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- Springer Journals
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- Copyright © The Author(s) 2023
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- 2197-8670
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- 10.1186/s40677-022-00230-5
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Abstract
Background The areas prone to geological hazards such as liquefaction need special attention with respect to social vulnerability. Though liquefaction by itself may not result in damage, it may trigger a series of ground failures such as ground oscillation, lateral spread, loss of bearing strength, etc., which cause heavy damage. Globally, during the past few decades liquefaction hazard analysis has become one of the important criteria in seismic risk analysis and mitiga- tion management, especially for urban areas. Greater Chennai is one of the million-plus population cities in India. The city also felt earthquakes/tremors in the past history. Method The present study aims to assess the social vulnerability of the population density of the Greater Chen- nai area due to liquefaction susceptibility using GIS technology. The liquefaction susceptibility map (hazard) for the Greater Chennai was prepared by integration of geological and geomorphological parameters and analyzed over socioeconomic parameters (exposure) using an integration of GIS and AHP. Results The result showed that around 53% of Greater Chennai’s households and population are very much exposed to liquefaction hazard. Conclusions This study can be used as a base level study for decision-making during land use planning as well as disaster mitigation planning. Keywords Earthquake, Liquefaction susceptibility, Hazard, Exposure, Urban sprawl, GIS amplify the social vulnerability by taking built environ- Introduction ment and the interaction among the community with the Urban area expansion and growing complexity of the territory. One of the most important aspects of managing cities present new problems in attempting to under- disaster risk reduction is understanding and measuring stand the complex relationships between different vulnerability. Only when effectively measured, vulnera - forms of urban vulnerabilities. Recent disaster events bility can give us an idea of the scale of the expected con- manifest how societies are growing more susceptible to sequences and can targets be set in developing resilient earthquake damages (Ganapathy 2011). The rapid and urban space (CGWB 2017; Srinivasan et al. 2010). Since unchecked population growth signaled an increasing in seismic hazard can’t usually be reduced, vulnerability the exposure (i.e. the elements at risk) which in turn will is one area where disaster risk reduction efforts can be made (Prasanna et al. 2010). Geomorphic settings of an *Correspondence: area is a clue to seismic activities (Praseedha and Gan- Ganapathy Pattukandan Ganapathy apathy 2020 a; b; Singh et al. 2016). One of the impor- seismogans@yahoo.com tant factors of seismic vulnerability is the unprecedented Centre for Disaster Mitigation and Management, Vellore Institute of Technology ( VIT ), Vellore, Tamil Nadu 632 014, India growth of urban landscape. Due to rapid, uncontrolled © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 2 of 22 sprawl of an urban area, even low to moderate seismo- city GDP2014, Brookings Institution Report, Greater logical activities can trigger a great loss. 1960 Morocco Chennai has an estimated GDPcontribution of $79 bil- earthquake (M = 5.8) and 1992 Dahshour earthquake lion to $86 billion making it one of the most productive (M = 5.7), even though both earthquakes were cat- metros of India. As per Bureau of Indian Standards (BIS egorized as moderate earthquakes, geological settings 2001) seismic zoning map of India, Greater Chennai along with the built environment triggered considerable has been classified under Zone III (Fig. 1). The majority social and economic damages and hundreds of life loss, of the city is covered in thick alluvium material, which thousands were injured (Pinto 2000). One the most sig- might increase the soil amplification in the city during nificant seismic hazard that can create a great impact in a seismological event. Also, most of the water bodies in urban disasters is soil liquefaction. It is also one of the the past century was filled and converted in to built envi - major threats for civil structures under seismic loads, as ronment. The filled-up soil will be easily liquefied dur - deduced from the damage surveys performed after some ing an earthquake of Magnitude more than 6.0. The aim strong earthquakes (Evangelista 2011). of the present study is to prepare a vulnerability assess- The study area, Greater Chennai, the sixth largest ment of Greater Chennai due to soil liquefaction based metropolis in India and one of the densely populated on geological and geomorphological settings along with urban centers in the word. It is one of the major eco- thematic integration of socio-economic parameters viz. nomic hubs of India. By 2025, the Confederation of population and number of households. This kind of vul - Indian Industry predicts Greater Chennai’s GDPwill have nerability map can be used in all stages of disaster man- increased by 1.5 times to a US$100 billion level. Greater agement, including prevention, mitigation, preparation, Chennai’s economy is mainly driven by IT services, auto- operations, relief, recovery, and lessons learned. When mobile industries, healthcare sectors, banking & financial building places for residential, commercial, or indus- services and hardware manufacturing. As per the Global trial usage in the prevention stage, planners might use Fig. 1 Seismic hazard representation of the study area M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 3 of 22 vulnerability maps to avoid high risk zones (Edwards 1989). The present study was carried using the data pub - et al. 2007). Though seismic zonation studies and lique - lished by the respective organizations, data published on faction susceptibility studies were being carried out for journal papers and open source data. This study would Chennai region, those studies are very much limited to not compensate for site-specific investigations, but can seismicity and liquefaction susceptibility themes. Social used as a tool for identifying an area which needs imme- vulnerability was hardly considered. Further, those stud- diate attention and further detailed investigations. Four ies were not carried out for the Greater Chennai region. parameters with respect to geology and hydrogeology namely, lithology, age of deposits, depth to groundwater Materials and methods and depth to bedrock are utilized for the liquefaction sus- Methodology ceptibility study. Exposure map was then prepared using One of the major causes of structural damage during two parameters namely, population density and density earthquakes is soil liquefaction. Soil liquefaction has his- of households. torically been observed in moderate and strong earth- Sediment properties like lithology, age of deposit and quakes (Ambraseys 1988). Globally many research works hydrogeological conditions like depth to groundwater, have been carried out on seismic hazard and liquefaction depth to bedrock can make an area favorable to seis- assessment based on geological and geomorphological mic wave amplification which in turn will make the soil settings of an area (Ganapathy et al. 2018, 2019; Gana- prone to liquefaction upon seismic shaking. Also, the pathy and Rajawat 2012; El May et al. 2010; Iwasaki et al. presence of different types of soil like clay, silty, sandy 1982; Wakamatsu 1992; Vipin et al. 2009; Obermeier soil along with the shallow groundwater will increase Table 1 Liquefaction Susceptibility of Sedimentary deposits present in Greater Chennai based on Geological and Geomorphological criteria (Youd and Perkins 1978) Type of deposit General distribution of Likelihood that cohesionless sediments, when saturated, would be cohesionless sediments in deposits susceptible to liquefy (by age of deposit) < 500 years Holocene Pleistocene Pre-Pleistocene River channel Locally Variable Very high High Low Very low Flood plain Widespread High Moderate Low Very low Alluvial plain Widespread Moderate Low Very low Very low Coastal delta Widespread Very high High Low Very low Estuarine Locally Variable High Moderate Low Very low Artificial compacted fill Variable Low Table 2 Liquefaction Susceptibility of the lithological units present in Chennai Lithology type Rank Liquefaction Sand fluvial-point bar deposit-sand and sandy clay 3 Possible Sand marine-beach deposit-medium grey brown sand with leaves 3 Possible Sand marine-strand flat deposit-medium grey brown sand 3 Possible Sand paleo tidal flat 3 Possible Black clay and sand tidal channel bar 2 Likely Black clay marine-tidal flat deposit-black clay 2 Likely Sand, silt and salt 2 Likely Clay and sand marine-estuary deposit-sand and silty clay black mud with shells 2 Likely Clay and silt flood plain deposit-black clay and sandy clay 2 Likely Shale 2 Likely Silt active levee deposit-sandy silt 2 Likely Charnockite 1 Not Possible Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 4 of 22 the soil liquefaction during strong earthquakes (El May Table 4 Depth to bedrock range of Greater Chennai with assigned ranks et al. 2009). The liquefaction susceptibility of a geological unit can be determined based on its depositional envi- Depth to bedrock (m) Rank ronment. For this study, the liquefaction susceptibility 5–15 1 of geological and geomorphological deposits has been 15–30 2 performed based on the Youd and Perkins (1978) criteria 30–50 3 (Table 1). 50–70 4 The liquefaction susceptibility of lithological units was 70–90 5 prepared by assigning ranks based on Iwasaki’s (1982) classification as in Table 2. It is a well-known fact that soil layer will be liquefied when it is saturated. So, the thematic maps are then integrated in QGIS to obtain the depth of groundwater is one of the important criteria liquefaction susceptibility map of Greater Chennai. for the estimation of liquefaction potential. Liquefaction Criteria’s like population density, population density susceptibility decreases with increasing groundwater of children under age 6 years, building density, housing depth. conditions with respect to each wards of Greater Chen- Obermeir’s classification (1996) which related lique - nai are considered to prepare the social vulnerability faction susceptibility with the age of geology and depth map. Population density along with building density of groundwater table was utilized (Table 3). Obermeir is very vital in disaster preparedness and mitigation as identified that liquefaction is typically observed at loca - both parameters directly deal with the social vulnerabil- tions where groundwater is only a few metres below the ity in risk areas. Moreover, a region with more popula- ground surface. Ground characteristics play a key role tion and more buildings are greatly exposed to hazards. in seismic activity of a region due to the amplification of Using AHP method weightage is assigned to each theme. seismic waves in different kind of deposits. Understand - Assigned weightage along with the normalized values for ings of bedrock conditions are immensely useful in esti- the sub categories are given in Table 7. The four thematic mation and anticipation of seismic activity of a region maps generated are integrated in QGIS to attain social (Ganapathy 2011). Depth to bedrock of Greater Chennai exposure map of Greater Chennai. For the four themes, was assigned with ranks 1 to 5 with 5 being very high cri- range was classified using geometric interval claasifica - teria and 1 being low criteria (Table 4). Liquefaction sus- tion method due to the nature of the data and the geog- ceptibility map with all the four above said criteria was raphy of the study area (Francisci 2021). The respective then prepared by thematic integration of those layers by thematic maps–liquefaction susceptibility and social multi-criteria weightage analysis. exposure—were subjected to overlay analysis to gener- Analytical Hierarchy Process (AHP) was then followed ate the vulnerability assessment map following the flow after assigning relative weightage to all the four layers shown in Fig. 2. depending upon its influences on the output. Highest weight was assigned to lithology as it has more effect on liquefaction. The different layers and their weights are Study area and administration listed in Table 5. Greater Chennai (Fig. 1), formerly known as Madras, is Then a pair-wise comparison matrix was prepared the capital of the state of Tamil Nadu. It is located on the using 1–4 scale with 1, being least importance and 4 is coast of the Bay of Bengal. The district lies within the lati - of very high importance (Table 6). The resulting four 0 0 0 tudes 12 58′ 10″ N to 13 09′ 50″ N and longitudes 80 11′ 16″ E to 80 18′ 20″ E. Chennai is bounded by Bay of Bengal on the east, Tiruvallur & Kancheepuram districts Table 3 Liquefaction Susceptibility of the near surface geological deposits present in Greater Chennai based on the ground water table depth during strong shaking (based on Obermeier 1996) Table 5 Thematic layers and weights assigned Depth to Age of deposit Thematic layer Weight groundwater latest Holocene Earlier Holocene Mesozoic table Lithology 4 Geomorphology 3 0–3 m High Moderate Nil Depth to Groundwater 2 3–10 m Low Low Nil Depth to Bedrock 1 > 10 m Nil Nil Nil M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 5 of 22 Table 6 Weighted comparison table for liquefaction susceptibility factors Lithology Geomorphology Depth to groundwater Depth to bedrock Normalized weightage Lithology 4/4 3/4 2/4 1/4 0.4 Geomorphology 4/3 3/3 2/3 1/3 0.3 Depth to Groundwater 4/2 3/2 2/2 1/2 0.2 Depth to Bedrock 4/1 3/1 2/1 1/1 0.1 Table 7 Weighted comparison table for social exposure indicators Theme Weightage Normalized values 4 3 2 1 Population Density : < 6yrs 0.35 Very dense Dense Moderate Average Population Density 0.25 Very dense Dense Moderate Average Building Density 0.20 Very high High Moderate Average Housing Condition 0.20 Very high High Moderate Average Fig. 2 Methodology for Vulnerability Assessment London. In 2011, Chennai Corporation has expanded on all of the other sides. Greater Chennai is a city district 2 2 the city limits from an area of 174 km to 426 km covering an area of over 426 km . and renamed it to Greater Chennai. Greater Chen- Greater Chennai Corporation is the governing body nai is classified into three major regions: North Chen - of Greater Chennai. The corporation was established nai, South Chennai and Central Chennai. It is further in 1688. It is the oldest municipal corporation in India divided into 15 zones, consisting of 200 wards. Greater and the second oldest corporation in the world after Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 6 of 22 Chennai falls under the Chennai Metropolitan Area difference is about 10 m to 28 m in most part of the city. (CMA). The beach sands and alluvial aquifers of the Adayar River in the Adayar and Besant Nagar regions were a good Physiography potential area in the past. But due to the indiscriminate Surface Topography plays a significant role in ampli - extraction of groundwater from this potentially rich fying the ground motion when the wavelength of the aquifer, the groundwater level has dropped below mean incoming seismic waves is smaller than the topographi- sea level and faces a serious risk of seawater intrusion cal irregularities (Pallav K et al. 2007). Greater Chennai (Prasanna et al. 2010). is a low-lying area and major part of the city is having a very flat topography. The elevation of the greater Chen - nai’s land surface varies from 6 to 10 m above msl in the Lithological units of greater Chennai west to sea level in the east. The average elevation of Lithology of Greater Chennai (Table 8) comprises hard Greater Chennai is 6.7 m. In the city during the mon- rock (Charnockite), clay formation, clay over hard rock, soons, flooding and water stagnation occur due to the clay–sand formations and clay-silt formations (Fig. 4). city’s flat geography and partial storm water drain cov - The south-western part of the city is covered by hard rock erage of its roads (ISWD 2014). Amplification effects of Charnockites. The outcrops exposed over few meters due to surface topography were not considered for this in St. Thomas mount area near Guindy as residual hills study as the surface topography of the study area is flat. (Prasanna et al. 2010). Black clay formation starts from northern part of the city near Kathivakkam and extends Geological and geomorphological units of greater Chennai till Uththandi, approximately a 40 km stretch. Sand for- The geological formations of the area can be grouped into mation can be seen on either side of the clay formation three units, namely (1) the Archaean crystalline rocks (2) linear stretch. Clay—silt formation is found in the North- recent alluvium (3) consolidated Gondwana and tertiary Western part the city. Clay—sand formation can be found sediments. Except for a few exposed crystalline rock for- in patches near the Cooum and Adayar estuaries. Most of mations such as charnockites in the Guindy area and the the city is covered by sand formation followed by clay— Adyar riverbed at Saidapet, the most of the geological sand formation (Ganapathy and Rajarathnam 2011a, b ). formations are obscured since they are covered by allu- The Gondwana sediments are represented by sandstones, vial sediments (Ganapathy and Rajawat 2014a, b; Gana- shales and clays. The shales and clays are highly consoli - pathy 2011). Charnockites, which form the major rock dated and dense. The dark grey Gondwana shales are types in can be seen as residual hills around Pallavaram, jointed/fractured (CGWB 2017). Tambaram, Vandalur, St.Thomas Mount. The Gondwana series which comprises massive pile of lacustrine and flu - Depth to groundwater vial deposits represent the upper Gondwanas of Jurassic Depth to groundwater is an important criterion for to lower cretaceous rocks and the marine beds of the cre- liquefaction susceptibility. An area is more suscepti- taceous age (CGWB 2017). These Gondwanas and Cre - ble to liquefaction when the ground water table is less taceous sedimentary rocks occur particularly along the than 10 m (Youd and Idriss 2001). There have been few coastal area of basal sediments, wherein these are over- instances of liquefaction in areas with groundwater that lained by quaternary sediments (Srinivasan et al. 2010). is deeper than 20 m (Prasanna et al. 2010). Based on the Also, the outcrops of Gondwana rocks are seen outside two reports that were taken in to consideration (CGWB the city and as sub-crops within the city. The occurrence 2008, 2017), the depth to ground water level in the city of the tertiary in Greater Chennai is not clearly demar- generally varies from 2 to 8 m (Fig. 5). Depth to ground- cated (CGWB 2017). water map was prepared using the pre—monsoon and Geomorphology of Greater Chennai (Fig. 3) mainly post—monsoon groundwater table reports published consists of alluvial plain, delta plain, coastal plain. Delta by Greater Chennai corporation’s metro water board plains can be found along the coastal region stretch. (CMWSSB 2020) between the years 2016 to 2020. North—Western part of the city is almost entirely cov- ered by alluvial plain and delta plain. Flood plains con- Depth to bedrock sisting of sand clay are found along the boundaries of The basement is relatively shallow in the southern side Araniar and Kosasthalaiyar rivers (Sivaraman and Thillai - of the city (5–15 m) and average in the central part of govindarajan 2004). Two types of alluvium formations the city (15–50 m). Basement depth of more than 50 m can be seen in the city. River and coastal alluvium. The (Fig. 6) can be observed in Western to Northern stretch thickness of the alluvium is highly variable spatially. The of the city. Table 9 shows the five zones demarcated in M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 7 of 22 Fig. 3 Geomorphological map of the study area Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 8 of 22 Table 8 The geological formation of Greater Chennai No Period Epoch Formation Lithology 1 Quaternary Holocene to Pleistocene Cuddalore Soils, Alluvium (River/Coastal), Coastal sand, Black clay, Laterite, Fine to coarse sand 2 Tertiary Eocene to Pliocene Sandstone, Shale, Green Shales, Marine sediments 3 Upper Gondwana Cretaceous Satyavedu, Sriperum- Black shale, Grey shale, Sandstone, Siltstone budur 4 Azoic Archaean Granites, Charnockites, Schist, Gneisses, Dolerite the Chennai city and the general nature of hydrogeology density of children under age 6 is concentrated in the and its composition (Vutla 2011). central part of the region along with patches of northern and southern region. Population of greater Chennai Chennai is the sixth largest metropolitan area in India Building density of greater Chennai and is experiencing rapid growth in population. Chen- Planetscope imagery which comprises four bands—Red, nai grew in stages both in land area and population. The Green, Blue, NIR with the spatial resolution of 3 m—of transition occurs from rural to urban in terms of employ- the Greater Chennai region, acquired on 19th of June, ment, social security, living environment and industry 2018 is considered (Planetscope 2018). Using object structure (Aithal and Ramachandra 2016). Chennai is not based image segmentation (OBIA) tool in SAGA soft- an exception to this phenomenon. In fact, available data ware, clusters are created and individual classes like indicate that till the beginning of nineteenth century pop- buildings, water, road, etc. are assigned. By using zonal ulation growth was slow and steady. But due to migration statistics method for the 200 wards of Greater Chen- of population from other parts of Tamil Nadu for reasons nai with respect to the building class raster which was like employment, environment etc. from earlier decades obtained as mentioned in the above step—building den- of nineteenth century population density of Chennai is sity map is prepared. The obtained building density map’s changing drastically. The population, which was 0.019 pattern is in accordance with the Planetscope imagery million in 1646, expanded to 0.04 million in 1669. The (Fig. 9). Majority of Greater Chennai area is overwhelmed surroundings of the fort area spreads over nearly 69 km with building density (Fig. 10). Especially the entire south and contains 16 hamlets within its boundary in a location to west region of the city is densely packed with build- were the city of Madras is constituted in 1798. Later on, ings. It can be noted that Greater Chennai’s households the city extended over an area about 73 km and had a are expanding rapidly along the outskirts. population of 0.54 million in 1901 (Jothilakshmy 2011). Table 10 clearly shows the phenomenal growth of pop- Housing condition of houses in greater Chennai ulation in Chennai city. After the city limit was expanded Using the 2011 census data published, 200 wards of to 426 km in 2011, the population of Greater Chennai is Greater Chennai are mapped with the building condi- 6.67 million. Greater Chennai is the most densely popu- tions namely—good, liveable, dilapidated. Almost the lated city in Tamil Nadu, very far ahead of the next most entire stretch of the coastal area has more houses which dense city–almost twenty times—Kanyakumari which fall under the category liveable. Similarly, the northern has density of 1,111 per square kilometer. Population part of the city is predominantly under liveable category. data was extracted from reports published by Greater Southern and packets of central region of the city, which Chennai Corporation which is the governing body of are historically known for well-established infrastruc- Greater Chennai. Report provides an average number of tures are in general good to very good condition (Fig. 11). persons per ward. Population density map of Greater Chennai (Fig. 7) Results and discussions was generated by calculating population w.r.t area of Liquefaction susceptibility of greater Chennai the wards using census data published by both Greater The resultant liquefaction susceptibility map (Fig. 12) of Chennai corporation (2017) and Census of India (2011). Greater Chennai—which was prepared by integration Similar methodology was followed for calculating popu- of geological and geomorphological parameters such as lation density of children under age 6 (Fig. 8) after taking lithology, geomorphology, depth to groundwater and the total population into consideration. Central part of depth to bedrock after assigning normalized weightage Greater Chennai is densely populated and the trend con- values (Table 6)—was divided in to three classes namely tinues towards northern parts. Distribution of population M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 9 of 22 Fig. 4 Lithological units of the study area Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 10 of 22 Fig. 5 Depth to ground water level M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 11 of 22 Fig. 6 Depth to bedrock map of the study area Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 12 of 22 Table 9 Depth to Bedrock in Greater Chennai No Zone Nature Bedrock depth Composition 1 North Coastal alluvium followed by Gondwana clay 28–90 Recent alluvium Sand-silt, Shale, Sedimentary rocks 2 South Crystalline rocks with top soil cover 25 Silt–clay, Charnockites, Weathered rocks 3 West Alluvium followed by Gondwana clay, Shales, 24–90 Mixed alluvium Clay Shales, Sand stones Crystalline rocks 4 Central River alluvium followed by Crystalline rock 30 Alluvium Silt–clay, Gondwana shales 5 East Coastal alluvium followed by Crystalline rock 5–30 Sand / Silt, Sand dunes, Marine fluvial clay Crystalline rocks liquefaction—likely, possible, not possible. 35% of Greater and high population density. Central part of Greater Chennai was identified as areas wherein which lique - Chennai is also heavily exposed due to population den- faction is possible. Those areas were observed along the sity, building density and housing conditions. coastal region and areas which are underlained by delta plain. Around 25% of the city falls under liquefaction may Social vulnerability assessment of greater Chennai occur category due to underlying soil conditions. Areas The resulting exposure map (Fig. 13) was then pro- with archean crystalline rock formations were identified cessed with liquefaction susceptibility map as per the as very low to low susceptible categories. equation Risk = Hazard x Exposure (Cardona et al. 2012) which has yielded the social vulnerability map of Social exposure of greater Chennai based on social Greater Chennai based on liquefaction hazard (Fig. 14). vulnerability indicators The highest vulnerability is shown to exist along the Social exposure indicators, namely–population den- coastal corridor and in areas of Santhome, Vyasarpadi, sity, building density and housing conditions for the 200 Purasaiwakam (Table 11). Areas like T.Nagar, Chet- wards were fused together after assigning proper weight- pet which are famous for shopping areas and buzzing age (Table 7). 16% of Greater Chennai has been normally crowd falls under highly vulnerable category. It has to exposed to vulnerable factors based. 40% has been highly be noted that, Greater Chennai is expanding along the exposed and 44% of Greater Chennai has been under coastal zone which is already creating a lot of problems very highly exposed category (Fig. 13). Almost all of the with respect to coastal zone management and disaster coastal line of the city falls under either highly exposed or mitigation. In addition, as per Greater Chennai corpo- very highly exposed category due to rapid expansion of ration’s 2026 master plan for the city, so many IT corri- the city which in turn results in dense built environment dors and industrial developments are planned along the coastal corridors which clearly fall under the moderate to high category in terms of vulnerability. Table 10 Population of Greater Chennai Year Population Area Population Conclusions (in millions) (in Sq.kms) density/Sq. The aim of this study is to assess the social vulnerabil - kms ity of Greater Chennai with respect to seismic hazard 1901 0.541 68.17 7936 risk, namely soil liquefaction as liquefaction studies 1911 0.556 68.17 8156 are crucial for disaster mitigation planning especially 1921 0.578 68.17 8479 in urban areas which are transforming so rapidly. Out 1931 0.713 68.17 10459 of 426 km 19.4% of the area falls under high category 1941 0.865 77.21 11203 and 33.5% fall in moderate to high category. It has to 1951 1.427 128.83 11077 be noted that northern and north–east parts of the 1961 1.749 128.83 13576 city falls under moderate category where economic 1971 2.469 128.83 19165 activities are catching up. Altogether from moderate 1981 3.285 176 18665 to high–53% of Greater Chennai’s population is very 1991 3.843 176 21835 much vulnerable to liquefaction hazard. Given the 2001 4.344 176 24682 rapid growth along the coastal stretch of the study area, 2011 4.681 176 26597 this paper exhibits the need for better urban planning 2011(After 6.672 426 15662 and disaster management framework. This is a first Expansion) M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 13 of 22 Fig. 7 Population density of the study area Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 14 of 22 Fig. 8 Population density of children less than 6 Years M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 15 of 22 Fig. 9 Planetscope false color composite (432) of Greater Chennai Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 16 of 22 Fig. 10 Building Density of Greater Chennai M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 17 of 22 Fig. 11 Housing condition of houses in Greater Chennai Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 18 of 22 Fig. 12 Liquefaction susceptibility of Greater Chennai based on geological and geomorphological units M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 19 of 22 Fig. 13 Social exposure of Greater Chennai based on population density, building density, household condition Manoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 20 of 22 Fig. 14 Social vulnerability map of Greater Chennai M anoharan and Ganapathy Geoenvironmental Disasters (2023) 10:1 Page 21 of 22 Cardona O-D, van Aalst MK, Birkmann J, Fordham M, McGregor G, Perez R, Table 11 Social vulnerability severity percentage Pulwarty RS, Schipper ELF, Sinh BT, Décamps H, Keim M, Davis I, Ebi KL, Social vulnerability Percentage Important locations Lavell A, Mechler R, Murray V, Pelling M, Pohl J, Smith A-O, Thomalla F (2012) Determinants of risk: exposure and vulnerability. 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India Int J Earth Sci Eng 4(2):233–240 Vellore Institute of Technology ( VIT University), Vellore, India, who provides all Ganapathy GP, Rajarathnam S (2011b) Zonation for seismic geotechnical the facilities and his encouragement about this work. hazard in urban areas–a case study Chennai city India. Int J Earth Sci Eng 4(3):436–442 Author contributions Ganapathy GP, Rajawat AS (2012) Evaluation of liquefaction potential The first author carried out the research, analysis and mapping, drafting of the hazard of Chennai city, India: using geological and geomorphological manuscript, editorial and finalization of corrections. The second author con- characteristics. Nat Hazards 64(2):1717–1729. https:// doi. org/ 10. 1007/ tributed to literature sourcing, editorial and structure review. Both the authors s11069- 012- 0331-1 read and approved the final manuscript. Ganapathy GP, Rajawat AS (2014a) Quantification of geologic hazard and vulnerability for Chennai city India. Int J Geomat Geosci 5(1):32–42 Funding Ganapathy GP, Zaalishvili VB, Melkov DA, Dzeranov BV, Chandrasekaran SS Not applicable. (2018) Mapping of soil liquefaction potential susceptibility for urban areas. Geol Geophys South Russ. https:// doi. org/ 10. 23671/ VNC. 2018.3. Availability of data and materials The datasets utilized and/or analyzed during the current study are available Ganapathy G P, Rajawat A S (2014b) Earthquake damage scenario analysis for from the corresponding author on reasonable request. Chennai City–using remote sensing and GIS techniques. 193–195 Ganapathy GP, Zaalishvili VB, Melkov DA, Dzeranov BV, Chernov Yu K, Kanu- kov AS (2019) Soil liquefaction susceptibility assessment of Mozdok Declarations City (North Ossetia, Russia). In: Proceedings of the VIII Science and Technology Conference “Contemporary Issues of Geology, Geophysics Competing interests and Geo-ecology of the North Caucasus” (CIGGG 2018). Atlantis Press, The authors declare no competing interests. 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ASCE J Geotech Eng Div 104:433–446 Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in pub- lished maps and institutional affiliations.
Journal
Geoenvironmental Disasters – Springer Journals
Published: Jan 9, 2023
Keywords: Earthquake; Liquefaction susceptibility; Hazard; Exposure; Urban sprawl; GIS