcr the risk of 110 combined seismic hazard (MMJr) Figure 7.3 Prohibited Building Height Distributions in Relation to 111 Soil Frequency .Figure 7.4 Suggested Ground Improvement-Required Areas ofRCe 112
xv CHAPTER ONE INTRODUCTION
1.1 Background
Eanhquakes occur when energy stored within the earth, usually in the form of strain in rocks, suddenly releases This energy is tran:.mitted to the surface of the eanh by earthquake waves, Bangladesh is not free from any possibilities of severe earthquake It is already dIvided into three earthquake zones of different intensity. Risk is high in those of urban areas having built environments rather than rural areas Day by day, the urban areas are growing with multistoried buildings, Push and pull factors generate increasing population to the urban areas. Planners have to think furthermore about the consequences. outcome of any disaster in the city in advance If possible damage caused by earthquake can be predicted and disseminated, then the responsible authorities will be careful about preventive measures, disaster preparedness, response and mitigation,
Information on earthquakes in and around Bangladesh is available for the last 250 years The earthquake record suggests that since 1900 mote than 100 moderate to large earthquakes occulTedin Bangladesh, out of which more than 65 events occurred after 1960. This brings to light an increased frequency of earthquakes in the last 30 years. This increase in earthquake activity IS an indication of fresh tectonic activity or propagation of fractures from the adjacent seismic zones (Banglapedia, 2004).
Rajshahi district lies within the zone of seismic activity and suffered somewhat severely from the earthquake of 1897. In the district ofRajshahi the shock was severe, especially on the eastern side, but loss oflife was comparatively small. The damage of property however was great Most of the pucca (Masonry) houses in Rajshahi town as well as in Natore and Noagaon were more or less damaged. Earth fissures occurred throughout the district and the roads were badly cracked in places. Several of the eanh fissures extended for more than half a mile and the width of one was 9 to 10 feet. On the railway the large bridges over the Atrai and Baral were damaged and many of the small bridges and culverts rendered unsafe (Siddiqui, 1976), The earthquake risk at any location depends 011the seismic hazard as well as the vulnerability of its structures The seismic hazard evaluation considers the likelihood of earthquake ofa particular magnitude or intensity affel::tinga site, and the evaluatioll of seismic risk in any city requires proper consideratioll of the strength of likely earthquakes in future, The seismic hazard for Bangladesh has recently been quantified (Sharfuddin, 2001). The seismic vulnerability, on the other hand, depends on the construction practice in the city and is related to quality of building stock (Islam, 2005) For old cilies like Rajshahi. a larger proportion of buJldmgs is very old and consequently vulnerable The local cunstruction practice has alS{) a very strong bearing on the seismic vulnerability since the use uf inherently strong building malerials will result in structures showing better resistance to earthquakes Every damaging earthquake reaffirms the importance of seismic hazard and risk analysis for estimating the consequences of an earthquake Here hazard means a threatening event, or the probability of occurrence of a potentially damaging phenomenon within a given time period and area, And risk means expected losses (such as lives, injury. property damage etc) due to a particular hazard fur a given area and reference period. Based on mathematical calculations, risk is the product of hazard and vulnerability. ,,lJthough some progress in the area of seismic prediction has been made, earthquakes canllot be accurately predicted in time, magnitude or location, Even if an accurate prediction were possible, the earthquake occurrence and consequent damage potential could not be prevented. Seismic hazard and risk cannot be eliminated, but it can be effectively analyzed and possibly reduced by combining the available regional geologic and geographic information with reeenllechnological developments.
A comprehensive regional setsmlc hazard and risk analysis is a fairly standard procedure that requires combining the effects of many factors Each of these factors usually involves the modeling and analysis of both 5patial and tabular data The amount of requisite information can often be overwhelming, even for a small region Recent advances in Geographic Information System (GIS) technology have created new opportunities for managing the large amount of data, for interfaclng with external analytical programs, and for presenting the result in a manner that may be useful for disaster planning, hazard and risk mitigation, and rehabilitation strategy comparison,
2 A geographic information system oan be used to integrate the various steps in regional seismic hazard and risk analysis in a modlilar framework The system is independent of analysis scale and geographic locatio~ allowing analysis at any level and in any area where the necessary information is available. Seismic hazard due to local sitc effects such as soil amplification (Rashid.,2000) and liquefaction can be estimated by combining the a"ailable soil parameter data with the current hazard models or by making use 0[' existing maps showing estimated levels of these collateral hazards Regional structural invelllone" often stored in extcrnal database management systems, are combined with the seismic hazards to produce damage distributions for th.e region analyzed Due to recent improvements in availability and quality of GIS technology. tabular database ,oft"are, as well as computer hardware, a significant amount of current research will be devoted 1lI incorporating GIS technology in seismic damage estimation
1.2 Objectives with specific aims and possible outcome
The goal of the proposed research is to compile available data on Rajshahi City from various sources and use GIS technology to process the data to assess the seismic risk of the Rajshahi city. The following are the spccific objectives of the research • To develop a GIS-based methodology for seismic damage assessment, given the data available for Rajshahi. • To identify zones of liquefaction and/or site amplification by developing seismic microzonation maps for Rajshahi City. • To identify the relation between the pattern of w1Jan development and seismIC risk. • To formulate specific recommendations for Rajshabi City based on the results of risk assessment.
It is expectcd that engineers, planners, emergency service providers, government officials, decision makers and other actors in disaster management will be benefited from this GIS-based seismic risk analysis by predicting potential consequences of seismic activity in a given region.
3 1.3 Conceptualization
To acwmplish the purpose Seismic Damage Assessment, firstly maps showing local site effects such as soil amplification and liquefaction are to be developed and combined for generating seismic hazard map Secondly, this hazard map is to be superimposed and combined with building distributions maps to produce maps visualiling regional damage distnbutions, lastl]. investigating the inf1uence of secondary effect; ;uch as liquefaction over primary eJl'ect has to be studied
1.4 Outline of the Methodology
A seismic damage model for Rajshahi City based on local site effCl,,1;S,such as site amplification, liquefaction etc ••.•111be developed in this research The analysis will also incorporate building inventories to understand building typologies and ground motion-damage (PGA-Oamage) relationships for this purpose,
The following steps will be done as methodolob')'. 1) At first, a G1S-based base map for 30 wards of Rajshahi City Corporation area will be collected and/or developed 2) Soil parameters such as grain siLe analysis (soil type and dlo) and Standard Penetration Test (SPT) data for several sites of Rajshahi City will be collected from different relevant organizations. owners of constructed house owners and for data checking, six bore holes at specific supervised locations will be drilled, 3) Based on the soil data obtained from step 2, seismic microzonation map based on site amplification and/or liquefaction will be developed 4) Then, geological information will be analyzed to assess risk 7.ones and liquefaction potentiality due to geological formation. 5) Bl.lilding inventory of sample areas of Rajshahi City will be collected; this inventory data together with census data will be used to understand building typologies, as risk varies with the types of buildings, For this purpose fragility curves proposed by Arya (2000) will be I.lsed. 6) Finally, microzonation maps, geological information, building inventory and other geographic information will be overlaid to predict locally distributed damage.
4 •
7) Thus seismic damage maps for Rajshahi City will be produced. 8) Different land lise scenarios for sample areas, particularly the recommendations of the Rajshahi Master Plan, would be evaluated against the microzonation maps.
1.5 The Study Area: Rajshahi City Corporation (RCC)
1.5.1 Gro'l'th (Ifthe city
Rajshahi City was simply a district town prior to 1947 that had become a dIVisional headquarters In 1947 Rajshahi town gained municipal status in 1876 during BritIsh reign and finally achieved the status of City Corporation in 1987, Now it is the 41h largest metropolitan city in Bangladesh next to Dhaka., Chittagong and Kltulna Over
the years, it has grov.m as the administrative headquarters of the Rajshahi Division, and flourished as a center of learning, Although agricultural activities have grown substantially in the hinterland, the growth in industrial and commercial activities have been very limited The situation is, however. expected to change due to the introduction of new railway link with the capital across the Jamuna Bridge, Hatikamrul-Bonpara road (an important shortcut corridor to Dhaka) and expected extension of the gas pipeline up to Rajshahi
With gradual increase in the importance of Rajshahi as an urban center, many government establishments and supporting land uses have developed in the city over the years. The original Rajshahi town was on mouza Srirampur, a large part of which is now ",ithin the river Padma Shaheb Bazar, the oldest part and the original commercial hub of the city, still continues with its full vigour. Harogram, on the w~1ern part of the city was chosen as a public office area. With the development of road netMlrk both the areas gradually expanded. Shaheb Bazar towards west and Harograrn towards east gradually fanned a conurbation of mixed use areas of residences, institutions and retail husiness, Important educational institutions, public and private offices are found in and around Shaheb Bazar area. During the 50s Rajshahi University was set up followed by an Engineering College (Now Rajshahi University of Engineering and Technology) in the 60s and later a medical college. -.
5 Rajshahi University served as a great impetus to the growth of Rajshahi City, the Engineering University and Medical College added 10this force
1.5.2 Demographic Change
The Rajshahi regIOn, comprising the greater Rajshahi Di~"trict,incll.ldes the present Rajshahi, Noagaon, Natore and Nawabganj districts, was moderately I.Irbanizedwith Rajshahi City as the primate city uf the region The size and gro\\th of the I.Irban popl.llationirr the region acwrding tu the 1991 and 2001 population censl.Iseshave been presented in Table t.l.
The popl.llatiunuf Rajshahi City (RCC) is 3.83 lakh (BBS, 2002). The comparisiun
shows that the Rajshahi region is around 17% urbanized, which IS less than the current uverall rate uf urbanization in the country. Of all the districts 1.11'theregiun Rajshahi is the must urbanized, around 32%, and this is due .to the locatiun of Rajshahi SMA in the district In fact as the primate city of the region, Rajshahi SMA accuunts for aruund 50% of the total urban pupulation of the region and nearly 90% of the district urban population Naugaun and Natore are the two least umanized districts of the region with around 8% urbanized.
The must striking fact is that the level of urbanization in the region as well as in the district ofRajshahi have remained unchanged in the last decade since 1991 Population Census. This signifies that uman growth in the regiun and in the SMA in particular, have been due, primarily, tu natural growth of the uman pupulatiun. The uther two proximate determinants of urban gro\\1h in Bangladesh, namely, migratiun ITomrural areas and fe-demarcation of the urban buundary have not been significant in Rajshahi as in the case of Dhaka Mega City. The last demarcation of the Rajshahi SMA boundary was during the 1991 Population Census and the boundary remained the same in the 2001 Population Census. The absence of rural migration as a majur growth factor in the ease of Rajshahi SMA signifies absence of its socio-economic pull factors. This is primarily due to lack of economic investments on a significant scale in the area, which has critical implications for its future growth and development. Lack of investment and consequent Jack of economic opportunities in urban Rajshahi, representing mostly the Rajshahi SMA, is also indicated by its
6 declining contribution to the District GOP compared to the rural areas of the district in recent years
Tablt: I.t Urban growth in the Rajshahi Region Component 1991 Population Census 2001 Population Census Districts of Total Urban % Urban Total Urban % 'he Population Population Population Po-pulation Urban Rajshahi (million) (million) (million) (million) Region I ,I i , Rajshahi of I 88 0577 30.70 :226 0741 328 which (0545) (0.646) (0.646) Rajshahi SYlA Naogaon 214 0.170 1.9 2.38 0198 8 1 Natore II387 0.159 ILS I 521 0.124 8.2 Nawabganj ]11 0218 18,6 I419 0.245 112 Rajshahi 6.57 1,124 17 II 7,58 1.308 113 Region Source, RaJshahl Metropolttan Development Plan (lUI.-fDP),2004
\.5.3- Gwlogy and Soil •
Rajshahi City funns a small part of the much larger Ganges and Jamuna River Basin (part of the Bengal basin of tectonic origin), which is primarily, a large flat alluvial basin made up of quaternary sediments having varied thickness ranging from a few hundred meters along the northern limil of the basin to 18 km at the deepest point in the south oflhe country. The physical characteristics of the basin under consideration are complex in that they have been the sites of sedimentary deposition by two of the world's mighty rivers to the braiding and meandering pattern of the recent flood plain further down stream The meandering streams of the Pleistocene surface (made up of cohesive material such as clay) between the Ganges and the Brahmaputra rivers shows numerous cut.-{)fi"andoKbow lakes indicating that the alluvial deposits (mainly fine sand with silt) are less consolidated (OSH, 1990; Khan. 1991),
7 ".". "'OS' "'.
•'" ,,
w•• , " ••..••1 (INDIA)
RAlSHAH!, D!STRICT".~ ------, OJ'''' ", Figure \.1 Location of Rnjshahi City Cmporation with respect to Bangladcsh (Bwtglap~dea, 20(4)
Th~ soil characteristics of th~ area can be described as the geological succession consisting of a series ofinK1"bcdded silt/clay and sandy layers. It is observed from the geological cross section that interbedded lay~rs of vcry loose to loose and loose to mediwn dense non-plastic fine ~andy SILT or silty FINE SAND exist in the area Interbedded layers of very loose to loosc and very sofHo-soft SILT or FINE SAND mixed with trace to little silt and traces of mica may be observed. Interbedded laycrs of mcdium dense SILT and fINE SAND and having granular composition and plasticity characteristics similar to the upper silt and FINE SAND layers then underline these layers.
• 1,5,4 General Topography, Natu'n111Drainage and Natural Fault
The bank of the Padma river from Gopalpur to Charghat (about 20 kIn) is at an elevated place From the court point to Sahapur, it is further elevated and protected by Rajshahi City Flood Protection Embankment, The general ground elevation in this area varies from 17 0 meter to 18 meter PWD But the embankment crest height is around 21 mcter PWD, The nalural ground slope 1Sfrom southwest to northeast (from the Padma riverbank) in the western side of the cily, but southeast to northwest direction (due to the influence oflhe Baral river basin) al the eastern side, at Charghat area, At the north, river Barnai flows from west to east and the natural slope is from west 10 east along the river course But the natural grOi.lndslope to the right bank of Barnai and further south, is from north to south RaJshahi City area landform has taken place by sedimentation process of the Padma and Barnai rivers, Thus some of the areas in between these rivers. the land is low and! or there exists Beels like Duari, Tikure Khal, Satbaria Khal, Latakhali Khal, Barajal Khal, and Hoja Khal etc, The Sib- Barnai river course may be considered as the major natural fault in the area, coming from the nonh (Niarnatpur Upazila) to south and taken to Naldanga Railway bridge in Natore. There is a fault across Hoja Khal on the north-east of Rajshahi SMA. There are other minor faults and lineaments in the area along the small rivers and khals All these fall within the rural-agricultural part of the Rajshahi SMA.
1.5.5 Laud use Palteru
As an urban center the major land ofRCC area falls under residential use followed by agricultural use, vacanl land, water body, education and research usc. Residential use covering about 33% of the urban space is the highest land usc (Table 1.2). Water bodies like, river, pond, ditch etc encompass 10.8%. About 19"10land is still being used for agriculture purpose, while about 11% land ( 1316acres) is lying vacant, Road infrastructure covers about 5.6% of the RCC area. Industry and storage together comprise only 0.8%, while buSiness and mercantile use constitute 2% of the total RCC area, felIresenting the low profile of economic condition of the city.
• 9 Table: 1.2 Existing Land use ofRajshahi City Corporation area Sl.no, Land use Area in Aere Area in Hectare % 1 Residential! Ilomestead 3972.58 1608.33 33.46 2 A rieulture 2224.23 900.50 18.74 3 Education and Research , 1246.43 504.62 10.50 4 Business and Mercantile 235.40 95.30 1.98 5 Publie Administration 52.43 21.22 0.44 6 Inslihltion 21.18 8,98 0,19 '7 Mixed u.~c 26.35 10.67 0,22 , 8 Induslrial and Stora e 96.59 39.11 0.81 9 iOcnsacc 130.28 52.75 1.10 10 I Asscmblv 43,65 17.67 0.37 11 Securitvl Defen~e 293.24 96.86 2.02 12 Public ulilities, communication 1118.76 48.08 1.00 and Transporl 13 Road 667.45 270.22 5.62 14 Railway 39.83 16.13 0.34 15 Va~antland 1316,79 533.11 11.09 16 Watcr body 1279.74 518.11 10,78 17 Char land 158.91 64.34 1.34 Total 11870,84 4806.00 100 Source: RMDP, 2004
1.5.6 Climate
Rajshahi is in a sub-tropical monsoon climate region. Temperature is low in January and varies between 8.Roe 10 25.9"C. From February the temperarure is found 10 incrcas~ and continue to rise up 10 June and lh~r~artcr dcdin~s slightly \;~cry month from Jul} to August. Fmm September the lemperature dcclines rapidly up to Janllill")'_ The people ofRajshahi generally feel the heal-wave during April to May. In 1995, the temperature rose up to 43,3°C in May, the highest in seven years record and fell at record levc14.7°C in January in the same year. 'The mean relative hwnidity is found 10 be low in March (60.2%) and high in August-September (88.4%). High wind speed is observed during April to June, most of the nor' weSler occur during this period. The average of seven years monthly rainfall data shows that mean annual rainfall is \,624.67 mm, which is lower than the national mean of 2,320 rom. About 77 percent
rainfall OCClilll during June-September and the rest 23 percent in the other eight months. Rainfall is very low in ~mber (3.14 rom) and high in July and September, 355.61 rom and 358.43 nun, respectively.
10 1.6 GIS and Seismic Damage Assessment
1.6.1 Understanding GIS
Geographic lnformation System (GIS) is defined as an information system that is used to input, store, retrieve, manipulate, analyze and output geographically referenced data or goo-spatial data, in order Ie SUpjmrt decision making for p\annmg and management of land usc, natural resources, environment. transportation. urban facilities, and other administrative records
There are many definitions for a GIS and there seems to be confusion as to what are the necessary components and capabilities of a true GIS, The most universal definition in the literatl.lrefor a GIS is given by the Federal Interagency Coordinating Committee as "A system of computer hardware, softv.iare,and procedures designed to support the capture, management, manipulatIOn. analysis, modeling and display of spatially referenced data for solving complex planning and management problems" (Islam, 2005). Figu", 1.2 is adapted from Frost, et al. (1992) and shows how different information systems work together of function as a fully - interacted GIS. Modern GIS technology has evolved from thematic cartography due of the combination of increased computational capabilities, refined analytical techniques, and a renewed interest in environmental and/or social responsibility Throughout this evolution the primary goal has been to take raw data and transform it, through overlays and other analytical operations, into new information that can support the decision making process (Parent and Church, 1987),
1.6.2 Tools for Analysis lind Modeling
One of the most important features of a geographic infonnation system is the manipulation and analysis of both spatial (graphic) and tabular (non-graphic) data. The procedures for data analysis typically found in most GIS programs include: • Map overlay procedures, including arithmetic, weighted average, comparison, and correlation functions. • Spatial connectivity procedures, including proximity functions, optimum route selection and network analysis.
Il • Spatial neighborhood statistics, such as slope, aspect ratio, profile and clustering • Measurements of line and arc lengths, of point-to-poim distances, of polygon perimeters, areas and volumes. • Statistical analysis, including histograms or frequency counts, regressions, correlations and cross-tabulation • Report generation. including maps. charts, graph" tables and other user- defined information
Automated M", Database Mapping ------Informatwn Management Systems System System , , , •, Spalla! Fully Integrated Non-Spahal Modeling GeographIc Modehng Systems Information System Systems , , , , , , , , , , , , , AnalystS and , L _ Modeling ------~ Systems
Figure 1.2 The inforrnatioll systems composing a fully integrated GIS (after Frost et a\., 1992)
Depending on the level of sophistication of a GIS, numerous application-specific analysis functions may exisl. These inclllde procedures such as Kriging of geotechnical data, air pollution dispersion, ground water flow, a highway traffic routing. Most systems include some sort of built-in programming capability usually in the fonn of a software-specific macro language. This allows the user to develop a set of functions or analysis procedures that can be stored in a user-defined library. Often, the GIS macro language is Vel)' simplified and doesn't have to handle very high-level. computational features such as recllrsioll, numerous simulations, subscripted
12 variables, and subroutines. For this reason, most GfS programs have the ability to communicate with external analysis and modeling programs. A system can typically output data in various formats to be used in various external programs such as spreadsheets, word processing, graphics, and other user-specified executable programs. The results of an external analysis can then be used by GIS as both graphic and non-graphic data for further manipulation and analysis, or lor final report and map generation.
Recently, the idea of using knowledge based engineering techniques in a GIS environment has emerged This requires the coupling of GIS software with an expert system, a computer program that performs an analysis of a given situation and determines an answer, or predicted outcome based on known information and rules. Application sucb as site selection of critical facilities, resource allocation studies, and retrofit of bridges and other structures has been shown to operate very effectively in the GIS~expert system analysis environment Westen ct. al (2002) describes application of GIS tor earthquake hazard and risk assessment for Kathmandu, Nepal Yal~iner (2002) introduces Urban Information Systems for Earthquake Resistant CIties for Pendik, IstanbuL Several other studies in this area are currently in progress. including many applications in the social sciences.
1.6.3 Function of GIS in this 5tudy
The regional earthquake hazard analysis requires a map of the region that identifies the potential seismic sources. this procedure typically requires several geologic and geographic maps of the region. The bedrock motion in the region resulting from the seismic event must first be determined. This is orren done by applying one of the attenuation functions within the GIS, or by linking the function as an external executable program. The GIS-based procedure fur estimating regional bedrock motion is straight-forward. Quantifying and integrating the seismic hazard due to local site effects (soil amplification and liquefaction) are the main areas of development presented in this dissertation. The procedure involves developing models for each of the effects, assembling the necessary geologic and geographic maps and databases, applying the models either within the GIS or as linked external programs, and then • overlaying and combining the resulting hazard maps.
13 ..~- The result obtained in the analysis is a regional damage distribution for study area Damage foreeasting typically requires a detailed and accurate structural inventory for the region, quantification of the regional seismic hazard, and ground motion-damage relationship for cach facility type. The spatial database structure of a GIS environment is ideal for this procedure. Structural inventory infonnation can be stored in tables within the GIS database of in a table externally linked database management program, The general procedure involves combining maps of seismic hazard with maps of building distribution according to to set mation-damage relationships, producing maps of regional damage distribution. The resulting maps are useful for purpose such a<; resollrce allocation and rehabilitation prioritisation.
Recent seismic events have demonstrated that the monetary loss from earthquake damage to major metropolitan areas can run imo the billions of dollars ( Kiremidjian, 1992). World-wide statistics of annual fatalities due to earthquakes are alarming. As with the damage forecasting, the GIS cnvironment is ideal for estimating distributions, The procedure typically involves combining maps of damage distribution with maps and database tables of regional distribution of buildings The resulting mierozone maps of regional damage distribution helps to illustrate areas requiring further study for possible earthqllake risk mitigation strategies. In this particular smdy, "Maplnfo Professional V 7,0" software was used. The mapplllg process for regional damage estimation through GIS is shown in I<'igure1.3.
1.7 Organization of The Study
Chapter One gives a description of thc methodology, study area and geographic information system (GIS). Spatial data structures and the functional elements of an integrated GIS are discussed. Analysis and Modelling capabilities additionally application of GIS Technology to Regional Seismic Hazard and Risk Analysis is also discussed The remaining parts of the thesis consist of seven chapters,
Chapter Two reviews background information (literature review) of the seismic environment prevailing in Bangladesh as a part of the evaluation of seismic hazard. Important tectonic features of Bangladesh, seismic zoning maps, earthquake hazard,
14 site amplifIcation, soilliquefaclion'll!l: described. Descriptions of the various types of damage and the motion-damage relationships are also described here.
Scenario event & BedrockMollon Surface Geology FaultLocallon
Ground Water Surface Elevation El~"at"m
Soil Amplification Liquefaction hazard Heuristic Modeling M"P M.,
Combined Seismic I B";lo'g In""",,, HIl.CMdMap M,p I I
Damage Distribution Comparison M'P
Seismic Damage Esllmalion
Figure 1.3 The mapping process for regional hazard seismic loss estimation through GIS (Maplnfo).
15 Chapter Three deals vvith the collection of basic data and their collection methodology. The data includes coHc<:tionof borehole data from different sources, statistical data ofBBS such as population, household, building and wall materials and sample building inventory data of one ward of Rajshahi City Corporation.
Chapter Four addresses the seIsmIC hazards due to local site effects Soil amplificalion and liquefaction are the local site effect.~considered in lhis study.
Chaptt"r Fivt" contains GIS-based methodologies for cornbwing slte altributes through a weighted average approach.
Chapter Six deals with the damage estimation of buildings both for combined hazards and only for earthquake ground motion. Results and seismic microzonation maps for various stages ofthe analysis process are presented.
Chapter Seven relates urban development and seismic risk to assess existing land use ofRCC, proposed land use of R.M.DPIRCCarea, suggests restricted height zoning and required ground improvement areas
Lastly, conclusions and scope for fi,turc works arc given in Chapter .Eight.
1.8 Basic Assumptions and Limitations
1 his study is done assummg all dwelling units as residential housing units. Residential housing units are building structures and classed as European i\1acro Scale [Appendi..: C] types (Table 3.4).
It has been assumed that there is no EMSD type building in Rajshahi City and EMSA type structures are located only in the periphery area. Also, the core wards in the CSD are occupied by EMSB, EMSC and rarely EMSF type structures. For building forecast, EMSA type buildings were replaced by EMSBl type in the core wards of the CBD.
16 A building inventory within ward 12 was made for 100 building units selected randomly, which were found homogeneously distributed on topo map. From this inventory, building structure was classified according to and in relation to EMS
It has been assumed that Rajshahi is a plain land with equal elevation from the sea level. buildings are homogenously distributed within the boundary of each ward and damages occur by area-ratio method.
The dwelling unit for this study was totecasted from Working Paper on Housing of Preparation of Structure Plan, Master Plan and Detailed Area Development Plan for Rajshahi Metropolitan City. At 2002, the number of dwelling units was 74,000 (with growth rate of 1 88) and at 2008, the number will be 81,222 (with growth rate 1.96) Therefore the forecasted number of dwelling units at 2004 is assumed [74,OOO+{(81,222-74,000)/6)*2}] or, 76,407. This value is distributed according to ward wise population ratio and then getting round off values, the adjusted number of dwelling units stand at 76)73. For this research this value is also distributed to different building types under European Macro Seale (EMS).
17 CHAPTER TWO LITERATURE REVIEW
2.1 EarthquakeFuudamentals
Earthquake is the trembling or shaklng movement of the earth's surface MOSl earthquakes are minor tremors, while larger earthquakes usually begin with slight tremors, rapidly take the lorm of one or more violent shocks, and end in vibrations of gradually diminishing force called aftershocks Earthquake is a form of energy of wave motion, which originates in a limited region and then spreads OUI in all directions from the source of disturbance It usually lasts for a few seconds to a miltute The point within the earth where earthquake waves originate is called the focus, .trom where the vibratiolts spread in all directions. They reach the surface first at the point immediately above the focus and this point is called the epieentre It is at the epicentre where the shock of the earthquake is first experienced. On the basis of the depth of focus, an earthquake may be termed as shallow focus (0-70 km), ilttermediate focus (70-300 km), and deep focus (>300 km). The most common measure of earthquake size is the Richter's magnitude. The Richter scale uses the maximum surface wave amplitude ilt the seismogram and the difference in the arrival times of primary and secondary waves for determining magnitude The magnitude is related to roughly logarithm of energy Earthquakes originate due to various reasons, which fall into two major categories viz non-tectonic and tectonic. The origin of tectonic earthquakes is explained with the help of 'elastic rebound theory'. Earthquakes are distributed unevenly olllhe globe. However, it has been observed that most of the destructive earthquakes originate within two well-defined zones or belts namely, 'the circum-Pacific belt' and 'the Mediterranean-Himalayan seismic belt' (Banglapedea, 2004).
2.2 Principal Types of Seismic Waves
Seismic waves generated by an earthquake source are commonly classified into three main types. The first two, the P and S waves.,are propagated within the Earth, while the third, consisting of Love and Rayleigh waves, is propagated a10Jlgits surface. The existen~ of these types of seismic waves was predicted during the 19th ~ntury, and modern investigators have found that there is a close correspondence between such theoretical calculations and seismographic measurements of the waves. The P (or primary) waves travel through the body of the Earth at the highest speeds, They are longitudinal waves that can be transmitted by ooth solid and liquid materials in the Earth's interior. With P waves, the particles of the medium vibrate in a manner similar to sound waves. and the transmitting rocks are alternately compressed and expanded, The other type of body wave, the S (or secondary) v,'ave, tra,els only through solid material within the Earth. With S waves, the particle motion is transverse to the direction of lra,el and involves the shearing of the transmitting rock Because of their greater speed, the P waves are the first to reach any point on the Earth's surface The tirst P-wave onset starts from the spot where an earthquake originates Love and Rayleigh waves are guided by the free surface of the Earth. They follow along after the P and S waves have passed through the body of the planet. Both Love and Rayleigh waves involve horizontal particle motion, but only the latter type has vertical ground displacements As Love and Rayleigh waves travel, they disperse into long wave trains, and at substantial distances from the sour~-ethey cause much of the shaking fel!during earthquakes.
At all distances from the focus, the mechanical properties of the rocks, such as incompressibility, rigidity and density, playa role in the speed with which the waves travel and the shape and duration of the wave trains. The layering of the rocks and the physical properties of surface soil also affect these characteristics of the waves. In most cases, elastic behaviour occurs in earthquakes, but the shaking of surface soils from the incident seismic waves sometimes resolts in nonelastic behaviour, including slumping (i e., the downward and outward movement of unconsolidated materia\) and the liquefaction of sandy soil. When a seismic wave encounters an interface or boundary that separates rocks of different elastic properties, it undergoes reflection and refraction. There is a special complication ira conversion between the wave types occurs at such a boundary: either an incident P or S wave can yield in general reflected P and S waves and refracted P and S waves, Boundaries between structural layers also give rise to diffracted and SClltteredwaves, These additional waves are in
19 part responsible for the complications observed in ground motion during earthquakes. Modem researcb is concerned with computing, from the theory of waves in complex structures, synthetic records of ground motion that are realistic in comparison with observed ground shaking. The frequency range of seismic wa~es is large. Seismic waves may have frequencies from as high as the audible range (greater than 20 hertz lHz]) to as low as the free o~ci1lation~ of the whole Earth, with gravest period bcing 54 minl.!tes (I.e., the Earth vibrates In various mode,;, amlthc mode with the lo •••..eM pitch takes 54 minutes to complete a single ~ihration, .~ee helo" Long-period oscillations of the globe). Attenuation of the waves in rock imposes high-frequency hmlts, and in small to moderate earthquakes measur",d surface waves have frequencies extending from about one \(I 0.005 Hz. Th", amplitude range of seismic "aves is also great in most earthquakes. The displacements of the ground ext",nd fmm 10-]0 to 10--1 metres. In the greatest earthquakes, the ground amplitude of the predominant P waves may be several centim",tres at periods of Iwo 10 five seconds. Very close to the seismic sources of great earthquakes, investigators have measured large wave amplimdes with accelerations 10 the ground exceeding that of gravity at high frequencies and ground displacements of one metre at low frequencies .
..- ," '. ,, ". --.
Figure 2.1 Physical Clues for Earthquake Prediction (Britannica, 2003)
20 2.3 Regional Tectonics of Indian Sub-continent
Plate tectonics provide a physically simple mechanism for large-scale horizontal motions of separate portions of the earth's crust. One of the central concepts of plate tectonics is thai a small number of large plates of high strength lithosphere, move ngidly with respect to one another at rates of I 10 20 em/lear over the low-strength asthenosphere, ;\.cc0rding to Ivlolnar and Tapponnicr (1975). for the past 40 million years Ihe Indian >ubeominent ha, been pushing northward agalnst Ihe Eura.lian plate at a rate of 5 em/year, giving rise to the ,everest earthquakes and m05t diver,e land lorms kno",n, Figure 2.2 sho",s India's northward drift over the last 70 milllon years
• .~---.-.-' j ~
! •
,~, ./ 71 MilliIm Years 1\;:. .~
• • Figure 2.2 India's northward-drift by last 70 million years (Molnar and Tapponne!r, 1975)
21 Recently, Billham eL al (2001) has pointed out that there is high possibility that a huge earthquake will o~~ur around Ihe Himalayan region ba~ed on Ihe difference between energy accumulations in this region, So there is a sei~mi~ gap that is accumulating stress, and that a huge earthquake may occur someday when the Slress will be relca<;ed. Figure 2.3 shows the estimated slip potential along the Himalaya (afler Hilham eI aL 2001).
~;~n501km 1,I'J !I , 0 ==== "
,'" , "'""'..."0-' \~.', ~'.'r-o.J_[i.Ol ...•• 'H.i91 ••• I;• ,c."I"", , '"',, • "."." • • ;c,-, '";,, , •••••• , " . • " . . , • ••" .,-.-,' •• • • • • iI!i?~'\. , " ". f
Figure 2.3 Estimated Slip pOlential along the Himalaya (after Bilham eI a1. 2001)
2.4 Sei$mo-tectonic Setup
The generalized Tectonic map of Bangladesh and adjoining areas are given in Figure 2.4. The junction bety,'een the platform and the foredeep nmning southwest from Mymensingh to Calcutta (the Hinge line) is considered to be a zoae of weakness. However, no association of the hinge with earthquakes has so far been established. The Foredeep is termiuallJd in the northeast by a major fault. the Dauki fault at the southern margin of the Shillong Plateau. Some major earthquakes can be related to • this fault. There arc numerous faults particularly in the eastern part oflhe folded flank of the Foredeep. Here again there is 110association WIth any major earthquake 11.1051 recorded earthquakes had ep'eenter further east in Burma
The eastern margin of the Indian plate is supposed to run through Myanmar, not far from the Bangladesh border. and northeast Assam (Arunachal Pradesh) is considered
10 be a comer orlhe northern and ea,tem margins oflhe plate 1 he j limalavan arc can
he regarded a, one of the mo,l intensely aCI;,e seismiC region.1 of the "orld In northeast India, the Shillong plateau and adjacent synta~t' between the two arcuate structures is one oflhe most ull>lablc regions '0 the Alpine-Himalayan belt and faced three major earthquakes of magnitude greater than 8 0 within the lasr two hundred year, (1897. 1934 and 1(50) At present, the southernmost rhrusting in the Himalaya- Shillong Plateau region could be taking place along the southern fringe of the plateau coincidiflg with the Dauki fault Currently. it is believed lhat the Shilloflg plateau ha, a thrust plane beneath it and 1Sundergoing southward thru,ting against a concept of \ertical tectonism along the Dauki fault. The Shillong plateau and ilS adjoining region including the northeastern part of Bangladesh have high ,eismic status The sei,mic activity along the Dauki-Haflong fault zone is comparatively lower and a seIsmic gap has been postulated alon!, this fault zone The major earthquakes that ha"e atTected Bangladesh since the middle of the last cenlury is prcsented in Table 2. t.
Tahlt 2.1 Greal hi,torical earthquakes ill and ,IHlllnd Bangladesh
I Date Name E ieentre M, nitude{Mt 10-01-1869 Cachar Earthquake I Jantla Hill, Assam 7.5 14-07-1885 Bengal Earthquake Sirajgonj, Bangladesh 7.0 12_06_1897 Great Ifldian Earthquakc Shillong Plaleau 8.7* 18-07-1918 I SrimangaJ Earthquake SrimangaJ, Sylhet 7.6 02-07-1930 I Dhubri Earthquake Dhubri, Assam 7.1 \5-0\-\934 Bi\:1ar-N al Earthrrnake Bihar, india gJ Recently modified as 8, I(M) (Ambraseys, 2000)
2,5 Major Seismic Sources
The seismic hazard is typically determined using a combination of seismological, morphological, geological and geotechnical investigations, combined with the history of earthquake in the region. Bolt (1987) analyzed diffe,eut seismic sources in and
23 • 10. , ,
t'igure 2.4 Twonic map of Bangladesh find adjoining areas (Banglllpcdea, 20(4)
Bround Bangladesh and arrived III conclusions relaled to maximum likely earthquake magnitude (Bolt. 1987). Boll identified the follO\\1ng fouf major sources: (i) Assam fault zone (ii) Tripura fwlt zone (iii) Sub- Dlluki fault zone (iv) Bogntfaultzone ,
Figure 2.5 sho'ws diSlnbution of faults and lineaments capable of producing damaging earthquakes. The magnitudes of earthquake suggt:sled by Bull (Table 2.2) are th~mmdmum magnitude generated in these blocks as rewrded in the historical seismIC catalogue. The hi~l()rical selsmlC catalogue of the regIOns covers approximately 250 years of (starting 17(2) earthquake data. for example, the Assam a
'_cgc~ds .,. ~.-"",,- .""""'" . sw.,,,",,,, •.~". ~""""" ~~ F",," '''''''''''''_00~~" -.---" -I eau~ S ,. I i I •I",,-•! •, ••• • •• 00 ••• •• Figure 2.5 Distribution of faults and lineaments in Bangladesh (Banglapedea, 2004) 25 , nJ Tripura fault zone, contain significant faults capable of producing magnitude 8.6 and 8.0 earthquakes respectively in future. Similarly maximum magnitude of 7,5 In Sub- Dauk; fault zone and Bogra fault zones are not unlikely events Table 2.2 Significant seismic sources and maximum likely earthquake magnitude in Bangladesh (Bolt. 1(87) I Location : i\Iuirnum like!)' earthquake magniUidc A. As,am fault zone • 80 8 Tripura /lwlr zone 7.0 C. Sub-Dauki fallIt 70ne "'I ,.' D. Bo a fault zone 7.0 After a thorough revic" of available data. All and Choudhury (] 992) recommended magnitudes of Operational Basis Earthquake> and ~laximum Credible Earthquakes as shown in Tabk. 2.3 Table 2.3 Operational Basis Earthquake. Maximum Credible Earthquake and depth of focus of earthquake, for dill'ercm sei,mic sources (Ali and Chowdhury. 1992) Location Operational basis Maximum crtdible Depth of I earth uakes earthquakes focus (km) I 1)-10 Assam falll\ zolle g 0 (Richte, Scale) Tripura faull zOlle 7.0 "80 0-10 Sub-Dauki fault zonc 73 7.5 0-70 ROQrafault zone 70 7.5 0-70 Reliable historical data for seismic activity affecting Indian subcontinent is available only for the last 450 years. Recently developed earthquake catalogue for Bangladesh and surrounding area (Sharfuddin, 2001) showed the most prominent historical earthquakes affecting Rajshahi City was listed in Table 2.4 Table 2.4 Magnitude, EMS Intensities and distances of some major historical earthquakes around Rajshahi City (after Sabri, 2001) Name of Earthquake Magllitude Illtensity (EMS) Distance at Rajshahi (km) 1885 Bengal 7.0 V 156 1897 Great Indian Earthquake 8.7 VIII 228 1930 Dhubri Earthquake 7.1 VI 207 26 2.6. Historical Eartbquakes felt in Rajsbabi City 2.6.1 The Bengal Earthqllake of 1885 There is no seismographic record a\ailabl~ f(,r lh~ B~ngal ~arthquake of Igg5. Only the fell reports and observed dam"g~ lo bUlI vcnts wcr~ d~scrib~d in (hc report 011 th~ Bengal earLh(juak~DV\fiddlem".' (lRRS) According (0 thc report. this earthqUilke \\as fdt with violen~e thmughOlll lhe Bengal province, 'lhe extent of felt are~s exlemJeJ westward into Chota Nagpur and Hihar, northwards into Shikim and Bhutan. and ea~l\\llnl inlo Assam. Manipur and former Burma, The area over which it w;u>sen~ibly felt may be roughly 6.00.000 sq, km. The area induJes Daltongunge (in Palamow). Durbhanga (in Bihar). Dmjeeling, Sibsagar. Manipur and Chittagong. The area co~ered h'b a radius of 490 km and the magnitude was 7.0 recalculating the magn;lud~ oflhe earthquake (Ms) using Ambrasey's formula by Bolt (1987). 2.6.2 The Great Indian Earthquake of 1897 Oldham (1899) as the head of the Geological Survey of India, direc~d and personally investigated the Great Indian e~hquake of IR97. He defincd a scale of intensity of six dcgrecs. The area over ",hich the shock was felt amounted to not less than 31,20,000 sq. km. This docs not include the detached areas near Alunedabad or any part oflhe Bay of Bengal, nor the large area in TIbet and Western China, OH,r which the shock was certainly sensible. If the area included in these tracts are taken into consideration, the total area over which the shock w;u> felt amnunt~ to 45,50,000 sq. km., while the area over which known serious damage (0 masonry buildings occurred was not less than 3,77,000 sq. Ian. Figure 2.6 shows the lsoscismal Map of this earthquake (Oldham, 1&99). 27 2.63 Tbe Dbubri F.arlbqUllke of 1930 The earthquake originated near the northwestern end of the Gam hills and the adjoining valley of the Hrahmaputra River, a short distance 10 the south of Dhubri to'Wn The dl~turbeu area of the earthquake wa,; ah()ul 3,35,000 sq. km. This earthqllllke had di~a';trow; results in northern Bengal anu in We~lern Assam, and was felt wry distinctly owr a '\lue area. n:tending from Dihrugarh and M'lllipur in the east. to Chittugong Figure 3.6 IsoseismaJ map of 1897 Great Indian earthquake (after Sabri, 2(01) 28 2.7 Seismic Zoning Maps In the Bangladesh Nalional Building Code (BNBC) published in 1993, a new seismie zoning map for Bangladesh has been presented. The pattern of ground surface acceleration contours having 200 }e(lT relLJJ1lperiod forms the basis of this seismic zoning map. Thc 1993 lINBC zoning map is shown in Figure 2.7. ,j , .." ! , .." I~ ' .." 'OT" •••• " ---_. Figure 3.7 Seismic Zoning Map of BlIngbidesb (after BNBC, 1993) 29 Bangladesh National Building Code (RNBC, (993) placed Rajshahi in Seismi~ zon~ 1. The seismic :wnes in the code are nol based on the analyticalasscssment of seismic hazard and are mainI} based on the location of historical data. An updated seismic map sho"Ml in Figure 2.8 based on analytical study was recently developed (Sharfuddin, 2001). This zoning was based on consistent ground motion criterion such as equal peak ground acceleration levels. Based on th~ philosophy behind the seismic zoning and experience from recent eanhquakes, it call r"asonably be a%umed that a major earthquake event in Rajshahi region is capabl<' of higher damage than that assumed in the existing zoning map (BNBC 1993) . • ,;} ;.-,,,,,-,,' ,,'- Q 5~ 100"" NEPAL ~-.~'~ Q ------7~ ,W'm - '. - INUlft '". '...._- ~- -.--,- " So•••••;.:Zone. :~ Zon.3-0.1~ " ' ~, Zone2=O.I~ - -' ,,- z.",., I = o.075~ Figure 2.8 Updated Seismic zoning IIlllPof Bangladesh (after SharfuddiIL, 2(01) 30 2.8 Relationship Between Shear Wave Velocity (Vo) and SPT (N) value There are several empirical relations correlating the SPT-N value and shear-wave velocity (V,) as shown in Table 2.5. One of the convenient ways to identify subsurface soil profiles is the use of penetration tests. The ~1andardpenetration test (SPI) has been widely used to investigate deposits in this regard, The empirical relations presented here will be used to convert SPI value into shear-wave velocity which is needed as one of the input paramcters for the program SHAKE, Table 2.5 Empirical Relations Correlating SPI N-value and Shear-wave Velocity (after Islam, 2005). Researchers Source Equation Tmaiand Yoshimura(1970) V,-76 Ohba and Toriumi (1970) V,- 84JiiO' Ohta and Goto (l F, = I.O(H); .h = 100 (clay) =13(P) = 1.09 (f. sand) TC4 (1993) = 1,07 (m.sand) = 1,14(c. sand) = 1.15(g. sand) = 1.45 (gravel) Imai (1977) V, ,N' , A= 102 b = 0,29 (Relay) = 81 =0.33 (H.sand) = 114 = 0.29 (p,clay) =97 =0.32 (P,sand) Okamoto et al. (1989) V, - 125 (p.saod) T_rn ~d Yamazaki V, 105.8 (2002) V. : Shear wave velocity (m/s) ; N. Corrected SPT blow count (N-value), D: Depth (m); H: Holocene; P: Pleistocene f., Fine; m: Medium; e: Coarse; g: Gravelly 31 2,9 Attenuation Law or Peak Ground Acceleration The quantitative assessment of seismic hazard at any particular site within a region requires an attenuation law for thc Peak Ground Acceleration (PGA) The maximum ground motion to be expected in the site constitutes a cNcial problem in earthquake engJOeenng Table 2.6 Published Attenuation Laws (After Islam, 2005) Author Law Duggal (1989) }=227xI0 (d+JOY ' .. ,McGuire (1978) }=O.OJ06e , , where 5=0 for rock and 5=1 for alluvium Katayama (1974) JogyZ 308 ! 637Jog(r+JO)+0.4J 1M , Sadigb, et al (1986) Lny -1406+11M 2,051 (R+l.35Je ) whereM>65 , Joyner and 800re (1988) logy 043 + 0.23 (M 6) log(! +h) o OOZ7(? + h1 }I,'l;for rock Ambraseys (1995) logy= 143+0.245Ms-0.OOlr-0.786Jogr I r=(,i+Z,7l)"'2 \ 800re et aJ (1997) lny - - 2424 + 0 527(M-f» 0778lnr 0.371 In (V, I 1 396) where,r =(r&1 +5.572)1'2 r&=epicentral distance in km, V, - averalt:e shear wavc velocitv of surface 30 m where, y =PGA, M = surface magnitude; d = epicentral distance, r = hypocentral distance; h = fOCllIdepth For Bangladesh, as in many other parts of the world, no PGA attenuation law has been developed, due mainly to the shortage of strong motion data. However, in order to assess the seismic hazard in this region, we have to adopt an attenuation law from the literature. A great amount of PGA attenuation relationships, predicting strong ground motions in terms of magnitudes, distance, site geology, and in some cases other factors, using various models and data sets are established for different parts of the world. Reviews of these laws arc presented in Campbell (1997). Some of the published llttenualion laws are presented in Table 2.6. 32 2.10 Soil Amplification 2.10.1 Research Efforts on Soil Amplification The effect of local so;1 conditions on the amplitude and frequency content of earthquake motions has been the subject of considerable interest and research ll\ recent years, Physically the problem ;s to predict the characteristics of the seismic motions that can be expected at Ihc free surface (or at any depth) of a soil stratum Mathematically the problem is one of wave propagation in a continuous medium. If the medium is linearly clastic and the geometry is relatively simple, analytical solutions can be obtained for any kind of ",aves In practice, since the wave content of a potential earthquake is hard to predict, solutions are often limited to the simple case of shear wave propagating vertically 2.10.2 Analysis Method for Soil Amplification Several methods for evaluating the effel.1:of local soil conditions on ground response during earthquakes are presently available Most of these methods are based on the assumption that the main responses in a soil deposit are caused by the upward propagation of shear waves from the underlying rock formation. Analytical procedures based on this concept incorporating non-linear soil behaviour, have been shown to give results in good agreement with field observations in a number of cases. Accordingly they are finding increasing use in earthquake engineeriog for predicting responses within soil deposits and the characteristics of ground surface motions The analytical procedure generally involves the follovvingsteps: • Determmallon of Ihe characterislics of the molions likely 10develop in lhe rock farmalioll underlying the site. and selection of all accelerogram wilh lhese characteristics for use in lhe analysis. The maximum acceleration, predominant period, aod effective duration are the most important parameters of an earthquake motion, Empirical relatiooships between these parameters and the distance from the causative fault to the site have been established for different magnitude earthquakes. A design motion with the desired cltarncteristics can be selected from .the database of strong motion accelerograrns. 33 • De/ermmation of the dynamic properties of/he soil depo,\'i/' Average relationships J;,i;,tweenthe dynamic shear moduli and damping ratios of soils, as functions of shear strain and static properties, have been established for various soil types. Thus a relatively simplc. testing program to obtain the static properties for use in these relationships will often serve to establish the dynamic properties with a sufficient deb'Tee of accuracy. HoweYer, more elaborate dynamic testing proCedlIn'S are required for special probkms and ror case, involving soil types for which empirical relationships with static properties ha~e not been <:stablishcd, • Computati"n rif the response of the wi! deI'",;t /0 the base rock mvtivns. A one dimensional method of analysis can be used If the soil structure is cssentially horizontaL Programs developed for performing this anal}sis are in general based on either the solution to the "'ave equation or on a lumped ma ••s simulation. Morc irregular soil deposil;> may require a finite element analysis. Featares of the Program The program can compute the responses for a design motion given anywhere in the system, Thus accelerograrns obtained from instruments on soil deposits can be used to generate ne'" rock motions which in turn can be used as design motion for other soil deposits as shoy,n in Figure 2.9 (Schnablc ct OIL, 1972), The program also incorporates non-linear soil behaviour, the effect of the elasticity ofthe base rock and system~ with variable damping. Theory to the Program The theory considers thc responses associated with vertical propagation of shear waves through the linear vi~o-elas1ic system shovm in FigUR 2.10. The system consists of N horilOntallayers which extend to infinity in the horizontal direction and ha~ a halfspace as the bottom layer. Each layer is homogencous and isotropic, and is characterized by the thickness h, mass density p, shear modulus G, and damping factor p. .t 34 Recorded Modified Ground Ground Motion .. lIIotion ______•••_ Ib>ck OuI Modified Base Rock Motion Figure 2.9 Schematic representation of procedure for computing effects of local soil conditions on ground motions (Schanbel et al., 1971) Description o/the program SHAKE Program SHAKE computes the responses in a system of homogeneous, visco-elastic layers of infinite horizontal extent subjected to vertically travelling shear waves. The system is ShOv>l1inFigure 2.10. The program is based on the continuous solution to the wave equation adapted for use with transient motions through the fast Fourier transfonn algorithm. The nonlinearity of the shear modulus and damping is accounted for by the use of equivalent linear soil properties using an iterative procedure to obtain values for modulus and damping compatible with the effective strains in each layer The following assumptions are implied in the analysis: (a) The soil system extcnds infinitely in the horizontal direction. Each layer in the system is completely defined by its value of shear modulus, critical damping ratio, density and thickness. Thesc values are independent of frequency. (b) The responses in the system are caused by the upward propagation of shear waves from the underlying rock formation. (c) The shear waves are given as acceleration values of equally spaced time intervals. Cyclic repetition of the acceleration time history is implied in the solution. (d) The strain 35 dependence of modulus and damping is accounted for by an equivalent linear procedure based on an average effective strain level computed for each layer. Coordinole Prop-oolion Properties ". , T " • • "m m , .•..,~.I••... m" ~ i Gm+1tlm+1Pm+t f-- • , ._~'----\~_'ooI' -_.• Reflect"" _ ••• G "=G +iOOT)=G(l+ZiP) Figure 2.10 One dimensional wave propagation system (Schanbel et aI., 1971) The program is able to handle systems with variation in both moduli and damping, and takes into account the effect of the elastic base The motion used as a basis for the analysis, the object motion, can be given in anyone layer in the system and new motions can be computed in any other layer. The set of operations can be performed by the program are: (a) Read the input motion, find the maximum acceleration, scale the values up or down, and compute the predominant period_ (b) Read data for the soil 36 deposit and compute the fundamental period of the deposit (c) Compute the maximum stresses and strains in the middle of each sub-layer and obtain new values for modulus and damping compatible with a specified percentage of the maximum strain. (d) Compute new motions at the lOp of any sub-layer inside the system or outcropping from the system 2.11 Soil Liquefaction 2.11.1 CnllsesofLiqllefaction Soil liquefaction is often described as the loss of shear strength in soil duc to e1cvated pore water pressure (Chang et ai, 1991). Earthquake shaking induces shear stresses in the soil lhal cause the saturated cohesion less granular soil particles to rearrange and excess pore pressures 10build up, The damaging effects of soil liquefaction have been well recognized since the Niigala and Alaska earthquakes of the early 1960s, The types of failures associated with liquefaction include: (i) Sinking or overturning of the ~tructures, (ii) Excessive differential settlement of the structures, (iii) Sand boils and (iv) Surrace lateral spreading, There are several factors that influence liquefaction such as the geologic history of the deposit, the depth of groond waler table, the grain size distribution, the density of soil, and ground slope, The basic cause of liquefaction of sands has been understood in a qualitative way for many years If a saturated sand is subjected to ground vibrations, it tends to compact and decrease in volume; if drainage is unable to occur, the tendency 10decrease in volume results in an increase in pore water pressure, and subsequently if the pore water pressure builds up to the point at which it is equal to the overburden pressure, the effective stress becomes zero, the sand loses its strength completely, it develops a liquefied state 1n more quantitative terms, it is now generally believed that the basic cause of liquefaction in saturated cohesion less soils during earthquakes is the build-up of excess hydrostatic pressure due to the application of cyclic shear stresses induced by the ground motions. These stresses are generally collSidered to be due primarily to upward propagation of shear waves in a soil deposit, although other forms of wave motions are also expected to occur. 37 Liquefaction WllS observed in almost all earthquakes. Liquefaction phenomena were recorded and devdoped in many" parts of the world where ground shaking is frequent and soils consists of loosc fmc sand close to water table. Bangladesh is largely an alluvial plain con~istlng of fine sand and silt deposits. The ground water table i.~quite deep (20 to 25 m) in most places except the areas near the rivers. Rajshahi City is located on the bank of the Padma. Clearly liquefaction is a serious component of the earthquake hazard in certam parts of Rajshahi City. 2.11.2 Liquefaelion Polential Based on N-Vaine. A simple method suggested by Seed et al. (1983) was used here to evaluate a liquefaction resistance factor, FL In this method required parameters arc SPT-N \'alues, grain-size distribution curves of soils, overbunkn p1Xs~ureand estimated peak surface acceleration. The assessment of the liquefaction resistance factor at any depth by this method involves comparison of the predicted c)'elic stress ratio (rio';,) that would be induced by a given design earthquake (L) with the cyclic stress ratio required to inducc liqucfaction (R). For this method, FL is calculated for a given depth by the following formula Liquefaction is judged to occur at that depth if FL is less than 1.0. FI.-R/L (2.1) The shear stresses developed at any point in a soil deposit during an earthquake appear to be due primarily to the vertical propagation of shear waves in the deposit. If the soil column above a soil element at depth 'h' behaved as a rigid body, the maximum shear stresses on the soil element would be- (r"."J,= (yh)/g .a!>MA<= u,)g. a:,- (2.2) 'where, ", - total overburden pressure a~ - estimated peak surface acceleration (in percentage of g) r - unit weight of the soil g - accelcration due to gravity ; 38 -..urn acc"""~lononthe a. Surf"" •• Auel •••.•_ on thoe I ~(~ ••••, StnfoCO' '..Aft , 0, 'I " . l"-J,}M~',,,)- streu blr. Seismic M_ I" lr '~I*I +. ! m•• '1 ~ [-f- ~M A\:celeartion Dn the Oase ..."L -., o Acc:ele.rtion onth ••u...e Figure 2.11 Cyclic shear stresses on a soil element during ground shaking (Iwasaki, 1982) MAXIMUM ••••• SHEAR STRESS -• I" 101 I" Figure 2.12 Procedure for determining maximum shear stress (after Seed et ai, 1983) J9 • Figure 2.11 illustrates the procedure for determining cyclic shear stress on a soil element during ground shaking and Figure 2.12 illu.'>tratesthe procedure for determining maximum shear stress. " . o ~., 0,: O.J ~.; ~: I i , ", AVERAGE VALUES 0, " RANGE fOR DIFFERENT ,~ SOIL PROFI1.ES " ;0 •w 0 " " " " '" Figure 2.13 Range ofValucs of, d for diflerent soil profiles (Seed ct aI., 19:B) Figure 2.14 Time history of shear stresses during earthquake (Seed et a!., 19113) Because the soil column behaves as a defonnable body, the actual shear stress at depth h. (T-J", lISdetermined by the ground response analysis will be less than (r...,J, and might be expressed by 40 (2.3) where, fa= a stress reduction factor with a value less than I given by (1- O.OI5z) in which z = depth of ground surface in meters. Computations of the value of fa for a ",ide vanety of earthquake mOlions and soil ~onditions lruving sand in the upper 50 ft. ha\"e shown that fa gl>J1L"faliyfallswithin the moge ofvalue~ sh(mn in Figure 2.13. It may be seen th,,( in (h" "pp"r 30 or 4() fl., the scau"r of the re~ull~ i~ not so great and, for any of Ihe depr'8it" lh" "rror involved in usmg (he average values shown by the dashed line would generall} be less than about 5%. Thus to a depth of about 40 fl., a reasonably accurate asses8ment of the maximum ~hear stress developed during an earthquake can be made for the relationship given in equation (2.15) by using values of fa to be taken from the dashed line in Figure 2.13. The actual time history of shear stress al any depth in a soil. deposit during an earthquake ",ill have an irregular foon such as that shown in Fig. 2.14. From such relationships it is necessary to determme the equivalent unifoon average shear stress. By appropriate weighting of the indi\"idual stress cycles, based on laboratory test data, this determination can readily be made. However, after making these determinations for a number of different cases il has been found that with a reasonable degree of accuracy, the average equivalent uniform shear stress, ."" is about 65% of the maximum shear stress '''''''" Combining this result with the above expression for 'max, the average cyclic stress ratio ('m/a;'! induced by an earthquake is given by the expression (Seed et aI., 1983): (2.4) where, effective overburden pressure 41 • • • Site_liquehdion • o Site -. no appll,ent • ~queraclio" ./ •• • ," •• ••• • • •.' •• , "U Q a ", , "C 1 " • • .... ~/. • • •• '.y. " : ~.' "..••••• • • /' ..",' , • ~." .' Modified Penet,.tion Resi_nee, N 1 _bk>w""" Figure 2.15 Correlation between field liquefaction behaviour of silty sands lUldcr level ground conditions and standard penetration resi'!ance (after Se"ll total. 1983) Corredioo FooelorC N ,CIAOJ; IlS 1.0 1.2 1.4 1.1 1.1 1.0 - r- .. . V ••• '- I. 1/ ~ .• - - , .. 1 i Figure 2.16 Recommended curve for detennination of eN (Murthy, 1991) 42 The cyclic Slress ratio required 'to eaus~ liquefaction has been evaluated usmg empirical relationship beh',een cyclic stress rulio and IV values. This curve is presented in Figure 2.15. Since the standard penetration resistance N mea~ured in the field aClually reflects the influcnce of the soil properties and the effective confining pressure, it hal; been found desirable to eliminate the influence of conftning pressure by using a normalized penetration resistance ;VI, where ,10,'1 is the measured penetration r~sistance of the soil under an dledi~e overburden pressure of I ton per sq,ft. So, before using the graph in Figure 2.16, normalization to (he field SP I-A value is needed as follows: JVI~C."I\' (2.5) Where, ,VI = modified}\' values C.,. = a correction factor The correction factor, C\' "vas provided by Murthy (1991) and presented here as Figure 2,16. The severity of foundalion damage caused by soil liquefaction depends to a great extent on the severity of liquefaction, which can not be evaluated soh:ly by Fl. Generally speaking, liquefaction under the following conditions tends to be severe if: • The liquefied layer is thick • The liquelied layer is shallow • The FL of (he liquefied layer is far less than 1.0. In order (0 take care of (he above effecl, the Japanese bridge code recommended a modification to the procedure suggested by Seed et aI. (1983). In this modification, the factor of safety value Fe against resistance to liquefaction have been computed for all the bore holes and these values have been subsequently been converted into liquefaction potential index (PJ. The PL is given by the following equation (Iwasaki eta!.,1982). PL=fF(<<)w(z)dz (2.6) o Where, 43 F(z) (I-FJ jo~f;LSI,O F (z) • 0 I"' }o1.>I.O W(z) (lO-O.5Z) jor z gO m W(z) () jo~ z >20 m P, > 15 very high possibility ofhquefm:tion 15 >\t> 5 high possibility of liquefa,tion 5 > fL> 0 low possibility of liquefaction P, • 0 very low possibility of liquefaction The value of liquefaction potential P" indicates that a soil mass is susceptible 10 liquefaction if PL > O. The greater the value of PI., the larger the susceptibility of soil to liquefy. 2.12 Damage Distributions Damage estimation for a region typi,al1y depends upon three fa,tors; (I) the Jewl of ~eismk hazard in the region induding the effect of local site conditions, (2) the ui~lribulion of facilities in the region according to earthquake engineering class, and (3) the definition of function Ihat relates the expected levels of damage for the various earthquake engineering classes to the estimated levels of seismic ha7.md. This section will provide an overview of the procedure for estimating regional distributions in the GIS environment. There are several definitions for damage and also several relationships for estimating damage due 10 given levels of seismic hazard for various buildillg types (EMS). 2.12.1 DeflnitlolU of Damage There are several parameters used to express earthquake damage and the terms such as Damage RaJio. Damage Factor and Damage Index have different meanings. Regional damage can be given, for example, in percent financial loss or percent of structures damaged to a certain degree. Damage to given stroctures can be described in terms of damage to the individual elements, often based on dynamic response measures. The term Damage Index is typically taken to mean the characterization of 44 parameters such as ductility ratio,' inter-story drift, and dissipated energy (park and Ang, 1985). These indices are generally too structure specific to be considered for regional damage description. The term Damage Ratio is typically defined as (Applied Technology Council, 1985): Damage RatialF(No. (Jj.llmcrureJ damage / To/a! flO, ojJtructureJ) (2 7) 2.12.2 Fragilit), curves for Bangladesh: Motion-Damage Relationship Fragility curves are used in the FEMN!\lBS methodology to estimate damage to buildings resulting from ground shaking (Whitman et at 1997), The !Tagility curves predict the probability of reaching or e" Building fragility curves are lognormal functions that describe the probability of reaching or exceeding structural and non-structural damage states, givcn detenninistic estimates of spectral responses, for example spectral displacement These curves take into account the variability and uncertainty associated with capacity curves propertIes, damage states and ground shaking I:ragility curves are used for estimation of damages of buildings in particular area A number of fragility curves exist for Indian Buildings prepared by Arya (2000) and for Nepalese buildings prepared by Bothara et aI, (2000). There also exist a number of fragility curves for different types of structure and for different earthquake intensities (Kircher et aI., 1997; Fall et ai, 2001; Yamazaki and Murao, 2000; Yamaguchi and Yamazaki, 2000; Bommer et ai, 2002), but the Indian and Nepalese curves may be the most suitable for Bangladeshi structures, until Bangladeshi researchers develop their own fragility curves. In this study, fragility curves for the buildings in Rajshahi were prepared by calibrating the existing fragility curves for Indian buildings prepared by Arya (2000) and for Nepalese buildings prepared by Botham et aI. (2000). Neither Arya (2000) nor 80thara et aI (2000) mentioned the types ofdamages (i.e" collapsed Of heavily or moderately damaged) to be estimated using those 45 fragility curves. Segawa et ,'II.(2Q02) used those curves after some calibration and quoted those curves to be developed for heavily damaged stlUctures. Figure 2.17 shows the fragility curves modified from Arya (2000) and Bothara et aL (2000), ," •••••~, 00 "._ .~,. "" ~,~" " ~,~" / ;0 ~li n ~ *, ~ ,~, • " " "0 " ,.' 0 / ;/ ~ ~ • /" ~ 7 • ~ " •" , ;/ ;0 L , /' " '" .' -'- 0 .- - 0 , Inlensity Caused by an Earthquake (% g) Figure 2.17 Vulnerability functions based on peak ground acceleration (after Atyil, 2000) 46 CHAPTER THREE BASIC DATA COLLECTION 3.1 Updated Administrative Boundary ofRCC Area RaJshahi City Corporation (RCC) is comprised of30 wards with an area of 4806 km (RlvTTJP,2004; 49.2 squarc km calculated in Maplnfo/GIS). An important issue ;n de,'e!oping a regional seismic damage assessment model is the selection of an appropriate geographIcal reference. which will generally be dr;\-en by the availability of mput data regarding soil condition and building stock, CIty corporation areas are divided into wards and wards are divided into Mahallas, For this study, ward wa<; adopted as geographil'al reference (gco-code) for the damage modeL Figure 3.1 shows the administrative layout of Rajshahi City Corporation Arca (''''. I' I " n' 1'" I I" WN Figure 3.1 Map Showing wards ofRajshahi City Corporation 3.2 RCC Built-np Areas El'>ceptplanned housing areas !:hereare no dear use zones in RCC area, Built-up areas can be classified illto two major categories - urban and ru11l1withrespect to housing characteristics. Within the urban area, however, there are a variety of housing areas based on type of dwelling construction, spatial growth, density of dwellings and access to infrastructure. Except for old parts ofthe city most Mahallas have scope for infilling. Central areas of the old part of the city are covered by Wards 9, 22, 23, 24, 12, 20 and 13 are mixed use areas of various ranges Shaheb Bazar and adjoining areas are overwhelmingly commercial use dominated. Other adjoining areas, like Rajarhat, Malopuru, Sultanabad, Sewil, Kadirganj, Ranibajar, Ghoramara are in different stages of transfonnation into non-residential uses \Vestern old parts of the city show admixture of housing and public institlltlOns These are Wards 10,8,7,5.6, 4,3, 1 and 2, Ward 4 accommodates public housing, while Ward No.2, 3 and 4 have more private housing Bahrampur, Horogram, Nagarpara and Daspara are important housing areas in this part Organized housing areas have developed on northern part ofthe city beyond railway line, Planned areas, like Upashahar Housing Estate, Padma Residential Area, Parijat Residential Area and Seroil Colony are located here, Due to availability of better facilities, houses in planned residential areas are increasingly being sought by big companies and government offices which threatens the residential environment of the areas Budpara, Meherchandi Budpara, Meherchandi Chakpara, '-feherchandi are low density eastern fringe spontaneous residential areas covered by Ward 10, where gro"th is slow. Lack of infrastmClure is observed here. The areas are mostly inhabited by low-income people. Areas like Noudapara under Ward 17 have extremely low density (2 person/acre) with semi-urban character All fringe residential areas have semi-urban character. 3.3 Poor Housing Areas Despite non-existence of large scale commercial and industrial activities in Rajshahi City the number of poor housing dwellers is no less than large towns. According to RCC sources neaf about one-third of the City's population live in slums and squatters (RnA, 2004). The poor housing areas arc mostly located in areas, like, Maldaha Colony, areas by railway line adjacent to TB Hospital, Srirampur, Pathanpara, Dingadoba Railway line areas, by the riverside at Keshobpur, Chandipur, Kazihata Ghoshpara, etc. Squatters usually develop on unused public land. Structures in these settlements are built of temporary and semi-permanent materials The dwellings are congested, unhygienic and lack in adequate sanitation and utility service facilities. 48 3.4 Building Types Based on Construction It is evident from Table 3.1. there has been over 100 percent increase of dwelling units in RCC area between 1981 and 1991, Over a period of 10 yean>. The most remarkable increase was recorded in semi-pucca structures., which recorded an increase by over 300 percent, Table 3.1 Housing Type Changes Within the RCC area. 1981-1991 Type of structure I--- Number ofulllls according to year 11-1981 1991 Kutcha 14048 8212 Sernl-pucca I5605 122449 Pucca 11226 18869 "iotal Housin Units 20874 149530 Source: Commumty Senes, Bangladesh Populatton Census 1981 and ]991 Table 3.2 Wall and Roof Materials ofRCC Area, 1991 Wall materials Roof materials Tota! StrawIBamooo TildC.!. Cement/Concrete Housing Sheel Units StrawlBamboo 6573 6121 12694 MudJUnburnl 1470 6503 ° 7973 Brick 1° C.r./Metal 45 4'" 0 491 sheet Wood 4 23 0 27 Cement/Brick 120 9356 18869 28345 Total 8212 22449 18869 49530 Source' Zilla Series, Bangladesh Population Census!991 49 Table 3.3 Housinrr Tvnes of RCC Area A COOTill\\'d to R00f Malena. 1 S, 1 991 Ward No, Roof materials Total StnlwJBambC>D TjlelC.r, Sheet CementIBrick 1 454 1,079 451 1,984 2 50S 925 221 1,651 3 365 906 695 1,966 4 265 823 436 1,524 5 121 728 1,063 ],912 6 241 871 \,038 2,150 7 251 581 473 1,305 8 126 471 691 1,288 9 30 353 323 706 10 '77_ 318 352 702 11 62 47~ 584 I, 121 12 117 693 609 1,419 13 20 352 450 822 14 12 161 487 660 15 49 500 649 1,198 16 267 761 2,066 3,094 I 117 246 1,051 705 2,002 i 18 634 1,021 1 552 2,207 19 622 867 i 644 2,133 1 20 907 1,363 431 2.701 21 108 434 765 1,307 22 166 513 588 1,267 23 26 2)4 875 1,135 24 178 654 450 1,282 25 288 874 364 \,526 26 218 833 595 1,646 27 6451 1,589 1,016 3,250 26 I 349 1,115 658 2,122 29 450 1,153 59 1,662 30 458 751 427 1,636 Total 8,262 22,499 18,769 49,530 Source' Commumty Senes, Bangladesh Population Census!99l 3.5 Building Inventory A building inventory was carried out to clarify the nature of distribution and strength of buildings in the study area The distribution of each type of building is also clarified to assess likely damage due to potential earthquake. The study area is not uniform in tenus of building construction, typologies, population density and el::onomie activity, The objective of the inventory was to classify the existing typologies in relation to EMS typologies, as the damage modeling will involve EMS 50 .,.. typologies to count motion-damage relationship. The inventory was made only in Ward nO.12. An idea can be made that the building stock ofRajshahi City exhibits a mix of several different building typologies (Figure 3.2). The most commonly used building categories are 1) Reinforced-concrete frame building with partition wall; 2) Brick masonry buildings with reinforced concrete roofs and using cement mortar, 3) Informal brick masonry buildings (which mayor may not use cement mortar 4) Buildings made of other materials such as tin sheets, thatch. mud, wood and other lightweight elements The first two categorics typically cons!itl.lte engineered construc!Jons III 'Which the assistance of qualified engmeers is usually taken at each stage. The last two categories are non-engineered constru~iions, wherein the services of skilled engineers may not have been employed, In Rajshahi city, it has been observed that many reinforced concrete and brick masonry buildings have been constructed without the assistance of qualified engineers. Due to this reason, these buildings are also not engmccred since they may be improperly deSIgned or constructed resulting in lower strength Table 3.4 Shows the building typologies ofRajshahi City Table 3.4 Definition of building typologies in Rajshahi City Corporation (after Islam, 2005) No Types Description , ,oof EMSA Moo structures, material " eilbef of GI ,,- 0' polythynelstrawlbamboo. 2 EMSBI I-storied brick masonry of tired bricks with cement or lime mortar, roof is either ofCI sheet or other materials. 3 EMSB2 l-storied brick masonry of fired bricks with cement or lime mortar with RCC roof 2-storied or taller brick masonry of fired bricks with cement or lime mortar; roof is generally made ofRCC slab. Some weak and - old reinforced concrete frame 4 EMSC Reinforced concrete •••• with low ciu<:tility; designed Eo, vertical load only. 5 EMSF Mainly bamboo, wooden and stool structures, .... Note: It ISassumed that no ~D" type bUlldlllg tS avatlable IIIRaJshahl CIty. 51 - -' --' -_••_--"'-- >"." -- --''''" ...-- - - '"---- 25 20 15 Number Ll EMSBl .f mEMSB2 Buildings 10 OEMSC 5 o "" &, "", Buildinll TypQIQIPe• • '" ".""ru.".,~ " .~ Numb., of Hoi/dinS' " '". " .=.=- ", • • ; • Numb ••. of Storeys • • Figure:J.2 Distribution of building types according to construction year, storeys and floor area (Field Survey, 2005) 52 3.6 Forecasting of Building Types According to EMS The dwelling unit for this study is forecasted from Working Paper on Housing of Preparation of Structure Plan, Master Plan and Detailed Area Development Plan for Rajshahi Metropolitan City (RDA, 2004). At 2002, the number of dwelling units was 74,000 (at a grOl'.1h rale of 1.88) and at 2008, the number will be 81,222 (with grol'.1h rate 1.96). Therefore the forecasted number of dwelling units at 2004 is assumed [74,000+{(81,222-74,OOO)/6)*2Jl or. 76,407 ThiS value is distrihuled accordmg to ward wise population ratio (in relation 10 Table 3.3) and then rounding off values, the adjusted number of dwelling units stand 76,173. Table 3.5 Building distribution panem according to EMS in Rajshahi City, 2005 Ward no. EMSA EMSBI EMSB2 EMSC EMSF Total units , 493 268 J>8 1,166 ">6 3,06! 21 4>0 223 264 970 679 2,546 3 488 265 m 1,155 809 3,032 4 378 206 244 8% 627 2,351 5 475 258 306 1.124 787 2,950 I 6 0 824 345 1,264 885 3,3181 7 0 500 209 767 537 2,013 I 8 0 494 206 757 530 1,987 9 0 270 4>5 29' 1,089 >0 0 269 1>2'" 4B 289 1,083 0 329 180 659 I 46' 1,729 " 0 543 228 834 584 2,189 "n 0 m U2 483 338 1,268 14 0 253 >06 m 1,0\9 0 459 '92 '"704 493 1,848 ">6 0 1,185 496 1 818 1,273 4,772 497 270 32' 1,177 824 3,089 18" 548 297 354 1,297 908 3,404 19 5" 2&8 342 1,254 3,292 20 0 1,035 433 1,587 1,111'" 4,166 21 0 501 2>0 768 538 2,017 22 0 486 203 745 521 1,955 23 0 435 667 467 I 751 24 0 491 205'" 753 528 1,977 25 0 585 244 897 628 2,354 26 409 222 264 967 677 2,539 27 807 438 521 1,910 J,JJ7 5,013 2. 527 286 340 1,247 873 3,273 29 413 224 267 on 684 2,565 30 406 221 262 96' 673 2523 To,", 6381 12,440 7,914 29,020 20,318 76173 53 For lhis research this value is also distributed to different building types (through t, crosschecking of Table 3.1 and Table 3.2) under European Macro Scale (EMS), It is assumed that core wards are free from EMSA type buildings and these units are replaced in EMSF type Table 3.5 shows the forecasted building units for Rajshahi Q City_ 3.7 Soil Data (SPT-f.i) from Primary & Secondary Sources A lOla! of 50 boreholes SPT data was coIJecled from different relevant sources including direct boring by the fimding orlhi, Sllldy Figure 3.3 shows the location of Primary and Secondary source points of borehole SPT data Among these data, 6 primary borehole data with SPI-A' values up to a depth of 100ft were funded by BUET and remaining 44 secondary borehole data with 50ft depth were collected from ditTerent soil testing and construction fann, 3.8 Ground Water Data Two aquifers are recognized in the Bangladesh Water Development Board Water Supply Paper 430 One is present in the Holocene alluvium and the other is in the Pleistocene alluvium located below the Barind clay residuum (Table 3.6). Table 3.6 Uoazillawise record of water level at soecified WDB wells, 1982 UpazilJai Location Well no. Elevation of Water level from measunn oint Tt.M measuflng point above 0 " " " E .~" E msl in ill 'iii 0 0 < ,E C E • • • •• 8.@•• ~.o~ ~ E "E Boalia Rajshahi Rs-84 119,94 3]-5-82 9,98 30-8-82 2.5 To~ P." Pili, Rs-85 17.5 10-5-82 7.0 06-9-82 3.6 Mohan ur Mohan ur Rs-28 \6 71 01-3-82 7.3 20-9-&2 2.92 Godagari Fazlepur, Rs-\25 21.16 07-6-82 9,52 13-9-82 0.62 Bannd. lanor lanor Rs-126 18.57 13-4-82 7.16 27-9-82 233 Bannd. Source: GSB, 199\ 54 , - , • -• - ,• • , -• - - - • • • • -• , • • , • -• • CHAPTER FOUR SEISMIC HAZARD ANALYSIS 4.1 Estimation of Bedrock Level PGA in the regional seismic lo>s estimation analysis it is needed to determine the bedrock motion in the region. The most common method involves the use of an empirical attenllation rc!atlOllsl1ip. These relationshlps express a given ground motion parameter in a region as function of the size and location of an earthquake event Applying statistical regression analyses to recorded data numerous relationships have been developed in the past Often these relationships are developed with different functional forms and with dlfferent definitions of ground motion, magnitude, distance. and site conditions. Figure 4.1 shows a flow chart for eanhquake analysis Geophysical modeL~ based on seismic source mechanisms and wave-propagation theory have been proposed, but these models onen require extensive source and site geology data and are computationally more intensive I Scenario Earthquake I So,1Properties I Attenuation Funct10n R"sponse Analysis Waveform at Bedrock Surface Amplification Waveform at Ground Surfac~ j, •• •• Intensity Distn buti on PGA Distribution Figure 4.1 Flowchart for earthquake Analysis In Bangladesh, no PGA based attenuation law exists. To get engineering bedrock level (depth of 30 m) PGA, equations presented in T2b1e 2.6 were used. Some famous historical earthquakes and its magnitude, epicentral distance, focal depth and intensity (Table 4.1) were considered in case studies 10 calculate the PGA value for study area The calculated PGA for different earthquakes is presented in Table 4.2. Table 4.1 Some historical earthquakes with their intensities. epicentral distance and focal depth with respect to Rajshahi City. Name Fault I Magnitude I El\fS DIstance Focal Depth Intensity Km) (Km) , BertgaJ I j Eart~~uake Bogra 7.0 V 156 72 ( 1885 Great Indian Earthquake Assam 8.7 VIII 228 60 (1897) , Dhuhri Earthquake Dhubri 7.1 VI 207 60 {l930) Source: Sabri, 200 I To select the mo,t sl.litable attenuation law from those listed in Table 2.6 for predicting rock motions (Table 5.3), 1885 Bengal earthquake, 1897 Great Indian earthquake and 1930 Dhubri earthquake were used. The criteria for selecting the attenl.lation law are as follows: (i) Applicability to the ground condition of engineering bedrock in the study area (1;:\=200mis). (ii) Ability to explain the observed or analyzed earthquake motion of 1885 Bengal earthquake, 1897 Great Indian earthquake and 1930 Dlmbri earthquake In this study, the engineering bedrock was assumed to be the layer at which the shear wave velocity (r~) exceeds 200 m!s, which exist almost 30 m deep from the surface. The attenuation law of Boore et aI. (1997) required shear wave velocity. Shear wave velocity for 6 borehole data up to a maximum depth of 30 meter are calculated by using equation of Tamura and Yamazaki (2002) presented in Table 2.5. Table 4.2 shows the shear wave velocities and it is observed that the values vary from 282 mig to 369 mls. 57 Table 4.2 Shear Wave Velocities at different locations ofRajshahi City Location Longitude Latitude Shear Wave Average Code Vel~ity @30m Shear Wave D~nt-h Velocit 30 m BT 1 88.571346 24381268 369 BT2 88.559347 24 375534 282 24369149 327 BTl 88 574942 347.5 BT4 88.604310 24396365 369 BT 5 88.630897 24375457 369 8T 6 88658538 24,369146 369 Source: FIeld Smvey, 2005 Distance versus PGA values for three earthquakes (1885,1897 and 1918) are plotted on log,log paper (sample sh01Nl1in Figure 42, after Islam, 2005). For intensity estimation, different isoseismal maps (Sabri, 2002) forthe three historical earthquakes were used. From these isoseismal maps, the epicentral distances of different locations and their intensities were found, These intensities were converted into PGA by following Trifunac and Brady (1975) equation (4 1) and were plotted on the figures For Boore et aI's equatioll, shear wave velocity of2oomls., 300mls and 400mls were considered : log(PGA) ~ O,014+O,3(M?vil) (4.1) Where, PGA ~ Peak Ground Acceleration /14.1.1/= values from Modified Marcelli Scale ofFelt Intensity [Appendix DJ From these plots, it is found that McGuire (1978) as well as Boore et al (1997) equations follow the PGA trend. Since, McGuire equation has already been used for Bangladesh for seismic hazard analysis (ShaJfuddin, 2(01) and due to its simple form it is selected for further use. Finally, Great Indian Earthquake (1897) with PGA value 0,0634g at bedr~k level for Rajshahi City Corporation was selected Table 4.3 presents the PGA values at bedrock level from dilTerentattenuation laws for different scenario events. 58 --~"'''" ------''''I''r' .". ~"'l ", ,.."..,>;'''~.,,~\~- ,, __ '00" "" ~"'): Vo"""" .,,-"'-, '00. "iI. om). V._JOOIo. \ , __.. '00- ~" ""..,,,, ~""'):..,,,,,,,,.v._ "'''''. \ \ \QGCl Distance"" (km) Distance versus PGA 'falues for Bengal earthquake (1885) 1000 116~7EQ,""'8 0, 0"60 ,m •• I • • • , "" ~" E 0 c " 0 ~ m •L @ __ UCC, •• 8 __ J •••. '''.,.O. Q'BSJ 4: __ s•••~,.Ut~I'" -.OO~ ""'(I""'),",-211"'0 ~ ODOR ••• t ~"I): .,_JUD.' "' .__ .OO~" •• ~'!IT)._,_'0'" • , •••• ~" ••.•• ml"" "" "" 1000 " Distance (km) DlstanCl:! varsus PGA values for Graet Indian Earthquake (1891) Figure 4.2 Distance verSliSPGA values fur historical earthquakes at Rajshahi City 59 Table: 4.3 PeA values (% of g) at Rajshahi City bedrock level from different attenuation laws for different scenario events Attenuation Law PGA for Earth uake Bengal Earthquake Gr;~I~d:::l m ~h~%~ Earthquake 188-Sl Earl uake 1897 I 1930 McGuire (1978) 003771 0.06340 0,03161 Sadigh el. ai, (1986) 0,01088 0.01669 000795 Joyner and Boore 001007 0.00786 000609 (1988) Boore el 0.00313 0,00415 000277 (1997) " I 4.2 Site Amplification Analysis Vibration characteri,tic5 at different points of the ,tudy area can be estimated by employing one dImensional wave propagation program SHAKE. The computalion, are made in the frequency range 0 to 20 Hz at every 005 Hz interval. The loss of energy of seismic waves in the soil layers is also considered. An estimation of the fundamental frequency and the maximum value of the amplification are obtained for each site. Typical graphic representalion of frequency versus amplitude is shown in Figure 4.3a, 4.3b and 4.3c Table 4.4 Presents site amplification factor and corresponding predominant frequency at different locations ofRajshahi City. By spatial interpolation (Inverse Distance Weighting) between these poims, a map of resonance frequencies over the whole study area is shown in Figure 4.4. and a map of the maximum amplifications observed at these fundamental frequencies is also shown in Figure 4.5. From the frequency map, ward areas of 1.3 times of and ].8 limes of generalired amplification are separated for simplicity. Figure 4.6 shows the map of 13 and 1.8 times amplified areas ofRajshahi City. 60 ,.•"----- LT 21 Mndified frnm 6T 1 '" 1\ \ / , /\ \ , \ \ / \ ! \ '--- i \ i / ~ LT 32 Mndlfied frnm 8T 2 8T2 " 0 1\ /\ " ' \ I ! j'", • \ ~ , i1f1 \\ \ J\ L' I •~ \i E 1 / /\ \ • / ,0 I " ! V f " " L-".-_~-C,L_~__,C.:---~-C,;,-~---;,:.-_\ Predomin~nt Frequency Figure 4.3a AmphficatlOn factor and corresponding predominant frequency 61 -- LT 7 MQd~ie.d flom BT 3 --6n " j\ , I, "\-+--+--+r ! • \ •, " ! -=• ! ! E " • \I / \"-- " \/W ..f--jL---+----+---+----+---, L-+-----c,L----,~,;----~,,:----C,:,--J Predominant Frequency LT 11 Modifted from 8T 4 an " f \ " f\ • " \ •! \---4-1 • " \ E , J • " / \ " ../ " 0 ~ 10 l~ Predominant Frequency Figure 4.3b Amplification factor and corresponding predominant frequency 62 Figure 4.3c Amplification factor and corresponding predominant frequency 63 Table 4.4 Results of Amplification factor and corresponding predominant frequency at differenllocalions ofRa;shahi City Location Code Lon itude Latitude Pre nene Am litnde m 88.601434 24.365360 ,. m 88.601607 24.365327 "' U en 88.600664 24.366231 5,9" L5 LH 88,600548 24,366921 6,6 L6 LT 5 88.600837 24362617 LTC 8U\\2452 2437\538 '.5" L5" LT7 \\R,580703 24369468 5,3 en \\8.577962 24370389 ", " I LT9 88.595843 24377877 'A" I LT 111 8R,594238 24,37\\845 "65 1 5 ILTll I 88.606612 24388387 6L l.5 un 88.005653 24 37857~ I LT 13 \\8.620295 24.378396 "9 7 " I LTH 88.59309 j 24379322 "IA LT 15 88.597850 2437301\\ 5.6" 1,4 , LT 16 I \\8.599077 24369470 SA 1.51 I LT 17 I 88.606416 2438139ll ',9 I 6 LT 18 \\8.603431 24,372193 I , 5 'A I LI 19 8U83l52 24368936 6,6 I, I LI 20 I 88.596732 24366360 5,7 I 3 LT 21 I \\8.578787 24,374280 U U LI22 I 88.600751 24,370585 65 '7 LTD 88.605768 24.388259 ',9 LT 24 88.587863 24,365128 " I LI 25 88.599228 24,412396 I " "J; LT 26 88.567J 75 24368825 " J; LTV 88.609222 24,40\\642 '" LJ I LT 28 88.6{),)16~ 24372374 " I, L1' 29 \\\\.578+\1 24,371)177 " '5 LI 30 88.603968 24,364058 " I, LT31 88.621246 24370262 "6,' I, LT 31 88.559194 24,38(J954 5' '6 LTJ3 \\8.627729 24,364372 H I 7 LT 34 88.627410 24305101 6,' LT35 88.621666 2437+761 5,7 "I 5 LT36 88.601925 24,369938 3,7 '7 LT37 88.602152 24,373019 IA LT 38 88.602537 24365075 ',6" '6 LT39 88.597001 24373045 '7 I, LI 40 88.600742 24,365887 I' LT41 88.610569 24,366365 "5' I,' LI42 88.605037 24,409884 9,9 J; LT 43 88.623587 24.365500 9,1 LT 44 88.589853 24.381268 5,3 U" Bn 88.571346 243780n 57 u B12 &11.559347 24375534 3,9 17 BTS 88.574942 24.369149 3,1 1,7 BT< 88,604310 24.3%365 3,1 LO BT5 88.630897 24.375457 2.7 17 BT6 88.658538 24.369146 3,9 I' 64 , z z N• •, ~ • • 0 • N• N•••N N '8 ~ c w .F w W ID U ID ~ ~• • ~l • ~, ., • " ~= • a • ~• e =e• ••" • • :; ~• 0 • = •• ~• " .e~ ~• ~ ~t= W N• li- • ~ • ~ ~ =• ~ z , z 0 0 z , 0 ," • " M ••N ••N N " ,o "e is ~ co III ~ w f ••ligtfj " "w w w w w W w =, ro ~ W a~ ~ ~• .-• w ~• w, 0 • w - 0 W • ~"" = ~ •0 ~ !.;;; w •w •••s " ~ .s~ .t~ ~• ~ ~ N• 0" w ~" • ~ • ~= '" z z z 0 z 0 N C • • - c • • • N• N N -N rn N w "N • •ro w ro" ~+OJ • 4.3 Liquefaction Analysis Borehole data from 50 points in Rajshahi City was collected. Almost all the boring data include SPT-N values measured at 1.5 meter interval. Table 3.5 shows the ground water level at different location of Rajshahi City. The liquefaction resistance factor h (equation 2 1) for the top 20 meter of soil, and the resulting liquefaction potential }',. (equation 26) for the 50 sites were calculated The flow chart of liquefaction analysis u>ed in this study is shown in Figure 4.7. Result of liquefaction potential was proVIded in a tabulated fonn in Table 4.5 and presented in Figure 4.8. Soil Properties S[l'Ilario Earthquake J. Pe2k Ground Ac[eleration (PGA) GroUl.d Water L evel I FLMethod I I l\nalysi.. nf Lique£'ldiou Resi.tanc~ Factor fnr each Layer (FL value) I hMethod I I Eotimotion ofLiqueCactillIl Potmtial for Each Site (PL..-alue) Figure 4.7 Flowchart ofLiquefaetion Analysis 68 • Table 4.5 LiQuefaction Potential of different locations ofRaishahi Citv Location Code Longitude Latitude LiquefactIOn Potentia! LT 1 88601434 24,365360 en 88,601607 24.365327 00'.' LT3 88.600664 24,366231 28.1 LT4 88,6()O548 24366921 17.9 LT5 88,600837 24,362617 0.7 \ L1'" \\8582452 24.37lS38 14.2 I L1'7 88580703 24,369468 00 I LT8 88577962 24 310389 21 7 I LT9 88595843 24,377877 I 00 L1' 10 88594238 24 378845 I 4.4 I L1' Jl 88606612 24,388387 136 LT 12 88605653 24 378575 4,11 I L1' 13 88620295 24,378396 I 3,8 L1' 14 88.593091 24379322 LT 15 88597850 24,373018 00" L1' 16 88,599077 24.369470 0.0 \L1'17 88606416 24381390 17 L1' 18 88,603431 24.372193 00 L1' 19 88583152 24.368936 17.8 L1'20 88.5%732 24366360 12.9 L1' 21 88518787 24.374280 0.5 L1'22 88,600751 24.370585 ••• LT 23 88605768 24,388259 10.9 L1' 24 I 88.587863 2.•.365128 5.1 Il.T25 • 88.599228 24.412396 12.8 LT26 I 88.567175 24.368825 ][1.8 I LT27 88.609222 24.408642 0.0 l.T28 88,609165 24.372374 6.8 LT 29 I 88578417 24.370277 30,6 LT 30 I 88.603968 24.364058 243 LTJI 88.621246 24.370262 0.0 I LT 32 88.559194 24.380954 00 LT 33 88.627729 24 364372 0.0 I LT 34 88.621420 24.365101 0.0 LT35 88.621666 24,374761 145 LT36 88.60/925 24.369938 8.8 LT37 88.602152 24.373019 9.2 LT 38 88.602537 24,365075 00 LT39 88.597001 24,373045 0.0 LT 40 88.600742 24,365887 26.6 LT 41 88.610569 24,366365 00 LT42 88,605037 24409884 00 LT43 88.623587 24,365500 0.0 LT44 88,589853 24381268 27.6 BT 1 88.571346 24.378078 L8 BT2 81U59347 24.375534 0.0 BT3 88.574942 24.369149 2' BT4 88,604310 24.396365 2.8 BT5 88.630897 24.375457 0.0 BT6 88,658538 24.369146 0.8 69 Summary of liquefaction potential is shov.n in Table 4.6. Figure 4.9 shows that 18.34 sq. km. area has low liquefaction potential, 29.05 sq km area have moderate liquefaction potential and only 1.82 sq km area have high liquefaction potential (MapTnfo/GIS) Only 3,69 percent area may be affected by severe liquefaction if the same earthquake like Great Indian Earthquake (1897) occurs again with same magnitude and same epicentral distance. Table 4.6 Summary orthe Liquefaction Potential Index , Liquefaction i Criteria Explanation I Potential High 15 70 • , 0 0 ro C 00 U ~ :• , l, " ~ "00 00 • - ~• ",• • , 0 w ~- 0 0 00 0 - ",• • '"•~ ~ w •0 ,0 ~ ~ •00 • ~• • "'-• ,•0 w , 00 00 ~ -00 ~ "'•0 00• , Ii' 00 ~ 00 " ~• • • • ., ! , • o- "• •" ~ •" • • "• w • ~ " • w • ~• CHAPTER FIVE SEISMIC HAZARD INTEGRATION 5.1 HlIzard and Integration The primary outcome of an earthquaKei,,trong ground motion and the consequences are destruction of the built environment and loss of human life. Due to liquefaction the secondary effect can be more destructive creating a more devastating situation. So" it is not feasible to resolve how much of the damage can be d,scretely attributed to each local site effect; consequently the ultimate regional seismic hw-arddistribution is estsblished on a weighted average combination of the hazards related with each eITect. 5.2 Integration of Site Effects in the GIS Environmellt Every analysis region is different; therefore the quantification of the secondary site effects and the 'Weighting,cherne for combining various seismic hazards is based on judgment and expert opinion about the influence oflocal ,ite conditions in the region, the accuracy of the available geologic and geotechnical information. The basic steps are described below, The bedrock-level ground shaking for Rajshahi City is determined The shaking is described in terms of peak ground motion values (PGA) or intensities (MMl) '1he regional distribution of bedrock-level shaking is assumed as 0.0634g, whieh is found from considering Great Indian Earthquake (1897) scenario event together with applying an attenuation relationship to the study area Bedrock level shaking is assumed as constant since the study area is small. For simplicity, the ground shaking parameter is assumed to be peak ground acceleration, A map showing the distribution of the surface-level ground shaking in the region is developed (Figure 5.2). This map is produced by simple multiplication of the PGA amplification factor map shown in Figure 4.6 with bedrock-level PGA value. Figure 5.1 shows the flow diagram of integration of site effects. , Scenario Earthquake Soil Properties Attenuation Law Response Analysis Wa\'eform at Bedrock Subsulface Amplification I Waveform at GroWld I Surface J. I I Surface Level PGA Surface Level Shaking Distribution Liquefaction Potentia! Heuristic Combinatiun Heuristic Quantification Rul•• Ru'" ,j Combined Seismic MlcmZoDlltian Map Figure 5.1 Flowchart ror Com biDed Seismic Hazard Mapping 74 - z • •N .f' u w o •o o , , z •N ,• ~ • • N • •N • N •N N • • .il' • • ~ i - U ] ~ • • ~• >'~ • .•• ~ 011iil "N "= -00 -; ""~ S ~ ~ N• ~ •• •00 ~• • "~• ~• 00 • •, "~ • ~ •00 • ..g• •.,= •• W ~ • •• • .~• ., • ~" .5, ~t~ ~• • • ~ N • "• ~ • ~ - ~, • l • The seismic intensity is basically a subjective one, based on the human sensations or damage during an earthquake (Appendix C). It is assumed thai the final combined seismic hazard would be quantified in terms of Modified Marcelli of Felt Intensity (Mlvfl) This assumption allows for the use of relationships between JI,fJo,fJ and Structural damage for computing regional damages. There are several relationships for converting PGA 10M},fJ. The equation used here was developed by Trifunac and Brady (1975) and is given by equation (4 I) in Chapter Four. Figure 5.3 shows the regional distribution of grOLlnd shaking hv.ard (A1A11"5) This map developed b~' applying equation (4,1) to the map of wrthee-Ievel PGA values was shown Figure 5.2 The MMI scale is subjective and assigned as integer values, therefore the AiM!,;s values in Figure 5.3 are rounded to the nearest 0 5. Figure 4.9 shows the regional distribution of liquefaction potential in the study area. Table 4.6 ",as used to sort out liquefiable area and fur simplicity it is categorized as high, moderate and low liquefaction potential. The following heuristic rules are used to quantify the seismic hazard due to liquefaction For regions with liquefiable soils with high liquefaction potential MMlt..IQ=MMIvs-'-2 (5.1) For regions with liquefiable soils with moderate liquefaction potential MMll1Q~ MMles+ 1 (5.2) Otherwise: MM!r.IQ~D (5.3) The rules for combining the various hazards are based on expert opinion (Stephanie and Kiremidjan, 1994) about the relative aCCl.lracyof the hazard information and the behaviour of the local geology. For this study, it is assumed that the grol.lnd-shaking hazard is the most accurate followed by liquefaction. Different types of structures, such as above ground and buried structures behave differently when subjected to local site effects. In this study, seismic hazard to surface structures i.e, building is considered only. Typically there are up to two hazards 10 be combined, ground shaking plus the secondary site effects caused by liquefaction hazard. For this study, six possible combinations and their assumed weights are shown in Table 5.2 The final '* combined hazard (MMIF) is computed as a weighted sum of the various hazards. The 77 •• weights in each role must sum• to .1.0, The additive factor in rules in Table 5.1 is to account [ortlie increase in hazard due to two or more hazards occurring Figure 5.5 shows the regional distribution of the final combined seismic peak ground acceleration and t'igure 5.6 shows the regional distribution of the final combined ,eismic hazard (JJlvlIF) is developed according above-mentioned steps for this study. ,l,.ccording the rules listed in Table 5.2 The final (M..'.fh) "alucs are rounded to the nearest 0,5 10 account for the subjectivity nflhe AiNfl scale. Table: 5.1 Quantilicalion rules for seismic hazard Weighting scheme for Final combined Rule Possible hazards I hazard I Anal ,sis 1 Ground shakin }"f}.,flrAfM/(js I Ground shaking + Analysis 2 MMfc= 0.55 MMlus + OA5MMluQ+{I,05 Liouefaction Where. MMf,..- =Final Combined Hazard (MMJ" S 12) MMJos = Ground Shaking Hazard M/14Iu9 = Liquefaction Hazard Table 5.2 CombHlation ofpos,ible hazards due to scenario earthquake 1897 in Rliishahi Cit Intensity PGA Figure Possible Combination ofPossibie Ar~~\ A,," Har..ards Hazard, :MMl km' I (O/~) 0' Ground 1.3 times Amplification VI 0,082 15,01 30.5 5Aa Shaking onlv 1.8 limes Amplificatioll vn 0,113 3.36 6.8 5.4b onlv Ground 1.3 times Amplification VIn 0,216 1.47 2.9 5.4c Shaking + I nlus !inuefaetion (hi ) Liquefaction 1.3 times Amplification VII 0.158 8.74 17.76 54d plus Liquefaction (moderate) 1.3 times Amplification VI 0.082 15.01 30,5 5.4a plus LiQllefaction (low) 1.8 times Amplir:~~i~~) Vlll 0.297 0.34 0.7 5Ae Ius Linuefaction hioh 1.8 times Amplification VIn 0.218 20,29 4\ 2 SAf i~uSLiqu:)faction moderate 1.8 times Amplir:~:i~ Vll D.1l3 3.36 6.8 5.4b nJus Linuefaetion low 78 z z 0 z ,0 C •" • • "• "• " " " " ,0 .~ ;;: w 0 , 0 < •ro M • - N ~ a • ,w • " •" • w >, b • -"=, w .~= b, =0 !E: •~ ••• <• • w ""~ ,0 • - • -"=, ~ .~ ~ w ~• b • " ~ • ~ •0 • ""~ z z • N• .," •0 'S W 0 " ~• < m rn • N ~ 0" W W N , N " W •00 w o w • •00 w w 00 • • z z z z • N• , • , • • •N •N •N •N w • > N w N• • w • o • 00 '" w ,"• z z ;, N , " N• •N • 0 'j .9 00o. 'ijQi lEg ". <'," ••, ." .."':;:1:< • w •"w ;,w w • • z z ~ z ,0 "• c 0 • • "N• •N " " • " w o• N W • w • • w ~io • -• ;,w o • , • z ~ , ", • • • • -" " " ""• "• ~ • • w • ~" ::" • • •• "• .'"~• ~ w •E • '"• • - - ~• ~ ~ • w .~ "• ~ •- • E• ~ ~ ~ •E W N -• - :• -• • -" '"0• " • 0 '.~• • -'-~ ;'i •~ E , ~ z • z • • "• • •" "• " " "" ~, u ~ w ;, ~•" l • z z 0 .;:J;:;:;N~::~"""""••••••MN •, acc::ic:ic::ic ~ 1iJ1000GJO • "" •-" <" ~ • z ez ~ " ~ ~e ~ • , • . "• "• z "~ w , 0 • " 0 • -z • ,e • 0 ~ " "~- " ~ ••~ 0 ~• w • ;, ~ • • • "~ '",r• , z • "• " ~ w :" w •-" : • • • • • • ~ •-" CHAPTER SIX • SEISMIC DAMAGE ASSESSMENT 6.1 Fundamentals of Damage Assessment Damage a~sessmentfor a region typically depends upon three factors such as the level of seismic hazard in the region, including the etTectsof local site conditions and the distributions of built structures and facilitIes in the region, according to earthquake engineering class. The estimation of regional seismic hazard, including local site effects, and classification and the development of building inventory as well as the regional distribution of facility is deseribed in earlier chapters. The purpose of this section is to provide an overview of the procedure for estimation regional damage distributions in the GIS environment. There arc several definitions for damage and also several relationships for estimation damage due to given levels of seismIChv.ard for various building types. In this study, motion-damage relationshIp given by Arya (2000) is used. It was assumed that buildings are homogenously distributed within the boundary of each ",ard and damages occur by area-ratio method. The investigations are carried out for two ways cases (according to Table 5.1) as follows' Analysis I Based all Ground Shaking Hazard (MMlcs) alone Analysis 2: Based on combined Seismic Hazard (MMld considering local site effects 6.2 Damage Assessment for Buildings It is to be noted that the result of this study are based 011 several simplifying assumptions. The analysis method and integration rules are chosen with the illtclI! using of GIS in a regiooal seismic hazard analysis and can easily be modified as additiOllalillformatioll boxomes available. A simplified methodology is used here 10 compute loss for building due to a scenario earthquake event equivalent to 1897 Great Illdian Earthquake. Although, the analysis presented here is simplified with some assumptions, the GIS based methodology can be extended 10 include more complex models as well as other illventory data. Figure 6.1 presents the detailed flowchart of damage estimation. Study Area Scenario BuildingTypes Earthquake Soil Parameter Seismic Haz ard MotiWl Damage M,p Relationship Damage Dim'ibution , Building Iterate for Databue Building Type DirectLo5S E5timation Integrllle for - BuildingTypes Figure 6.1 Flowchart of damage estimation methodology for a given Intensity. Table 6.1 Calculated Motion-Damage Ratio for thi, ,tudy retrieved from Fragility curve by Arya (2000) PGA(O/.g) MMI EMSA EMSBI EMSB2 EMSC EMSF 0,082 VI 0.39 017 0,28 0.03 0 0,113 VI 0.46 0,22 035 0.04 0 0.!58 VII 0.55 0.29 0.42 0,07 0 0.216 VIII 0.63 0.40 0.51 0.08 0.01 0.218 VIIT 0.63 0.40 0.51 0,08 O.oJ 0.297 Vlll 0.76 0.52 0.60 0,17 0.02 88 6.2.1 Damage Ertimation Based 011 Analysis 1 (MMIG!d Overlaying the building distribution map on the ground shaking hazard map, damage distribution was derived. Damages are calculated from Table 6.1 according to fragility curve prescribed by Arya (2000) Table 6.2 Ward wise damaged buildings based on Analysis 1 ofRajshahi City WARD NO EMSA EMSBI EMSB2 EMSC EMSF TOTAL I 227 59 III 47 0 4'4 2 163 39 74 30 0 306 ) 101 '15 '9 ]5 Q ]60 4 149 35 69 28 0 281 5 192 47 89 36 Q ]64 6 0 140 96 J9 0 275 7 0 86 59 24 0 169 8 0 86 60 23 0 169 9 0 51 34 13 0 98 1O 0 45 31 12 0 88 11 0 59 54 21 0 134 12 0 117 80 33 0 2)0 I] 0 60 41 16 0 117 14 0 43 30 12 0 85 15 0 78 5] 22 0 153 16 0 207 143 56 0 406 17 194 47 92 36 0 369 18 224 lOS 42 0 425 19 242 62" 117 48 0 469 20 Q 214 144 59 0 417 21 0 110 73 30 0 213 22 0 107 72 30 0 209 23 0 96 fA 28 0 24 0 109 72 30 0 2ll'" 25 0 129 86 36 0 251 26 188 48 9J 39 0 368 27 362 92 177 73 0 704 28 242 63 119 50 0 474 29 189 49 9] 39 0 370 30 187 49 92 J8 0 366 Total 2,750 2,426 2,512 1,025 0 8,713 % 4 3 3 1 0 11 Only for ground shaking, total estimated damage is about 8,713 out of 76,173 buildings within Rajshahi City. Approximately 11 percent buildings are estimated to 89 be damaged. Among different building types, 4% of A type, 3% ofBltype, 3% ofB2 type and 1% C type will be damaged All F types is found not affected by such scenario earthquake. Building damage distribution according to EMS type in Rajshahi City is shown in Figure 6.2a through Figure 6.2d. Tolal building damage distribution is also shown in Figure 6.3. 6.2.2 Damage Estimation Based on Analysis 2 (Millh) "Ihc grade of damage depends on the intensity of earthquake motion and the strength of the buildings The strength of bUIldings has a close relation 10 the building Estimated building damage of 30 wards for combined hazard is presented in Table 6.3 Tota! estimated damage is about 11,188 out 01'76,173 buildings within Rajshahi City. Approximately 15 percent buildings are estimated to be damaged. Among different building types, 5% of A type. 4% of BI type, 3% of 82 type and 2% of C will be damaged. A negligible percentage of F type may be affected by such a scenario earthquake. Building damage distribution according to EMS type in Rajshahi City is shown in Figure 6.4a through I'ignre 6.4t. Total building damage distribution is also shown in Figure 6.5. 90 Table 6.3 Ward wise damaged buildings based on Analysis 2 ofRajshahi City WARD NO EMSA EMSBI EMSB2 EMSC EMSF TOTAL I 3ll 107 III 93 8 630 2 213 60 74 59 I 407 3 211 55 89 44 I 400 4 168 43 69 39 0 319 5 216 59 89 50 I 415 6 0 167 96 50 I 0 313 I 7 0 96 59 271 0 182 I 8 0 157 60 50 3 270 9 0 53 34 14 01 101 \01 0 51 3 I 14 0 96 III u 71 54 26 I I I 152 12 ! 0 178 80 67 3 I 328 13 0 87 41 28 I 157 14 0 55 30 16 0 101 15 0 ll3 53 38 0 204 16 0 211 143 58 0 412 17 244 67 92 51 0 454 18 270 78 105 65 4 522 19 290 90 ll7 75 4 576 20 0 239 144 72 0 455 21 0 P,- 73 28 I 244 22 0 154 72 56 JI 285 23 0 121 64 36 I 222 24 0 198 72 61 5 336 25 0 234 86 72 61 398 26 255 81 76 6 i 5\7 27 484 157 177" 145 10 I 973 28 3JI ll4 119 \00 9 673 29 259 89 93 78 7 526 30 256 88 92 77 7 520 Total! 3,S()l\ 3,41\ 2,512 1,675 811 \1,18& % 5 4 3 2 01 15 91 , z • • • • " 00 00 MN ee - " •" • •" ~• • z z • z • ~ •" • • • • •""• " " "" ~, u w 0 0 "• 0• •- •• 0 .,;. 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U w 0 • 0" " '0• • " "• .,N • w -. • <"• • •0 ••• ~• • ~ • ~• • ••~ v,= ~ ••~ ,• ~• ~ • w •• .,~-• • ., • ~ • "• • £• • • " ~• • ~ • ~ •" ~ z • •" •~ • o.cc • N_ ~ _.O g£! _c ., .0 • - ~ •• • ~ • <, ] ~ ~ w ;g g: • .i • ,.~• N ~= ~ •~ • ~ • ~ z •~ "• • • • •" •" " " " " •~ • • ~ '" Cl co co 1-"'«r<,Q'" oSSS.s tIlc:>-~- ]; ...... -'" w w0mOO • •" ~ -• z , , z • • "• ,. -" -• •- -• "•- w • -., >.• o <" o o ~ ~ ~ o w ~ '; •'" ~ ~ >. "- ~ '"w .i1 Z+ iffN z z z • z • "• • • -• •" "" -" " • • ~ • u z z" ••• ~" ~ " •" .," - • <'"" " w ~" 0" • • • z" • • ,~" z" ~ ~ • - E" ~ ~" S ~-" " ~s~1p'[J .2" ;;c;;;;;- ~ z- ~ .," ~;;~ - .;; ~ .,"• 0 0 z• ~ ~ " • • ~ • -~ ~ ::•" , . N ~ •e • • .- ~. ..c e• < ..c • en'" • .~ ~• • ~ •e .-c • " _. 2 -E 0 7.1 Introduction In this chapler, the relation between the pattern of urban development and seismic risk is described Specific recommendations are also prescribed with respect to seismic risk assessment Section 7,1 identifies existing prominent establishments under risk. section 7.3 reviews risk in light of the Rajshahi Metropolitan Development Plan (&'-1DP), section 7.4 suggests zones of building height restnetions based on risk analysis and section 7.5 recommends zones where ground improvement is suggested 7.2 Existing I,and Use Under Risk Section 1.5,5 describes the existing land use pattern of Rajshahi city. As 33.4% area is covered by residential use, it can be easily understood that human hves are most vulnerable to seismic risk in RCC area By superimposing the regional distribution of combined seismic hazard (MMIF) map (Figure 5.6) on existing land use map, spatial distribution of risk areas can be defined (Figure 7.1) Rajshahi University campus, Rajshahi University of Engineering and Technolob'Y campus, Padma Residential Area, Bangladesh Telephone and Telegraph Board (BTTB) headquarter, Bangladesh Rifles (BDR) headquarter, Forest office, Postal Academy, Physical Training College, Rajshahi Development Authority (RDA) building, Bangladesh Small and Cottage Industries Corporation (BSClC) building. Shaheb Bazar area, Rajshahi College, Power Development Board (PDB) office, BTTB office, Mission Hospital, Rajshahi Development Authority (RDA) Rest House, Television Centre, Radio Centre, Bangladesh Bank and Rajshahi Court building are most vulnerable as they fall under VIII-MMII EMS Intensity hazard zone. Buildings within this zone may suffer from cracks in columns with detachment of pieces of concrete, cracks in beams, severe damage to the joints of the building skeleton with destruction of concrete, protrusion of reinforciog rods, partial collapse and/or tilting of columns [Appendix-C]. But, buildings with lift cores (like the RDA building) are 104 relatively safer Buildings with, lift cores have el(tra strength against seismIC vulnerability The District Commissioner's (DC) office, Public Works Department (P'WD) quarters, Police line, Cantonmem, Rajshahi Medical College Hospital, Tuberculosis Hospital, Laboratory High School, New Market, Upashahar, Shishu Academy and Central Jail are located within a relatively less risk zone of VI- .MMII EMS Intensity. Thesc buildings may sustain damage of fine cracks in plaster over frame members and in pal1itions. a few suffer damage of hair-lme cracks in columns and beams. mOl1al'falls from the .l0i~ts of suspended wall panels, cracks in partition walls. fall of pieces of brittle cladding and plaster [Appendix-C] Therefore. first priority should be gil'en for retl'Otitlingto the buildings within the zone ofVIII-MMl/ EMS lrnensity 7.3 Evaluation nf RMDP (2004-2024) with respect to Seismic Risk Rajshahi Metropolitan Development Plan (2004-2024) proPosed a land use plan of which RCC area is Oldya part "Iherc is no indication that seismic vulnerability was considered in formulating the RMDP, E;<:istingagricultural lands are proposed to be converted to residential use in RMDP IfRMDP is implemented, two-third areas with residential use will be under seismic risk. Among them, more than 50% residential area ~i1l be under VB to VJIl- M,\.1J! EMS Intensily zonc. A large open space provided at the nOl1h-easlernpart oflhe city is a wise decision This can serve as an evacm\.tionsite. Existing prominent eslablishments will remain under Ihe same risk, as those are not proposed to be shifted to other places. Figure 7.2 shows thc RMDP proposed land use areas of RCC overlaid on the regional distribution of combined seismic hazard (MM/P). According to RMDP, RCC area consists SPZ 8 (Ward 17), SPl 13 (Ward 26), SPZ 14 (Wards 14, 15 and 19), SPl]5 (Wards 1, 2 and 4), SPZ 17 (Wards 3,5,6,7,8,9,10,11 and 13), SPl]8 (Wards 12, 20, 21, 22, 23, 24, 2S and 27) and SPZ 19 (Wards 28, 29 and 30), Ward 1 of SPZ 15; part of Wards 3 and 8 of SPl 17; pari of wards 12, 22 and 23, Wards 24 and 25, pari of ward 27 of SPl 18, and Wards 28, 29 and 30 are under the VIII-MMIlEMS Intensity hazard zone. Many buildings within this zone of vulnerability class EMSC may suffer damage of grade 2 [Appendix-C]. Many 105 buildings of class EMSB and 11few of class EMSC may suffer damage of grade 3, Many buildings of class EMSA and a few of class EMSB may suffer damage of grade 4; a few buildings of class EMSA may suffcr damage of gradc 5, Part of Wards 2 and 4 of SPZ 15; Ward 17 of SPZ 8; Wards 20 and 21 of SPZ 18; and part of Wards 15 and 19 ofSPZ 14 are within the VII- MMI! EMS Intcnsity hltZard zonc, Within this 70ne, many buildings of vulnerability class EMSB and a few of class EMSC may suffer damage of grade 2. Many buildings of cla.~sEMSA and a few of class EMSB may suffcr damage of grade 3; a few buildings of class EMSA may suffer damage of grade 4. Damage may be particularly noticeable m the upper parts ofbuildmgs The rest of the ReC areas are covered by Vl-l\1MI/ EMS Intensity hvard zone "'lIh a possibility to sustain damage of grade 1 and a th>•. may suffer damage of grade 2 7.4 Suggested Zones of Building Height Restrictions Except for buildings constructed with a lift core, the vulnerability of housing units with different storeys has a relation to soil frequency, The relation e: engmeers - j=lIr (7,1) T~OIN (7.2) where, f= soil (natural) frequency T= time period N~no. of storeys From Equations (7.1) and (7 2), j=101N (7.3) By using Equation (7.3), some zones can be:suggested for restricting building heights or storeys. Figure 7.3 shows the zones of restricted building heights within the RCC area, Within a zone of a particular maximum building height, buildings can be constructed with more height or lower height if greater safety precautions are adopted. 106 • 7.5 Suggested Zones of Ground Improvement With reference to the liquefaction potential index (Table 4.6), the characten,tics of the Rajshahi Metropolitan Development Plan (RMDP 2004) Spatial Planning Zones (SPZ) can be described and ground improvementrecommended as follows- SPZ 8: Ward 17 (part); ground improvement is required, investigation of impurtant structure, is indispensable. SPZ 13; Ward 26; ground improvement is required. investigation of important structures 1S indispen,able SPZ 14; Ward, 14 (part), 18 (part); ground improvement is indi,pensable Wards 15 and ]9 (part), ground improvement is required, investigation of important structures is indispen,able Ward 16; investigation of important structures is required. SPZ 15: Wards 1, 2 and 4; ground improvemenl is required, investigation of important structures is indispensable SPZ 17: Ward, 3, 5, 6 and 7; investigation of important structures is required Ward 8, ground improvement is indispensable. Wards 9, 10,11 and 13, ground improvement is rcquircd, investigation of important struclllres i, indispen,able, SPZ 18: Wards]2 and 22; ground Improvement is indi,pen,able, Ward, 20 and 21, inve,tigation of important structure, is required. Ward, 23, 24, 25 and 27; ground improvement is required, investigation of important structures is indispensable SPZ 19; Wards 28, 29 and 30; ground improvement is required, investigation of important structures is indispensable Figure 7.4 ,hows areas requiring ground improvement within RCC boundary. 7.6 Other Recommendations for Risk Mitigation From the study, it is evident that Rajshahi City CO/poratioo has no defense system against a potential strong earthquake, Under the direction of proper plan, each ward must take and prepare necessary measures for seismic disaster mitigation. It IS also necesSary to clarify the role of community in disaster prevention efforts such as first aid, evacuation and infonnation collection and dissemination. 107 Emergency Response: The Rajshahi City Corporation must have enough capacity for emergency response, such as supply food, water, medicine, tools for preliminary rescue operations and electricity-supplying generators. Iderrtification and designation of evacuation sites for the people living in the Rajshahi City Corporation is quite important There are few suitable open spaces to serve as evacuation sites in the Rajshahi City Corporation area. More open spaces should be designated as evacuation sites in residential as well as commercial areas Retrofitting: It is imperative to retrotit structurally weak schools and public facility buildings in the Rajshahi City Corporation area The resistance of school buildings against a strong earthquake is not sufficient The earthquake resistance of each school building should be checked immediately, and necessary retrofitting, reconstruction and even school relocation should be implemented. Public facilities such as the hospitals or clinics, and related public buildings should also be checked and necessary reinforcement of these buildings should be conducted Priority, may be given to facilities identified in section 7,2. There is immense scope to construct buildings v.rith Anti Seismic Design within Rajshahi University campus, Rajshahi University of Engineering and Technology campus and Padma Residential Area (a new housing area), as these areas are still not fully occupied by development activities. BTT8 headquarter and BDR headquarter should be relocated v.rithin safe zone, The Postal Academy and Physical Training College arc more or less safe (according to height restrictions prescribed in Figure 7.3) and can be useful in an emergency as they are surrounded by sufficient open space for possible evacuation The Rajshahi Development Authority building with a lift core and the BSCIC building are safe, but emergency evacuation exits are required. Rajshahi College, PDB office, BTIB office, Mission Hospital, RDA Rest House, TV Centre, Radio Centre, Bangladesh Bank, Rajshahi Court building, DC office, PWD quarters, Police line, Rajshahi Medical College Hospital, Tuberculosis Hospital, Laboratory High School, New Market, Shishu Academy and Central Jail need sufficient retrofitting, as these are old structures and have higher possibilities to match soil (natural) frequency. Wire mesh, external column for load sharing and lift core like additional construction can reduce vulnerability. 108 24.425 +EM !21 VIII- MMV• INTENSITY IT] VII - MMI/ INTENSITY B VI - MMI/ INll'NSITY II AGRICULTURE [ill ASSEMBLY D BUSINESS o CHAR LANf) Ill! EDUCATIONAL & RESEARCH • INDUSTRIAL & STORE • INSTITUTION III MIXED USE Gl ADMINISTRATION [J UTILITIES & TRANSPORT Ell ROAD & RAilWAY mJ RESIDENTIAL III SECURITY/DEFENSE o OPENI VACANT LAND 24.35" WATER BODY 880375.E 88,562o"E 88.5885"E 88,5125"E 886375"E o Figurt 7.1 Existing Land use of RCC area under tile risk of combined seismic hazard (MMh) 1(l'J _.~_..- 14.25 H ~!~~~ & '" vJ VIII. Mt:1l1INTENSITY" rn VII . mw INTENSITY 8 VI . r.l~'I' INTENSITY D ASS~MULY D BUSINESS DellA/lLANO m EDUCATIONAl'\ RESEARCH • INOUSTRIAL'\ STORE II INS l1TllTl014 m ~'IXEO USE o ADMIN1STRAIlON o 11111.ITlf:S.\ TRANSPORT g ROAD.\ RAILWAY B UESIOENllJIl. III SE:ClIllIIY!DHEHSE o Of'ftll VACANT LAND 14.)~' WAIOIIlODY 885375"E 98562S'E 89S8QS'E 99612S'E 911 611$ "E o Fill.llrt 7.2 RMn p (2004-20H) llmflll~ffi Inncl!I'C IIndrr thc ri,1; of comhillttl 'l'illll it h~r:lnl pUII.I p 1m z "•N • •N •N :;)" • "" •> • ~ •••"• •• ']I •••••• ~ ~"~ w • "N < w o t- • • • " ~" W ~• W • •• • • .,• ~ "• W • "N • W • w - W ~• .i::l Q" ~• .~ W • W ~ "W C• • ~ ~ Q• ~• w ." :2 N• " • • ~ ~ • =• l z , z • , •N • • • ~ " " •N •N •N •N I • ~ • -•~ U ~ U Z • ~ 0 • •0 <• •, ~ = • ~ • ~ Z ",•0 >• ::,;::;:;. f i~ggm! w • i" N " •, ••• • • •- " ~ " ,=• ~ ~t~ ~ w ii •N II • V. • ,•, •~ ~ CHAPTER EIGHT CONCLUSION 8.J Overview of the Research This study provides a preliminary methodology for earthquake risk assessment as a basIc step in the mitigation of earthquake risk and it is abo an attempt for quantification of the problem of earthqlIake loss. It shows the effectiveness of a geographic information system for use in conducting regional earthquake hazard and risk analysis, Several maps were used for showing the different types of summary information or results, The hazard integration scheme for combining the secondary effect of liquefaction can be very effective in the GIS environment. The flexibility of the methodology will allow improved hazard models expanded with geologic data, and enhanced weighting schemes in future analyses. A soil database from 50 boreholes was used to develop site amplification and soil liquefaction potential maps of the study area Both of these site effects are integrated in GIS platform for combined hazard assessment Three past historical earthquakes were evaluated as scenario events namely the 1885 Bengal earthquake, the 1897Great Indian earthquake and the 1930 Dhubri earthquake. Intensity values obtained for these events were calibrated against attenuation laws to check the applicability of the laws for the study Bedrock Peak Ground Acceleration (PGA) values were estimated using different attenuation laws, Finally, the Great Indian Earthquake of 1897, with the attenuation law of McGuire (1978) was chosen as the scenario earthquake, as it shows highest bed rock I-'GA (0.0634g). I-'GA value was converted into MMJ values to integrate the effect of site amplification as well as liquefaction and then a combined hazard map was proposed for this study area. Only for, ground shaking, approximately 11 percent buildings are estimated to be damaged. Again for ground shaking and liquefaction, approximately 15 percent buildings are estimated to be damaged. By superimposing the regional distribution of combined seismic hazard (MMlJ.) map on existing land use map, spatial distribution of risk areas were defined. Some major critical facilities were fOlindmost vulnemble as they are in the VIII_MMI/lntensity hazard zone The RMDP (2004-2024) proposed a land use plan, where of seismic vulnerability was not considered, If RMDP is implemented, two-thirds ofRCC areas with residential use will be under seismic risk 8.2 Recommendations Based on soil (natural) frequency. some zones are suggested tur building height restrictions using thumb rule, According to ;;oil liquefaction analysis, liquefaction potential index helps to identify particular zones where ground improvement is suggested. Suggested building height restrictions are based on a thumb rule. Therefore it mav not be wise to follow it as a hard-and-fast rule rather those heiQ.hts , , - may be discouraged only. Further research is needed as described in section 8,3, Damage states should be dependent on the structure typc because each structural system has different modes of failure. The motion-damage relatio'nships used in this dissertation are based on expert opinion and use Modified Mercalli of Felt Intensity (J1JvfJ) (assumed equal to EMS Intensity) as thc ground motion parameter So ne\\' relationships are needed that estimate damage as a function of measured structural rcsponse in the conte"t of Bangladesh, People's participation and public awareness on s.eismicdisaster prevention should be promoted. First-aid rescue operations are the most important in saving human lives and this is why it is quite essential to promote community participation in seismic disaster management by raising awareness on disaster prevention, Hazard such as faulting and shaking can be mapped to identify the existence of the specific hazard. Re<:entdecades have seen the development of a variety of new methods for soil improvement and liquefaction mitigation, including soil mixing, stone columns, soil wicks and chemical and pressure grouting, to name only a few. Primary damage mlltgation IS the purview of design professionals, who have developed a large toolkit for bracing, stTCllgthening,or otherwise improving the eanhquake performance of buildings, nonstructural elements, equipment and contents. 114 Secondary damage is typically due'to the interaction of several problems, (UldC(Ulbe a very complex is~ue_ It is therefore be~l mitigated prior to the earthquake, through better handling of materials and improving of infrastructure. Since lhi~ e(Ulnol be done everywhere, it mll~t also be mitigateJ via improved emergency re8pon~e, i.e., via analysis of the prohlem. acquisition of the necessary equipment, and ongoing exercises. 8.3 Scope fOI"Further Reseal"ch In this dissertation. soil mnplifieation was modeled by II ~impl~ multiplication factor; liquefaction was modeled ",ilh a qualitative descriplion or high, moderate and lo\\- potential. More quantitath-e models fur thcsc site effects that can be applied over a large region arc needed. Computational power and storage is becoming less of a concern, therefore models that require three-dimensional soil parameters can and should be implemented in the GIS environment. Again, hazard moods contained scveral simplifYing assumptions for the damage estimation model. Improvements arc needed in the models together ,,~th the quantification of the hazard~_ The heuristic weighted average approach to the hazard integration ean also be improved. In dealing with local site effects, nncertainty is present in the spatially varying soil properties, since only limited number of borehole dala were used that may not capture the ~ariation of soil properties. Further research is needed to develop methods for treating uncertainty that can be applied over a large region Building mass, construction type, material~ and age should be considered to develop better relationship bet\\'een soil (natural) frequency and practised design heights of building struerures to assess vulnerability in Bangladesh. Aerial photography/satellite images could be used to identifY a number of distinct zones of the study area with apparently nnifonn development patterns. Ground srnveys could be done covering a suflicient sample (perhaps 15-20%) of the buildings in each such zone to enable the characteristics of that zone to be quantified both in terms of the distribution of construction types and its density of occupation (dwellings!km\ the outcome of the snrvcy could then be applied to aU wards within the zones identified. 115 REFERENCES Ali, M.H. and J.R. Choudhury (1992). 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The Middle East University, Turkey. 122 APPENDIX - A: Earthquake Chronology of Bangladesh 1548 The first recorded earthquake was a terrible one Sylhet and Chittagong were violently shaken, the earth opened in many places and threw up water and mud of a sulphurous smell. 1642 More se'vere damage occurred in Sylhet district Buildings were cracked but there was no loss oflife 1663 Severe earthquakc In t\ssam, which continued for half an hour and Sylhet d,stnct was not free from its shock 1762 The great earthquake of April 2, \lihich raised the coast of Foul island by 2.74m and the northwest coast of Chedua island by 6 71m abolie sea level and also caused a permanent submergence of 155.40 sq km ncar Chittagong The earthquake proved liery violenl in Dhaka and along the eastern bank of the Meghna as far as Chiltagong, In Dhaka 500 persons lost their lives, the riliers andjheels were agitated and rose high abolie their usual levels and when they receded their banks were strewn with dead fish A large river dried up. a tract of land sank and 200 people with all their cattle were lost, Two volcanoes were said to have opened in the Sitakunda hills 1775 Severe earthquake in Dhaka around April 10, but no loss of life, 1812 Severe earthquake in many places of Bangladesh around May 11 The earthquake pmved violent in Sylhet 1865 Terrible shock was felt, during the second earthquake occurred in the winter of 1865, although no serious damage occurred 1869 Known as Cachar Eanhquake, Severely felt in Sylhet but no Joss of life The steeple of the church was shallered, the walls of the courthouse and the circuit bungalow cracked and in the eastern part of the district the banks of many rivers caved in. 1885 Known as the Bengal Eanhquake. Occurred on 14 July with 7.0 magnitude and the epicentre was at Manikganj. This event was generally associated with the deep-seated Jamuna Fault. 1889 Occurred on 10 January with 7,5 magnitude and the epiccntre at Jaintia Hills. It affected Sylhet town and surrounding areas. 1897 Known as the Great India Earthquake with a magnitude of8.7 and epicentre at Shillong Plateau. The great earthquake occurred on 12 June at 5.15 pm, caused serious damage to masonry buildings in Sylhet town where the death toll rose to 545. This was due to the collapse of the masonry buildings. The tremor was felt throughout Bengal, from the south Lushai Hills on the cast to Shahbad on the west. In Mymensingb, many public buildings of the district town, including the Justice House. were I-Iffeckedand very few of the two-storied brick-built houses belonging to landlords survived. Heavy damage was done tu the bridges on the Dhaka"Mymensingh railway and traffic was suspended for abuut a fortnight. The river communication of the district was scriously affected. Loss of life was not great, but loss of property was estimated at five million Rupees Rajshahi suffered severe shocks. especially on the eastern side. and 15 pcrsons died In Dhaka damage to property was heavy In Tippera masonry buildings and old temples suffered a lot and the total damage was estimated at R, 9.000 1918 KnowTlas the Snmangal Earthquake Occurred on 18July with a magnitude of 7.6 and epicentre at Srimangal, Maulvi Bazar. Intense damage occurred in Srimangal, but in Dhaka only minor effects were observed. 1930 Known as the Dhubri Earthquake. Occurred on 3 July with a magnitude of7 I and the epicentre at Dhubri, Assam. The earthquake caused major damage in the eastern parts ofRangpur district. 1934 KnowTl as the Bihar-Nepal Earthquake. Occurrcd on 15 January with a magnitude of 8.3 and the epicentre at Darbhanga of Bihar, India Thc earthquake caused great damage in Bihar, Nepal and Uttar Pradesh but did not affect any part of Bangladesh. Another earhquake occured on 3 July with a magnirndc of7.1 and the epicentre at Dhubri of Assam, India Thc earthquake caused considerable damages In greater Rangpur district of Bangladesh. 1950 Known as the Assam Earthquake. Occurred on IS August with a magnitude of 8.4 with the epicentre in Assam, India. The tremor was felt throughout Bangladesh but no damage was reported. 1997 Occurred on 22 November in Chittagong with a magnitude of 6.0. It caused minor damage around Chittagong town. 1999 Occurred on 22 July at Maheshkhali Island with the epicentre in the same place, a magnitude of 5.2. Severely felt aroond Maheshkbali island and the 124 adjoining, Houses cracked and in some cases collapsed, 2003 Occurred on 27 July at Kolabunia union of Barkal upazila, Rangamati district with magnitude 5 1, The time was at 05' 17:26.8 hours, Source: Banglapedia. 2004 125 APPENDIX - B: Building Inventory Format Survey Format Part A: General information: I) Inturmation on House-owner 2) Location and address 3) Settlement type 4) Effects of previous earthquake event!s, and 5) Process of building construction Part B: Building details: I) Constmcllon date & registration (age, storeys) 2) Current usage 3) Informalion on design and supervision 4) Existence of open space surrounding the buildmgs S) Informalion on occupancy 6) Geometry (plan, area, information on door, windows, stmctural elements etc) 7) Site conditions (terrain type, building position with respect to adjacent buildings, potential local hazards) 8) Shape of buildings in plan and elevation, configuration problems 9) Infonnation on foundation, construction materials (typology), details on walling materials and section, infonnation on roof and /loors ]0) Presence oheismic-rcsistant features such as lintels, wall plate, roofband, comer bars, thorough stones II) Defects in the buildings Part C: Remark ItsBuilding Category by EMS Type: Observation of the above collected information and classification of the surveyed building units into EMS typologies. 126 APPENDIX - C : European'Macro Seismic Seale Vulnerability Classification for Different Types of Building Structures Vulnerability Class Type of Structure A B C D E F rubble stone field stone 0 adobe (earth brick) simple stone ,. I.. massive stone ta6i z 1= .. 1 0" ~ Llnreinforced brick I < , concrete blocks /..0..I unreinforce brick with RC floors I..0 reinforced brick (confined masonry) ,...Iaf-.....I RC withoul antiseismic w design (ASD) I..-1<: I uE RC whh minimum I".. o~Z level of ASD I.. uu l'- ~~ RC with moderale u level of ASD I... 0 101 ~" Z RC with high @ level of ASD I-jo[ " wooden structures a0 bamboo made structures 0 I.. ~ pt 127 Damage Grade (or Masonry Buildings Oassificlition of Damage to Masonry Buildings Grade I Negligible to sligbt damage (no structural damage) Hair-linecracksin very few walls, fall of smallpieces of plaster only. {-'al! of loose stones from upper parts of buildings in very few da.ss Grade 2 ;\Ioderate damage (sligbt structur.aJ damage, mooerate non-structural damage) Cracks in many walls; fall of fairly large piecesof plaster, parts of chimneysfall down Grade 3 Substantial to' heavy damage (moderate structural damage, hea~y non-structural damage) Largc and extensive cracks in most walls, pantiles or slates slip off Chimneys are broken at the roof line, failure of individual non-structuralelements. Grade 4 Very Hravy damage (heavy structural damage, very heavy non-structural damage) Serious failure of walis, partial strucwrll1failure. Grade 5 Dmructi.nll (very It.tllvy structural damage) Totalor near IOlalcollapse. 128 Damage Grade for Buildings of Reinforced Concrete Classification of Damage to Buildings of Reinforced Concrete Grade I Negligible to slight damage (no structural damage) Fine cracks in plaster over frame membersand in partitions. Gr:lde 2 Moderate damage (slight i structural damage, moderate non-struclural damage) Hair-line cracks in columns and, beams; mortar falls from the joints I of suspended wall panels, cracks in partition walls; fall of pieces of brittlecladding and plaster. Grade 3 Substantial to beavy damage (moderate struelural damage. heavy non-structural damage) Cracks In columns with detachment of pieces of concrete, cracks in beams. Grade 4 Very hel'lV'J damage (heaV'J structural damage, very heavy non-SlruclurllJ d:lmllge) Severe damage to the joints of the building skeleton with destruction of concrete and protution of reinforcing rods; partial collapse; tiltingof columns. Grade 5 Destruction (very heavy structural damage) Totalor near total collapse. 129 Definition of Intensity Scale Arrangement of the scale: a) Effects on humans b) Effects on objects and on nallire (excluding damage to buildings, effects on ground and ground faillire) c) Damagc to buddings Introductory remark; The single intensity degrees can include the effects of shaking of the respective lower intensity degree(s), also whcn these effects are not mentioned explicitly. 1. Not felt a) Not felt even under the most favorable circumstances b) No effect. c) No damage II. Scarcely felt a) The tremor is felt only by a very fev. (less than 1%) individuals at rest and in an especially receptive position indoors. b) No effect. c) No damage ill Weak a) The eanhquake IS felt indoor by a few. People at rest feel a swaying or light trembling. b) Hanging objects swing slightly. c) No damage. IV. Largely observed a) The earthquake is felt indoors by many and felt outdoors only by very few. A few people are.awakened. The level of vibration is not frightening. The vibration is 130 moderate Observers feel a slight trembling or swaying of the building, room or bed, chair etc. b) China, glasses, windows and doors rattle. Hanging objects swing, Light furniture shakes visibly in a few cases. Woodwork creaks in a few cases, c) No damage V. Strong a)The earthquake is felt indoors by most. outdoors by few A Fe'" people are frightened and run outdoor~ Many sleeping people awake Observers feel a .~trong shaking or rocking of the whole building. room or fumiture b)Hanging objects ~;v..ing considerably. China and glasses clatter together Small, top- heavy and/or precariously supported objects may be shifted or fall down. Door; and windows swing open or shut. Tn a few cases windowpanes break Liqllids oscillate and may spill from well-filled containers. Animals indoors may become uneasy. c)Damage of grade 1 to a few buildings. Vi Slightly damaging a) Felt by most indoors and by many outdoors, A few persons lose their balance. Many people are frightened and run outdoors b) Small objects of ordinary stability may fall and furniture may be shifted. In few in- stances dishes and glassware may break Farm animals (even outdoors) may be frightened, c) Many buildings sustain damage of grade 1;a few suffer damage of grade 2. VD. Damaging a)Most people are frightened and II)' to run outdoors, Many find it difficult to stand, especially on upper floors. b)Fumiture is shifted and top-heavy furniture may be overturned, Objects full from shelves in large numbers. Water splashes from containers, tanks and pools. c)Many buildings of vulnerability class B and a few of class C !>\lfferdamageof grade 2. Many buildings of class A and a few of class B suffer damage of grade 3; a few 131 buildings of class A suffer damage of grade 4 Damage is particularly noticeable in the upper parts of buildings. VIII. Heavily damaging a) Many people find it difficult to stand, even outdoors. b) Furniture may be overturned. Objects like TV sets, typewriters etc. fall to the ground. Tombstones may occasionally be displaced, tWIsted or overturned Waves may be seen on ver)' soft ground. c) Many buildings of vulnerability class C suffer damage of grade 2 Many buildings of class B and a few of class C suffer damage of grade J. Many buildings of class A and a few of class B suffer damage of grade 4, a lew buildings of class A suffer damage of grade S. A few buildings of class D suffer damage of grade 2 LX.Destructive a) General panic. People may be forcibly thrown to the ground, b) Many monuments and columns fall or are twisted, Waves are seen on soft ground c) Many buildings of vulnerability class C suffer damage of grade 3 Many buildings of class B and a few of class C sufTer damage of grade 4. Many buildings of class A and a few of class B suffer damage of grade 5. Many buildings of class D suffer damage of grade 2; a few suffer grade J A few buildings of class F suffer damage of grade 2. X. Very destructive a) Many buildings of vulnerability class C suffer damage of grade 4. Many buildings of class B and a few of class C suffer damage of grade 5, as do most buildings of class A. b) Many buil XI. Devastating a) Most buildings of vulnerability class C suffer damage of grade 4. Most buildings of class B and many of class C suffer dornage of grade 5. 132 b) Many buildings of class 0 suITerdamage of grade 4. A few suffer grade 5 Many buildings of class F suffer damage of grade 3; a few suffer grade 4. Many buildings of class F suffer damage of grade 2, a few suffer grade 3. XII. Completely devastating a) Practically all structure, above and below ground are destroyed, 133 • APPENDIX - D: Modified Marcelli Scale of Felt Intensity A number of different intensity scales have been set up during the past century and applied to both current and ancient destructive earthquakes For many years the most widely used was the ]o-point scale devised by Michele Stefano de Rossi and Fran~ois-Alphonse Fore! in 1878. The scale now generally employed in North America 15the Mercal1i scale, as modified by Harry 0 Wood and Frank Neumann in 1931, in which intensity is considered to be more uniformly graded, An abridged form of the modified Mercal1i scale is provided below. Alternative scales have been developed in both Japan and Europe for local conditions The European (MSK) scale of 12 grades is similar to the abridged version of the Mercalli (Britannica, 2003). Modified Mercalli Scale of Felt Intensity I:MMI (193 I; Abridged) I, Not felt. Marginal and long-period effects oflarge earthquakes, n, Felt by persons at rest, on upper floors, or otherwise favourably placed to sense tremors. lII. Felt indoors Hanging objects swmg. Vibrations like passing of light trucks Duration can be estimated. IV. Vibration like passing of hea~1' trucks (or sensation of a jolt like a heavy ball striking the walls) Standing motorcar, rock. Windows, dishes, doors rattle, Glasses clink. Crockery clashes. In the upper range oflV, wooden walls and frames creak V. Felt outdoors, direction may be estimated. Sleepers wakened, Liquids disturbed, some spilled. Small objects displaced or up5ct. Doors swing, open, close. Pendulum clocks stop, start, change rate. VI. Felt by all; many frightened and run outdoors. Persons walk unsteadily. Pictures fall off walls, Furniture moved or overturned. Weak plaster and masonry cracked. Small bells ring (church, school). Trees, bushes shaken. 134 VII. Difficult to stand Noticed by drivers of motorcars. Hanging objects quiver, Furniture broken. Damage to weak masonry. Weak chimneys broken at roofline, Fall of plaster, loose bricks, stones, tiles, cornices. Waves on ponds; water turbid with mud. Small slides and caving along sand or gravel banks. Large bells ring Concrete irrigation ditches damaged, \TII Steering of motorcars affected Damage to masonry; partial collapse Some damage to reinforced masonry: none [0 reinforccd masonry designed to resist lateral forces. Fall of stueco and some ma,onry walls Twisting, fall of chimneys, factory stacks, monumems, lOwers,elevated tanks Frame houscs moved on foundations ifnol bolted down; loose panel \vall, thrown out Decayed pihng broken off Branches broken from trees. Changes in flow or temperatLlreof springs and wells. Cracks in wet ground and on steep slopes IX. General panic. Weak masonry destroyed; ordinary masonry heavily damaged, sometimes with complete collapse; reinforced masonry seriously damaged. Serious damage to reservoirs, Underground pipes broken Conspicuous cracks in ground In alluvial areas, sand and mud ejected, earthquake fountains, sand craters, X Most masonry and frame structures destroyed with their foundations. Some well- built wooden structures and bridges destroyed, Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc Sand and mud shifted horizontally on beaches and flat land Railway rails bem slightly. XI, Rails bem greatly. Underground pipelines completely out ofservlce, XII. Damage nearly total. Large rock masses displaced. Lines of sight and level distorted, Objects thrown into air. 135 APPENDIX- E : BuildingTfPol~es in Rnjshahi City EMSB2 type lit Shaheb BIIZIlf EMSD type; The City Corporation EMSF type It Baker More Building f!l:l , • 136 \ , , 0 , c. 0 , 0 , > , 0 ,, 8 > , • • c , 0•- • 0 ••0 •• , 0 • - - M - , • ,• •c. •0 0 ••0 0 0 - ~ • •- • • - - •- - • • •" • 0 " 0 " 0 M - , - - •• -N • • - • - • • " ------" """"" " e. :'= e. " • e• iJ ~ > e , Ji:' 0 ¥, • C " . " I I ! l I • N 0 0 0 0 0 , 10 • 0 N• •• N • - • • • - " --" - :? •• "- i 0 0 e , -ro 0 " 0 , 0 N 0 M • , 0 c• ,• N 8 - 0 - • 8 •• , , 0-. • 0• 0 " • 0 M 0 0 ,•• , • • - 0 ,,• 0 • 0• 0 - • • " • ~ - ~ •, " 0 ~ "., 0 0 - • • ; ,, • • - • • - " •- •" - " - " - -- - "" - " , • • C• a • Ji 'i E" • &' ~ " ~ , 0 0 0 0 0 0 0 0 0 '"I t -. - •• •••MM N • ••••• • - -- " " - is'" . z 0;- jI ~ " Location "'C Soil Type YM) Loc1llion 6l'1 Soil T~'pc ~M) 4 1.5244 6 1,5244 6 3,0488 4 3.0488 7 45732 6 Silly Clay 4.5732 8 6,0976 8 60976 7 7,622 12 7,622 ~ 7 9.1463 15 9,1463 Fin~ Sa"d 6 10.6707 11 10.6707 Clayey Sill 10 12.1<)51 6 - 12.1951 10 11.71<)5 5 13.7195 35 15.2439 n SIllY Clay 15,2439 BTl BT4 20 1676n 14 16,7683 5 182927 ~. l() 18,2927 23 19,8171 30 198171 16 213415 39 21.3415 15 22,R659 50 - 228659 38 243903 50 24.3903 Finc Sand l'''lC Sand 34 25,9147 50 25,9147 33 27.4391 'iO 27 4391 28 28,9635 50 28,9635 Clay~'YS,lt 31 304879 I 50 30.4879 So-urce:Field Survey, 2005 - 138 I J, .". Location .soil Type Z(M) Location SPT .sOliT;pe ~MI '"6 1.5244 2 L5244 2 3,04&& 6 3 0488 ]j 45732 10 4.5732 14 6,0976 5 6,0976 5 7,622 7 7.622 5 9.1463 Clayey Silt 9.1463 -' 13 10,6707 " 10.6707 8 Silty Clay 111951 32" 12.1951 32 13.7195 16 13.7195 15.2439 21 15.2439 Bn BT' "10 16.7683 18 16,7683 15 1&,2927 JI 1U927 15 19,&171 19,8171 17 21,3415 '" 213415 9 22.865~ " 22 8659 29 24,39U3 "35 Fine Sand 24,3903 37 25,9147 41 25,9147 50 Fine Sand 274391 «, 27.4391 50 2&,9635 28,9635 P ~-'~-:ai,"""": 50 304879 "50 /, ':<.\ 304879 Source: Field Survey, 2005 !/r~\-'",~I,~..I ,c -, \, /,,1 ~ .<, ',l,I = k i:,\1:/ >..... l0 I"'~,j n "'f.\ 1'1' Ile'I;;-C) "I ~,,\;\ ." \f1'..- ' '-""V':-::I '" I ! , 139 '\~~:~:>/, •."--~' ,'t;)