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INTRODUCTION

On a global scale, humans have become the majorcause of a rapidly changing marine environment.This will have far-reaching implications for thefuture of this environment. Karachi, the largest cityof Pakistan, is situated along the coastline in close

proximity of Indus Delta. The NW-SE orientedcoastline of Karachi, situated between the CapeMonze and the Phitti Creek along Bundal Island, isabout 70 km long. On the west, it is bounded by the

Hub River and on the east by the mangrove swampsandcreeks of theIndusDelta.

The coastal zone of Indus Delta is under stress from

progressively reduced inputs of nutrients,sediments and freshwater because of reduced IndusRiver discharge. This situation has resulted inincreased ground water salinity and seawaterintrusion into the deltaic areas of Sindh.Consequently, the Indus estuary areas in most partof Indus Delta have shrunk considerably (Amjad

., 2004).

Recent data showed that a cyclonic event in 1999had a negative impact on the Left Bank Out fall

Drain (LBOD), a man made drainage system on theleft bank of Indus River. Breaches have occurred inthe tidal link, resulting in major geomorphic andecological changes due to sea water intrusion (Inam

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Pakistan Journal of Oceanography, Volume 3(1):37-52 , 2007 37

GEOLOGICAL HAZARDS ALONG THE SINDH COAST WITH

SPECIAL REFERENCE TO KARACHI COAST

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Asif Inam, Mohammad Moazzam Rabbani, Khalid Mehmood, Syed Mozzam Ali,

Syed Mohsin Tabrez, Mohammad Danish, Shamim Ahmed Sheikh

National Institute of Oceanography, ST. 47 Clifton Block 1, [email protected]

Department of Geology, University of Karachi, Karachi

The coastal zone of Indus Delta is under stress from progressively reduced inputs ofnutrients, sediments and freshwater because of reduced Indus River discharge. Thissituation has resulted in increased ground water salinity and sea water intrusion into thedeltaic areasof Sindh.Karachi, situated on theSindhcoast of Pakistan,is oneof thelargestcities in the world in terms of both population as well as size. Sindh coast is exposed tonatural hazards like cyclone, tsunami, and earthquake. The subsidence of the Indus Delta

due to sediment starvation could possibly increase the over all impact of sea level rise. Ithas already been resulted in the sea water intrusion upstream of the delta. The regionaltectonics, beach morphology and slope indicate that possibility of development of severalmeter high tsunami wave exist along the Pakistan coast. Continuous interplate movementat the triple junction in the northernArabian Sea, presence of active onshore and offshorefaults, subduction of the oceanic plate offshore Makran coast, and history of devastatingearthquakes in theRann ofKutch indicatesthat thecoastal belt is susceptible toearthquakeof moderate to high intensity. The data and information presented in the paper indicatesthat the coastal belt may experience severe damage by earthquake due to ground motionamplificationand liquefaction.

Tectonic plates, triple junction, tsunami, IndusDelta, seismicity, liquefaction,ground motion amplification.

ABSTRACT

Keywords


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., 2004). Ground investigation and theinterpretation of satellite imageries indicatemomentouserosion ofcoastal islands in thevicinityof Indus Delta (Inam ., 2004). The acceleratedhydrodynamic changes haveoccurred probably dueto deepening and widening of the approachchannels of Port Bin Qasim resulting in

destabilisation of sediments in older Indus Delta(Inam .,2004).

The recorded sealevel rise at Karachi andadjoiningIndusDeltaic area, basedonthedataforthe past 100years, is 1.1 mm/year and it is expected to be morethan double during the next 50 to 100 years,resulting in 20-50 cm rise in sea level (ESCAP,1996). Man made changes coupled with natural

physical forcing in the Indus Delta and adjoiningareawillconspicuouslychange the geomorphic andhydrodynamic setting of the delta. Associatedchanges in the prevailing physical processes in turnwill have a negative influence on coastal resources,infrastructures, industries, ecosystems, and socio-economy ofthe area(Inam .,2004).

The shelf off the Indus Delta is very flat. Between100-m water depth and the shelf break (135 m), ithas a gradient of only 2-3 m/km (von Rad & Tahir,1997). The delta front slope ranged between 0.2and 0.3, whereas the shelf gradient offshore thedelta front was typically less than 0.1 (Giosan

., 2006). The Indus Delta receives the highestdeep water wave energy of all deltas globally as itreceives in a day as much wave energy as theMississippi coast in a year (Wells & Coleman,

1984).

The once tide dominatedIndus Delta is nowrapidlychanging to wave dominated delta mainly due tohuman induced sediment deprivation (Inam .,2007). If the present trend of sea level rise (SLR) atKarachi continues, in the next 50 years the sea levelrise along the Pakistan Coast will be 50 mm (5 cm).Since the rising rates of sea level at Karachi withinthe global range of 1.2 mm/year, the trend may betreated as eustatic sealevel rise (KhanandRabbani,2005). However, this rate of rise in sea level wouldsignificantly change if the expected subsidence ofland were added into it. There are no direct

measurements available on subsidence rates in theIndus Delta, experience in other deltas of the worldindicate that subsidence rates here must haveincreased due to lack of sediment flux and the

subsidence rate is probably between 2 and 4mm/year. If one adds the projected rate of globalcomponent of sea-level rise of up to 6 mm/year inthe next century, Indus Delta could experience arelative riseof sea level ofup to8 to10 mm/year.Atthis pace, the inundation of the delta could be rapid,at therateof several m/year (Haq,1999).

Cyclones and storm surges in the Arabian Seausually develop in the inter-monsoon period in thesouthern part of Arabian Sea. To date almost allcyclones developed in the Indian Ocean or northArabian Sea have moved towards northwest ornortheast direction hitting the Arabian Peninsula orIndia-Pakistan coast.Thelongfetcheshaveresultedflooding in association with swellsgeneratedby thestorms and monsoon depressions in the south ofPakistancoastline.

The aim of this paper is to have a holisticassessment of geological and oceanographic setupthat may have a potential to trigger a naturaldisaster. The basic purpose is to develop awarenessin the scientific community as well as to allconcerned. Discussion about the mechanism ofnatural and man made hazard to Karachi is beyondthescopeof this paper.

Area of Study

Karachi is the hub of major industrial/commercial

activities and the most populous city of Pakistan.The city expands over an area of approximately3,530 square kilometers. The proximity of Karachito the Indus Delta exposes it (to the variable extent)tothe processes and forces inactionon the delta andcreeksystem. It's coastlinein theeast is linkedwithcreeks, that extend up to the Indus Delta coveringthe most extensive and ecologically sensitive areaofPakistan coast.The Clifton beach is located at thesouth eastern shore line of Karachi Metropolis.Towards the west is Cape Monze, an area markedwith projecting sea cliffs and rocky sandstone

promontories .

All geological and geophysical data presented herewas collected by NIO during its various research

projects.

MATERIAL AND METHOD

Inam et al., Geological hazards along the Sindh Coast 38


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Grain SizeAnalyses

Seismicdataanalyses

SubbottomProfiling

SidescanSonar

A total of 14 stations were selected during January

December 2006 for the sediment sampling from thecoastal area of Karachi (Fig 1). The procedureadopted for pretreatment and dispersion of sampleswas in accordance with British Standard 1

otal sampleusing distilled water. S

sieves(1.0mm, 0.5mm, 0.25 mm, 0.125 mm, andpan).

2D multi-channel seismic data collected from theKarachi offshore area by Lasmo Oil, UK in 1998 by2 D s ei sm ic v es s el S /V We st er n Wa ve .Subsequently NIO obtained the data through the

Directorate General of Petroleum Concession,Government of Pakistan (DGPC) for research

purpose. The data was interpreted for this study on

SeisVision for the determination and marking offaults in offshore sediments of the Arabian Sea offKarachi.

GeoAcoustics (ORE) sub-bottom profiling systemModel #132B was used to obtain bottom/sub-

bottom information (NIO, 1995). The filters wereset at2 kHz to 5 kHz with variable gain settings. Thesub-bottom data wasrecorded in analogue form on athree channel Dowty 200/138 Thermal GraphicRecorder.

GeoAcoustics (ORE) Side ScanSonar Model#1500was used. Due to shallow water depths and better

377(British Standard Institution, 1975). Pretreatedsamples were sieved through a 63m (0.063 mm)sieve to separate sand fraction from he

ample retained on the 63m(0.063mm) sieve wasdried andsieved through a setof

t t

Fig. 1. Locations of sampling stations along Karachi coast andadjoining area.



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image, the range setting was kept 75 m per channeli.e. a total swath of 150 m along the track (NIO,1996).

The Bathy-500MF survey single beam EchoSounder was used for the data acquisition (NIO,2007).

The beach and near shore sediments along Karachicoast are very fine to coarse sandy in nature (Table1).The sediment samples obtained from the HawksBay area are moderately sorted and of differentcolour and composition mainly due to the absenceof mica. The median grain size of Hawks Bay andadjoining Buleji and Pacha is classified as very finesand(Table 1).

The beach gradient at Hawks Bay is relativelysteeper as compare to the Clifton beach. The beachand bottom material near Clifton is predominantlycomposed of micaceousvery well sortedmedium tofinesand (Table 1).

The Clifton beach and coastal/offshore area iscomposed of low gradient, flat, and homogenous

fine sand as indicatedby theSide Scan Sonar recordcollected earlier by NIO scientists (Fig. 2). Ingeneral, the side scan sonar records reveal a smoothandfeature less seabed along theCliftonbeach.

The sea floor topography in the Hawks Bay area isirregular and rugged as depicted by the echogram

painted by the single beam digital echosounder(Fig. 3). On the other hand, the Clifton beach isrelatively gentlehowever;thereis sudden change inthebeach gradient off Korangi Creek as depicted bythe3.5 kHzsubbottom acoustic profiler (Fig. 4).

In this study, 2D multi-channel seismic (MCS) linesacquired by the oil & gas industry from the areaoffshore Karachi are used for the mapping of faults(Fig. 5 &6).

The southern end of the 2D MCS line that runsperpendicular to the Karachi coast is important not

only due to its proximity with Karachi but also tothe junction area of the three tectonic plates (Fig.5). Many active reverse faults observed due tostress development from SW to NE direction. Thefaults in SW directions are relatively shallow andmay apparently indicate that the area may betectonicallyactive.

Bathy-500MFSurveyEchoSounder

RESULTS

S. No Sample # D50 Wentworth Size Class

1 0.11 Very fine sand2 0.12 Very fine sand3 Sandspit Low water 0.13 Very fine sand4 Sandspit High water 0.20 Fine sand5 Hawks Bay 0.21 Fine sand6 Manora 0.31 Medium Sand7 Entrance Ch. Breakwater wall 1.7 Very coarse sand8 Clifton Beach Near NIO 0.13 Very fine sand9 Clifton Beach near Bilawal 0.125 Very Fine sand10 Clifton Beach at Casino 0.25 Medium sand11 Clifton Beach at Sea View 0.63 Coarse sand12 Golf Club 0.125 Very fine sand

13 Bundal High water Line 0.35 Medium sand14 Bundal Low water line 0.12 Very fine sand

PachaBuleji

Table 1. Percentile Values of D50in mm (onProbabilityScale),



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Fig.3. RuggedseaflooroffHawksBayarea.

Fig. 2. Side scan sonar image of Clifton Beach indicatesformation of sand bars.



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The 2D MCS line that runs parallel to Karachi coastand Indus Delta also shows reverse faultsi nd ic at in g t he a re a i s b ei ng e xp os ed t ocompressional forces (Fig.6) .

Based on the data and information collected by the National Institute of Oceanography from Karachicoast over the years, an effort is being made here toassess the risk to Karachi coastal area from thenatural hazards.

Karachi is located approximately 150km east of thetriple junction between the Arabian, Indian, andEurasian plates. The collision of Indian plate withEurasian plate has initiated a compressional stressregime in a northwesterly direction, very differentfrom that at the time of rifting, and the reactivationof these normal faults in a reverse sense isestablished (Khattri, 1994; Chung, 1993; Chungand Gao, 1995). The western and north-trendingarms of the triple junction sustain convergent andtranscurrent rates of 28-33 mm/yr respectively(Apel 2006). The area in the west andnorthwest of Karachi is limited by Kirther Fold Belt

andthe PabRange. Miocene outcrops in thearea arepresent in the form of isolated hills of low relief,structurally, the strata of Oligocene-Miocene ageare folded into an asymmetrical anticline plunging

towards southwest(Raza, 2004).

West of Manora the coast is composed ofQuarternary beach sand deposit bordering to themangrove swamp deposit (Quraishi ., 2001).The coastal geology along the Clifton beach isdominated by Quarternary beach sand deposit

bordering to the Quarternary sandbar deposits.

The land subsidence in the Indus Delta could also possibly affect coastal area of Karachi. Thesituation could become even worst due touncontrolled ground water extraction in Karachiand adjoining costal areas of Sindh. Wateravailabilityon a percapita basis hasbeen decliningat an alarming rate. It has been decreased fromabout 5,000 cubic metersper capitain 1951 to about1,100 cubic metes currently, which is just above theinternationally recognized scarcity rate. It is

projected that water availability will be less than700 cubic meters per capita by 2025 (Pak-SCEA,2006). Pakistan is heavily dependent on thegroundwater for domestic, agricultural, and evenindustrial consumption. Uncontrolled extraction ofgroundwater and extended dry periods has alsocaused its depletion and drying up of some of theground water sources.A study in Kirther shows that

the water table has dropped by 3 meters per year onaverage (WWF, 2007). Historical records show thatthe Malir valley was once known for its richness inarable land and water resources. There were 30

DISCUSSION

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Fig. 4. 3.5kHz profile off Korangi Creek shows noticeable changein gradient.



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wells dug by the Karachi Municipal Board atDumloti in Malir to supply potable water toKarachi. The water table in the Malir Valley hasgone down from 60-70 ft (in the 1960s) to 300-700ft (UN, 2006).

The fall of the water table due to ground waterextraction may lead to ground subsidence as it is

being observed in many places around the world. Inthe Bangkok area of the Chao Phraya Delta, groundwater extraction during 1960-1994 increasedaverage relative sea-level rise by 17 mm yr(Sabhasri and Suwarnarat, 1996). Similar severeland subsidence has been experienced in the OldHuange and Changjiang deltas of China (Chen,1998; Chen and Stanley, 1998). Suzhou City,located at the lower reaches of the Yangtze River insoutheastern Jiangsu Province, is one of the fewcities in China, which suffer from severe groundsettlement (Chen ., 2003). The subsidence

observed in Mexico City is one of the most studiedcases, with measured subsidence reaching morethan 9 meters in some areas of the city. Subsidencehas also been reported in Bangkok (Ramnarong,1999), Calcutta (Choudhury ., 1997), andJakarta (Schmidt 1988). Shanghai started

pumping groundwater for the city water supply in1860. Theold city of Shanghai sank almost2 metersin the period 1921-65 (Endersbee, 2005).Subsidence is continuing, and the authorities arenow trying to correct it by injecting water into theaquifers.

Such ground subsidence in densely populated cities

has caused great economic losses, as well aspresenting a hazard to buildings and people. It isreported that Shanghai has suffered economiclosses estimated at $35 billion in the past 40 yearsdue to destructive flooding and tidal effects caused

by subsidence, mainly caused by groundwaterextraction (Endersbee, 2005). No published orunpublished literature is available about themonitoring of ground subsidence in the coastal beltof Karachi. Immediate measures need to be taken todetermine the present ground level and that has to

bemonitored on a regular basis.

Ground subsidence in the Indus Delta has already

been resulted in the sea water intrusion upstream ofthe delta - at places extending up to 80 km in thecoastal areas of Thatta, Hyderabad and Badindistricts (Panwar, 1999, Inam ., 2007). Sindh's

Irrigation and Power Department (IPD) hasrevealed that seawater intrusion has resulted in tidalinfringement over 1.2 million acres of land in theIndus Delta (Inam ., 2007). The Indus Delta issubjectedto thehighest average wave energy of anymajor delta in the world (Wells and Coleman,1984). This is mainly due to the intense monsoonalwinds, which produce high energy levels. Anextreme level of wave energy and little or nosediment contribution from the Indus River istransforming the Indus Delta into a true wavedominated delta and development of sandy beachesand sand dunes along the former deltaic coastline isunderway.

The seismicity around Karachi is generallymoderate to low, however, the area around Karachiis susceptible to earthquake of moderate to highintensity as several faults are present both onshore(Loya ., 2000; Quraishi ., 2001; Bilham

., 2007) and offshore (Fig. 5 & 6). Loya .,2000 described three major faults in the area as PabFault, Ornach-Nal Fault, and Rann of Kutch Fault.Bilham ., 2007 also included Chaman Fault,Hab Fault, Sonmiani Fault, Korangi Fault, Surjan,Lakhni, Jhimpir, Nagar Parkar Fault, and AllahBund Fault in thelistof faults.

The Allah Bund is a major fault that traversesShahbundar, Pakistan Steel Mills, and continues tothe eastern parts of Karachi - ending near CapeMonze (Pararas-Carayannis, 2006). This fault has

produced a major earthquake and destroyedBhanbhor in the 13th century (Pararas-Carayannis,

2006). Another major earthquake in 1896 wasresponsible for extensive damage in Shahbundar(Pararas-Carayannis, 2006). Nakata (1991)identified a possibly active surface scarp on theKorangi fault on theeastern outskirtsof Karachi.

Hab and the Pab faults are thought to be active,although neither slip-rate estimates nor localearthquake recordings are available for either ofthem(Bilham .,2007). The presenceof two hotsprings in Karachi that give out water laced withchemicals like sulphur strongly suggests the

presence of active faults in Karachi. One of the hotwater springs is situated near Manghopir and the

other near Karsaz (Zaigham, 2005). The watertemperature at Manghopir and Karsaz hot springwas reported to be 50C and 39C respectively(Todaka ., 1999). A pparently, the

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compressional movements along the active faultsprovide paths for the deep circulation of water andthus raising their temperature (Demirel, .,2004).

Despite the fact that several faults are present bothonshore and offshore Karachi, the city with the

population of more than 17 million has to date notexperienced any damaging earthquakes in the past150 years. However, the hazard of major anddestructive earthquakes can not be ruled out inKarachi due to its proximity to the junction of thethree major plates, subduction zone and the numberof known active faults (Bilham ., 2007). Just200 km southeast of Karachi, the Rann of Kutchsystem has produced two massive earthquakes of7.7 M in 1819 and 2001 (Bilham ., 1998;

Bilham ., 2007; Stein ., 2002). Rann ofKutch system concealed under the loose sedimentsof the Indus Delta appears to continue to the west,

passing through the metropolitan area of Karachiand extending into the Arabian Sea, where itintersects another systemof faults associated with amajor tectonic boundary (Jones & Johnson, 2001).

No reliable information about the impact of theearthquake of 1819 on Karachi is available but theearthquake of 2001, with an epicenterabout 371 kmwest in Bhuj, jolted Karachi. Scientists working in

NIO laboratory, which is located near the Cliftonbeach, felt a shock wave passed through the floor oftheir rooms. It is likely that the Indus Delta andKutch rift zones could host several rupturescontiguous with the 1819 event, with importantconsequences for the city of Karachi as M>7

earthquake within 50 km of Karachi cannot beexcluded(Bilham .,1998;2007).

One of the major causes of destruction during anearthquake is the failure of the ground surface. Theground may fail due to fissures, abnormal orunequal settlement, or complete loss of shearstrength of soil (Loya . 2000; Humar .,2001; Kumar, 2006; Tsang ., 2007). A loosesaturated sand deposit when subjected to vibration(orcyclic loading) tends to compact and decrease involume. During longer shaking of loose saturatedsand deposit, theground loses itscompleteshearingstrength and results in settlement and tilting of

structures (Khan, 2007). The ground movement orshaking can be locally amplified by unconsolidatedsedimentsor artificial land fills that mayresult more

damageas compare to theareas havingcompact andhard ground (Loya . 2000; Humar ., 2001;Kumar, 2006; Tsang .,2007).

The geology of the coastal areas of Karachi asdepicted in Table 1 indicates that theground motionamplification and liquefaction factor may have acritical role in case of any earthquake with anepicenter closer to Karachi. Loya ., 2000interpreted the minor earthquake (< 4 M) of 1998 inKarachi that was only felt in the coastal belt ofKarachi and concluded that the reason for this wasthe presence of significant land fills and weakunconsolidatedsoil deposits in the area.

The ground motion amplification due to theunconsolidated sediments was believed to be themajor cause of destruction during the Bhujearthquake of 2001 (Humar ., 2001; Kumar,2006). The most intense damage was confined to

areas where buildings and other structures weresituated on top of loosely consolidated, watersaturated soils. Loosely consolidated soils tend toamplify shaking and increase structural damage.Water saturated soils compound the problem due tot h ei r s u sc e p ti b il i ty t o l i qu e fa c ti o n a n dcorresponding loss of bearing strength (Moffat,2007). Liquefaction in water saturated soils in theIndus Delta is not a new phenomenon as a severeearthquake, to theeast of Kutch,occurredin 1668 inwhich 15,000 houses reportedly sunk into theground (Oldham 1883).

Earthquake-induced liquefaction can significantly

affect the amount of structural damage incurredduring a seismic event(Moffat, 2007). Liquefactionis a physical process that takes place during someearthquakes that may lead to ground failure.Because of liquefaction, soft, young, water-saturated, well sorted, fine grain sands and silts

behave as viscous fluids rather than solids.Liquefaction takes place when seismic shear waves

pass through a saturated granular soil layer, distortits granular structure, and cause some of its porespaces to collapse (USDI, 1998). The collapse ofthe granular structure increases pore space water

pressure, and decreases the soil's shear strength(Raaijmakers 2005). If pore space water pressureincreases to the point where the soil's shear strengthcan no longer support the weight of the overlyingsoil, buildings, roads, houses, etc., then the soil will

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flow like a liquid and cause extensive surfacedamage. Loose, water saturated, well sorted finesands are susceptible to liquefaction (USDI, 1998;Raaijmakers2005).

The presence of medium to fine sand and silt in the

coastal belt (Table 1) and the saturation ofsubsurface soil with the saline water make the areaalong the Karachi coast highly susceptible not onlyto the ground motion amplification but also toliquefaction during the earthquake of moderate tohigh intensity (Loya ., 2000; Bilham .,2007). The situation may be even worst as evident

by an incident that happened just 300 meters fromthe Clifton beach as in September 2006 a 80 feethigh water tank in DHA Karachi, verticallysubmerged70 feet into theground duringa very lowintensity earthquake. The earthquake was only feltin the coastal belt. An investigation in this contextrevealed that liquefaction induced by local seismic

activity resulted in the submergence of the tankstructure(Mahmud & Sheikh, 2008). An interestingobservation was made during the construction ofroad along the Clifton beach. The residents alongthat road felt tremors in their apartments while theroad rollers were in operation. These tremors weredue to the amplification of low intensity seismicwavesproducedby theRoad Rollers while crushingstonesto a desired level.

The history of tsunami affecting the Karachi coasthas been discussed by various authors (e.g.,Bilham, 1998; Jones & Johnson, 2001; Mahar &

Nayar, 2006; Rasheed ., 2006; Qureshi, 2006;

Pararas-Carayannis, 2006; Maqsi, 2007; Hussain,2007). However, the review of the literature in thisregard shows that the information provided iswithout any scientific evidence or proof. Thoughthere is an agreement about the potential of tsunamihitting the Karachi coast, the degree of their hazardassessment is different. Without indulging in anydebate on this issue, the emphasis here wouldentirely be based on the offshore faults (Fig. 5 & 6),slope gradient, and shallow water topography ofKarachi coast as discussed earlier and depicted inFig. 3 & 4. Any vertical displacement along thesurface/subsurface faults offshore Karachi (Fig. 5& 6) or any seismic activity in and around the triple

junction may generate tsunami. The beachmorphology and slope along the Clifton indicatethat possibility of development of several meter

high tsunami wave exist along the Karachi coast(Fig. 2 & 4). The beach slope in the Hawks Bay areais also indicative of providing momentum to theapproaching water mass created by a tsunami.However, the rocky and rugged topography alongtheHawks Bay maydiminish the destructiveness ofthewaves (Fig. 3).

The above discussion clearly indicates the hazardsKarachi may have to face in future. The situationdescribed above may become more vulnerable bycontinued anthropogenic interference to the naturaldefence system which, to date, was able to protectKarachi's coastal area from direct impact ofcyclones andstorms. Oneof thetwo natural defencesystems is the barrier islands between Korangi andPhitti Creeks. The other natural system is provided

by the beach sands along the coast. The barrierisland is facing sediment starvation due to upstreamdamming of the Indus River (Inam ., 2007). Inthe absence of this line of natural defence, Karachiwould be exposed to storm surges, cyclones and

possiblyto tsunami.

It is here concluded that continuous inter-platemovement at the triple junction offshore Karachi,

presence of active faults, and history of devastatingearthquakes in the Rann of Kutch indicate that thearea around Karachi is susceptible to earthquake ofmoderate to high intensity. The presence of mediumto fine sand and silt in the coastal belt and thesaturation of subsurface soil with the saline watermake the area along the Karachi coast highlysusceptible not only to the ground motion

amplification but also to liquefaction during theearthquake of moderate to high intensity. Theinstallations constructed on the unconsolidated/uncompacted sediments need to be artificiallyreinforced where ever possible. Cyclones ortsunami may have different impact on different

parts of the Karachi coast. The Hawks Bay site ofthe coast is expected to face less destruction ascompare to theCliftonbeachand adjoiningareas.

P r of e ss o r S a ro s h L o di , C h ai r ma n C i vi l

Engineering Department, NED University, Karachiis gratefully acknowledged for his detaileddiscussions and technical input on the seismic

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ACKNOWLEDGMENT



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a c ti vit y a r ound K a ra c hi , gr ound m oti onamplification and liquefaction possibilities in thecoastal areas of Karachi. Comments made by Dr. A.R. Tabrez, Head of Marine Geology & Geophysics,

N IO a nd ot he r r e vi e we r s a r e gr at e ful lyacknowledgedas it helpedus in the improvement of

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