Category Archives: Disaster Risk Reduction

Quote: Marcia McNutt

“A natural hazard need not become a human disaster if society learns and applies lessons in preparation and resilience.”

Marcia McNutt, National Academy of Science, Engineering and Medicine.

Massive earthquake threat lurking beneath Bangladesh

A megathrust fault could be lurking underneath Bangladesh, India and Myanmar, exposing one of the most densely populated regions in the world to the risk of a large earthquake, according to new research published in Nature Geoscience.

A new GPS study measuring tiny ground movements since 2003 in the south Asia region has found strong evidence suggesting that a large tectonic fault beneath Bangladesh and east India is seismically active.

Steckler_el2016
The new active fault beneath Bangladesh. Image from original paper, Steckler et al. 2016

The team, consisting of scientists from the USA, Singapore and Bangladesh, calculate that the megathrust fault could be accumulating strain energy at rates of about 15 mm per year.

Importantly, the researchers believe that the fault is “stuck” and has been storing energy for more than 400 years without a major earthquake; since the Mughal conquest of Bengal and the establishment of Dhaka as the Bangladeshi capital in the 1600s.

An earthquake occurs when the stresses become large enough that it causes the fault to break and releases all the stored energy. The 400 years of energy accumulation at 15 mm per year could result in a devastating magnitude 9 earthquake, similar in size to the Japanese quake that destroyed huge sections of the country’s northeastern coast in 2011.  Such an event would have enormous consequences for more than 140 million people living within 100km of the megathrust in Bangladesh and India.

Steckler_el2016_2
Earthquake hazard and vulnerable populations in Bangladesh and India. Source: Steckler et al. 2016

The tectonic activity of south Asia is a consequence of the collision of the Indian subcontinent with Asia, a process that began nearly 50 million years ago and is still occurring today. This monumental collision resulted in the uplifting of Tibet and the formation of the Himalayan mountain range. Over millions of years these mountains have been slowly eroded and deposited their rich soils onto the Bangladeshi plains by a network of giant rivers. The thick sediments have made the Bangladeshi plains some of the most agriculturally productive in the world.

While the sediments can take up some of the energy along the newly proposed fault, they’re not especially stable, particularly around the rapidly developed eastern outskirts of Dhaka. If a major earthquake strikes, the sediments could even amplify the seismic waves, causing further destruction.

“Dhaka’s basically like building a city on a bowl of Jell-O [jelly],” says Steckler, lead author of the new study, implying that even small earthquake shaking could be amplified by the sediments.

The Savar building collapse in 2013, which resulted in over 1100 deaths, showed the world that building codes in Bangladesh are not strictly enforced. If buildings are collapsing on their own, it is a terrifying prospect to consider what would happen during an earthquake. The lack of preparedness is clear and it is essential for the Bangladeshi government to make long-term changes to promote greater seismic awareness and stricter enforcement of building codes.

More information:
[1] The original paper: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2760.html

Quote: Marc Forni

“Disaster risk is a function of the hazard, the exposure and the vulnerability.”

Marc Forni, The World Bank

Istanbul: On the brink of an earthquake disaster

Istanbul is an ancient and beautiful city with a long history at the centre of major empires including the Roman, Byzantine, Latin and Ottoman. It is a city inundated with rich culture and history. In 2010 it was named a European Capital of Culture, which helped make it the world’s tenth most popular tourist destination. Home to over 11 million people, it is also one of the most populated cities in the world.

But this thriving and seemingly indestructible metropolis sits on a loaded spring: The North Anatolian Fault. The most active and earthquake prone fault system in Turkey, and the source of the 1999 magnitude 7.4 earthquake that killed nearly 18,00 people in the city of Izmit.

izmit
A building destroyed in the 199 Izmit earthquake. Wikimedia Commons

The North Anatolian Fault is about 1300km long running along the entire length of northern Turkey, from the Aegean Sea in the west to Lake Van in eastern Turkey.

Curiously, large earthquakes on the fault have tended to follow a successive sequence, i.e. an earthquake will often occur on the section of the fault adjacent to the last rupture. The current sequence started in 1939 with the magnitude 7.9 Erzincan earthquake, which killed over 30,000 people, and has been progressing to the west in a series of 8 large events.

Researchers in 1997 used this observation to successfully predict the location of the 1999 Izmit earthquake (if not the exact time). Worryingly the Izmit earthquake ruptured less than 100km to the east of Istanbul. Further work has led other researchers to predict a major earthquake, possibly another large magnitude 7.4, in the Istanbul region within the next 20 years!

Current westward progression of earthquakes along the North Anatolian Fault.

So what can we do? Firstly, we need to better understand the science behind the cause of earthquakes in this region. The FaultLab project based at the University of Leeds involves research on the the ground movements around the North Anatolian Fault during various stages of the earthquake cycle. A greater understanding of the fault system can be used in forecasting models to give a better idea of the seismic risk.

Secondly, more engineering work needs to be done to reinforce vulnerable buildings that would collapse in the event of ground shaking. In May 2012 the Turkish government passed a new Urban Transformation Law requiring all buildings that do not conform to current earthquake hazard and risk criteria to be demolished.

BamEq
Is it too late?

This effectively means nearly 6 million buildings throughout Turkey will be demolished over the next two decades! This massive project is expected to generate over USD 500 billion worth of construction industry over the next decade.

A new rail line that runs beneath the Bosphorus Straits and links the east and western parts of the city will be able to withstand shaking from a magnitude 9 earthquake.

The new airport terminal for the Sabiha Gokcen international airport that serves the city of Istanbul has also been built to withstand shaking from a magnitude 8 earthquake and importantly, remain operational afterwards. This is critical, as when a disaster does strike the airport will be one of the main entry points for international relief and aid.

But the key question is: will Turkey and Istanbul in particular be able to finish all its ambitious redevelopment plans before the next major earthquake?

I certainly hope so!

Ekbal

More information:
[1] Progressive failure on the North Anatolian fault since 1939 by earthquake stress triggering, 1997, Geophysical Journal International, v 128, pp 594-604
[2] Parsons, T., Shinji, T., Stein, R. S., Barka, A. A., Dietrich, J. H.; Heightened Odds of Large Earthquakes Near Istanbul: An Interaction-Based Probability Calculation, 2000, Science, v 288, pp 661-665
[3] http://www.invest.gov.tr/en-US/infocenter/news/Pages/220213-turkey-urban-transformation-project-foreign-investors.aspx

Plight of the Bangladeshi

Lying on the floodplains of the mighty Ganges, Brahmaputra and Meghna rivers Bangladesh is a rich, fertile land. These giant river systems meet in the centre of the country and flow together into the Bay of Bengal which, at over 1600km wide, is the largest delta in the world.

Rising Sea Level

Bangladesh is often cited as one of the countries that will be most negatively affected by rising sea levels from human induced climate change. Two thirds of the country lies less than 5m above of sea level. With vast regions to the south much less than a 1m above sea level. The Intergovernmental Panel on Climate Change (IPCC) claims that just 1m rise in sea level could directly expose nearly 14 million people and result in potentially 17% land loss in southern Bangladesh.

Floods

Most of the country receives on average more than 2.5m of rainfall a year, 80% of which falls in about 4 months during the peak monsoon season, resulting in large annual floods. The flood waters bring nutrient rich clays and silts from the high Himalayas and deposit them on the river floodplains. These rich soils produce bountiful harvests of rice and other crops. Unsurprisingly, farming is the most common profession.

bangladesh_flood_NASA
A flooded street. Source: NASA

However floods, once welcomed by farmers and their families are now harbingers of disaster. Human induced climate change has resulted in more erratic monsoon weather patterns with often larger than normal volumes of water being delivered in shorter time intervals. The resulting floods have had devastating effects on the Bangladeshi people. In 2012 three large floods hit the country in swift succession between the months of July and September directly affecting more than 5 million people. These are now a common annual occurrence.

Cyclones

Bangladesh is also subject to annual tropical cyclones, storm surges and tornadoes. Some of the worst natural disasters in recorded history were results of cyclonic storms in the Bengal region. Among them, the 1970 Bhola cyclone which claimed over 500,000 lives! Worryingly new research into the impacts of climate change has shown that large cyclonic storms will become a more common occurrence in the years and decades to come.

Earthquakes

The foothills of the great Himalayan mountain belt has historically been the location of many large earthquakes. Earthquakes in the continent tend to be more infrequent compared to regions such as Japan and California. However this makes them more unpredictable and often unexpected. But when one does occur it can result in significant ground shaking. The 1897 magnitude 8.1 and 1950 magnitude 8.7 Assam earthquakes were two of the biggest to hit the region in recent times. The current building stock in Bangladesh is poorly built and most are not built to withstand ground shaking in an earthquake. The collapse of poorly built buildings is the greatest hazard during an earthquake.

Dhaka_Savar_Building_Collapse_W.Commons-rijans_edited
The Savar building collapse near Dhaka Bangladesh, which killed 1129 garment factory workers. Source: Wikimedia Commons

So what can we as earth scientists do?

Bangladesh has a population of over 160 million and among the highest population density of any country in the world. With the majority of the country built on river floodplains combined with widespread corruption and ignorance a large earthquake could quite possibly result in the greatest natural calamity to have ever hit the country!

Bangladesh needs to increase its resilience if its people are to survive the multitude of natural hazards they face. Earth scientists are well placed to understand the risks involved from these hazards and can play a key role in all aspects of building a resilient infrastructure.

Climate science research is ongoing and needs to continue to better understand the affect human induced climate is having and will have on the annual monsoon. This knowledge needs to be translated into rainfall variation and flooding potentials and communicated with the people who need this information. The socio-economic issues of a rising sea level needs to be addressed and plans put in place to allow big cities to efficiently absorb and cater for migrants moving away from hazard prone coastal regions. Hydro-geologists and geochemists are helping to find sustainable clean, arsenic free water sources for drinking and farming. Seismologists and earthquake scientists are working to better understand the seismic risk in the Himalayan foothills; produce more accurate hazard maps and importantly identify the active faults within the region.

These are to name but a few of the ways earth scientists can get involved. I believe it is our moral duty to translate the practical aspects of our science into real benefits for people.

Ekbal

More information:
[1] http://www.ipcc.ch/ipccreports/tar/wg2/index.phpidp=446
[2] http://www.guardian.co.uk/global-development/2013/jan/23/bangladesh-floods-harbingers-disaster
[3] http://reliefweb.int/disaster/fl-2012-000106bgd
[4] http://en.wikipedia.org/wiki/List_of_Bangladesh_tropical_cyclones
[5] http://en.banglapedia.org/index.php?title=Main_Page

Mangrove forests protect against tsunamis

The tsunami in 2004 demonstrated that land protected by mangrove forests suffered far less damage than areas felled for resorts and farming.Mangrove_Peyri_Herrera_Flickr2

Sustainable development using earthquake resistant bamboo houses

By Dalmeet Singh Chawla

Governments should pay more attention to the role that bamboo and rattan can play in building more sustainable and greener economies, a pressure group has told a UN meeting.

“Bamboo and rattan are not always seen as tools to deliver on the Sustainable Development Goals. We believe they bring major opportunities,” the International Network for Bamboo and Rattan (INBAR), an intergovernmental group based in Beijing, China, told the UN Forum on Forests in New York, United States earlier this month.

“Modern bamboo houses are more flexible in an earthquake, as they flex and absorb some of the energy.”
Hans Friederich, International Network for Bamboo and Rattan

For example, bamboo can reduce soil erosion and restore degraded lands, and ultimately help protect the livelihoods of people who depend on forest ecosystems. Products derived from the two plants could also bring income to millions of people in developing countries, the group says.

INBAR, which has 40 member states, called on policymakers to include bamboo and rattan in their action plans for forest development.

Construction of a 100% bamboo house in Martinique, certified earthquake and cyclone resistant. Credit: J'ai pris cette photo
Construction of a 100% bamboo house in Martinique, certified earthquake and cyclone resistant.
Credit: J’ai pris cette photo

INBAR also presented the Global Assessment of Bamboo and Rattan, an initiative that aims to exchange knowledge and data about bamboo and rattan. The assessment is expected to be launched at the World Forestry Congress in Durban, South Africa, in September 2015.

Bamboo and rattan grow across much of the developing world, including in many equatorial countries in Asia, Africa, Latin America and the Caribbean. They make good alternatives to wood charcoal and cotton fibres, and bamboo can be burned or used in biogas systems to provide a sustainable source of bio-energy.

Bamboo can grow at a rate of up to one metre per day, and can be harvested for productive use after 3-7 years, compared with 10-15 years for conventional trees. Hence, using bamboo as a replacement for other wood would lead to fewer trees being cut down for processing, INBAR says.

“Because bamboo grows quickly it also absorbs carbon quickly, and is what we call a strategic forest resource in the battle against climate change,” says Hans Friederich, director general of INBAR.

But Ramadhani Achdiawan, a researcher from the Centre for International Forestry Research in Indonesia, underlines the importance of forest planning for the long term if countries want to use bamboo and rattan for economic growth. For instance, Achdiawan says that “rattan needs trees to support its growth, so maintaining big trees in forests is very important”.

In its statement, INBAR also told UN representatives about bamboo and rattan’s potential as construction materials to build strong houses and furniture that will withstand natural disasters.

“The recent terrible earthquake in Nepal has highlighted the need to build better for natural disasters,” Friederich says. “Modern bamboo houses are more flexible in an earthquake, as they flex and absorb some of the energy.”

This article was originally published on SciDev.Net. Read the original article.