The devastating earthquake that struck the Kutch area of Gujarat, Indiaon January 26, 2001, India’s Republic Day, was the most severe naturaldisaster to afflict India since her independence in 1947. Thedevastation was major in terms of lives lost, injuries suffered, peoplerendered homeless, as well as economics. The author visited theaffected areas between February 12 and 16, 2001, as a member of areconnaissance team that was organized by the Mid-AmericaEarthquake Center based at the University of Illinois at Urbana-Champaign and funded by the National Science Foundation. Thisreport is based partly on his first-hand observations from that visit andpartly on information gathered from several sources, including othervisiting teams, news reports and technical literature. The authortouches upon seismological/geotechnical aspects of the earthquakeand discusses the performance of engineered buildings. Bridges, non-engineered buildings and other structures are excluded from the scope.Precast concrete construction, including non-building uses of precastconcrete, is discussed. In concluding the article, the building codesituation in India is briefly commented upon.

The Bhuj earthquake of January 26, 2001 struck at 8:46a.m. Indian Standard time and had a Richter magni-tude of 7.7 (United States Geological Survey, revised

from an initial estimate of 7.8). The epicenter was located at23.36oN and 70.34oE, less than 30 miles (50 km) to thenortheast of Bhuj, an old, walled city with a population of160,000 (see map, Fig. 1).

Although the official death toll never exceeded 35,000, un-official estimates of casualties have ranged from 100,000 to150,000. Conservative estimates of economic losses sufferedstand at 5 billion U.S. dollars.

SEISMOLOGICAL AND GEOTECHNICAL ASPECTS

According to a press release issued by the Mid-AmericaEarthquake Center, the India earthquake provided a mirror

image of the geology and earthquake history of the NewMadrid earthquakes of 1811 and 1812, the largest earth-quakes to occur in the U.S. continental 48 states, evengreater than the 1906 San Francisco earthquake. Researchingthe geophysics and related damage of this earthquake wasconsidered a once-in-a-lifetime learning opportunity to betterprepare Mid-America for a future repeat of the New Madridearthquake. This Gujarat earthquake was considered to bethe largest intraplate earthquake, not associated with a sub-duction zone, since the 1811-1812 events.

The India earthquake was felt to have very important im-plications for the nature of ground motion in the foreseeablenext major New Madrid earthquake and how our infrastruc-ture will respond, since both events involve intraplate faultshaving very large magnitudes and long attenuation distances.However, according to some seismologists,1 the tectonic set-ting of the Kutch region is not well understood. It has been

Observations From the BhujEarthquake of January 26, 2001

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S. K. Ghosh, Ph.D.PresidentS. K. Ghosh Associates, Inc.Northbrook, Illinois

March-April 2001 35

characterized as a stable continental re-gion (SCR), but its proximity to theHimalayan front and other active geo-logic structures suggests that it may betransitional between a SCR and theplate boundary.

Earthquakes, of course, are not un-known in India. Fig. 2 shows the epi-centers of earthquakes of Richter mag-nitude 6.0 and higher that haveoccurred in the short time span be-tween 1964 and 2001. Table 1 pro-vides a list of significant earthquakesoccurring since 1819.

The land of Kutch, Gujarat wasstruck by a massive earthquake at 6:45 p.m. on June 16, 1819. CaptainMcMerdo, a British agent stationed atAnjar at that time, described the devas-tating aftermath of the earthquake in aletter that has resurfaced since the re-cent earthquake. In many respects, in-cluding seismological and geotechni-cal, the January 26, 2001 earthquakewas a case of history repeating itself182 years later.

Captain McMerdo described in hisletter how the ground water level rosein most places and how the under-ground water turned sweet in areas

Fig. 1. Map of earthquake-affected area. Courtesy: MAE Center.

Fig. 2. Map ofIndia showingepicenter of recentearthquakes.

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where it was salty earlier. He alsomentioned fissures in the earth, and ofthe Indus river changing its course.

On February 14, almost 3 weeksafter the Bhuj earthquake, groundwater was observed to be bubbling outat one location near the village of Lodi.There were reports from that and otherlocations of geysers, several feet tall,erupting after the earthquake. Thegroundwater coming up near Lodi wassweet, as evidenced by algae growingon already accumulated water, whereasthe groundwater in that part of Gujaratis typically salty. Ground failure andliquefaction were quite widespread(see Figs. 3 and 4).

PERFORMANCE OFENGINEERED BUILDINGSPerformance of engineered construc-

tion was investigated by the Mid-America Earthquake (MAE) Centerteam in Ahmedabad, Morbi, Gandhid-ham, Bhuj and Bhachau, located ap-proximately 155, 71, 31, 30, and 19miles (250, 115, 50, 48, and 30 km)away from the epicenter, respectively.

Ahmedabad

The only strong motion instrument inthe entire area affected by the Bhuj earth-quake was in the basement of a multi-story building in Ahmedabad, approxi-mately 155 miles (250 km) away fromthe epicenter. The recorded peak groundacceleration was 0.1g (see Fig. 5).

Ground motion of this intensityshould not cause significant structuraldamage to properly engineered con-struction. Yet more than 70 multistoryresidential buildings collapsed inAhmedabad. The reasons for such dis-proportionate damage were fairly ap-parent.

Building Period Versus GroundMotion Period – Short-period compo-nents of ground motion typically die outfaster than the long-period componentsof ground motion as earthquake shockstravel away from the source of an earth-quake. Typically, at long distances awayfrom the epicenter, the ground motionhas predominantly long-period compo-nents.

From the copy available to the MAECenter team of the sole ground motionrecord, it was not possible to discern

Date Location Scale

June 16, 1819 Kutch, Gujarat 8.0

January 10, 1869 Cachar, Assam 7.5

May 30, 1885 Sopor, Kashmir 7.0

June 12, 1897 Shillong Plateau 8.7

April 4, 1905 Kangra, Himachal 8.0

July 8, 1918 Srimangal, Assam 7.6

July 2, 1930 Dhubri, Assam 7.1

January 15, 1934 North Bihar 8.3

June 26, 1941 Andaman Islands 8.1

October 23, 1943 Assam 7.2

August 15, 1950 Arunachal Pradesh 8.5

July 21, 1956 Anjar, Gujarat 7.0

December 10, 1967 Koyna, Maharashtra 6.5

January 19, 1975 Kinnaur, Himachal 6.2

August 6, 1988 Manipur 6.6

August 21, 1988 North Bihar 6.4

October 20, 1991 Uttar Pradesh Hills 6.6

September 30, 1993 Latur, Maharashtra 6.3

May 22, 1997 Jabalpur, M.P. 6.0

Table 1. Major earthquakes in India.

Source: Indian Meteorological Department.

Fig. 3. Ground failure caused by earthquake. Courtesy: MAE Center.

March-April 2001 37

the predominant period. However, itwould be safe to speculate that the pre-dominant periods were 0.5 second andlonger. This in itself would explain thelack of damage to shorter buildings inAhmedabad.

The buildings that collapsed were inthe ground plus four to ground plusten-story height range. Buildings inthis height range, particularly consider-ing the type of construction, mostlikely had elastic fundamental periodsin the range of the predominant periodsof the ground motion. The consequentnear-resonant response must havebeen, at least in part, responsible formuch of the damage sustained.

Soft Soil – Goel2 has made an im-portant observation with respect to thesoils on which the collapsed Ahmed-abad buildings were founded. Accord-ing to him, “Although a cursory analy-sis of location of building collapseswould indicate no particular pattern, acareful analysis reveals that most ofthe buildings that collapsed lie alongthe old path of Sabarmati River…Notethat the path of most of the buildingsthat collapsed in areas west of theSabarmati River are closely alignedwith the old path of the river…justwest of the present river path. Thesouth, southeast of the city, especiallythe Mani Nagar area, where additional

Fig. 4. Liquefaction caused by earthquake. Courtesy: MAE Center.

Fig. 5. Accelerogram recorded at basement of a building in downtown Ahmedabad.

collapses were observed, falls betweentwo lakes, indicating the presence ofeither poor soil conditions or possiblyconstruction on non-engineered fills.While the evidence presented…isstrong, it would be useful to furtherverify these conclusions with field test-ing.”

Type of Construction – Multistoryresidential buildings (and most othermultistory buildings) in Ahmedabad,

the rest of India, and indeed in much ofthe world, are constructed of rein-forced concrete frames, with the open-ings in those frames infilled with unre-inforced clay brick masonry.

There is a problem inherent in theuse of unreinforced masonry infills.Initially, while they are intact, they im-part significant stiffness to a buildingwhich, as a consequence, attractsstrong earthquake forces. The resulting

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deformations are often more than suffi-cient to cause cracking or even explo-sive failure of the infilled masonry.When that happens, the period of thebuilding lengthens significantly all of asudden.

Although this usually is beneficial interms of attracting less earthquakeforces, depending on the nature of theearthquake ground motion, the oppo-site may be the case. For example, inthe 1985 Mexico earthquake, with thepredominant 2-second period of theground motion in downtown MexicoCity, a building attracted strongerearthquake forces with the loss of theinfill. Also, very importantly, the al-tered earthquake forces must be re-sisted essentially by the bare frame. Ifthe frame lacks that capability, severedamage or collapse may result.

Stiffness Discontinuity or Soft Story –In virtually all Indian cities, the multi-story residential buildings of the typedescribed above have open ground sto-ries for parking of automobiles, be-cause the small lots on which suchbuildings are typically built do notallow for open parking (see Fig. 6).This means an almost total absence ofinfills at the ground level, thus creatinga very distinct stiffness discontinuity ora soft story.

Virtually all the earthquake-induceddeformations in such a building occurin the columns of the soft story, withthe rest of the building basically sway-ing uncontrollably. If these columnsare not designed to accommodate thelarge deformations, they may fail,leading to a catastrophic failure of theentire building, as was the case withmany buildings in Ahmedabad andelsewhere.

Discontinuity of Vertical Load Path –The local municipal corporation inAhmedabad imposes a Floor SurfaceIndex (FSI), which restricts the groundfloor area of a building to be no morethan a certain percentage of the lotarea. It is, however, permitted to covermore area at the upper floor levels thanat the ground floor level. The same isthe situation in many other Indiancities as well. Thus, most buildingshave overhanging covered floor areasat upper floors, with overhangs fre-quently ranging up to 5 ft (1.52 m) ormore.

Fig. 6. Typical soft-storyresidential building.Courtesy: Tiziana Rossetto,Imperial College,London.

The columns on the periphery of theupper floors do not continue down tothe ground level. The columns at theground floor level also may or may notalign with the columns at the upperlevels. Significant vertical discontinu-ities are, therefore, generated in the lat-eral-force-resisting system.

Non-Ductile Detailing – Goel2 hasreported: “The columns for low-riseresidential buildings, up to ground plusfour stories (G + 4), rest on shallowisolated footings located about 5 ft(1.52 m) below the ground level. Fortaller buildings, say up to ground plusten stories (G + 10), the column foun-dations are still open footings locatedat a depth of 8 to 10 ft (2.44 to 3.05m); sometimes the foundation mayalso have tie beams. The column sizesfor low-rise buildings (G + 4) areabout 9 x 18 in. (230 x 460 mm) withties consisting of smooth No. 2 mildsteel bars at a spacing of about 8 to 9in. (200 to 230 mm). The beams tendto be much deeper to accommodatelarge spans and overhangs, giving riseto strong beam-weak column construc-tion. The column sizes for taller build-ings tend to be a little bigger, usually12 x 24 in. (300 x 600 mm) with No. 3

deformed steel ties at a spacing of 8 to9 in. (200 to 230 mm). The beam sizein taller buildings may be similar to thecolumn size. These ties always end upwith 90-degree hooks.”

Such non-ductile detailing of rein-forced concrete construction is com-mon practice around the world, includ-ing pre-1973 reinforced concreteconstruction in California, althoughdetails vary from place to place anddepend upon the age of the building. Inaddition to all of the above, column re-inforcement is typically spliced rightabove the floor levels; splice length inthe columns as well as the beams isoften insufficient; and continuity ofbeam reinforcement over and into thesupports is often also insufficient.

The large deformations that takeplace in soft story columns also imposeextreme shear demands on them. Themeager lateral reinforcement describedabove not only provides poor confine-ment; the shear strength available isalso quite low. As a result, manyground floor columns failed in a brittleshear mode, or in a combined shearplus compression mode, bringingdown the supported buildings (see Fig.7). Many times, in columns that had

March-April 2001 39

not failed, diagonal shear cracking wasevident (see Fig. 8).

Torsion – The typical soft-story resi-dential building described above is tor-sionally quite flexible at the groundfloor level. If appreciable eccentricitiesbetween the center of mass and the cen-ter of rigidity are introduced because ofasymmetric placement of walls or otherreasons, significant torsional motionsmay result. These may subject columnson one side of a building to excessivedeformations. If not adequately de-signed to accommodate such deforma-tions, the columns may fail, contribut-ing to building collapse. According toGoel,2 “deformations due to torsionmay have contributed to failure of atleast one building” in Ahmedabad.

Detailing of Shear Wall Core andConnection to Remainder of Structure –The typical soft-story residential build-ing described above relies upon theshear wall core(s) around stairwell(s)and/or elevator shafts to resist most ofthe lateral load at the ground floorlevel. Up the height of the building, theshear walls do unload increasing per-centages of story shears onto the

Fig. 7. Non-ductile detailing of column. Courtesy: MAE Center.

frames, provided the floor diaphragmsconnecting them are rigid enough in-plane to impose equal displacementson the shear walls and the frames. Sev-eral deficiencies were observed.

The ratio of cross-sectional area ofshear walls to plan area of building

was often quite low. The shear wallsare typically about 4 to 6 in. (100 to150 mm) thick with very light rein-forcement consisting of two layers ofmesh formed with No. 3 or No. 4 barsat vertical and horizontal spacings ofabout 18 in. (460 mm).

Such detailing was often insufficientto resist the lateral loads at the groundfloor level; severe shear cracking ofshear walls at the ground level was fre-quently observed. The shear crackingoften did not extend above the groundfloor level, reflecting reduced shear de-mand on the walls.

The shear wall core was often con-nected to the rest of the building onlythrough the floor slabs, with no beamsframing into the shear walls. The an-chorage of slab reinforcement into theelevator core was often insufficient. Asa result, the shear walls sometimes justpulled out from portions of the build-ing, leaving them devoid of much lat-eral resistance.

Material Quality – There were in-dications that deficient material qual-ity might also have contributed tostructural damage, or even collapse.Goel, in his recent paper,2 showed thebottom of a column in a partially col-lapsed building. “The concrete hassimply disintegrated within the rein-forcement cage, when touched, theconcrete felt sandy with little cement.Also, note that the 90-degree hookshave opened up, which leads to littleFig. 8. Shear cracking of column. Courtesy: MAE Center.

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or no confinement of the concrete.Many times, the concrete cover to re-inforcement was noted to be less than0.5 in. (13 mm), where most of thecover was provided by the plasterused to smooth the column surface. Itis worth noting that most of the watersupply in the outer part of the city isthrough ground water which is saltyin taste. Usually, the same water isused in preparing the concrete forconstruction. Therefore, the presence

of salts may have also affected theconcrete quality.”

Other Cities

Observation of the performance ofengineered buildings in four other cities– Morbi, Gandhidham, Bhuj andBhachau – did not produce substantiallynew technical information. As the epi-central distance decreased, even rela-tively short buildings were not spared.

In Gandhidham, there was an inter-

Fig. 9. Ground level column punching through floor slab of a building.

Fig. 10. Core separated from rest of building.

esting case of several ground-storycolumns in a building (in which thesoft ground story had collapsed) hav-ing punched through the first sus-pended slab (see Fig. 9).

In another case, the shear core of abuilding had completely separatedfrom the rest of the building (see Fig.10). The right wing of the building hadcollapsed. The left wing was stillstanding up.

Finally, in Bhuj, one example of avery few overturned buildings was ob-served (see Fig. 11).

PRECAST CONSTRUCTIONAccording to an Earthquake Engi-

neering Research Institute (EERI) Spe-cial Earthquake Report,1 some single-story school buildings in the Kutchregion are made of large-panel precastreinforced concrete components for theslabs and walls, and precast reinforcedconcrete columns. The EERI report in-dicates that a typical design using thisconstruction has been recently repli-cated all over Gujarat, including theearthquake-affected region. The reportalso indicates that approximately one-third of 318 such schools in the Kutchregion had roof collapses.

Inadequate connection between theroof panels led to a lack of floor-di-aphragm action, and insufficient seat-ing and anchorage of the roof panelsover the walls and beams led to dis-lodgment of the precast roof panelsfrom the tops of the walls. These phe-nomena have been observed in manypast earthquakes across the world. Theauthor did not have the opportunity toobserve the performance of any ofthese precast schools first-hand.

Precast concrete has found fairlypopular use in railroad ties (sleepers).The railroad network in the affectedarea was closed for inspection immedi-ately following the earthquake. Itturned out that there was surprisinglylittle damage to the network. It wasmade operational up to Ghandidhamon January 29.

The Gandhidham to Bhuj railwaysegment was closed at the time of theearthquake for gauge conversion (nar-row gauge to broad gauge) and wasscheduled to become operational onJanuary 31. This segment became op-

March-April 2001 41

erational on February 3. Fig. 12 showsprecast sleepers supporting the newbroad-gauge railway track near Morbi.

Precast concrete also is used in alimited way in utility poles and fencepoles. In cities such as Bhuj, there wasdamage to many of these poles, aswould be expected. However, therewas also damage to metal poles.

INDIAN CODES ANDSTANDARDS

India has, for quite some time now,had sophisticated codes and standards.The three documents relevant to thisdiscussion are:

1. IS1893:1984 – Indian StandardCriteria for Earthquake ResistantDesign of Structures (Fourth Revi-sion).

2. IS 4326:1993 – Indian StandardEarthquake Resistant Design andConstruction of Buildings – Codeof Practice.

3. IS 13920:1993 – Indian StandardDuctile Detailing of ReinforcedConcrete Structures Subjected toSeismic Forces – Code of Prac-tice.

IS 1893 states: “It is not intended inthis standard to lay down regulationsso that no structure shall suffer anydamage during earthquakes of all mag-nitudes. It has been endeavored to en-sure that, as far as possible, structuresare able to respond, without structuraldamage to shocks of moderate intensi-ties, and without total collapse toshocks of heavy intensities.”

IS 1893 contains a seismic zoningmap. The object of this map is to clas-sify the area of the country into a num-ber of zones in which one may reason-ably expect earthquake shock of moreor less the same intensity in the future.The modified Mercalli Intensity asso-ciated with the various zones is V orless, VI, VII, VIII, and IX and abovefor Zones I, II, III, IV, and V, respec-tively.

It may be noted that Bhuj is in Seis-mic Zone V, while both Ahmedabadand Mumbai (Bombay) are in Zone III.

IS 4326 is intended to cover thespecified features of design and con-struction for earthquake resistance ofbuildings of conventional types. In thecase of other buildings, detailed analy-

Fig. 11. Overturned building.

sis of earthquake forces is required.Recommendations regarding restric-tions on openings, provision of steel invarious horizontal bands and verticalsteel in corners and junctions in wallsand at jambs of openings are based onextensive analytical work. Many of theprovisions have also been verified ex-perimentally on models by shake tabletests.

IS 4326: 1976 “Code of Practice forEarthquake Resistant Design and Con-

struction of Buildings,” while coveringcertain special features for the designand construction of earthquake resis-tant buildings, included some detailsfor achieving ductility in reinforcedconcrete buildings. With a view tokeeping abreast of the rapid develop-ments and extensive research in thefield of earthquake resistant design ofreinforced concrete structures, the de-cision was made to cover provisionsfor the earthquake resistant design and

Fig. 12. Precast railroad ties (sleepers).

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detailing of reinforced concrete struc-tures separately.

IS 13920 incorporates a number of im-portant provisions not covered in IS 4326:(a) As a result of the experience

gained from the performance inearthquakes of reinforced concretestructures that were designed anddetailed according to IS 4326:1976, many identified deficiencieswere corrected in IS 13920.

(b) Provisions on detailing of beamsand columns were revised with theaim of providing them with ade-quate toughness and ductility so asto make them capable of undergo-ing extensive inelastic deforma-tions and dissipating seismic en-ergy in a stable manner.

(c) Specifications on seismic designand detailing of reinforced con-crete shear walls were included.

The other significant items incorpo-rated in IS 13920 are as follows:(a) Material specifications are indi-

cated for lateral-force-resisting el-ements of frames.

(b) Geometric constraints are imposedon the cross section for flexuralmembers. Provisions on minimumand maximum reinforcement havebeen revised. The requirements fordetailing of longitudinal reinforce-ment in beams at joint faces, andsplices and anchorage require-ments are made more explicit.Provisions are also included forthe calculation of design shearforce and for detailing of trans-verse reinforcement in beams.

(c) For members subjected to axialload and flexure, dimensional con-straints have been imposed on thecross section. Provisions are in-cluded for detailing of lap splicesand for the calculation of designshear force. A comprehensive set

of requirements is included on theprovision of special confining re-inforcement in those regions of acolumn that are expected to un-dergo cyclic inelastic deforma-tions during a severe earthquake.

(d) Provisions have been included forestimating the shear strength andflexural strength of shear wall sec-tions. Provisions are also given fordetailing of reinforcement in thewall web, boundary elements,coupling beams, around openings,at construction joints, and for thedevelopment, splicing and anchor-age of reinforcement.

While the common methods of de-sign and construction have been cov-ered in IS 13920, special systems ofdesign and construction of any plain orreinforced concrete structure not cov-ered by that code may be permitted onproduction of satisfactory evidence, re-garding their adequacy for seismic per-formance by analysis, or tests, or both.

It is interesting to note that the pro-visions of IS 13920 apply to reinforcedconcrete structures that satisfy one ofthe following conditions:

(a) The structure is located in SeismicZone IV or V;

(b) The structure is located in SeismicZone III and has an importancefactor greater than 1.0;

(c) The structure is located in SeismicZone III and is an industrial struc-ture; and

(d) The structure is located in SeismicZone III and is more than five sto-ries high.

Thus, the residential buildings inAhmedabad with ground plus four sto-ries are exempt from the requirementsof IS 13920.

The above codes, as noted earlier,are quite sophisticated. IS 13920:1993is, in fact, greatly influenced by ACI

318-89. However, code enforcementpractically does not exist in India.

Central and State governmentswould at times require code compli-ance for buildings owned by them. Forother buildings, code requirements areseldom, if ever, enforced. Local juris-dictions typically do not have a mecha-nism in place to enforce code require-ments. This not only explains much ofthe damage observed to engineeredbuildings, but also indicates that thepromise of a bright new future is noton the horizon.

ACKNOWLEDGMENTThe author is indebted to Mr. R.N.

Raikar, Managing Director, StructwelDesigners & Consultants Pvt. Ltd.,who acted as de facto host to the MAECenter team. He is also grateful to Dr. Kirit Budhbhatti, who facilitatedarrangements and logistics for theMAE Center team. Dr. Kirit Budhb-hatti’s untiring efforts were crucial tothe success of the seismology-relatedundertakings of the MAE Center team.

REFERENCES

1. “Learning From Earthquakes: Pre-liminary Observations on the Originand Effects of the January 26, 2001Bhuj (Gujarat, India) Earthquake,”EERI Special Earthquake Report –April 2001, EERI Newsletter, V. 35,No. 4, Earthquake Engineering Re-search Institute, Oakland, CA, April2001.

2. Goel, R. K., “Performance of Build-ings During the January 26, 2001Bhuj Earthquake,” to be publishedin Earthquake Spectra, EarthquakeEngineering Research Institute,Oakland, CA.