Tremors and built environment of Hyderabad, Telangana, India: safety of buildings using recorded ground motions

Abstract

Although the city of Hyderabad in Telangana, India lies in seismic zone II, low to medium intensity tremors that pose a serious concern towards safety of the built environment are not uncommon. One such series of tremors occurred during 13-20 October 2020, in the financial district of Hyderabad and created a panic situation due to perceivable shaking and jolts with loud sounds associated with hydro-seismicity. To understand the safety of the city's built environment, a study was conducted on low, medium and tall buildings using ground motions recorded at the International Institute of Information Technology (IIIT), Hyderabad, which is 2.3 km from the epicentre. The amplification of ground motion on the second floor of the Nilgiri Building in IIIT, Hyderabad was 1.2-2.3. The vibrations recorded on the ground floor of the Nilgiri Building were used to develop a site-specific response spectrum. This was further used to obtain the peak responses of the considered buildings through response spectrum analysis. The present study suggests that the low-rise buildings, mid-rise buildings and non-structural elements in high-rise buildings are under threat in the case of high-intensity earthquakes.

Full text

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*For correspondence. (e-mail: pulkit.velani@research.iiit.ac.in)
Tremors and built environment of Hyderabad,
Telangana, India: safety of buildings using
recorded ground motions
Pulkit Dilip Velani1,*, Neelima Patnala1, Bharat Prakke1, S. L. N. Shastry2 and
R. Pradeep Kumar1
1Earthquake Engineering Research Centre, International Institute of Information Technology, Hyderabad 500 032, India
2International Institute of Information Technology, Hyderabad 500 032, India
Although the city of Hyderabad in Telangana, India lies
in seismic zone II, low to medium intensity tremors that
pose a serious concern towards safety of the built envi-
ronment are not uncommon. One such series of tremors
occurred during 13–20 October 2020, in the financial
district of Hyderabad and created a panic situation due
to perceivable shaking and jolts with loud sounds associ-
ated with hydro-seismicity. To understand the safety of
the city’s built environment, a study was conducted on
low, medium and tall buildings using ground motions
recorded at the International Institute of Information
Technology (IIIT), Hyderabad, which is 2.3 km from the
epicentre. The amplification of ground motion on the
second floor of the Nilgiri Building in IIIT, Hyderabad
was 1.2–2.3. The vibrations recorded on the ground floor
of the Nilgiri Building were used to develop a site-speci-
fic response spectrum. This was further used to obtain
the peak responses of the considered buildings through
response spectrum analysis. The present study suggests
that the low-rise buildings, mid-rise buildings and non-
structural elements in high-rise buildings are under threat
in the case of high-intensity earthquakes.
Keywords: Built environment, ground motion, hydro-
seismicity, microtremors.
THE Information Technology (IT) corridor of Hyderabad,
Telangana, India, experienced earthquake tremors of
magnitude 0.8 during the second and third week of Octo-
ber 2020 (ref. 1). In the past, similar events have occurred
in the Hyderabad region. In 1982, an earthquake of mag-
nitude 3.5 occurred near Osman Sagar reservoir, followed
by aftershocks for five weeks. The event was attributed to
the north northeast (NNE) fault trending the area2. A total
of more than 50 tremors were reported to have occurred
according to the catalogue of earthquakes of M  3 (ref.
3). In 1983, an earthquake of magnitude 4.5 occurred
along the Musi lineament, causing minor cracks in a few
buildings; some boulders were also displaced near the epi-
central area4. The Jubilee Hills area has experienced a
sequence of microtremors regularly from 1994 to 2016.
The west northwest–east southeast (WNW–ESE) trending
shear zone extending from Banjara Lake through Kasu
Brahmananda Reddy National Park and going up to Dur-
gam Cheruvu was related to this microtremor activity5.
In 1984, three tremors were reported in Saroornagar, an
area close to Vanasthalipuram. The maximum magnitude
was 2.2. On 22 October 2010, localized micro-seismicity
with subterranean sounds was reported in Vanastalipuram
area located in the eastern part of Hyderabad city4. Table 1
shows the decade-wise list of microearthquakes. Table 2
lists the significant earthquakes that have occurred in the
past in Hyderabad.
Tectonics and seismicity of the region
The Indian peninsular region is one of the oldest Archean
shield regions of the world. It was deemed to be devoid
of major seismic activity. However, in the past 50 years,
there have been occurrences of few moderate to large
earthquakes associated with major damage to property
and loss of lives. The city of Hyderabad lies at 17.38°N
lat. and 78.48°E long., in peninsular India, at an elevation
of 576 m amsl. Geomorphically, the surrounding area of
Hyderabad is characterized by undulating terrain with re-
sidual hills, inselbergs, pediplains and pediment zones,
and valley fills. The general geology of the region con-
sists of Archean granites and gneiss of the Precambrian
era, which extend several kilometres from the surface to
Table 1. Decade-wise microearthquakes in
Hyderabad, India
Decade
No. of microearthquakes
1970–80
5
1980–90
63
1990–2000
13
2000–10
47
2010–20
71
Source: refs 2, 4, 13.

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Table 2. List of earthquakes that occurred in Hyderabad, Telengana, India
Date
Location
Latitude
Longitude
Moment magnitude
1876
Secunderabad
17.5
78.5
5
14 January 1982
Gandipet
17.43
78.35
3.5
27 January 1982
Gandipet
17.4
78.3
3.3
30 June 1983
Medchal
17.6
78.5
4
Source: ref. 3.
Table 3. List of earthquakes that occurred near Hyderabad (within 300 km radius)
Date
Location
Latitude
Longitude
Moment
magnitude
Date
Location
Latitude
Longitude
Moment
magnitude
18 October 1800
Ongole
15.60
80.10
4.30
9 June 1990
Manuguru
17.90
80.60
4.00
31 December 1820
Nellore
14.50
80.00
4.30
9 June 1990
Manuguru
17.90
80.50
5.00
12 March 1843
Hyderabad
17.50
78.50
3.70
9 June 1990
Bhadrachalam
17.90
80.50
5.00
21 July 1859
Guntur
16.30
80.50
4.30
18 October 1992
Maharashtra
18.07
76.86
4.77
24 July 1861
Krishna
16.40
77.30
3.70
02 November 1992
Maharashtra
18.22
76.56
4.35
11 March 1867
Ongole
16.00
80.30
3.70
29 September 1993
Maharashtra
18.09
76.44
5.28
13 October 1956
Ongole
15.70
80.10
5.00
29 September 1993
Maharashtra
18.07
76.45
6.30
12 October 1959
Ongole
15.70
80.10
5.00
30 September 1993
Maharashtra
18.16
76.66
4.86
08 October 1960
Ongole
16.00
80.30
4.30
30 September 1993
Maharashtra
18.09
76.52
4.94
27 March 1967
Ongole
15.60
80.00
5.40
08 October 1993
MH-AP
17.93
76.40
5.03
14 April 1968
AP
18.00
80.80
6.10
29 October 1993
KT-AP
17.37
77.47
5.28
27 July 1968
Bhadrachalam
17.60
80.80
4.50
12 November 1993
Maharashtra
18.12
76.53
4.94
16 January 1969
Rayachoti
14.10
78.70
4.10
24 May 1995
Guntur
15.60
79.40
4.00
13 April 1969
Bhadrachalam
17.90
80.60
5.70
14 December 1995
Maharashtra
18.13
76.54
4.69
14 April 1969
Kothagudem
18.00
80.50
5.70
04 August 1996
Addanki
15.80
80.00
4.10
11 July 1970
Bhadrachalam
17.90
80.60
4.10
10 November 1996
Maharashtra
18.30
76.70
4.52
28 July 1971
Ongole
15.50
78.60
4.30
03 February 1999
Yellandu
18.10
80.40
4.00
02 October 1980
Rajamundry
16.90
82.00
4.00
19 June 2000
Maharashtra
18.01
76.49
4.77
27 January 1982
Gandipet
17.40
78.30
3.30
6 September 2007
Maharashtra
18.06
76.54
4.09
30 June 1983
Medchal
17.60
78.50
4.00
19 September 2011
MH-KT
17.92
76.56
4.43
3 December 1987
Ongole
15.30
79.80
4.00
25 January 2020
Jaggayyapeta
16.68
79.90
4.86
3 December 1987
Ongole
15.50
80.20
4.00
–
–
–
–
–
Source: ref. 5.
the deep crustal interiors6. The hard rocks are devoid of
porosity, but the joints, fractures, faults and lineation can
hold large volumes of groundwater, which is transported
deeper. Like precipitation, surface run-off, etc. hydrological
events at the earth’s surface cause water to travel deeper
through the joints, fractures and faults, triggering vibra-
tions with thudding sounds. This phenomenon is called
hydro-seismicity. From an analysis of the Indian Remote
Sensing satellite 1D Linear Imaging Self-Scanning Sen-
sor-III (IRSID LISS-III) satellite image acquired from the
National Remote Sensing Agency (NRSA), Hyderabad,
nearly 20 lineaments were mapped7. The main orienta-
tions of these lineaments are north–south (NS), north
east–southwest (NE–SW) and east southeast–west north-
west (ESE–WNW).
A series of minor and moderate earthquakes have occur-
red in Hyderabad (Table 2). Often, moderate earthquakes
occur in Bhadhrachalam, Guntur and Ongole areas that fall
within a 300 km radius of Hyderabad. There is a trend of
occurrence of microearthquakes in the above regions at
regular intervals. On the night of 25 January 2020, an
earthquake of magnitude 4.5 occurred at 32 km southwest
(SW) of Jaggayyapeta town which is 190 km from Hydera-
bad. Quakes were reported to be felt in Hyderabad. Table 3
presents the list of earthquakes within 300 km radius
from Hyderabad. Figures 1 and 2 show the seismicity
near Hyderabad region.
Behaviour of buildings during past earthquakes
During an earthquake, buildings are deemed to be safe
when there is neither loss of life nor loss of contents of
buildings, appendages to building and also no disruption
to the services and utilities8. The overall size and configu-
ration of reinforced concrete (RC) buildings play a crucial
role in their performance during an earthquake. One of
the common features in multi-storey buildings across India
is the presence of open ground storey for vehicular park-
ing. During an earthquake, buildings with such features
either collapse or the structural elements on the ground
floor are severely damaged. Figure 3 a and b shows the
collapse and severely damaged columns of two separate
buildings in Ahmedabad, Gujarat, during the 2001 Bhuj

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Figure 1. Seismicity near Hyderabad region (M = 3.3–6.3) from 1800 to 2020 (data source: ref. 5).
Figure 2. Seismicity near Hyderabad region (MD = 0.9–4.7) from 1996 to 2010 (data source: ref. 14).
earthquake9. It has also been observed from the past earth-
quakes that buildings with intermediate soft and weak
storeys are prone to failure. Similarly, buildings with
floating columns and overhanging beams are a potential
threat for failure during lateral shaking. Figure 4 a and b
shows the failure of buildings due to overhangs and float-
ing columns respectively, in Ahmedabad, during the 2001
Bhuj earthquake9. Majority of the multi-storey buildings
in Hyderabad also possess the features mentioned above
and are vulnerable to seismic hazard. Figures 3 c and 4 c
depict the construction practice of open ground storey
with unidirectional columns and buildings with large over-
hangs present in Hyderabad respectively.
In addition to the structural features, non-structural ele-
ments (NSEs) in high-rise buildings are more sensitive to
ground motion compared to those in medium-rise and low-
rise buildings. The recent 2013 Wellington earthquake,
2015 Gorkha earthquake, and 2016 Central Italy earthquake

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Figure 3. a, Collapse of an apartment building in Ahmedabad city, Gujarat during the 2001 Bhuj earthquake
(image courtesy: Murty et al.9). b, Severely damaged open ground storey column which did not collapse (image
courtesy: Murty et al.9). c, Typical example of open ground storey for car parking with unidirectional column ori-
entation in Hyderabad city.
Figure 4. a, Perimeter columns of building supported by tapered cantilever beams (image courtesy: Murty et
al.9). b, Shear cracks in beams supporting floating column (image courtesy: Murty et al.9). c, A typical RC build-
ing with large overhang cantilever beams in Hyderabad city.
Figure 5. In-plane and out-of-plane damage in a high-rise building
during the 2015 Gorkha earthquake, Nepal (image courtesy: Lizundia et
al.10).
Figure 6. Photograph of Niligiri Building, International Institute of
Information Technology (IIIT), Hyderbad.
are few cases that highlight the poor performance of NSEs.
Figure 5 depicts the damage to masonry infill walls of
Parkview horizon complex, Kathmandu, Nepal10. In addi-
tion, it has been observed that the locations close to the
epicentre are subjected to ground motions which contain
short-period pulses that are potentially dangerous to
NSEs in high-rise buildings. The study of the performance
of NSEs in India and the world is still in its nascent stage
and beyond the scope of this work.
Ground motions due to tremors
The engineering characteristics of tremors observed in
the last week of October in Hyderabad were studied using
building vibration sensors installed at IIIT, Hyderabad
(Figure 6). The epicentre has been reported at 17.4337°N,
78.3322°E located near ‘My Home Vihanga’ residential
complex1. The instrument was located at IIIT Hyderabad
at a distance of 2.3 km. The structural health of the Nilgiri
Building was monitored using the building vibration sen-
sors installed (Figure 7). Since the established epicenter
of the tremors was near the building under study, the
ground vibrations obtained on the building ground floor

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Table 4. Engineering characteristics of ground motions observed during tremors at Hyderabad
PGA (cm/sec2)
Predominant period (sec)
Trifunac’s
Event ID
Date
Time
NS
EW
UD
NS
EW
UD
duration
(sec)
117
18 October 2020
12:44
4.0068
4.9731
2.9080
0.12–0.23
0.06–0.08
0.11–0.15
3.9
221
18 October 2020
14:31
0.7534
0.6083
0.2711
0.04–0.05
0.06–0.08
0.13–0.18
5.4
121
18 October 2020
14:31
0.6226
0.3572
0.1579
0.04–0.06
0.05–0.08
0.08–0.23
2.4
126
18 October 2020
17:04
0.2153
0.2736
0.1145
0.06–0.23
0.10–0.16
0.06–0.10
3.0
131
18 October 2020
18:36
0.2476
0.5573
0.1316
0.04–0.05
0.04–0.08
0.09–0.13
3.0
133
18 October 2020
19:11
0.2192
0.0746
0.0992
0.04–0.05
0.13–0.20
0.11–0.16
6.0
137
18 October 2020
21:07
2.4631
3.1111
0.9642
0.12–0.17
0.06–0.07
0.10–0.17
9.0
139
18 October 2020
21:17
0.6929
0.2714
0.1954
0.04–0.05
0.05–0.08
0.07–0.16
4.8
140
18 October 2020
21:18
0.685
0.3016
0.1743
0.04–0.05
0.06–0.07
0.11–0.15
6.0
148
19 October 2020
05:21
0.2055
0.1127
0.0763
0.04–0.06
0.04–0.05
0.06–0.09
2.1
NS, North–South; EW, East–West; UD, Up–Down.
Figure 7. Plan view of Nilgiri Building with sensor location.
Figure 8. System configuration and the set of installed sensors.
were analysed to understand the engineering characteris-
tics of ground motion during tremors.
The sensors were installed with a permanent network
set-up and connected to a server. Figure 8 shows the system
configuration and installation. The ambient vibration res-
ponse of the building was recorded continuously. Data
were acquired at a sampling rate of 100 and frequency of
0–50 Hz in the north–south (NS), east–west (EW) and
up–down (UD) directions. The sensors include network-
connected seismometers developed and standardized at
the IT Kyoshin Consortium, Japan. The NS and EW com-
ponents of sensors were oriented along shorter and longer
dimensions of the building respectively.
Figure 9. Flow chart of data processing.
The recordings from the ground floor were extracted
from 16 to 22 October 2020, resulting in 74 events from
the installed sensor. From the continuous ambient vibration,
the peak was identified as a tremor. Around the peak,
1 min before and after, data were extracted for further
processing. Performing baseline correction and filtering
resulted in obtaining 45 accepted seismic tremors. The
baseline correction was done using the standard MATLAB
function, and a fourth order Butterworth band-pass filter
was used for the filtering with suitable lower and upper
cut-off values of 0.03 and 25 Hz respectively. From the
corrected accelerogram, arrival of the P-wave was consi-
dered as the start of the record. The time step at which the
vibration become normal, i.e. back to ambient vibration,
was considered as the end time of the record. Figure 9 is
a flow chart of the entire process adopted. Table 4 shows
the engineering characteristics of the ten most critical
tremors observed in one week. Figure 10 shows the 10
acceleration time histories with maximum peak ground
acceleration (PGA).
From an engineering perspective, the most essential
ground motion characteristics include PGA, predominant

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Figure 10. Ground motions recorded at the Block II, Nilgiri Building, IIIT-H.
Figure 11. Fourier amplitude spectra of ground motions along north–
south direction.
frequency range and effective duration. PGA is the abso-
lute maximum value of acceleration in the time history of
ground motion; predominant frequency range is defined
by the half-power bandwidth measured as the range of
frequencies that has
1/ 2
times the maximum Fourier
amplitude of the ground motion. Effective duration is de-
fined as the time difference between instants at which the
amplitude is greater than 5% and becomes less than 95%
of the cumulative acceleration11.
Figures 11 and 12 show the Fourier amplitude spectra of
all the ground motions recorded during tremors in the NS
and EW directions respectively. The maximum value of
Fourier amplitude from ground motions in the NS direction
was 2.91 cm/sec2 and in the EW direction it was 3.18 cm/
sec2. From the definition of half-power bandwidth, the value
of
1/ 2
times maximum Fourier amplitude is 2.06 cm/
sec2 in the NS direction and 2.25 cm/sec2 in the EW di-
rection. Likewise, the predominant period range of the
top events is located at 0.05–0.20 sec. This observation
also indicates that the ground motions are critical for

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Table 5. Acceleration and displacement response along with amplification of Niligiri Building (Block II), International Institute of Information
Technology (IIIT-H) for the highest peak ground acceleration (PGA) tremor
Acceleration (cm/sec2)
Displacement (cm)
Floor level
Along shorter direction
(NS)
Along longer direction
(EW)
Along shorter direction
(NS)
Along longer direction
(EW)
Second floor (ITK08)
7.109
5.980
0.0061
0.0026
Ground floor (ITK06)
3.460
4.690
0.0026
0.0013
Amplification ratio (ITK08/ITK06)
2.055
1.275
2.324
1.983
NS, North–south; EW, East–west.
Figure 12. Fourier amplitude spectra of ground motions along east–
west direction.
Figure 13. Comparison of 5% damped design spectrum specified in
IS 1893: 2016 and that developed from the observed ground motions
for the location under consideration.
those buildings with a natural period ranging between 0.1
and 0.3 sec. The match of the natural period of buildings
with the predominant period of ground motion creates reso-
nance-like conditions leading to large inelastic deforma-
tions. Although the recorded tremors have minimal PGA
values, amplification of the same ground motion causes a
concerning factor for the low- to mid-rise buildings. The
effect of the recorded ground motions on the structure can
be well understood from a site-specific response spec-
trum.
Site-specific response spectrum
Any building is designed for a lateral force equal to a certain
percentage of seismic weight that depends on the seismic
zone, the importance of structure, lateral load resisting
system, and the spectral acceleration observed by the
building present on a particular type of soil. According to
IS 1893 (Part 1): 2016, Hyderabad lies in seismic zone II
with an expected PGA of 0.1 g. The maximum spectral
acceleration prescribed is 2.5 for the structures present in
the city. However, these code-specified values are adopted
from past earthquake data observed during macro-seismic
studies. Therefore, it is crucial to verify the spectral am-
plification evident during the recent tremors observed.
A site-specific design spectrum indicates the effect of
tremors on the existing building stock in the city. The
design spectrum was developed using the standard pro-
cedure12. Figure 13 shows the design spectrum obtained
from ground motion data observed during the recent
tremors compared to the design spectrum specified by the
standard code IS 1893 (Part 1): 2016. The generated spectra
were used to determine the response of different catego-
ries of buildings in the preceding section.
Experimental study
As discussed earlier, the building response of Block II of
the Niligiri Building was recorded successfully. Figures
14 and 15 show the acceleration and displacement res-
ponse recorded for the highest PGA tremor respectively.
The highest PGA experienced at the ground level was
3.460 and 4.690 cm/sec2 along the shorter and longer
building dimensions respectively. This value was ampli-
fied by 2.06 and 1.28 times along the shorter and longer
side of the building respectively, resulting in a maximum
acceleration value of 7.109 and 5.980 cm/sec2 respectively
on the second floor of the building (Table 5). Similarly,
the displacement on the second floor was amplified by 2.32
and 1.98 times the displacement on the ground floor along
the shorter and longer side respectively. It was observed
that both acceleration and displacement were too low to
cause any damage to the building. However, there was
good certainty that amplification of acceleration and

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Table 6. Structural details of the buildings analysed
Niligiri Building
G + 1
G + 3
G + 16
B1 + G + 40
Number of storeys
3
2
4
17
42
Typical storey height (m)
3.6
3.0
3.0
3.2
3.3
Total height from base (m)
10.80
6.00
12.00
54.40
145
Plan dimension (m)
36.4 × 49.7
5.1 × 12.6
9.0 × 9.0
42.0 × 30.0
32.0 × 28.0
Usage
Educational institution
Residential
Residential
Office
Residential
Structural system
Moment resisting frame (MRF)
MRF
MRF
MRF + structural wall (SW)
SW
Maximum natural period (sec)
–
0.240
0.550
1.122
3.513
Soil type
–
Type I
Importance factor (I)
–
1
Response reduction factor (R)
–
3
G, Ground floor; B, Basement.
Figure 14. Acceleration time history of ground floor and second floor
sensors of Niligiri Building, IIIT Hyderabad.
Figure 15. Displacement time history of ground floor and second
floor sensors of Niligiri Building, IIIT Hyderabad.
displacement would be in the range of 1.2–2.3 times the
shaking at the base level of the building. Further study of
the same block was done with the help of an analytical
model subjected to site-specific response spectra.
Analytical study
The Niligiri Building, whose response to tremors has been
discussed above, was modelled first. This is necessary
since details of this building are well known. The instru-
mented Block II of the Niligiri Building is the (G + 2) RC
structure used for academic purpose. Further, to deter-
mine the effect of tremors on the existing building stock
in Hyderabad, four more RC buildings representing the
typical architectural and structural feature were modelled
and analysed using the commercial Finite Element Mod-
elling (FEM) software ETABS (version 18.1.1). To ensure
diversification, buildings were selected such that they
cover low-rise (up to two storeys), mid-rise (<18 m) and
tall (>50 m) structures. Among the four RC representa-
tive buildings, two represent low- and mid-rise residential
buildings respectively. Out of the remaining two, one rep-
resents a commercial building used as an office having a
simple rectangular plan. The other represents a tall resi-
dential buildings to be constructed in the Cyberabad region.
Table 6 provides the basic details of all the five buildings
considered in this study. Figures 16 and 17 show the plan
and elevation of these buildings.
Block II of the Nilgiri Building was modelled exactly
as it exists, whereas the remaining four buildings conside-
red in this study were assumed to be designed by IS 1893:
2016 seismic code. According to the specified regulation
in the seismic code, Hyderabad is in seismic zone II. The
buildings considered have been designed for importance
factor (I) of 1 and response reduction factor (R) of 3. The
soil profile of Hyderabad is rocky, type-I soil, which was
opted for the design.
All the five buildings were assessed based on site-spe-
cific design spectra generated using the observed local
tremors. Five assessment load cases were considered to
determine the effect of tremors on the buildings. For case
one, the response spectrum analysis was done by amplify-
ing site-specific design spectra with an actual observed
highest PGA of 4.97 cm/sec2. The remaining four cases
of response spectrum analysis were considered by ampli-
fying the site-specific design spectra for PGA values of
seismic zone II–V as specified in IS 1893:2016, i.e. 0.1,
0.16, 0.24 and 0.36 g respectively. For the above five
cases, lateral load was applied to the structure, and linear
inter-storey drift was checked against the limiting value
specified according to IS 1893:2016.

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Figure 16. Elevation and plan of analytical model of Block II, Nilgiri Building, IIIT-Hyderabad.
Figure 17. Plan and elevation of buildings under consideration: (a) G + 1; (b) G + 3, (c) G + 16, (d) B + G + 40 (G, ground; B, basement).
Observations and discussion
As specified above, response spectrum analysis based on
site-specific design spectra was carried out for all the five
buildings. The percentage of inter-storey drift values was
consolidated for each building for all site-specific spectra
analyses (Tables 7 and 8). The observed maximum PGA
of recorded tremors was 4.97 cm/sec2, which is about
0.005 g. When the site-specific design spectrum was am-
plified with this value, the inter-storey drift was found to
be much less and within the code-specified inter-storey
drift limit. This is true since the applied force is much
less than the equivalent force for zone II for which the
buildings were designed. However, as an assessment was
carried out with the respective PGA values of zones II–V,
the inter-storey drift values were found to increase for
linear analysis.
While observing the inter-storey drift values of Niligiri
Building, the drift along the shorter (X) side of the build-
ing was more compared to that on the longer side (Y) for
all five cases. Further, inter-storey drift values were higher
than the remaining four buildings, since the Niligiri
Building is the oldest among all and is designed based on
IS 1893:1984. However, it is interesting to note that the
inter-storey drift limit did not cross the code-specified
limiting value for all five cases. Assessment showed that

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1183
Table 7. Analytical study results of Block II, Nilgiri Building, IIIT-H
Inter storey drift (%)
Analysis of Block II, Nilgiri Building, IIIT-H
Along shorter direction
Along longer direction
Code-specified limiting value
Inter-storey drift limit (IS 1893 (Part-1): 2016)
0.4000
0.4000
Site-specific design spectra
Maximum PGA of the tremor is 0.005 g (4.97 cm/sec2)
0.0086
0.0080
Zone II: 0.10 g
0.0849
0.0787
Zone III: 0.16 g
0.1358
0.1259
Zone IV: 0.24 g
0.2038
0.1889
Zone V: 0.36 g
0.3056
0.2834
Table 8. Inter-storey drift values (%) based on site-specific design spectra assessment
G + 1
G + 3
G + 16
B1 + G + 40
Analysis
Inter-storey drift (%)
Code-specified limiting value
Inter-storey drift limit (IS 1893 (Part-1):2016)
0.4000
0.4000
0.4000
0.4000
Along the X direction
Site-specific design spectra
Maximum PGA of the tremor is ~0.005 g
(4.97 cm/sec
2
)
0.0024
0.0044
0.0019
0.0022
Zone II: 0.10 g
0.0236
0.0436
0.0189
0.0221
Zone III: 0.16 g
0.0377
0.0697
0.0302
0.0354
Zone IV: 0.24 g
0.0565
0.1045
0.0453
0.0531
Zone V: 0.36 g
0.0848
0.1568
0.0680
0.0797
Along the Y direction
Site-specific design spectra
Maximum PGA of the tremor is ~0.005 g
(4.97 cm/sec
2
)
0.0032
0.0044
0.0023
0.0020
Zone II: 0.10 g
0.0315
0.0436
0.0223
0.0202
Zone III: 0.16 g
0.0504
0.0697
0.0357
0.0323
Zone IV: 0.24 g
0.0756
0.1045
0.0535
0.0485
Zone V: 0.36 g
0.1340
0.1568
0.0802
0.0727
the current tremors were insignificant and did not cause
any damage to the buildings designed according to IS 1893
of the current or previous version. However, higher-mag-
nitude earthquakes might damage non-engineered build-
ings. Among the four representative sample buildings
considered in the present study, the mid-rise building of
G + 3 was found to have maximum inter-storey drift
compared to the other three buildings. The linear study on
limited buildings in the present case shows that high-rise
buildings are relatively safe against such local seismic ac-
tivity. Considering the importance and occupancy rate in
such buildings, much care is taken while designing and
executing them. However, it must be ensured that such
buildings do not come up on a lake-filled area or on soft
soil. Soil investigation is a must for such sites to study
amplification of seismic waves due to soil properties. On
the other hand, many a times low- to mid-rise buildings
are non-engineered in nature and are of higher stiffness.
Such buildings are greatly affected by local seismic activity
since they attract higher force due to inherent relative
higher stiffness. Vulnerable features such as large over-
hangs and soft storeys should be avoided in such build-
ings. In future, it is suggested that all such buildings must
be designed and executed by competent engineers. For
the existing building stock in Hyderabad city, rapid visual
screenings (RVS) should be taken up to identify the
common seismic vulnerable features and the ward having
a maximum number of such building stock. Findings
from RVS will help the municipal administration to plan
mitigation efforts and revise the city building bylaws to
design better buildings.
Conclusion
A study was conducted on the ground motion and build-
ing response recorded at IIIT, Hyderabad, 2.3 km from
the epicentre. Initially, the ground motion recordings
were studied in detail and later, a site-specific design
spectrum was developed. From the experimental study of
the instrumented building at IIIT, Hyderabad, it was
found that the existing tremor did not cause any damage
to the building. However, amplification of acceleration
and displacement in the second storey will be in the range
1.2–2.3 times the shaking at the base level for all such fu-
ture micro-tremors originating from the study area. Fur-
ther, four representative buildings were considered in the
analytical study, viz. G + 1, G + 3, G + 16 and B +

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1184
G + 40 stories. The inter-storey drift values for all five
buildings were found to be within the code-specified limi-
ting value when checked using response spectra analysis
with site-specific spectra, amplified to the highest observed
PGA of 4.97 cm/sec2 (approximately 0.005 g) and various
seismic zone PGA values (0.10–0.36 g). It can be con-
cluded that if the tremors are amplified, there is a high
chance of risk/threat to low-rise buildings, mid-rise build-
ings and non-structural elements in high-rise buildings.
To precisely understand the vulnerability of the existing
building stock in Hyderabad city, RVS followed by a de-
tailed assessment has to be carried out.
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Received 29 January 2021; re-revised accepted 11 February 2022
doi: 10.18520/cs/v122/i10/1174-1184