STH stormwatch : Cyclone Thane, first cyclone (and last) cyclone of the year in the Bay of Bengal

 

Incredibly, as the year draws to an end, the first and most certainly the last cyclone to form in the Bay of Bengal in 2011 has made landfall on the shores of Tamil Nadu.
It is just this sort of weather phenomenon that STH along with IMD (Sikkim) has established an SMS based early warning system which worked well in 2011 and which we hope to expand in 2012

At the year end , a sombre warning and a typical reaction - denial and disbelief

News report on the American Geophysical Union (AGU), Fall Meeting 2011, San Francisco, 05-09Dec2011

 US SEISMOLOGIST WARNS OF DEADLY KASHMIR QUAKE

Experts Call For Valley’s Micro-Seismic Zoning

Srinagar, Dec 9: A study by a prominent US based seismologist has warned that Kashmir Valley is likely to be hit by an earthquake of largest ever magnitude. But the study does not specify any particular time-frame.

However, the Kashmir based experts recommend the state government to undertake micro-seismic zoning in the Valley to minimize loss of human lives in case of any such eventuality.
The study conducted by Roger Bilham, a seismologist and professor of Geology at the University of Colorado at Boulder US, states that the major quake with magnitude 9 is likely to trigger landslides that would dam the Jhelum river, which drains from the Kashmir Valley into Pakistan.
“That could put the Kashmir Valley under water within three months - and would also threaten disastrous flooding in Pakistan if the waters were released too quickly. The two nations should develop a cooperative plan to deal with the aftermath of a Kashmir mega-quake,” Prof Bilham states in the study.
Prof Bilham states that his new Global Positioning System (GPS) data readings revealing the gradual movement of rocks in the Zanskar Mountains north of the Kashmir Valley show that earlier estimates of the maximum possible quake in the region were too low.
“In this region, the Indian plate is slowly burrowing under the Tibetan plateau. Studies on where the relative movement of the Tibetan plateau was slowest, indicates where compression is building up, and a rupture is eventually likely to occur. I expected this to be in the Pir Panchal range, to the south of the Kashmir Valley, but instead it was in the Zanskar range to the north.”
“This means that the zone likely to rupture when a quake eventually happens could be 200 kilometres wide, rather than about 80 kilometres, as was previously thought. The zone would encompass the Kashmir Valley - including the city of Srinagar, home to some 1.5 million people. If slippage occurs over a length of 300 kilometres, as is possible, a mega-quake of magnitude 9 is the likely result. Given building codes and population in the region, that could mean a death toll of 300,000 people,” the study states.
Pertinently the 9-magnitude earthquake which hit Japan on May 11 this year devastated the country.
Bilham points out in the study that seismologists have been caught out by recent mega-quakes, including the 9-magnitude Tohoku quake that hit Japan in March, by basing their estimates on historical patterns, rather than physical measurements. “I think you have to plan for the worst case,” he says.
Bilham revealed his findings at the American Geophysical Union meeting in San Francisco this week.
Prof Muhammad Ismail Bhat, former Head Department of Geology & Geophysics at the University of Kashmir said the earthquake of 9 magnitude can be catastrophic for the Valley.
“We have seen the impact of 7.6 magnitude earthquake in 2005. According to the study, a new fault has been identified in Simthan and Shopian side. It is an active fault. The problem is that we don’t have the relevant data to identify the earthquake vulnerable zones. It is high time for undertaking micro- seismic zoning across the Valley to identity the places which are vulnerable to earthquakes,” Prof Bhat said.
Prof Shakeel Romshoo, Associate Professor, Department of Geology and Geophysics however, said there is no mechanism to predict earthquakes. “But it is a known fact that Himalayas in Kashmir are tectonically active and highly vulnerable to earthquakes,” he opines.
Kashmir is placed in seismic zone five, making it highly vulnerable to earthquakes. Incidentally, the Valley was hit by a 7.6 magnitude earthquake with its epicenter in Muzaffarabad in Pakistan-administered-Kashmir causing massive destruction of life and property in the affected areas.
In August this year, five tremors of moderate intensity were recorded in the Valley with one of them having its epicentre in Jammu and Kashmir. The earthquakes occurred from August 19 to 23 with magnitude ranging between 4.8 to 5.1.
Prof Bilham who has been studying the earthquakes in Himalayan region for past 20 years, had visited Kashmir in 2007 alongwith Dr Susan Hough of US Geological Survey, Pasadena California.
They had interacted with experts here and recommend many measures including identifying locations of future earthquakes, research effects of historical earthquakes, determine their recurrence intervals and educate common masses and people associated with construction about measures to limit losses and save lives.
However, most of the recommendations are yet to be implemented. “We don’t have funds to implement the recommendations or undertake more research on earthquakes in Kashmir. The Government only act when a disaster strikes. Till then it is in a slumber putting the lives and property of people at risk,” said a senior seismic expert of the Valley wishing anonymity.
“The State Government is not prepared to deal with any eventuality arising out the earthquakes. It is high time for the concerned authorities to take the study seriously and gear up to meet any eventuality,” he said.
When contacted officials associated with Disaster Management Cell of Kashmir refused to comment on the issue.
________________________________________________

A typical reaction to the above warning is the one given by Pakistan Meteorological Department, Director General below :-

“Talking to this scribe PMD Director General Arif Mehmood played down the findings about any major earthquake in the Kashmir region and said the recent earthquake in Haiti is a grim and embarrassing reminder that seismologists cannot predict earthquakes.
He said if anyone predicts major earthquake anywhere in the world it means he tries to over-simplify a much complicated issue because there is no evidence in the recorded history that anyone was able to rightly predict any earthquake before its occurrence. “The researchers have been doing hectic work and may be sometime in future we are able to rightly predict earthquakes but at the moment I am not ready to believe any such prediction because no science or methodology is yet available to do so,” he said.”

Comment by Praful Rao
Having just gone thru 6.9R earthquake recently and with predictions that we may expect another big one in this region , I find the above reaction of the DG, Pakistan Met Department a typical one, which I am sure we in India share whole-heartedly.
And so rather than work  urgently and proactively towards disaster preparedness.we prefer to live in a world of denial and disbelief.

You may read a more about the AGU meet in San Francisco (USA) here

Earthquake activity in Darjeeling-Sikkim Himalaya - Dec2011

As per IMD there were no earthquakes in the region in Nov2011.


Source of above report is here

Praful Rao

Something of interest : Prof Jack D Ives at ICIMOD (Mar2010)

Excerpt from Sikkim NOW! (27Nov2011)

Stability drastically degraded, future threats present major challenges
SIKKIM MINES & GEOLOGY DEPT SUBMITS REPORT ON IMPACT OF EARTHQUAKE ON SIKKIM’S LAND AND ROCK MASS


Study of 150 earthquake-induced slides flags 12 for urgent attention and recommends longterm measures for another 32. Disaster preparedness plans should seek out local inputs

GANGTOK, 27 Nov: With more than 150 landslides triggered off all over the State by the 18 September Earthquake, there is now genuine concern over the stability of the soil and rock formations and whether they will be able to withstand the next monsoon. Concern over the safety and security of life and property in the coming seasons has become a top priority with the State government now with the Mines & Geology Department reporting that there are likely to be numerous slides next monsoon as the slopes and hill sides have been destabilized and considerably weakened by the impact of the earthquake. Not just landslides, there is also a threat of glacial lake outbursts in North Sikkim.

According to the report, “The overall stability of land and rock mass has undergone drastic degradation. Keeping in view the changed scenario, the safety of life and properties is of great concern in years to come. The challenging task is to unravel the threat that is likely to be encountered in future.”

The report, which was recently submitted to the government, informs that numerous cracks have developed on the slopes throughout the State; with Sikkim being a terrain where landslide and slope modification process are still active, the risk and probability of earthquake induced landslides are very high.

Not just landslides, there is also the danger of mass mobilization. As the report states: “Due to the impact of recent earthquake, the risk of landslide and mass mobilization has risen to alarming stage and disaster mitigation task will be a challenging task for the future before the onset of next monsoon”.

The preliminary investigation, on which this report is based, identified more than 150 earthquake induced landslides out of which 12 landslides are reported to need urgent attention and another 32 slides identified for long term measures. It was observed by the experts during investigations that the impact of the earthquake was more pronounced on crystalline rocks mainly on its quartzites and variants with adverse slopes and on landmasses adjoining steep slopes and water-ways.

Short term measures recommended by the officials include soil compaction on fissures on landmass to minimize seepage and use of local technologies to retain unstable boulders. Apart from recommending identification of risk areas, it is also proposed that a disaster mitigation cum preparedness plan be put in place.

Importantly, it is also underlined that the involvement of local authorities and public will be vital in minimizing further threats and in coming up with local solutions. Also recommended is the creation of watch-posts or police posts at suitable places for timely rescue in road sections falling in high risk zones.

As part of long term measures, a detailed investigation of high risk zones is proposed with vulnerability of inaccessible areas to be accessed by remote sensing and high resolution aerial photographs. The investigation of these areas should be completed in advance to facilitate preparation of disaster mitigation plans ahead of the ensuing monsoon.


THE REPORT’S APPRAISAL OF NORTH SIKKIM
The Mines and Geology department has just concluded its preliminary assessment of the earthquake affected areas in the state and submitted its report to the government. A copy of the report has been accessed by NOW! The report, though preliminary and involving only accessible areas, consists of an area wise assessment of locations in the State which were affected by the earthquake of 18 September. Accordingly, some of the affected areas and slopes examined and which have been found to be posing a threat have been highlighted as areas needing urgent attention.
NORTH SIKKIM
The areas falling between Chungthang and Lachung have been found to be among the worst affected, especially the river bank slopes; besides the landmass has also been found to have developed cracks and fissures here. The area between Lema and Lempokhari experienced the worst situation and a large chunk of landmass was washed away by a flash flood which was found to be even greater than the impact caused due to glacial lake out-bursts flood of the previous century. What is of particular concern, as per the report, is the formation of near vertical slope all along the river bank and formation of cracks on the landmass. In this context the report highlights Lema, Lephkha & Bop areas as needing urgent attention.
It was also studied that the rocks here are brittle and susceptible to weathering and jointly forming geologically vulnerable zones with the recent earthquake having led to further aggravating the degradation. The report further states that “…the area being under frost and thaw environment, the chances of rock bursts at higher elevation is high”. This area needs to be further examined in detail.
The major damages at Lachung area were found to have caused due to earthquake induced flash flood with obstruction of streams by the debris from hill slope resulting in landslide in the area. “There is also apprehension of the threat of glacial lake outbursts. The glacial lakes need to be monitored on regular basis to assess the threat,” states the report.
Lachen was found to have remained comparatively safe except for the development of minor cracks on buildings; besides the Chungthang-Lachen section was also found to be subjected to development of instable zones threatening vehicular movement.
There was also a massive landslide between Lachen and Zemu; however the report states that the exact position of future threat is not known at present and that the area needs to be investigated to assess the future threat. The same goes for areas beyond Zema which also reported severe damages.
Upper Dzongu area was among the worst affected by the earthquake with villages there having taken substantial damage and many killed. Here, the report states that the rocks being brittle in nature and there is apprehension that the vulnerable zones have developed which pose threat to life and property of local people in future. However as far as slides are concerned, as most slides were found to have occurred in inhabitable areas any instability due to degradation should not have future impact on life and property, the report states.
For Lower Lingza too, it is reported that landslide and slope failure have not been noticed within the visible zones the formation of unstable landmass and rocks cannot be ruled out and the area needed further investigation.

Comment by Praful Rao
It is coincidental that this statement by Dept of Mines, Govt of Sikkim comes just days after our Workshop on "Hazards and Critical Environmental Issues of Darjeeling-Sikkim Himalaya" on 23Nov2011, where my talk on "5 Months to go for the next monsoons" emphasized on the very same points made above.

Emerging issues from the workshop on "Hazards and Critical Environmental issues", 23Nov2011 at Kalimpong

The workshop went of very well with Shri LN Sherpa (WBCS), Sub Divisional Officer (SDO), Kalimpong as the Chief Guest, Shri Shailesh Anand (IFS), Div. Forest Officer as the Special Guest and Shri PR Pradhan, distinguished educationist of this area as the Presiding Officer. Approximately 500 people attended the workshop in the Town Hall and the workshop was widely covered in several regional dailies of the region as well as by local TV channels.
The salient issues which emerged and recommendations are placed below :-

1.      Speaker : Wg Cdr Praful Rao (President , SaveTheHills) 
Topic: “5 months to go for the monsoons”
Gist of talk :- Disaster Management still mired in relief-centric mode.
It was brought out by Wg Cdr Praful Rao (retd) of SaveTheHills in his presentation “5 months to go for the monsoons” that despite the Disaster Management Act 2005 and the purported  “paradigm shift” in disaster management towards prevention/preparedness and mitigation, nothing has changed at the grass roots level and that management of disasters in this part of the country was still totally relief centric .
Thus, with barely 5 months left for the next monsoons in May2012 and with many areas and structures weakened by the 6.9R earthquake of 18Sep2011, virtually nothing has been initiated towards:-
a) Identifying areas which require urgent attention.
b) Prioritizing & commencing preventive work in vulnerable areas.
c) Setting up an early warning system to alert communities in this region.
d) Building capacities of vulnerable communities.
e) Improving the drainage in landslide prone urban areas and rural hamlets such as Algarah (Kalimpong subdivision) -since all the deaths caused by landslides in Darjeeling & Sikkim in 2011 took place in built-up areas and were related to drainage problems.

As such, instead of commencing landslide preventive and disaster preparedness works on a war footing to shore up our defenses before May2012 ( ie monsoon commencement), we seem to be frozen in a stupor and it is certain that we will walk into the monsoons of 2012 having wasted valuable time and in a very vulnerable state.
Recommendation : Landslide and disaster prevention/ preparedness/ mitigation works may be initiated without further delay.

2.      Speaker : Wg Cdr Praful Rao (President , SaveTheHills) 
Topic: “5 months to go for the monsoons”
Gist of talk : Sharing of data from non- IMetD instruments for monitoring meteorological  elements (rainfall, pressure, humidity, wind etc).
While responding to a question, Wg Cdr Praful Rao brought out the fact that even though the number of  automatic weather stations (AWS) and automatic rainfall gauges (ARGs) installed by the I Met D needed to be increased for better monitoring of rainfall data etc, there were already some  digital monitoring instrument s installed by the following departments in the district :-
a) Sericulture dept.
b) Agriculture dept.
c) Forest dept.
d) NHPC
Recommendation : Meteorological data/information from instruments maintained by the above departments maybe shared with IMetD in order to improve the accuracy of forecasting. This information may also be uploaded onto their  websites on a daily basis so that they maybe available organizations such as SaveTheHills , research scholars and institutions.

3.      Speaker :  Dr Malay Mukul (Dept of Earth Sciences, IIT Mumbai)
Topic : “Seismicity of the Darjeeling – Sikkim Himalaya”
Gist of talk : A Great Earthquake in the Darjeeling-Sikkim Himalaya  still possible.
Dr Malay Mukul of IIT Mumbai stated the recent 6.9R earthquake in this region should not lull people to thinking another big earthquake was not expected. He said that based on GPS readings, a great earthquake measuring 7R and above was still possible and that the 18Sep2011 earthquake was just a wake up call.
In this regard, Dr Mukul cautioned people to pay due regard to building codes and standards so that it would make living safer in the mountains.
Answering a question, Dr Mukul said that urban settlements in the foothills eg Siliguri would be equally if not more susceptible to damage in the event of a great earthquake in this region due to liquefaction of the alluvial soil in the area.
Recommendation : An intense and sustained awareness campaign must be undertaken to enlighten the public regarding Dr Mukul’s observation and building codes.
Mock drills/ landslide studies maybe introduced in educational institutions.
Also, since this area is prone to earthquakes, the density of GPS stations in this area maybe increased to understand the movements of the earth and faults lines more accurately.

4.      Speaker :  Ms Gayatri Kharel (Structural Engineer, SHED)
Topic : “Earthquake resistant and non-engineered structures”
Gist of talk : People urged to construct earthquake resistant buildings in Darjeeling- Sikkim Himalaya.
Ms Gayatri  Kharel, structural engineer, during her discourse urged people to go in for earthquake resistant structures in this region (quake proof buildings though technically possible would be exorbitantly costly).
She said there was an urgent need to make people aware about quake resistant buildings and also the fact traditional stone and masonry structures which had sustained large scale damage during the quake of Sep2011 could also be made earthquake resistant.
She also spoke about the need to retrofit existing lifeline buildings in order to make them quake resistant and also urged the administration/people to go in for load bearing tests of the soil before embarking on construction of heavy structures in the hills.
Recommendation: An intense and sustained awareness campaign be undertaken to enlighten the public regarding earthquake resistant structures.
Retrofitting of lifeline buildings maybe initiated in order to may them quake resistant.

5.      Speaker :  Ms Priya Shreshta (WWF, Gangtok)
Topic : “Drying springs in the Darjeeling-Sikkim Himalaya and ways to recharge them
Gist of talk : Need for water conservation and Dhara Vikas Project of Sikkim
Ms Priya Shrestha of WWF, Gangtok spoke of drying natural springs (dharas) all along the Himalayas  which would result in severe water crisis in the Himalayas even as demand was skyrocketing due to burgeoning population and tourism. She said this was caused by increased runoff of rainwater due to increased urbanization and deforestation.
She described in detail the Dhara Vikas Program in Sikkim which had shown promising results in recharging underground aquifers and had increased the water outputs from springs which were drying up.
Recommendation: Natural springs are the lifeline of mountain communities and even though ambitious water supply projects (such as pumping water from Balasun river to Darjeeling and from Teesta river to Kalimpong) may solve water problems of towns, springs will continue to be the main source of water supply to the rural areas and farming communities. As such a detailed mapping of these are required with a view to determine
a) Those springs which are perennial.
b) Those which are seasonal (ie rain-fed) and dry up during the non-monsoon season.
c) Springs which have dried up due to landslides, deforestation and other human activities.
d)  Studies need to be undertaken to find long term solutions to drying springs and their impact on agriculture as well as a source of potable water especially in rural areas.

6.      Speaker : Mr Roshan Rai,( DLR Prerna, Darjeeling)
Topic : “Solid waste management in the Darjeeling- Sikkim Himalaya”
Gist of talk : Community awareness and responsibility as regards solid waste disposal in the hills.
Mr Roshan Rai (of DLR Prerna) urged mountain communities to be more aware about the fragile mountain environment and shoulder their share of responsibility as regards solid waste disposal. Mountain communities must learn to segregate and compost their biodegradable solid waste so as to reduce waste generated, he also said that simply throwing garbage into the nearest jhora or stream was not a solution to waste disposal. He suggested numerous ways in which people could produce less waste by making small adjustments in their life style and also urged govt authorities to provide waste treatment plants in the vicinity of large urban settlements and also linkages for recycling of solid waste products (eg there is no way in which people from Kalimpong can send used PET bottles for recycling).
Recommendation : Organizations such as DLR Prerna should be funded and tasked to carry out an intense and sustained awareness program. Solid waste treatment plants should be built in the vicinity of large mountain urban settlements.

7.      Speaker : Mr GN Raha (IMetD, Gangtok)
Topic: : Trends in weather patterns in the Darjeeling-Sikkim Himalayas”
Gist of talk: Unpredictable weather patterns in the mountains would lead to more frequent disasters.
Unsettled and often unpredictable weather trends in the mountains may lead to intense bursts of rainfall which could trigger of landslides as was seen in the recent past. Mr GN Raha of IMetD , Gangtok speaking during the workshop said that there was a need to have a higher density of weather monitoring systems to improve forecasting and to provide early warning to mountain communities so that lives maybe saved.
Recommendation : An SMS based early warning system about onset of adverse weather/heavyrain, such as that which has been established by SaveTheHills in conjunction with I MetD (Gangtok) must be made available to the lay person with the text messages being sent in the local dialect.

Praful Rao

STH activities :18Nov2011

STH has in the past (see 1 and 2) has had the unique privilege of hosting two seminars where Prof Leszek Starkel of Polish Academy of Sciences, Kracow, Poland and a legendary figure amongst geomorphologists, was our main speaker.

Continuing this liaison, we had two young scientists ie Dr Łukasz Wiejaczka (red jacket), hydrologist and geomorphologist and Dominik Płoskonka (extreme left) soil scientist from the same institute with us the whole day on 18Nov2011.

They along with Mr Lakhpa Tamang (PhD student from North Bengal Univ) and Ms Dipmala Gurung (MSW intern from Visva-Bharti, Shantiniketan) toured landslide affected areas on the western face of Kalimpong and also visited earthquake damaged buildings in Kalimpong town.




Praful Rao

Seminar on Disasters and Environmental issues in Kalimpong : 23Nov2011

Praful Rao

GSI report on Sikkim landslides of 18Sep2011

 

You can read the complete report here

Praful Rao

Quake report : 11Nov2011

Date of Occurrence:

11.11.11

Time:

15:27:32 IST

Magnitude:

3.8

Epicentre:

Lat. 26.7°N Long.89.4°E  

Region:

North Bengal (Jalpaiguri, INDIA)

Source :http://earthquakesummary.info/

Praful Rao

STH activities :Workshop at Tindharia (05Nov2011)

STH would like to thank Prof Jeta Santkrityayana, (Dean, Faculty of Arts , Commerce & Law), University of North Bengal, Prof Indira Lepcha (Head of Dept of Geography) University of North Bengal, Dr Kaushik Bandopadhyay, Associate Prof Dept of Construction Engineering, Jadavpur University, for their concern, time and effort - we would also like to thank Methai Dara SHG and particularly Mr Suren Chhetri for all the effort in making the seminar a success.

Praful Rao

Quake report : 29Oct2011

Date of Occurrence:

29/10/2011

Time:

06:13:41.0 HRS(IST)

Intensity:

SLIGHT

Magnitude:

3.5

Epicentre:

Lat. 27.4°N Long. 88.4°E

Region:

SIKKIM, INDIA 

Source :http://www.imd.gov.in/section/seismo/dynamic/PRLMNEW.HTM

No loss of life or damage reported

Praful Rao

Affordable & effective means of erosion control/slope stabilization

Whereas traditional engineering methods (such as gabion retaining walls, river training etc) and new technologies (see here) for landslide mitigation and soil erosion control are effective, most are exorbitantly costly, requiring huge investments.
Placed above are some other methods of slope stabilization which are much more affordable and therefore do-able at the community level and which are also very effective.
For those interested some more literature on use of jute geotextile and bamboo check dams for slope stabilization are here (1 & 2) and most of the 10,000 saplings of vetiver grass that we planted  in the monsoons are doing well. Next year we plan large scale plantation of this grass in this area.

Photo credits : Suren Chhetri (Tindharia) and self

Praful Rao

Picture of the day :20Oct2011 (Water Crisis in Kalimpong)

As the placard carried by the retired policeman suggests the water crisis in Kalimpong is largely due mismanagement, a faulty distribution system and huge amount of leakage which is never rectified - this was further exacerbated, when some pipelines were damaged by landslides in Sep2011.
Availability of potable water is already a huge crisis in many towns all over the Himalayan region as natural springs dry up due to a variety of reasons . As demands increase, due to burgeoning population and tourism, contractors supplying water from dubious & untested sources are thriving whereas little thought is being given to long term solutions to a disaster in the offing.

Praful Rao

STH stormwatch : Trouble brewing in the Bay (18Oct2011)

Excerpt from IMD midday bulletin

The low pressure area over eastcentral Bay of Bengal now lies as a well marked low pressure area over eastcentral and adjoining westcentral & northwest Bay of Bengal with associated upper air cyclonic circulation extending upto midtropospheric levels. The system may concentrate into a depression during next 24 hours.

• Widespread rain/thundershowers would occur over Nagaland Manipur, Mizoram and Tripura.
• Fairly widespread rain/thundershowers would occur over Arunachal Pradesh, Assam & Meghalaya, coastal areas of Gangetic West Bengal & Orissa, Tamil Nadu, Kerala, Lakshadweep and Andaman & Nicobar Islands.
  
  Praful Rao

Quake report : 17Oct2011

Date of Occurrence: 17/10/2011

Time: 18:34:50 HRS(IST)

Intensity: SLIGHT

Magnitude: 3.5

Epicentre: 27.3 N,88.4 E

Region: SIKKIM

Source : http://www.imd.gov.in/section/seismo/dynamic/PRLMNEW.HTM

No loss of life or property reported

National level workshop on "Landslide Hazards" in Hyderabad :15-16Nov2011

For more information/details on the workshop, see here

Praful Rao

All about rainfall

End of the Monsoon report (excerpts from IMD report)

• For the country as a whole, the rainfall for the season (June-September) was 101% of its long period average (LPA).

•  Seasonal rainfall was 107% of its LPA over Northwest India, 110% of its LPA over Central India, 100% of its LPA over south Peninsula and 86% of its LPA over Northeast (NE) India.

• Four depressions formed during 2011 monsoon season as against the normal of 4-6 monsoon depressions per season.
  
  
  The Flood Meteorological Office at Jalpaiguri (W Bengal, India) has signed off its operational watch from 14Oct2011 due to withdrawal of the SW monsoons from the Sikkim & W Bengal region.
  
  Praful Rao

An article from 'The Hindu'

Periphery shaken by Centre's neglect

Recalling the September 18 earthquake, Sikkim University Vice-Chancellor Prof. Mahendra P. Lama says the hill areas lack sensible disaster management.
Interview of  Prof Mahendra P Lama, in The Hindu of today.

What are the lessons learnt from the September 18 earthquake that left a trail of devastation across Sikkim?

There are quite a few lessons we have learnt from this calamity. Firstly, our ability to cope up with natural disasters is still very nascent and limited.

We have not developed any formal institutions in this regard in the real sense of the term. More seriously, we suddenly realised that the robust system of community-based, voluntary management of natural calamities which remained the most pre-dominant phenomenon for centuries together is also fast vanishing. Today the disaster management task has become government centric whereas traditionally it used to be essentially community centric. Many of the States including Sikkim still do not have proper disaster management plans. We, therefore, must rethink our strategy.

Secondly, the communication system and other physical connectivities are also in a state of infancy despite so much of plans and projects.

Thirdly, the entire development dynamics in the mountain areas need to be reconsidered and reoriented in view of the fact that the casualties and destruction could be unprecedented and unmanageable if such calamities recur.

Fourthly, scientific studies and research on issues like seismology, hydrology, geo-morphology and the very nature and dimensions of natural disasters and their impact on the hills and mountain areas need to be strengthened and disseminated to the people at the grass roots. This has to be blended with traditional wisdom and belief about the impending disasters so that the communities are involved in disaster forewarning and management.

And finally, each disaster in the mountain areas is intensely integrated with other national interest issues including national security, physical dislocations and environmental injuries. This is more so as these theatres of disasters are located in the geo-politically sensitive border locations.

How can the challenge of roads blocked by landslips, hampering relief and rescue missions in States like Sikkim, be overcome?

Massive concrete-based development works that go in the mountain areas pose a serious threat to the carrying capacity of these roads. Unless the entire road construction contracting system is reviewed and a five-year guarantee is ensured by these road agencies with strong punitive measures; and techniques like covering toe-cutting edges of the streams and rivers down below is used, the situation is going to be more pathetic and vulnerable. All these are time consuming and demand a lot of engineering wisdom and precision.

Key agencies like the Border Roads Organisation have to rethink both the techniques and technology of road building in the mountain areas. Two very vital traditional wisdoms on road building in the hill and mountain areas have been blatantly ignored. Firstly, the road has to have a drain on the hill slope side so that the water trickling down can be channelled. Secondly, the sinking area requires very careful maintenance and rocks and mud pouring to fill up the sinks must be avoided.

The basics of disasters and their management have to be taught at the village and community levels and also in all the educational institutions.

Universities, with their colleges and other outreach programmes, could in fact be a major bastion for disaster related studies and management.

What role do you envisage for the government, people and private players for effective disaster management?

This disaster has again brought forward the critical issue of connectivity — both physical and virtual — in the Northeast and the mountain areas. This has to be seen in the context of both centre-periphery disconnects and deprivations, say between Delhi and Meghalaya, and also in the larger context of national security needs. This region provides comprehensive security to the nation. However, the blatant lack of political sagacity, absence of bureaucratic resurgence and the feebleness of the civil society to do something substantive and leap-frogging for this region has eaten into the vitals of this so-called Indian periphery.

We are not only ill-prepared but also myopic in our thought process. One accident or a small landslip could dislocate the entire national highway for hours and sometimes days together. Disasters only shake us and do not wake us up.

For us in this region, BSNL is another white elephant. It just does not want to move an inch from its routine activity and tunnel-like thinking. The role of private players in the aftermath of the earthquake needs to be thoroughly inquired. The communications stopped working when you needed it most. We need to really delve into their social responsibilities and make them sensitive and robust to cope with unforeseen calamities.

Popular perception is that the multiple dams on the Teesta have adversely affected the fragile ecology of Sikkim and induced seismicity.

Energy is required for national and local development. For that, a potential renewable source is the unharnessed rivers flowing in the mountain areas. If done properly it can transform the entire development dynamics in the region. Bhutan is a good example.

People are not against the hydel power projects as such. They are against the way these projects are done, the casualness with which the environmental impact assessment is conducted and clearances are given and the way project developers are selected. The location, size and scale of these projects, the knowledge and experience of these project developers, the capability of project regulating agencies and the way projects have been designed and the technology used have been questioned all across the fragile Himalayan ecology. Unfortunately, in many cases these issues come up for public discussion only in the aftermath of disasters.

What are the short-term and long-term impacts of the disaster on Sikkim's economy and growth prospects and what needs to be done now?

The short-term impacts are, of course, the scar on ordinary people's psychology about the fear of recurrence; the time and resources taken to rebuild the devastated areas; disruption in the flows of tourists and other productive activities; and the disengagement of governmental machineries from their regular delivery systems and governance. The long-term impacts are more in the form of formidable challenges in terms of material and service demands on the State and the government; reorienting the development strategies; refurbishing and implementing the building regulations and proper urban planning; checking on the quality of construction works; integrating the system with agencies like BRO and GREF and several other central agencies like the Geological Survey of India.

Praful Rao

Look, Ma! - no Cyclones!

Cyclones, depressions and low pressure areas which form in the Bay of Bengal usually cause periods of intense, heavy downpours which result in landslides in the Darjeeling-Sikkim Himalayas. As such STH has been plotting/tracking these phenomena on the Internet for some time now (see 1, 2, 3, 4 & so on) .

A record of the cyclones which brewed up in the Bay of Bengal in 2010 (with date and surface wind) is placed above and what is absolutely amazing is that in 2011, we have not had a single cyclone forming in the Bay till date and the number of depressions which have formed is also below normal.
All this when the Philippines has been hit by 3 major back-to-back typhoons within the last one week!
But then our cyclone season lasts upto December ....
For those interest please find below the Classification of bad weather phenomenon as per the IMetD :-

Classifications of cyclonic disturbances for the north Indian Ocean region are given below:-

Weather system                               Maximum wind speed

1. Low pressure area…………………..Wind speed less than 17 kt (31 km/h)

2. Depression………………………….. Wind speed between 17 and 27 kt (31 and 51 km/h)

3. Deep Depression…………………….Wind speed between 28 and 33 kt (52 and 61 km/h)

4. Cyclonic storm ……………………….Wind speed between 34 and 47 kt (62 and 88 km/h)

5. Severe cyclonic storm……………… Wind speed between 48 and 63 kt (89 and 118 km/h)

6. Very severe cyclonic storm…………Wind speed between 64 and 119 kt (119 and 221 km/h)

7. Super cyclonic storm ………………..Wind speed 120 kt (222 km/h) and above

Praful Rao

From the Bengal Post - The Earth shook & all hell broke loose

The Sikkim Earthquake is a prelude to bigger disasters. Constructing even concrete houses in the region is fraught with risks.

The Darjeeling-Sikkim Himalaya sits in a seismically high-risk zone. This was a fact that almost everyone in the hills has known fora while. However, there is no record of any great earthquake (less than7.0 Richter scale magnitude) in the history of the Darjeeling-SikkimHimalaya. This led to a sense ofcomplacency in the hills and urbanisation and development mushroomed. The “Ikra” Assam type houses gave way to “plainstype” flat- roofed multi-storeyed concrete houses that were more often than not built by slicing-up hill-slopes like “tosh-roti” (bread) or on precariously balanced stilts on hill slopes. Those who were aware shivered at the very thought of a great earthquake occurring in the Darjeeling-Sikkim Himalaya and collectively yelled from every available roof-top about the earthquake hazard and the associated disaster we were like to face.

Nevertheless, dams are being built on the Teesta, tunnels are being driven deep into the hills of Darjeeling-Sikkim based on the fact that the largest earthquake that the Darjeeling-Sikkim Himalaya recorded before September 18, 2011 was of a magnitude of 6.2 earthquake on November 19, 1980 which did not cause much damage. As Seismic Zonation is done on the basis of the highest magnitude earthquake recorded in a region, the Darjeeling-Sikkim Himalaya was put at IV rather than V.
This made sense till the mid 1990s when Global Positioning System (GPS) came along and changed the whole game. The Global Positioning System allows us to measure positions on the surface of the earth very accurately and also determine how much the point is getting displaced over time. This information gets translated into surface velocities that give us an insight into how the ground is moving even when earthquakes are not being recorded. GPS measurements tell us that India is moving like a car towards Northeast at about 5 cm/year and slamming into a wall-like Tibet in extreme slow-motion along the Himalayan boundary that decelerates it from 5 cm/year at Bangalore to 4.7 cm/year in North Sikkim; the Himalaya is the front end of this colliding and continuously crumpling car. The difference of 0.3 cm of motion is being absorbed into the Darjeeling-Sikkim Himalaya as strain energy every year since millions of years. The accumulated strain keeps getting released as earthquakes when it crosses a particular threshold determined by the strength of the rocks. Given this fact, not experiencing a great earthquake is not good news. It merely points to the fact that the strain that has gone into the Darjeeling-Sikkim Himalaya has not been released in a significant manner.

The front-end of the colliding car has not finished crumpling! Every new crumple results in a major earthquake. This is the backdrop against which the September 18, 2011 earthquake occurred.
The good: There were a number of good things about this earthquake. First, its epicentre was located in the Kanchenjunga Range far away from populated regions and not in Mangan. So, the location of the epicentre was fortuitous. Second, the earthquake was a moderate 6.9. Not quite a great earthquake but, as Bharat Mani Pradhan put it, “Powerful enough to shake us and hopefully stir us into some action”. The third good thing about this earthquake was that it was a strike-slip earthquake which is basically similar to the motion of rubbing your hands when held vertically. In terms of the colliding car, it was not a new crumple developing in its front end but just a big scrape on its side during the process of frontal head-on collision.

Would the scrape on its side slow its forward motion and prevent new crumple zones from developing? That is a question that future GPS measurements will be able to address. For now, we have to view this earthquake as a wake-up call and get our act straight.
The bad: It is obviously the confirmation of our worst fears and the resultant death and destruction that was caused by the earthquake.

Reinforced cement concrete (RCC) buildings are bad in seismically active zones. The risk of having concrete over our head was established beyond doubt for Darjeeling- Sikkim during this earthquake. Earthquakes also trigger landslides and the double whammy of earthquakes and landslides is something we have to be aware of, expect and plan for in Darjeeling-Sikkim. The less we mess around with intact rock in widening roads or tunnelling deep into the mountains, the better. The fact that tunnels collapsed in Chungthang and multiple landslides impeded the ability to transport relief and rescue teams has to be viewed with extreme seriousness. An honest evaluation of the performance of the dams during the earthquake must be carried out to assess how they will behave when earthquakes of higher magnitude strike the Darjeeling-Sikkim hills. Will the dams increase the speed of our colliding car and cause it to crumple sooner? That is again a question that needs to be revisited in the aftermath of September 18, 2011. The earthquake has forced us to address some tough question sooner rather than later.
The ugly!: This has to be the realisation that we are grossly under prepared to tackle a calamity that would descend upon us if a great earthquake with an epicentre in the Teesta Valley would strike us. Also, it confirms what GPS results are telling; the Darjeeling-Sikkim Himalaya is continuously getting strained and it is only a matter of time before we get a great earthquake. The ugly truth of the situation is that we cannot predict earthquakes in human time-scales because the processes in the earth operate in a super-slow mode spread over millions of years. However, science is letting us know that we are overdue for a great earthquake in our space. The other ugly part of the situation is that a vast majority of us have already committed our lifetime’s savings into constructing the spacious and “pucca” RCC dream houses. Can we financially afford to abandon the houses that we have built even after the realisation that we may be living in buildings that may end up being tombs? Like it or not, we have to make very tough personal decisions. We have to decide if we want to risk it all and continue to live in our RCC houses and hope that we can find a “triangular space of life” in our collapsed concrete structures when the big ones strikes. A real “Ram Bharose” or “whatever will be, will be” existence as Wing Commander Prafulla Rao put it. The other choice is to cut our losses and go back to not having concrete over our heads. That is the tough and ugly personal choice each and every one of us will have to make. The least we can do is to not build any new concrete over our heads and keep the earthquake hazard in mind when making decisions on all future developmental activities in the Darjeeling-Sikkim Himalaya. We owe it to each and every person who had to sacrifice their lives on September 18, 2011 to give us this wake-up call and this lesson. This has to be the lasting legacy of this tragic event and the best way to pay our respects to those who were taken away from us on September 18, 2011.

- Published in the Editorial of Bengal Post (04Oct2011)

Dr Malay Mukul is an ex-student of
Dr Graham’s Homes, Kalimpong & is presently
Associate Professor,
Department of Earth Sciences,
IIT (Mumbai)

Praful Rao

To insure or not to insure (your home)

One of the after effects of the 18Sep2011 earthquake in our area will be that the insurance companies will be thronged by people who will want to insure their homes or buildings against earthquakes and maybe landslides. This is a good thing and I strongly advise insurance of homes and assets.
However, a word of caution - insurance companies can be tricky people and not all of us have the time or patience to read the small print in the "terms and conditions", so more often we end up signing on the dotted line and leaving the rest to the insurance agent.
Having had personal experience of this earlier, here are some words of advice :-

• If possible visit the insurance company office, talk with the Branch Manager and ask him to send an agent who is responsible and a good service provider.
• When the agent arrives, confirm that the insurance policy covers landslide and earthquake damage. (A reputed insurance company representative told me last week that they may stop insurance against these hazards in this area since we are in a high risk zone and they would lose large sums of money if they continued the insurance)
• Confirm that the retaining walls of the house/building will also be covered by the insurance.
• Check the depreciation that will be levied on your building/structure and be sure that old buildings will be valued at considerably less than what you might think!
• While filling up the insurance papers, be specific and list each building/structure separately – with dimensions.
• Some companies require details of contents of the building/home to be listed out before insuring –provide this information if necessary.
•        Ask the insurance agent  about the procedure to be followed in case of claim :-

o                   An FIR is to be made at the police station immediately after damage.

o                   Land ownership documents and site plan will be required.

o                   Approved building plan also will be required.

•  When your building is damaged, intimate damage on telephone and writing immediately to the agent and Insurance Company office. DO NOT START REPAIRS.

• Photograph all damages and cracks with a camera which has a date stamp.

• On getting your intimation, the company will send a representative to assess the damage. Discuss the claim procedure with him and commence repairs only after getting his clearance. Go thru the claim form that he hands over to you and clarify any doubts. You will require an engineer to be available to prepare an estimate of the costs.
  
  Comment by Praful Rao
  Would appreciate any comment on the above since financial wizardry is not exactly my forte...
  

Will there be another big earthquake tonight? plus this and that...

• Judging by the periodicity of occurrence of mega-quakes shown above, it is extremely  unlikely that a big quake will occur here in the near future.
  So those who are busy spreading rumors about another big one rattling us tonight, just shut up and let ordinary people get on with their lives and more importantly, let the relief and reconstruction work go thru without people jumping out of their skins at the slightest noise or vibration by a passing vehicle.
• And there is no volcano in north Sikkim (despite the hot springs which exist there) so where is the question of one erupting ?
• What is far more likely to happen is, there will be landslides if it rains the way it did two days ago (yes! the monsoons are still active in this region and the cyclone season in the Bay of Bengal lasts upto Nov - see here). The reason for this is obvious :-
• The soil is absolutely saturated after almost 5 months of rain.
• Many places are cracked and weakened by the recent 6.9 Richter earthquake and   are likely to crumble in intense, heavy downpours.  

• So with all our buildings and homes cracked and damaged, I think we all learnt a lesson and should get our home insured as soon as possible, right?
  Wrong!
  What I was told by an insurance company representative is that most probably insurance companies will stop insurance against earthquakes and maybe landslides too in this region (since it makes poor business sense to insure property in a high risk area).
  So before you dole out the premium to the insurance agent, just turn the page and check the fine print – you might just end up insuring your house against fire and theft only !
  
  Praful Rao

Image of the day (26Sep2011)

48hr rainfall statistics of Darjeeling
26Sep2011 - 44mm
25Sep2011 - 37mm

Impact on Education
Since the landslide makes the school, St Joseph's School, North Point,  virtually unapproachable by taxis and conventional transport, the administration has declared an extended Puja festival vacation from today (26Sep2011) until 17Oct201.
Mt Hermon School, in the same area, is another institution which will decide on whether they should close early.


Praful Rao

Photo credit : Mr Mohan Lama (Darjeeling)

STH storm watch : Bad news - Low pressure west of Darjeeling / Sikkim

I have been tracking this depression/low pressure since 22Sep2011 (see here). After moving  inland on 22Sep, it has somehow swerved towards us and now lies to the west of us (red dot). As per meteorologists the system is likely to move in a northeasterly direction and may come over the Darjeeling-Sikkim Himalaya which has already had heavy and incessant rain for 24hrs. This is certainly bad news for us, who are struggling to cope with the aftermath of the 6.9 Richter EQ of 18Sep2011 and also because the heavy rain is coming down on earth which is thoroughly saturated after 5 months of rain.
I urge all readers of this blog from this region to remain updated about the movement of the system from this page.
Rainfall in Kalimpong for the past two days has been :-

• 26Sep2011 - 28mm till 11.30am
• 25Sep2011 - 52mm
• 24Sep2011 - 31mm
  
  Praful Rao

Images from Kalimpong : 6.9 Richter Earthquake on 18Sep2011

Praful Rao

STH storm watch : Depression in the Bay of Bengal, 22Sep2011

Since most of the landslides in this region are rain-induced, it is our business to keep a close track of developments in Bay of Bengal in order to give early warning of adverse weather.

Placed below is the Infra -Red image of a depression in the Bay along with the IMetD forecast.

“The well marked low (WML)over Nothwest Bay off Orissa-West Bengal coast has further concentrated into a Depression over North Orissa -West Bengal Coast and lay centered this morning at 0830 hrs IST near latitude 21.5 deg North and longitude 87.5 deg East. 50 km SSE off Digha and 50 km ESE off Balasoere. The system likely move West Northwest direction and cross coast between Balasore and Digha by today evening dated 22.09.11.”
- Source http://imd.gov.in

Praful Rao

Detailed report from IMetD on Earthquake (M:6.8),18Sep2011 in Sikkim-Nepal border

An earthquake of magnitude 6.8 occurred on 18th September at 18:11 hrs IST in Sikkim-Nepal Border region. The preliminary hypo-central parameters of this earthquake, as estimated by the Seismic Monitoring Network of India Meteorological Department (IMD) are given below:

Date of occurrence : 18/09/2011

Time : 18:11 hrs (IST)

Magnitude : 6.8

Focal depth : 10 Km

Epicentre

Latitude & Longitude : 27.7o N & 88.2 o E

Region : Sikkim-Nepal Border region.

The event, which comes under the category of “Moderate earthquake”, was also reported widely felt in Sikkim, Assam, Meghalaya, northern parts of West Bengal, Bihar, parts of other eastern and northern regions of India. The epicentre lies in a seismically known and active belt called, Alpide-Himalayan seismic belt. The location of the earthquake is shown on the seismicity map of Sikkim and neighbouring areas given at Annexure-1. The main shock was followed by a few aftershocks. A list of aftershocks of magnitude 3.0 and above recorded till 09.30 hours IST of 19th September, 2011, is given below. It may, however, be mentioned that the magnitude and frequency of aftershocks will reduce with the passage of time.

S.No.	Date	Time of aftershocks Hr:Min (In IST)	Magnitude
1	18.09.2011	18 :42	5.3
2	18.09.2011	19:24	4.6
3	18.09.2011	20:35	3.0
4	19.09.2011	00:57	3.4
5	19.09.2011	03:21	3.8

The earthquake source parameters have been disseminated to all concerned state and central government agencies related with initiating relief and rescue operations in the region. The information is also put on IMD‟s website for public use. The aftershock activity is being continuously monitored and information on significant aftershocks is being transmitted to all the concerned agencies.

The source parameters of the event are estimated using data of a total of 77 seismic stations in India and across the globe spread more or less in all azimuths (Annexure-2). The details of various magnitude estimates are given in Annexure-3. The preliminary faulting mechanism of the subject earthquake, as estimated through Centroid Moment Tensor (CMT) and Moment Tensor (MT) solutions are given in (Annexure- 4 & -5). The faulting mechanism indicates reverse faulting associated with the tectonic processes related to the collision of Indian and Eurasian plates along the major thrusts in the region. The centroid moment depth indicated by the CMT solution (10 km.) for the present event matches well with the hypo-central estimates. The CMT and MT solutions are obtained from waveform modelling making use of Body and Surface waves respectively.The process essentially involves in simulating the synthetic seismograms by assuming a known source, path and instrumental characteristics. These synthetic seismograms are then matched with the observed ones at various stations in an attempt to arrive at the characteristics of the source, which produces the best synthetic seismograms matching with the observed ones.
2. A slight magnitude earthquake (M:3.9) also occurred at 06 hours 22 minutes IST on 19th September, 2011 in the Latur district of Maharashtra. This event is located about 1500 kms away from the epicenter of the earthquake in Sikkim-Nepal border region of 18th September, 2011 and hence felt not directly related to it.
3. Strong Motion Accelerographs (SMAs), meant for recording strong ground vibrations of the kind experienced during the subject event, are deployed by academic institutions, viz., IIT (Roorkee), IIT (Kharagpur), etc. in the Himalayan region including northeast India through sponsored projects supported by MoES. These data sets would provide valuable information for designing earthquake resistant structures in the region in future.
4. Past seismicity of the region
Historical and instrumentally recorded data on earthquakes show that the Sikkim and adjoining area lies in a region prone to be affected by moderate to great earthquakes in the past. Some noteworthy earthquakes that have affected the region are:
(i) Cachar earthquake of 10.01.1869 (M: 7.5),
(ii) Shillong plateau earthquake of 12.06.1897 (M: 8.7),
(iii) Dhubri earthquake of 02.07.1930 (M: 7.1),
(iv) Bihar-Nepal Border earthquake of 15.01.1934 (M: 8.3),
(v) Arunachal Pradesh – China Border earthquake of 15.08.1950 (M: 8.5),
(vi) Nepal-India Border earthquake of 21.08.1988 (M: 6.4)
(vii) Sikkim earthquake of 14.02.2006 (M: 5.7)
(viii) Bhutan earthquake of 21.09.2009 (M:6.2)
The Sikkim and adjoining region is known to be part of the seismically active region of the "Alpide-Himalayan global seismic belt", with four great earthquakes of the world of magnitude 8.0 and above occurring in this region. The occurrence of earthquakes in the region is broadly associated with the tectonic activity along well known faults in the Himalayas, namely, Main Boundary Thrust (MBT), Main Central Thrust (MCT). Other prominent geological / tectonic features in and around Sikkim include: Tista lineament, Kunchenjunga lineament, Purnea-Everest lineament, Arun lineament and Dhubri fault in the southeast.
In the seismic zoning map of India prepared under the auspices of Bureau of Indian Standards (BIS code IS: 1893: Part I 2002), by a committee of experts representing various scientific institutions including India Meteorological Department (IMD), the entire area of Sikkim lies in Zone IV. The seismic Zone IV is broadly associated with seismic intensity VIII on the Modified Mercalli Intensity (MMI) scale. It may be mentioned that the seismic intensity VIII on MMI scale corresponds to a horizontal ground acceleration range of 51-350 cm / sec2 or an average acceleration of 172 cm / sec2 in any direction. The ground acceleration and hence the intensity of an earthquake at a place depends on magnitude of earthquake, distance from the focus, duration of earthquake, type of underlying soil and its damping characteristics and liquefaction potential. The damage to the buildings founded on soft soil or filled up earth is higher than that in the similar type of buildings having their foundation on hard bedrock. Also, the damage will be higher for higher magnitude and long duration earthquakes, less epicentral distance soft soil conditions and areas with high liquefaction potential.
Presently, there is no scientific technique available anywhere in the world to predict occurrence of earthquakes with reasonable degree of accuracy with regard to space, time and magnitude. It is, therefore suggested that appropriate steps may be taken to ensure that the dwellings and other structures in the region are designed and constructed as per guidelines laid down by Bureau of Indian Standards (BIS) to minimize the losses caused by earthquakes. The choice of seismic factor to be adopted for designing and engineering the structures depends on horizontal ground acceleration and various other factors including type of structures, the ground conditions and also importance of structures. For important and critical structures, site specific spectral studies have to be carried out before assessing the seismic design parameters. Suitable seismic design parameters may be adopted as per recommendations of National Committee on Seismic Design Parameters (NCSDP) for designing and engineering Hydroelectric Projects.
5. Causes of earthquakes
Earthquakes are the result of a process, wherein the underground rocks suddenly break, along a plane of weakness called „fault’, when the prevalent stresses exceed the elastic strength of the rock. The buildup of stresses and subsequent release of the strain energy in the form of earthquakes is a continuous process, which keeps repeating in geological time scale. A number of theoretical assumptions that explain the forces, which cause accumulation of stresses inside the earth include: drifting of continents and mountain building process, shortening of Earth‟s Crust due to cooling and contraction, disturbance of mass distribution on the Earth‟s surface as a result of erosion of high lands and deposition of sediments in the sea and generation of heat by radioactive material inside the Earth‟s Crust.
6. Classification of earthquakes
Based on magnitude (M), earthquakes may be classified as Micro- (M<3.0), Slight- (M:3.0 -4.9), Moderate- (M:5.0-6.9), Great- (M:7.0-8.0) and Very great- (M>8.0). Earthquakes may also be classified as shallow-focus, intermediate-focus and deep-focus depending upon their focal depths. Shallow-focus earthquakes, which constitute about 80% of total energy release on the globe, have their foci at a depth between 0 and 70 km. and occur along collision and subduction zones, oceanic ridges and transform faults. Intermediate-focus earthquakes (focal depth between 71 and 300 km.) and deep-focus earthquakes (focal depth greater than 300 km.) occur in subduction zones, such as Andaman-Nicobar island region and northeast India. Most earthquakes originate within the crust and beneath the Moho, the number falls abruptly and dies down to zero at a depth of about 700 km. On an average, it is expected that about two earthquakes of M~8.0, ~20 earthquakes of M~7.0, ~100 earthquakes of M~6.0 and ~3000 earthquakes of M~5.0 are likely to occur every year over the globe. A list of significant earthquakes in the recent past in and around India is given below:

•  Uttarkashi earthquake of October 20, 1991 (M: 6.6).

•  Latur earthquake of September 30, 1993 (M: 6.3).

•  Jabalpur earthquake of May 22, 1997 (M: 6.0).

•  Chamoli earthquake of March 29, 1999 (M: 6.8).

•  Bhuj earthquake of January 26, 2001 (M: 7.7).

• Sumatra earthquake of December 26, 2004 (Mw:9.3)

•  Muzaffarabad earthquake of October 8, 2005 (Ms:7.6)

7. Seismic Zoning of India
Bureau of Indian Standards [IS-1893 (Part-1): 2002], based on various scientific inputs collected from a number of agencies, has grouped the country into four seismic zones, viz. Zone-II, -III, -IV and –V. Of these, Zone V is seismically the most prone region, while zone II is the least. The Modified Mercalli (MM) intensity, which measures the impact of the earthquakes on the surface of the earth, broadly associated with various zones is as follows:
               Seismic Zone MM Intensity
              II (Low intensity zone) VI (or less)
              III (Moderate intensity zone) VII
              IV (Severe intensity zone) VIII
              V (Very severe intensity zone) IX (and above)
Broadly, Zone-V (12% of land) comprises of entire northeastern India, parts of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Rann of Kutch in Gujarat, parts of North Bihar and Andaman & Nicobar islands. Zone-IV (18%) covers remaining parts of Jammu & Kashmir and Himachal Pradesh, Union Territory of Delhi, Sikkim, northern parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat and some portion of Maharashtra near the west coast and Rajasthan. Zone-III (27%) comprises of Kerala, Goa, Lakshadweep islands, remaining parts of Uttar Pradesh, Gujarat and West Bengal, parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhatisgarh, Maharashtra, Orissa, Andhra Pradesh, Tamilnadu and Karnataka. Zone-II (43%) covers remaining parts of the country.
8. Seismic Hazard and Risk Microzonation
Microzonation is the process of dividing a geographic domain into small units of likely uniform hazard level and nature. This classification is done based on Geoscientific, Geotechnical, Seismological and Engineering seismological parameters. The Hazard micro zone map is transformed into seismic risk microzonation map with inputs on Vulnerability of Built environment and Anthropological / Sociological inputs. As earthquake prediction is not possible precisely in time and space, seismic Hazard microzonation provides an important tool for generating parameters for site specific structural designing, land use planning and disaster mitigation. Seismic microzonation studies have been completed for Delhi (1:50,000 scale), Guwahati (1:25,000 scale), Sikkim (1:25,000 scale) and Bangalore city (1:25,000 scale). Microzonation map for NCT of Delhi is further being refined at 1:10,000 scale. It is planned to take up microzonation studies for all State Capitals and cities with a population density of half a million lying in Zones III, IV and V. The work will be taken up in phased manner and 30 cities have been indentified to start with. In this connection, detailed guidelines have been prepared for standardization of procedures / methods for adoption taking up these studies.
9. Disaster mitigation
Loss of lives during an earthquake is mostly due to damage or collapse of houses/ structures. However, any structure can bear the vibration from an earthquake if it has enough strength and sturdiness. Bureau of Indian Standards (BIS) has published criterion for construction of
earthquake resistant structures. The design of structure should be such that the whole structure behaves as one unit at the time of vibration rather than assemblage of parts. Important structures like hospitals, fire stations etc. should be made earthquake resistant. However, it is not economical to demolish and reconstruct most of the poorly built structures; for such poorly built structures BIS has prepared guidelines for their retrofitting. In addition to this, HUDCO & BMTPC have also published guidelines and brochures for construction and retrofitting of buildings. Further, losses due to earthquakes can be considerably reduced through proper planning and implementation of pre- and post-disaster preparedness and management strategies by respective state government agencies by working out the possible earthquake effects for various seismic zones.
10. National Program on Earthquake Precursors (NPEP)
It is now recognized that earthquake generation processes are so complex and site specific that often, no two different tectonic environments behave in similar manner in terms of providing clues about the ongoing physical processes in the earthquake source region. It is, thus, necessary to adopt an integrated approach of generation, assimilation and analyses of a variety of earthquake precursory phenomena in critical seismotectonic environments in the country in a comprehensive manner. Towards meeting this objective, a National Program on Earthquake Precursors (NPEP) has been initiated recently by MoES through a multi-institutional and multi-disciplinary mechanism. As part of this, a suite of Multi-Parametric Geophysical Observatories (MPGOs) have been set up at Ghuttu, Shillong and Koyna to monitor various earthquake precursory phenomenon such as, seismicity patterns, crustal deformations, gravity anomalies, electrical resistivity changes, electromagnetic perturbations, water level changes, geo-hydrochemical changes, Radon and Helium anomalies and thermal anomalies, etc. Preliminary analyses of these data sets have provided useful leads on the ongoing tectonic processes in the Koyna-Warna region. It is proposed to intensity these investigations during the XII FYP.
11. Deep drilling program in Koyna region
The Koyna Dam located in Maharashtra, western India is the most outstanding example of Reservoir Triggered Seismicity (RTS), where triggered earthquakes have been occurring in a restricted area of 20x30 sq km since the impoundment of Shivajisagar Lake in 1962. These include the largest triggered earthquake of M~6.3 on Dec 10 1967, 22 earthquakes of M>5, about 200 earthquakes of M~4, and several thousand smaller earthquakes since 1962. Considering the importance of deep borehole investigations, it is proposed to undertake a suite of observations in deep borehole(s) in the Koyna area. The work will be carried out in collaboration with ICDP and the observations will include stress regime, pore fluid pressure and its variations, heat flow and its variation, orientation of faults, study of chemical properties of fluids, before, during and after earthquake. The proposed investigations through the borehole will facilitate i) observation and analysis of data, generated through the operation of borehole for 4-5 year of time, when it is anticipated that a few earthquakes of magnitude ~3 would occur in the immediate vicinity of borehole, ii) continuous observation to study the data in the far and near field of the earthquake and temporal variation w.r.t. occurrence of earthquake and iii) development of a model of RTS mechanism.
12. The critical structures viz., nuclear power plants and dams in the country are designed taking into consideration the past seismicity and the expected ground motions in the region, estimated through a detailed site specific analysis using probabilistic and deterministic approaches carried out by earthquake engineering community.
13. Efforts are being made to improve the understanding of earthquake processes and their impacts towards better management and mitigation of the effects of earthquakes in future. A document detailing the proposals planned to be taken up during the XII FYP is attached for kind information.

My thanks to Mr GN Raha of IMetD (Gangtok) for this report, the pdf version is here


Praful Rao