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Why Indonesia’s tsunamis are so deadly



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MAST IRHAM/EPA

Anja Scheffers, Southern Cross University

The magnitude 7.5 earthquake, and subsequent tsunami, that struck Indonesia days ago has resulted in at least 1,200 deaths.

Authorities are still gauging the extent of the damage, but it’s clear the earthquake and tsunami had a devastating effect on the Sulawesi region, particularly the city of Palu.

It’s not the first time earthquakes have caused mass destruction and death in Indonesia. The tsunamis that follow are particularly damaging. But why?

A combination of plate tectonic in the region, the shape of the coastline, vulnerable communities and a less-than-robust early warning system all combine to make Indonesian tsunamis especially dangerous.




Read more:
Would a better tsunami warning system have saved lives in Sulawesi?


Tectonic plates

Indonesia covers many complex tectonic environments. Many details of these are still poorly understood, which hampers our ability to predict earthquake and tsunami risks.

The biggest earthquakes on Earth are “subduction zone” earthquakes, which occur where two tectonic plates meet.

In December 2004 and March 2005, there were a pair of subduction zone earthquakes along the Sunda Trench offshore of the west coast of Sumatra. In particular, the magnitude-9.1 quake in December 2004 generated a devastating tsunami that killed almost a quarter of a million people in countries and islands surrounding the Indian Ocean.

But only looking out for these kinds of earthquakes can blind us to other dangers. Eastern Indonesia has many small microplates, which are jostled around by the motion of the large Australia, Sunda, Pacific and Philippine Sea plates.

The September quake was caused by what’s called a “strike-slip” fault in the interior of one of these small plates. It is rare – although not unknown – for these kinds of quakes to create tsunamis.

The fault systems are rather large, and through erosion processes have created broad river valleys and estuaries. The valley of the Palu river, and its estuary in which the regional capital Palu is located, have been formed by this complex fault system. Studies of prehistoric earthquakes along this fault system suggests this fault produces magnitude 7-8 earthquakes roughly every 700 years.

The sea floor shapes the wave

Another important factor for tsunamis is the depth and shape of the sea floor. This determines the speed of the initial waves. Strong subduction zone earthquakes on the ocean floor can cause the entire ocean water column to lift, then plunge back down. As the water has momentum, it may fall below sea level and create strong oscillations.

The bulge of water moving outward from the centre of a earthquake maybe of limited height (rarely much more than a metre), but the mass of water is extremely large (depending on the surface area moved by the earthquake).

Tsunami waves can travel very fast, reaching the speed of a jet. In water 2km deep they can travel at 700km per hour, and over very deep ocean can hit 1,000km per hour.

When the wave approaches the shallower coast, its speed decreases and the height increases. A tsunami may be 1m high in the open ocean, but rise to 5-10m at the coast. If the approach to the shoreline is steep, this effect is exaggerated and can create waves tens of metres high.

Despite the fact that the waves slow down near the coast, their immense starting speeds mean flat areas can be inundated for kilometres inland. The ocean floor topography affects the speed of tsunami waves, meaning they move faster over deep areas and slow down over submarine banks. Very steep land, above or below water, can even bend and reflect waves.

The coastlines of the Indonesian archipelago are accentuated, in particular in the eastern part and especially at Sulawesi. Palu has a narrow, deep and long bay: perfectly designed to make tsunamis more intense, and more deadly.

This complex configuration also makes it very difficult to model potential tsunamis, so it’s hard to issue timely and accurate warnings to people who may be affected.




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


Get to high ground

The safest and simplest advice for people in coastal areas that have been affected by an earthquake is to get to higher ground immediately, and stay there for a couple of hours. In reality, this is a rather complex problem.

Hawaii and Japan have sophisticated and efficient early warning systems. Replicating these in Indonesia is challenging, given the lack of communications infrastructure and the wide variety of languages spoken throughout the vast island archipelago.

After the 2004 Indian Ocean disaster, international efforts were made to improve tsunami warning networks in the region. Today, Indonesia’s tsunami warning system operates a network of 134 tidal gauge stations, 22 buoys connected to seafloor sensors to transmit advance warnings, land-based seismographs, sirens in about 55 locations, and a system to disseminate warnings by text message.

However, financing and supporting the early warning system in the long term is a considerable problem. The buoys alone cost around US$250,000 each to install and US$50,000 annually for maintenance.

The three major Indonesian agencies for responsible for earthquake and tsunami disaster mitigation have suffered from budget cuts and internal struggles to define roles and responsibilities.

Lastly, the Palu tsunami event has highlighted that our current tsunami models are insufficient. They do not properly consider multiple earthquake events, or the underwater landslides potentially caused by such quakes.

No early warning system can prevent strong earthquakes. Tsunamis, and the resulting infrastructure damage and fatalities, will most certainly occur in the future. But with a well-developed and reliable early warning system, and better communication and public awareness, we can minimise the tragic consequences.

With earthquakes that occur very close to the beach – often the case in Indonesia – even an ideal system could not disseminate the necessary information quickly enough. Indonesia’s geography and vulnerable coastal settlements makes tsunamis more dangerous, so we need more and concerted efforts to create earthquake and tsunami resilient communities.The Conversation

Anja Scheffers, Professor, Southern Cross University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Would a better tsunami warning system have saved lives in Sulawesi?


Jane Cunneen, Curtin University

The death toll from the magnitude 7.5 earthquake and resulting tsunami that struck near Palu, Indonesia, on Friday evening continues to rise, with several regions yet to be reached by rescue teams.

But the size and location of the earthquake should not have come as a surprise. Palu is situated at the end of a long, narrow bay which is the surface expression of a very active fault, the Palu-Koro fault.

The area is at high risk of tsunami, with several large earthquakes and tsunamis occurring along the fault within the past 100 years.




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


Details of Friday’s incident are limited, but already there are questions being asked about the effectiveness of Indonesia’s tsunami warning system.

It was developed after the devastating 2004 Boxing Day tsunami that occurred after an earthquake near Sumatra, but in this recent event the warning did not reach many of the people who were affected.

The tsunami occurred in an area where there are no tide gauges that could give information about the height of the wave. There are reports that a more high-tech system could have saved lives if it had been fully implemented.

Most of Indonesia’s deep ocean tsunameter buoys, specially designed to detect tsunamis in the open ocean, have not been working since 2012.

The Indonesian Tsunami Warning System issued a warning only minutes after the earthquake, but officials were unable to contact officers in the Palu area. The warning was cancelled 34 minutes later, just after the third tsunami wave hit Palu.

Tsunami history of Palu

Large earthquakes are not uncommon in Palu, with 15 events over magnitude 6.5 occurring in the past 100 years. The largest was a magnitude-7.9 event in January 1996, about 100km north of Friday’s earthquake.

Several these large earthquakes have also generated tsunamis. In 1927, an earthquake and tsunami caused about 50 deaths and damaged buildings in Palu. In 1968 an earthquake with magnitude 7.8 near Donggala generated a tsunami wave that killed more than 200 people.

Despite this history, many people in Palu were not aware of the risk of a tsunami following the earthquake. Ten years on from the 2004 Boxing Day tragedy that killed at least 226,000 people, there were concerns about tsunami warning systems across the region.

An advanced warning system currently only in the prototype stage may not have helped the people of Palu, as the tsunami struck the shore within 20 minutes of the earthquake.

Such early warning systems are most useful for areas several hundred kilometres from the tsunami source. In regions like Palu where the earthquake and tsunami source are very close, education is the most effective warning system.

It is not yet clear whether Friday’s tsunami was caused by movement on the fault rupture from the earthquake, or from submarine landslides within Palu bay caused by the shaking from the earthquake.

The sides of the bay are steep and unstable, and maps of the sea floor suggest that submarine landslides have occurred there in the past.

If the tsunami was generated by a submarine landslide within the bay, tsunami sensors or tide gauges at the mouth of the bay would not have sensed the tsunami wave before it struck the shore in Palu.

Communication networks

High tech tsunami warning systems are able to send out warnings through phone networks and other communications channels, and reach the community through text messages and tsunami sirens on the beaches.

But in areas where a devastating earthquake has occurred, this infrastructure is often too damaged to operate and the warning messages simply can’t get through. In Palu, the earthquake destroyed the local mobile phone network and no information was able to get in or out of the area.

Timing is also crucial. Official tsunami warnings require analysis of data and take time – even if it is only minutes – to prepare and disseminate.

This time is crucial for people near the earthquake epicentre, where the tsunami may strike within minutes of the earthquake. Those living in such areas need to be aware of the need to evacuate without waiting for official warnings, relying on the earthquake itself as a natural warning of a potential tsunami.




Read more:
Be prepared, always: the tsunami message from New Zealand’s latest earthquake


The need to raise awareness of the risk becomes even more challenging when large tsunamis occur infrequently, as in Palu. Many residents would not have been born when the last tsunami impacted the town in 1968.

So high tech warning systems may not be effective in areas close to the earthquake epicentre. Ongoing awareness and education programmes are the most important part of a tsunami warning system in coastal areas at risk of tsunami, no matter how infrequently they occur.The Conversation

Jane Cunneen, Research Fellow, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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.




Read more:
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.




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


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.

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.




Read more:
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.




Read more:
How earthquake safety measures could have saved thousands of lives in Nepal


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.




Read more:
Bali’s Agung – using ‘volcano forensics’ to map the past, and predict the future


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.




Read more:
I’ve always wondered: do nuclear tests affect tectonic plates and cause earthquakes or volcanic eruptions?


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.




Read more:
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.

Aftershocks hit Papua New Guinea as it recovers from a remote major earthquake


Sabin Zahirovic, University of Sydney; Gilles Brocard, University of Sydney; John Connell, University of Sydney, and Romain Beucher, University of Melbourne

Another powerful aftershock hit Papua New Guinea this weekend as the recovery effort continues following February’s deadly magnitude 7.5 earthquake, with many thousands of people dependent on humanitarian aid.

Aid organisations such as CARE Australia and UNICEF are still seeking donations. The Australian government has sent medical staff and other support to help.

Some have criticised the PNG government’s efforts as “too slow”.




Read more:
The science of landslides, and why they’re so devastating in PNG


But the earthquake highlights the challenge for emerging economies like PNG in deploying relief efforts into remote areas to deal with natural disasters.

And the same geological features that make PNG a rich source of mineral deposits are also part of its earthquake problem.

The earthquake hits

The February earthquake struck the western Highlands provinces of the Pacific island nation, and a series of aftershocks, including several of magnitude 6 or more, continued to shake the region during the following weeks.

Although parts of PNG are particularly earthquake-prone (especially in the north and the islands, along the plate boundary), February’s earthquake was quite exceptional.

It occurred in a usually less active part of the plate boundary and was remarkably powerful when compared with the short (modern) instrumental earthquake record. The strength and frequency of the aftershocks has posed an additional threat to local populations and key economic infrastructure.

On average 10-20 major earthquakes (magnitudes 7 and greater) occur on Earth every year. Most of them occur far from densely populated regions, such that only a few draw media attention.

The mountainous regions of New Guinea, known as the fold and thrust belt, have been geologically active for millions of years. But the long recurrence interval of major earthquakes (every few centuries) combined with the short period of the instrument records (just a few decades) gives us the false impression that seismicity is uncommon in this region.

The February earthquake occurred due to the activation of a major fault system in the forested foothills, between the Papuan highlands to the north and the Fly River lowlands to the south.

Australia collides

The Papuan highlands have risen due to the collision between the Australian and Caroline/Pacific tectonic plates over the past five million years.

An animation of Australia’s tectonic journey as it broke away from Gondwana more than 100 million years ago. (Credit: Sabin Zahirovic)

Despite this collision, the Australian plate continues to move at about 7 cm a year to the northeast, in geological terms a quite remarkable speed, leading to a build-up of strain in the continental crust.

Much of this strain is released at the plate boundary along northern New Guinea, usually with more frequent but less powerful swarms of earthquakes. It is this motion, driven by the churning interior of our planet, that leads to major adjustments to the GPS datum and reference coordinates for the entire Australian continent.

But few people are aware that this very motion of the Australian continent is what causes the seismic and volcanic activity in New Guinea and parts of Southeast Asia.

As Australia moves northward, the entire New Guinea margin acts as a bulldozer, collecting Pacific islands, seamounts and other topographic features. New Guinea represents the leading edge of the advancing Australian continent, which causes continental crust to fold and crumple over a broad region.

This is a well-known process in plate tectonics, where the oceanic plates are known to behave quite rigidly, whereas the continental regions tend to deform over broader diffuse boundaries that resemble plasticine over geological timeframes.

When continents are squeezed during tectonic collisions, the crust crumples and folds over geological timescales. (Credit: Romain Beucher)

But the continental deformation process results in poorly defined (often due to the thick tropical vegetation cover) and intermittently active fault systems in the continent.

Over the duration of mountain building in the past five million years, the areas of highest deformation have shifted across the range. Today most of the deformation in PNG takes place north of the mountainous area, where it generates a lot of earthquakes.

Underground riches at risk

Some substantial crumpling of the continental crust still occurs across the southern foothills. The folding and thrusting has generated geologically young folds, within which a large part of PNG’s gas and oil wealth has accumulated.

The intense tectonic activity has also led to the enrichment of mineral resources, including mines sourcing gold, copper, silver, nickel, cobalt and a suite of other ore types.

Distribution of the aftershocks magnitude 4+ since the main quake (as of April 9, 2018). The size and colour (small to large, yellow to red) indicate aftershock magnitude and D+ the number of days after main shock. The white shaded ellipse represents the area of greatest slip during the main shock. Green diamonds represent the main gas fields.
USGS/Gilles Brocard, Author provided

It is this tectonic activity that determines the delicate interplay of economic benefits from raw materials, and the often-devastating and usually-unpredictable effects of natural disasters on society.

Although the February earthquake occurred at the very heart of one of the largest and newest gas fields in the country, the industrial installations, at the highest international standards, have not suffered major damage from the tremors.

But the ongoing disaster triggered a temporary halt in gas extraction, as the facilities require inspections and repairs. Unfortunately, and unusually, the earthquakes have struck in some of the most remote parts of the country.

Coping with disaster

Hela province is one of the poorest in PNG and its people are unprepared and ill-equipped to deal with a disaster of this scale. As many as half a million people were reported to be affected by the earthquake. At least 145 people reported killed.




Read more:
Five active volcanoes on my Asia Pacific ‘Ring of Fire’ watch-list right now


The Highlands Highway, the one real road into the region, was badly damaged and this is the major source of food and medicines. Many feeder roads have gone.

Papua New Guineans are resilient but it is likely that more external assistance will be needed to ensure that a physical disaster does not become a greater human tragedy.

Even so the full extent of the disaster has still to be revealed, while aftershocks continue to trigger secondary hazards including major landslides that have isolated a large number of communities.

The ConversationNot only are local communities facing the immediate hazards of further earthquakes and landslides, they face a protracted and costly recovery ahead.

Sabin Zahirovic, Postdoctoral Research Associate, University of Sydney; Gilles Brocard, Post doctoral associate, University of Sydney; John Connell, Professor of Human Geography, University of Sydney, and Romain Beucher, Postdoctoral Research Associate in Computational Geodynamics, University of Melbourne

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

Nepal earthquake reconstruction won’t succeed until the vulnerability of survivors is addressed



File 20171114 27595 18ntolw.jpg?ixlib=rb 1.1
More than 600,000 buildings were fully damaged in the 2015 earthquake in Nepal.
Jason von Meding, Author provided

Jason von Meding, University of Newcastle; Hari Darshan Shrestha; Humayun Kabir, University of Dhaka, and Iftekhar Ahmed, University of Newcastle

In April 2015 the Gorkha earthquake brought Nepal’s vulnerability sharply into focus. Alongside massive damage to the built environment, the terrible impact on the people of Nepal sent shockwaves around the world.

Despite good intentions to rebuild Nepal to be more resilient, 30 months on little progress has been made. Of more than 400,000 homes that were earmarked for reconstruction, only 12% have been rebuilt. Little of the US$4.4 billion in aid pledged for reconstruction has been disbursed.

The Nepali government instituted a reconstruction program in October 2015 that identifies beneficiaries and entitles them to three instalments of compensation. The payments are dependent on progress and building code compliance. Those who do not own land are locked out of reconstruction support.


Read more: The science behind the Nepal earthquake


Nepal has robust building codes, developed over recent years. Serious efforts to implement the codes predate the Gorkha earthquake.

Unfortunately, despite such efforts, there are still more than five million existing buildings standing after the earthquake that are not to code. Many of these are “informal” and built by traditional masons. There is also a large stock of old, dilapidated buildings. These buildings will be a particular risk in Nepal when future earthquakes strike.

Widespread retrofitting would protect lives and property in the future. Strictly speaking, all new buildings must meet the code – something difficult to monitor and enforce. Forcing people into compliance also has drawbacks: it can lead people to bypass it by unlawful means, and can be particularly onerous for the poor.

Nepal needs a strategy for “safe building” that is acutely aware of the resource inequalities and other social impediments that block progress on code compliance.

Many people live in informal homes in Nepal.
Ifte Ahmed

Housing typology and quality in Nepal

Of the more than 600,000 buildings that were fully damaged by the earthquake, most predated building codes and were built from stone and mud. The death toll of around 9,000 was lower than may have been expected, considering the number of buildings destroyed. By contrast, the 2010 Haiti earthquake is estimated to have claimed more than 300,000 lives while fewer than 300,000 buildings were fully damaged.


Read more: Two years after the earthquake, why has Nepal failed to recover?


Traditional building knowledge is clearly a valuable asset in determining how to save lives in an earthquake – but technical advances have been made that must now be integrated during reconstruction. The five million buildings that survived the earthquake require urgent retrofitting.

In Nepal, 80% of human settlement is often referred to as “informal”. These are households that are not in compliance with building norms and planning regulations. This can be a measure of marginalisation and can bring spatial segregation and discriminatory treatment.

In addition, Nepal is rapidly urbanising. The temptation in urban areas is to build higher, but in a country like Nepal this could have fatal consequences in an earthquake. Local engineers fear mass casualties if heavy, reinforced concrete structures (as are being widely built) collapse in the future.

Why has reconstruction stalled?

Rebuilding has been slowed by a range of technical, social and political challenges.
Jason von Meding

The government housing grant is available in three instalments on the basis of progress; Rs50,000 (US$477) upon signing an agreement; Rs150,000 (US$1,437) after completion up to plinth level; and Rs100,000 (US$958) upon completion of the structure.

More than 400,000 households entered into an agreement, but so far only 12% have completed the program.

The National Reconstruction Authority (NRA) undertook a lengthy consultation period in the name of building back better. Development of a building code compliance process and a catalogue on rural housing took 18 months to produce and disseminate.

By the time guidance was finally available, many beneficiaries had spent the first instalment on other priorities – many of those affected struggle to provide for the basic needs of their families.

Due to the remoteness of many reconstruction properties in the mountainous terrain, checking for compliance is a major challenge. In addition to the delays in establishing a suitable mechanism, the NRA has been unable to provide enough technical experts in remote, rural areas to implement their own policy.


Read more: What can tourists do to help, not hinder, Nepal’s quake recovery?


Safe, affordable and high quality construction is possible

Safe building is inherently difficult in a developing country like Nepal. For many people, putting food on the table is a daily struggle. Investing in earthquake-resistant housing measures is simply not within reach.

Some in Nepal are forced to live in buildings that could fall down at any time.
Jason von Meding

In such situations, people are forced to accept acute risk in the course of just surviving. This includes living in buildings that might fall down at any time. In Nepal, people have continued with life since the 2015 earthquake and have reoccupied dangerous premises.

Beyond simply improving the effectiveness of building code enforcement, it’s important we don’t neglect social and economic aspects of the dilemma in Nepal. While affordability is critical, quality is achievable by adapting Indigenous building techniques. If safe building is valued, people would voluntarily comply with codes and regulations.

The ConversationThe potential for change will be wasted if we fail to understand and address the chronic vulnerability of people recovering from this disaster. Not everyone has the same access to opportunities and resources – so better codes and regulations only go so far.

Jason von Meding, Senior Lecturer in Disaster Risk Reduction, University of Newcastle; Hari Darshan Shrestha, Associate professor Disaster Management and structural Engineering; Humayun Kabir, Professor, DRR expert, University of Dhaka, and Iftekhar Ahmed, Senior Lecturer, University of Newcastle

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

New Zealand’s Alpine Fault reveals extreme underground heat and fluid pressure



File 20170517 24350 bor3lx
The drilling project at New Zealand’s Alpine Fault is the first to investigate a major fault that is due to rupture in a big earthquake in coming decades.
John Townend/Victoria University of Wellington, CC BY-SA

Rupert Sutherland, Victoria University of Wellington

An international team that drilled almost a kilometre deep into New Zealand’s Alpine Fault, which is expected to rupture in a major earthquake in the next decades, has found extremely hot temperatures and high fluid pressures. The Conversation

Our findings, published today in Nature, describe these surprising underground conditions. They have broad implications for understanding what happens in the buildup to a major earthquake, and may represent the discovery of a new type of geothermal energy resource.

Seismic forces building up

The Alpine Fault is one of the world’s major plate boundaries and New Zealand’s most hazardous earthquake-generating fault. It runs for 650 kilometres along the spine of New Zealand’s South Island and we know that it ruptures on average every 300 years, producing an earthquake of about magnitude 8.

The last time the Alpine Fault did this was in 1717, when it shunted land horizontally by eight metres and uplifted the mountains a couple of metres. It is expected to rupture in a major earthquake in the next few decades and, even though this may not happen in the next 30 years or even 100 years, we know that the fault is at the end of its seismic cycle.

Other projects around the world have drilled into major faults, but usually just after a major earthquake. The Deep Fault Drilling Project, which involved more than 100 scientists from 12 countries, gave us an opportunity to take a close look at a fault as it builds up to its next rupture. It is the first time this has ever been done on a major fault that is due to fail in coming decades.

Drilling into New Zealand’s most hazardous fault.

Hot water at depth

We drilled two holes and during our second attempt made it to 893 metres deep. As we drilled deeper, the temperature increased rapidly, at a rate of about 15 degrees Celsius per 100 metres in depth. This is much higher than the normal rate of about 3°C per 100m in depth. At a depth of 630 metres, the water at the bottom of the drill hole was hot enough to boil, if it had been allowed to rise to the surface. The high pressures at depth stop it from boiling.

The hottest boreholes on Earth are mostly found in volcanic regions. We discovered a geothermal gradient – a measure of how fast temperature increases with depth – that is similar to the hottest geothermal energy boreholes drilled into volcanoes of the central North Island; but there are no volcanoes near the Alpine Fault.

How does it get so hot

There are two processes we think explain the extreme underground conditions at our drill site. An earthquake on the Alpine Fault has two geological effects: mountains are pushed higher and the shaking breaks up rocks.

During an earthquake and over time, the fractured rocks come down in landslides and rivers carry them to the sea. This limits how high the mountains can get. This process has operated for millions of years, with the height of the mountains staying about the same. Eventually, hot rocks from great depth (about 30 kilometres deep, at 550°C) were transported to the surface quickly enough (on geological time scales) that they did not have time to fully cool. Heat is transported from depth by the rock movement.

The other process that helps explain our findings is the rock fracturing, which allows rain water and snow melt to percolate downwards into the mountains so fast that it can move heat towards the valley, where water wells up and discharges. The flow needs to be fast enough so that the heat is not lost along the way, just as a water pipe in your home moves heat from a hot water cylinder to your bath before having time to cool. Water flowing through the rock concentrates heat and raises fluid pressure beneath the valleys.

The hot, high-pressure water beneath the valleys is mostly invisible at the surface, because it mixes with shallow, cold groundwater that flows to a depth of about 50 metres at our drill site. However, most of the valleys in the region where we drilled have a few warm springs that hint at this deeper source of hot water.

Better modelling of future hazards

The unexpected results of our research are important beyond New Zealand. Other faults around the world that we know are similar to the Alpine Fault may also have extreme conditions that have never been investigated.

Perhaps most significantly, we can now describe and estimate conditions on a geological fault that will rupture in an earthquake. This will help us to develop better computer models of earthquake rupture. It may also help us to explain how some types of geology (for example certain types of gold mineralisation) have formed as a result of similar conditions in ancient earthquakes.

Economic benefits

The extreme underground conditions we discovered may result in substantial economic benefits for New Zealand by providing a sustainable and clean geothermal energy resource that could be used by industry and local communities. We expect that similar hot geothermal conditions exist in other nearby valleys, and maybe in some other places in the world that are geologically similar to western New Zealand.

More drilling and measurements are needed to establish the scale of this local resource, its possible uses, and if it is safe to develop.

Rupert Sutherland, Professor of tectonics and geophysics, Victoria University of Wellington

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