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Submitted to:
Dr. M.K. ShrimaliDr. S.D. BhartiStructure Engineering DepartmentMNIT, Jaipur.
Submitted by:
Anurag SharmaStudentMtech Structural Engineering MNIT, Jaipur.
A SEMINAR REPORT ON
Recent Earthquakes in Indian Subcontinent
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NORTH ANDAMAN (DIGLIPUR) EARTHQUAKE OF 14 SEPTEMBER 2002
SUMATRA EARTHQUAKE AND INDIAN OCEAN TSUNAMI OF DECEMBER 26, 2004
2005 NORTH KASHMIR EARTHQUAKE OF OCTOBER 2005
SIKKIM EARTHQUAKE OF 14 FEBRUARY 2006
2011 SIKKIM EARTHQUAKE
AFTER THE BHUJ EARTHQUAKE
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Earth cooled down
masses became integrated together
heavier ones going towards the center
lighter ones rising up.
EARTH AND ITS INTERIORS
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Distinct layers of masses
Earth primarily consists of four distinct layers
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The inner core
The outer core
The mantle
and the crust
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Cluster of a number of plates of various sizes.
This differential movement of the plates provides the basis of the foundation of the theory of tectonic earthquake.
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Flow of hot mantle upwards to the surface of the earth at the ridges due to convective circulation of the earth’s mantle.
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Major tectonic plates on the earth’s surface (Source: Murty, C.V.R. “IITK-BMPTC Earthquake Tips.”Public domain, National Information Centre of Earthquake Engineering. 2005. http://nicee.org/EQTips.php - accessed April 16, 2009.)
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RADIOACTIVITY INSIDE THE EARTH.
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Types of interplate boundaries (Source: Murty, C.V.R. “IITK-BMPTC Earthquake Tips.” Public domain
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Types of fault (Source: Murty, C.V.R. “IITK-BMPTC Earthquake Tips.” Public domain, National Information
Centre of Earthquake Engineering. 2005. http://nicee.org/EQTips.php - accessed April 16, 2009.)
Click icon to add picture
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The U.S. Geological Survey (USGS) is responsible for providing information about earthquakes to other government agencies and to the public.
SCALES
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The ML scale is often called the “Richter scale” by the press and the public.
The moment magnitude scale (abbreviated as MMS; denoted as MW) is used by seismologists to measure the size of earthquakes in terms of the energy released
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The Medvedev-Sponheuer-Karnik scale, also known as the MSK or MSK-64, is a macro seismic intensity scale used to evaluate the severity of ground shaking on the basis of observed effects in an area of the earthquake occurrence.
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On 14 September 2002, at
03:58:31 AM a
ML 6.0 (IMD) Mw 6.5 (USGS)
earthquake struck the Northern Andaman Island region of the Andaman & Nicobar Islands (Union Territory) of India.
NORTH ANDAMAN (DIGLIPUR) EARTHQUAKE OF 14 SEPTEMBER 2002
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The epicenter 165 km NE from Port Blair, the administrative head quarters of A&N Islands sea about 24 km SE of Diglipur
Lcation of the epicenter is 13.013°N 93.147°E (USGS), and the focal depth is 33 km.
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After shocks, the largest of them being M 5.3 on 14 September at 04:44 hours and
M 5.2 on 15 September at 01:29 hours.
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Most severe seismic zone V of the Indian Seismic Zone map.
Sandwiched between the Indo-Australian plate on the western side and the Eurasian plate in the north and the east.
PAST SEISMICITY
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Region is witnessing a new phase of seismic activity.
Ongoing post-seismic relaxation
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Shibpur, Aerial Bay Jetty and Kerala estimated to be VII on MSK scale.
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Many schools, community and residential buildings in
Nabagram
Kalighat
Ramanagar and
Kishorinagar suffered damage.
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Pounding damage was noted to jetty slabs.
Truss members in the old cargo shed at the jetty and their connections failed.
Mahatma Gandhi Degree College, developed cracks in their seismic deficient masonry and RC buildings.
Traditional timber and bamboo structures were not affected to any noticeable degree on these islands, even in the areas of stronger shaking.
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GEOLOGY AND SOIL CONDITIONS OF THE REGION
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Often these walls are not tied together to create the necessary box-action in masonry construction required for lateral resistance.
No positive connection is provided between the wall and truss members resting on them.
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The Nabagram Panchayat building, suffered extensive damage to its ground floor columns near the side farthest from the stiffer side near the stair case block. Many of the columns were severely cracked and damaged near beam-column joints and at mid heights.
No transverse stirrups (ties) were present over a length greater than 350 mm for the 200 mm wide columns.
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The RC columns were not designed for earthquake forces and required ductility.
Creating the open first storey
And by the lack of transverse stirrups in that storey where shear resistance is most needed.
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Diglipur Harbour (Arial Bay Jetty)
The entire approach and berthing structure consists of
400 mm square reinforced concrete piles connected at the top by a box-type pier cap made of beams, columns, braces and slabs.
HARBOUR STRUCTURES
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Pounding damage was afflicted to the jetty slab across at expansion joints, which was later repaired. Subsequent to the earthquake, vertical cracks were noticed on the piles supporting the jetty;
Mayabunder Harbour
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The flexible airstrip developed on unconsolidated marshy land developed cracks near the centerline. The cracks were filled with Grade 80/100 bitumen.
The terminal building under construction did not experience damage. However, the 1.5 m high boundary wall of the airport premises fell at many places.
AIRPORT
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The Mw 9.0 earthquake of December 26, 2004 struck at 06:28:53 am.
The maximum intensity of shaking (on the MSK scale) was VII; along the mainland Indian coast, it was V.
Sumatra Earthquake and Indian Ocean Tsunami of December 26, 2004
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The Tsunami arrived in the states of Andhra Pradesh and Tamil Nadu along the southeast coast of the Indian mainland shortly after 09:00 a.m.
At least two hours later, it arrived in the state of Kerala along the southwest coast
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The total number of Indian fatalities was 10,805, with over 5,640 persons missing, according to official statistics (www.ndmindia.nic.in 2005). The state of Tamil Nadu had the highest number of fatalities — 8,010 (www.tn.gov.in/tsunami 2005) — with the district of Nagapattinam alone accounting for 6,065.
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The western coast of the Middle Andaman Islands shows emergence of new shallow coral beaches near Flat Island, suggesting an uplift of up to 0.3 m.
A mud volcano in the Middle Andaman became active after the earthquake and gray mud and colorless gases were emitted; this resulted in the formation of a sub circular mound of about 70 m in diameter.
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Many traditional structures are made of wood, and they performed well in the earthquake shaking.
However, a number of new, poorly constructed reinforced concrete (RC) structures suffered severe damage or even collapse due to shaking. The tsunami waves caused severe destruction in the coastal areas of the southern islands.
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Not all buildings are properly designed and built to ensure ductile response.
This building had experienced column damage due to inadequate lateral reinforcing ties in the 2002 Mw 6.5 Diglipur earthquake
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A newly constructed 268 m long RC bridge over the Austen Strait, connecting the North and Middle Andaman Islands on the Andamann Trunk Road, had to be closed to even light vehicles.
Three middle spans of the superstructure were displaced laterally by about 70 cm and vertically by about 22 cm and fell off the bearing.
Damage to Infrastructure
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Jetties at Sagar Dweep and Arial Bay were damaged due to ground shaking,
The 20 MW Suryachakra power plant in the Bamboo Flat area of Port Blair was adversely affected by the tsunami waves, which flooded the entire plant.
.
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Misalignment of turbines caused disruption of electric generation, which was only partly restored after ten days.
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The Mw 7.6 earthquake on October 8, 2005 struck at 8:50:38 AM local time (9:20:38 India Standard Time)
epicenter located at 34.493°N, 73.629°E (USGS), which lies in the Pakistan-occupied territory of Kashmir (POK).
2005 NORTH KASHMIR EARTHQUAKE OF OCTOBER 8, 2005
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The epicenter is located at 19 km northeast from the major neighbouring town of Muzaffarabad, which is 170 km west-northwest of Srinagar.
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The official death toll of 47,700 in Pakistan
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This earthquake at a focal depth of 26 km.
Tectonic plate moving northward at a rate of 40 mm/yr giving rise to Himalayan mountain ranges.
Worst affected major towns on the Indian side of LoC are Tangadhar in Kupwara district and Uri in Baramulla district.
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The maximum of VIII at Uri, VII at Baramulla and Kupwara and V at Srinagar on MSK scale.
Top two high risk seismic zones of IV and V of Indian seismic code IS:1893 with the expected intensity of IX or more in the zone V and intensity of VIII in the zone IV.
GENERAL OBSERVATIONS
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Major civil engineering projects in the area are highways, bridges, small dams and micro hydro-electric projects and a few RC framed buildings.
The housing units are largely low rise brick and stone masonry load bearing types often in association with timber.
The diaphragms varying from pitched flexible roofs to mixed flexible and rigid concrete floors and roofs.
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Primary lateral resistance against the earthquake forces is provided by the membrane action of the diaphragms (floors and roofs) and bearing walls.
In Kashmir traditional timber-brick masonry construction consists of burnt clay bricks filled in a framework of timber to create a patchwork of masonry, which is confined in small panels by the surrounding timber elements.
PERFORMANCE OF STRUCTURES
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No collapse has been observed for such masonry even in the areas of higher shaking.
This timber-lacing of masonry, which is locally
referred as Dhajji-dewari (meaning patch quilt wall) has excellent earthquake-resistant features.
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The army present in the area was the first one to respond for rescue and relief despite being seriously affected by the earthquake.
RESCUE &RELIEF OPERATIONS
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Moderate earthquake (reported as Mw 5.3 by USGS and as ML 5.7 by IMD) occurred in the state of Sikkim (India) on February 14 2006 at 06:25:23 a.m. local time.
At 27.35°N 88.35°E, near Ralang (South Sikkim), with a focal depth of 30 km (www.usgs.gov)
At 27.7°N 88.8°E, near Lachung (North Sikkim), with a focal depth of 33 km.
SIKKIM EARTHQUAKE OF 14 FEBRUARY 2006
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The shaking was also felt in the North-Eastern states of India and in the neighbouring countries.
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Sikkim is located in the seismic zone IV of Indian seismic zoning map with the expected maximum intensity of shaking as VIII on the MSK scale.
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The entire Himalayan belt is one of the most seismically active regions in the world.
In last 110 years, four great earthquakes (magnitude equal to or greater than 8.0) have occurred along this subduction zone causing large scale damage in the surrounding areas (Bilham 2004).
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Common practice in Sikkim to build residential buildings using wood/bamboo.
Until tourism industry got a boost.
Most major old buildings in Sikkim are made of stone masonry with mud mortar.
CONSTRUCTION PRACTICE
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Except for a very few RC buildings involving major projects
Analysis and design are generally not carried out.
the structural drawings are prepared simply based on previous experiences of engineers on the basis of a few thumb-rules
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Roof generally consists of GI sheets supported on wood/bamboo trusses which laterally connect the parallel walls
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Undressed stones used without proper bonding between adjacent courses of masonry, and also at the corners.
The mud mortar used as bonding material in these buildings further aggravates their lateral strength capacity.
Masonry Constructions
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These buildings were only “repaired” and not adequate retrofitted against future events.
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Floating columns in upper storeys.
Intermediate soft storey in multistoried buildings.
Poor reinforcement detailing.
Reinforced Concrete Constructions
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Tashiling Secretariat, State Legislators’ Hostel, Geological Survey of India (GSI) building at Deorali, suffered varying degree of damages
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The nine-storey masonry infill RC frame hostel building at
Sikkim Manipal Institute of Medical Sciences (SMIMS)
Tadong, Gangtok suffered damages in walls and columns.
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Poor material quality,
Poor connection between perpendicular masonry walls
Resulted in out-of-plane failure of one infill wall, and severe damages to other infill walls in the building.
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On National Highway 31A, which connects Sikkim to the rest of country. In the Tarkhola Bridge between Melli and Rangpo, spalling of concrete was observed at the top of central pier near bearings.
LIFELINE STRUCTURES
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An RC pedestrian foot bridge constructed in 1989 near STNM Hospital at Gangtok sustained minor damage in the form of spalling of cover concrete in one RC beam
corrosion of reinforcement bars.
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The 2011 Sikkim also known as the 2011 Himalayan earthquake, was a magnitude 6.9 (Mw)
Kanchenjunga Conservation Area, near the border of Nepal and the Indian state of Sikkim
At 18:10 IST (12:40 UTC) on Sunday, 18 September
2011 SIKKIM EARTHQUAKE
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The quake came just a few days after an earthquake of 4.2 magnitude hit Haryana's Sonipat district, sending tremors in New Delhi.
“Continental Indian and Eurasian Plates” Converge with one another
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STRIKE-SLIP FAULTING
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Three aftershocks since the earthquake,
occurring at magnitudes of 5.7, 5.1, and 4.6 (Mw) within 30 minutes of
the initial earthquake.
Kathmandu experienced two aftershocks that both had a magnitude of 4.8 Mw.
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Strengthening of existing buildings.
Increasing the lateral strength in one or both directions, by reinforcement or by increasing wall areas or the number of walls and columns.
Giving unity to the structure
REPAIR, RESTORATION ANDSTRENGTHENING OF BUILDINGS
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Avoiding the possibility of brittle modes of failure by proper reinforcement and connection of resisting members.
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The main purpose of repairs is to bring back the architectural shape of the building so that all services start working and the functioning of building is resumed quickly.
Repair does not pretend to improve the structural strength of the building and can be very deceptive for meeting the strength requirements of the next earthquake.
Repairs
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Shotcrete
Epoxy resins
Epoxy mortar
Gypsum cement mortar
Quick-setting cement mortar
REPAIR MATERIALS
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Strengthening existing walls
External binding
Strengthening RC members
Strengthening of foundations
TECHNIQUES TO RESTORE ORIGINAL STRENGTH
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National information centre for earthquake engineering.
Wikipedia.
http://web.archive.org/web/20061009053106/http://www.asianews.it/view.php?l=en&art
REFERENCES
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http://news.ifeng.com/mainland/detail_2011_09/19/9294991_0.shtml.
Sikkim quake: ITBP buildings collapse, Pegong area badly hit, The Economic Times, 18 September 2011
"The Times of India.Sp.m.timesofindia.com. http://sp.m.timesofindia.com/PDATOI/articleshow/10071212.cms. Retrieved 22 September 201
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◦ Nalbant, S., Steacy, S., Sieh, K., Natawidjaja, D., and McCloskey, J. "Seismology: Earthquake risk on the Sunda trench." Nature. Vol. 435, No. 7043, 756–757. June 9, 2005. Accessed 2009-05-16. Archived 2011-11-18.
◦ Jayasuriya, Sisira and Peter McCawley, "The Asian Tsunami: Aid and Reconstruction after a Disaster". Cheltenham UK and
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THANKS A LOT
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