Lombok earthquakes: different building designs could lessen future damage



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A 6.9 magnitude earthquake led to the collapse of thousands of houses in the northern parts of the Indonesian island of Lombok.
Adi Weda / AAP, CC BY-SA

Graeme MacRae, Massey University

The series of earthquakes in North Lombok and others further east goes on. But hopefully the worst is over and the intensity will recede from now.

Hundreds of people have been killed and a lot more injured, many of them seriously. Nearly all this human suffering was caused by collapsing buildings. The subsequent homelessness will go on for many months for hundreds of thousands of people.

But a lot of this suffering need not have happened.




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After devastating earthquakes, Indonesia must embrace radical change


Changing building standards

The strongest quake on August 5, 6.9 in magnitude and at a relatively shallow depth, is large by any standard. But, as photos and video footage show, not all buildings collapsed. Among the landscape of devastation are many buildings that appear to have suffered little if any damage.

According to one estimate, 70% of buildings suffered serious damage, which means 30% did not. In many parts of the world, such as Japan, New Zealand and Chile, buildings are designed to withstand earthquakes of this scale and many of them do, repeatedly.




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About 70% of buildings suffered serious damage in the Lombok earthquakes, but some stood up to the shaking.
AAP, CC BY

Traditional buildings in most of Indonesia, including northern Lombok, were built of timber framing with thatched roofs. In an earthquake they flex and sway but rarely collapse. If they do, it is likely to happen slowly and incompletely and any falling roofing is relatively light and soft.

But over recent decades, building materials and methods have changed. Timber and thatch have become scarce and expensive and popular tastes have shifted towards houses that look, at least superficially, like those of the global modern middle class – little villas with plastered walls, glass windows and tiled roofs.

But underneath the (often picturesque) facades, the construction is of brick or concrete blocks, held together only with weak mortar and supported by little or no framing. The better ones may have some concrete framing, but the quality of the concrete is usually poor and the steel reinforcing, especially at joints, is minimal. These facades do not reliably support infill materials and they are heavy when they fall.

Roof tiles are only loosely secured and ceilings below them are too light to catch them. If one had to design a system of construction for easy collapse and maximum injuries, this would be the perfect model.

Learning from past earthquakes

In Yogyakarta, in central Java, in May 2006, at least 150,000 houses of exactly this kind collapsed in less than a minute of shaking caused by a lesser earthquake than the largest in Lombok. Nearly 6,000 people were killed and thousands more injured. Farm animals housed in traditional buildings mostly survived.

A massive international humanitarian aid response and significant government programmes followed and within a year Yogyakarta was largely rebuilt – an astonishing result in the circumstances. Both government and international agencies went to considerable lengths to design safer methods, educate people about them and offer support, materials and incentives to “build back better”.

An expert report ten years later (unfortunately not yet published) concluded that:

The overall poor quality of construction however has almost certainly placed more people at increased risk of larger, heavier building elements collapsing upon them.

Northern Lombok has not had this kind of experience in recent decades and, because it is a relatively poor part of Indonesia, until 20 years ago, many people outside the urban areas lived in traditional houses. However, over recent years, partly as a result of tourism revenues, many houses have been built or extended in the new style and construction.

Here too, construction standards tend to be low, and even lower for poorer households. The video evidence shows exactly the kind of failures as in Yogyakarta 12 years ago, because of exactly the same basic weaknesses of design. The next earthquake, wherever it may be in Indonesia, will almost certainly have the same effects.

Houses in Lombok collapsed because of design failures similar to those in Yogyakarta 12 years ago.
AAP, CC BY

No easy solutions

A recent article makes similar points and blames inadequate enforcement of building codes and lack of government commitment. Unfortunately the reality is not so simple.

The Yogyakarta experience shows that even with a massive campaign by government and international agencies, and with the fear of earthquakes still fresh in people’s minds, the rebuilding was little better than what it replaced. Building codes do exist in Indonesia, but they are rarely followed, easily evaded, and rarely enforced, least of all at the level of owner-built local housing.

Even if there were a serious effort to implement codes, it would be undermined by well-known levels of bureaucratic inefficiency and corruption, as well as public resistance and evasion. It would also have unintended consequences, including making decent housing even less affordable, especially for poorer people.

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The Conversation

There will be no easy solutions, but national education in basic structural design principles, subsidised design, production and distribution of cheap and simple hardware for mitigating the most common failures of design and financial incentives for appropriate construction might be worthwhile places to start.

Graeme MacRae, Senior Lecturer in Social Anthropology, Massey University

This article was originally published on The Conversation. Read the original article.

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After devastating earthquakes, Indonesia must embrace radical change


Jonatan A Lassa, Charles Darwin University

An earthquake on Lombok island in Indonesia has left 98 people dead and 20,000 people homeless, according to the National Disaster Mitigation Agency.

Around 70% of North Lombok’s housing stock has either collapsed or been severely damaged. Just a week earlier, a 6.5-magnitude earthquake hit a nearby region, destroying tens of houses and claiming 10 lives, and injuring more than a dozen people.




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Two types of tectonic plate activity create earthquake and tsunami risk on Lombok


As the area recovers, we need to ask: how can Indonesia address its vulnerability to earthquakes?

We know that Indonesia can improve its response to natural disasters, which has happened with tsunami preparedness. The next challenge is to apply these lessons to seismic activity.

Prepare for tourists

Thousands of tourists were caught in panics after both earthquakes. It’s time for Indonesia’s emergency systems to address the vulnerability of foreign visitors as well as its own citizens.

With tourism on the rise in many earthquake-prone areas, solid preparation measures need to be put in place. Vulnerable hotels and fragile houses can jeopardise tourism’s future.

The past 30 years have been filled with wake-up calls. A 1992 earthquake that struck Flores island caused 15,000 houses to collapse in a single district alone. It took almost 20 years for tourism to recover.

More technology isn’t the answer

It’s often easier to attract international funding to sophisticated new technology for hazard prediction and monitoring – for example, the Australia-funded Inasafe, which has the potential to help government to develop scenarios for better planning, preparedness and response activities, and the US-funded Inaware which is a disaster management tool aimed at improving Indonesia’s risk assessment and early warning systems.

At the same time, it is not clear how these technological advancements will serve to help small hotels or households in earthquake-prone regions. What people really need is need help to build structures in accordance with proper construction codes, so that they don’t become death-traps during an earthquake.

This points to a deeper problem. Such building codes already exist, but local governments are currently showing little desire to comply with national building regulations.

For example, before 2011, less than 12% of local governments adopted and endorsed the Building Law 2002. By 2016 that figure had risen to 60% – an improvement, but still not enough.

In North Lombok, where most houses collapsed in the recent earthquakes, the local government only endorsed national building regulations in 2011. It will take years for the local administrators to actually implement them.

The no-regreat approach

To save lives, we need to move beyond the idea that perfect risk assessment exists.

Seismic mitigation measures need to start immediately, at the local level. Thousands building are built every day and right now, while many are rebuilding after disaster, is the time for local governments to put into practise the codes and standards that exist at a national level.

Local and central governments can embrace innovation. Central government and local governments in Indonesia must focus on transforming the way houses are built, including checking earthquake preparedness when issuing building permits.

Can local government radically audit all vulnerable houses? And can we create a machine of local bureaucrats who can deal with the risk assessment on every single house in earthquake prone regions?

It may seem hard, but good practices are already available. Apart from creating incentives for local engineers, contractors, and building consultants to be mindful of seismic measures, local governments can also gradually audit critical public buildings, which are particularly crucial to disaster to response (and may be especially dangerous if they collapse).

Indonesia could even follow California’s example and publicly shame the owners of buildings that the building code.

A sign from California alerting passers-by to a potentially dangerous building.

It will require radical reform in public administration, including construction at local level. Without this radical change, the status quo will remain and people will continued to be killed by their houses when moderate to big earthquakes hit their area.




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The ConversationThe present approach is failing. Stronger political and administrative commitments are needed at all levels.

Jonatan A Lassa, Senior Lecturer, Humanitarian Emergency and Disaster Management, Charles Darwin University

This article was originally published on The Conversation. Read the original article.

Two types of tectonic plate activity create earthquake and tsunami risk on Lombok


Jane Cunneen, Curtin University and Phil R. Cummins, Australian National University

Several large earthquakes have struck the Indonesian island of Lombok in the past week, with the largest quake killing at least 98 people and injuring hundreds more.

Thousands of buildings are damaged and rescue efforts are being hampered by power outages, a lack of phone reception in some areas and limited evacuation options.

The majority of large earthquakes occur on or near Earth’s tectonic plate boundaries – and these recent examples are no exception. However, there are some unique conditions around Lombok.

The recent earthquakes have occurred along a specific zone where the Australian tectonic plate is starting to move over the Indonesian island plate – and not slide underneath it, as occurs further to the south of Lombok.

This means there is earthquake and tsunami risk not only along the plate boundary south of Lombok and Bali, but also from this zone of thrusting to the north.




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Jammed subduction zone

Tectonic plates are slabs of the Earth’s crust that move very slowly over our planet’s surface. Indonesia sits along the “Pacific Ring of Fire” where several tectonic plates collide and many volcanic eruptions and earthquakes occur.

Some of these earthquakes are very large, such as the magnitude 9.1 quake off the west coast of Sumatra that generated the 2004 Indian Ocean tsunami. This earthquake occurred along the Java-Sumatra subduction zone, where the Australian tectonic plate moves underneath Indonesia’s Sunda plate.

But to the east of Java, the subduction zone has become “jammed” by the Australian continental crust, which is much thicker and more buoyant than the oceanic crust that moves beneath Java and Sumatra.

The Australian continental crust can’t be pushed under the Sunda plate, so instead it’s starting to ride over the top of it. This process is known as back-arc thrusting.

The data from the recent Lombok earthquakes suggest they are associated with this back-arc zone. The zone extends north of islands stretching from eastern Java to the island of Wetar, just north of Timor (as shown in map below).

Earthquake hazards along plate boundaries near Indonesia. The dates in the map show historical earthquakes, and Mw indicates earthquake magnitude.
Edited by P. Cummins from an original by Koulali and co-authors

Historically, large earthquakes have also occurred along this back-arc thrust near Lombok, particularly in the 19th century but also more recently. (Dates and sizes of past earthquakes are shown in the map above).

It is thought that this zone of back-arc thrusting will eventually form a new subduction zone to the north along from eastern Java to the island of Wetar just north of Timor.




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Tsunami risk

Lombok’s recent earthquakes – the August 5 6.9 magnitude quake plus a number of aftershocks, and the 6.4 magnitude earthquake just a week before it – occurred in northern Lombok under land, and were quite shallow.

Recent earthquakes on Lombok were also felt on the neighbouring island of Bali.
US Geological Survey

Earthquakes on land can sometimes cause undersea landslides and generate a tsunami wave. But when shallow earthquakes rupture the sea floor, much larger and more dangerous tsunamis can occur.

Due to the large number of shallow earthquakes along the plate boundaries, Indonesia is particularly vulnerable to tsunamis. The 2004 Indian Ocean tsunami killed more than 165,000 people along the coast of Sumatra, and in 2006 over 600 people were killed by a tsunami impacting the south coast of Java.




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Explainer: after an earthquake, how does a tsunami happen?


The region around Lombok has a history of tsunamis. In 1992 a magnitude 7.9 earthquake occurred just north of the island of Flores and generated a tsunami that swept away coastal villages, killing more than 2,000.

Nineteenth century earthquakes in this region also caused large tsunamis that killed many people.

The areas around Lombok and the islands nearby, including Bali, are at high risk for earthquakes and tsunamis occurring both to the north and the south of the island.

The ConversationUnfortunately, large earthquakes like the ones this week cannot be predicted, so an understanding of the hazards is vital if we are to be prepared for future events.

Jane Cunneen, Research Fellow, Curtin University and Phil R. Cummins, Professor, Australian National University

This article was originally published on The Conversation. Read the original article.