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It’s not my fault

1 May

A line on a map is important. In the Beverly Hills region of Los Angeles a series of mapped fault lines are now the cause of a major controversy. Communities have been alarmed, money has been lost and legal proceedings are ongoing.

It started in 1992. James Dolan and Kerry Sieh, two earthquake geologists at the California Institute of Technology, published a map in a field trip guidebook about the Los Angeles Basin. The map in question included suggestions of two potentially active earthquake faults in the north of the basin – the West Beverly Hills Lineament and the Santa Monica Fault – though neither of them had been confirmed by detailed study.

In the two decades since the situation has slowly spiralled out of control. Dolan and Sieh’s original map has been included in a whole series of academic papers and in 2005 the faults were added –as dotted lines – to an official map from the United States Geological Survey. Then, in 2010, the state published a map in which it labelled both faults as ‘active’.

Map released by the Los Angeles metro company at the press conference in 2011. Red lines show suggested active faults and BHHS is the Beverly Hills high school.

Map released by the Los Angeles metro company at the press conference in 2011. Red lines show suggested active faults and BHHS is the Beverly Hills high school.

Eldon Gath, from Earth Consultants International, has been reflecting on the escalating situation at the EGU General Assembly 2014. “What was a hypothesis,” explains Gath, “became a fact without any new information. Every subsequent map has reproduced these faults without even questioning whether they are right.”

These careless assumptions have now come back to haunt the people of Beverly Hills. Metro, the Los Angeles underground company, are proposing a new ‘Subway to the Sea’, an underground line from Los Angeles to the coast that would pass directly through Beverly Hills and Santa Monica. In 2011 they held a press conference to announce the results of some geotechnical surveys they had commissioned and duly claimed that a whole series of active earthquake faults ran through the proposed train route and, crucially, right under the local Beverly Hills high school. The metro company also proposed a new route for their underground line to avoid some of the faults.

Beverly Hills high school. (Credit: Eldon Gath)

Beverly Hills high school. (Credit: Eldon Gath)

“It came as a big shock to everyone,” says Gath, “this was dropped on the local community at a press conference and there was no advance notice that the map was going to be released. The high school found out about this fault map when the Los Angeles Times called them. That’s just not good public relations.”

Immediately after the press conference the school decided to launch its own investigations. It commissioned new boreholes and a trench that stretched from the front door of the school right across the proposed location of the fault. If the fault was there, then the trench would reveal layers of sediment that had been offset in previous earthquakes. But nothing was found; 50,000 year old sediments were entirely undisturbed. At a nearby location one fault was found, but the sediment ages revealed that it hadn’t moved for at least the last 200,000 years. After all the disruption, it appears that the faults don’t even exist.

Trench excavated in front of the school. No evidence of past earthquakes was found in the trench. (Credit: Eldon Gath)

Trench excavated in front of the school. No evidence of past earthquakes was found in the trench. (Credit: Eldon Gath)

To date the school has spent an estimated three million dollars on these studies and at least three other property owners in the vicinity have commissioned similar work. “It’s unfortunate that they had to spend so much money,” says Gath, “but the lawyers are now feasting at the trough.” Multiple lawsuits have been filed and a couple of cases have already been successful.

But why were these mistakes allowed to happen? “I think there was a paradigm-driven interpretation,” explains Gath. In the original work done by the metro company, “every kind of mismatch was interpreted as a fault. It was a fault-driven interpretation. But they didn’t pay any attention at all to the sediment ages.” It is also alleged that competing financial and political interests have played a role.

The current situation can hardly be blamed on Dolan and Sieh’s original map, but their initial tentativeness has been lost somewhere in the Chinese-whispers-style translation.

In the future, we must make sure that someone takes responsibility for the faults.

By Tim Middleton, University of Oxford

Reference:

Gath et al., 2014: The West Beverly Hills Lineament and Beverly Hills High School: Ethical Issues in Geo-Hazard Communication. Geophysical Research Abstracts, Vol. 16, EGU2014-1131-1

GeoTalk: Steven Smith on fossil faults and fantastic faulting

24 Apr

This week in GeoTalk, we’re talking to Steven Smith, a Lecturer from the University of Otago. Steven takes us on an Earth-shaking journey, explaining how ancient faults reveal what’s happening under the Earth’s surface and delving into the future of fault zone research.

First, could you introduce yourself and tell us a little about what you are currently working on?

Last September I started as a Lecturer at the University of Otago in New Zealand. My work focuses on understanding the structure and evolution of tectonic fault zones in the continental crust. I graduated from Durham University (England) back in 2005 and remained there to complete my PhD, studying a large fault zone exposed on Italy’s Island of Elba. My Italian connection continued as I then moved to Rome for 4 years to undertake a post-doc with Giulio Di Toro and Stefan Nielsen at the INGV (National Institute of Geophysics and Volcanology). In Rome I was working on a large group project funded by the European Union. The project involved integrating field and experimental work to better understand some of the extreme deformation processes that occur in fault zones during earthquakes. When my post-doc finished, I relocated to New Zealand, attracted by the research opportunities available here and the wonderful places waiting to be explored!

Steve on the summit of Lobbia Alta (3,195 m), a peak in the Adamello area of the Italian Alps. This area is part of a large Tertiary magmatic batholith that is cut by several fault zones Steve studied as part of his post-doc work. (Credit: Steven Smith)

Steve on the summit of Lobbia Alta (3,195 m), a peak in the Adamello area of the Italian Alps. This area is part of a large Tertiary magmatic batholith that is cut by several fault zones Steve studied as part of his post-doc work. (Credit: Steven Smith)

Last year, you received a Division Outstanding Young Scientists Award for your work on the structure of shear zones. Could you tell us a bit more about your research in this area?

I work mainly on so-called “exhumed” fault zones – those that were once active and have been brought to the surface of the Earth by millions of years of uplift and erosion. By studying the structure of exhumed fault zones we can understand a lot about the physical and chemical processes that are active when faults slip. I have worked on fault zones in Europe that were exhumed from both the middle and upper crust. I’m particularly interested in the crushed-up rocks in the cores of fault zones (better known as fault rocks) and what these can tell us about fault zone rheology and deformation processes.

In the last few years, we have identified a number of previously-unrecognised textures in the cores of large normal and thrust faults in Italy. These include faults with highly reflective “mirror-like” surfaces and small rounded grains resembling pellets. Our work focused on trying to understand the significance of these textures, and in doing so we had to develop new experimental methods to deform fault zone materials under more realistic conditions. By comparing our field observations to the experimental data, we realised that the textures we identified probably represent ancient “fossil” earthquakes preserved in the rock record.

When thinking of a fault zone, you don’t often think small. How can you scale down what’s going on to create a laboratory-sized experiment?

That’s a very good question, and something that experimentalists have to be aware of all the time. It’s generally not possible to reproduce in the laboratory all of the conditions that a natural fault enjoys, which is why laboratory work ideally has to be integrated with other data, such as field observations of natural faults and theoretical modelling. But it is possible to perform experiments at quite realistic pressures and temperatures, and some deformation apparatus can deform fault zone samples over a very wide range of slip velocities – the sort you would expect during the seismic cycle along natural faults.

Laboratory experiments allow us to produce data on rock strength and fault zone behaviour that simply wouldn’t be possible by any other means. At the same time, it’s important to bear in mind that a small laboratory experiment might represent the behaviour of only a single point on a much larger fault surface – that’s where complementary field and geophysical observations come in. Looking at fault geometry and fault zone evolution over time helps put lab studies into context.

Admiring the inner workings of a fantastic fault on the Italian Island of Elba. (Credit: Bob Holdsworth, Durham University)

Admiring the inner workings of a fantastic fault on the Italian Island of Elba. (Credit: Bob Holdsworth, Durham University)

How does deformation differ across the world’s fault zones?

In the last few years, seismologists have detected different types of slip behaviour along active faults, from those that creep along steadily at rates of a few millimetres per year to those that fail catastrophically in earthquakes. In between there are other types of slip behaviour seen in seismological signals (such as seismic waves) from the deeper parts of fault zones like the San Andreas fault and the Alpine fault in New Zealand. Understanding the basic controls of this rich variety in fault slip behaviour is one of the key goals of modern earthquake science. Geologists studying exhumed fault zones have also long recognised that fault zone structure in the crust is very complex and highly dependent on factors like the type of host rock, level of exhumation, availability of fluids and so on. A future goal for geologists like me is trying to understand whether different types of fault slip behaviour recognised in modern-day seismic signals are preserved in the structure of fault zones in some way.

Is digital mapping an essential tool for the modern-day structural geologist? How does it help?

As in most branches of science, digital technologies are now increasingly used for geological mapping purposes, although a majority of universities still favour the traditional pen-and-paper approach to training students in geological mapping. In many mapping situations – ranging from reconnaissance-scale mapping to detailed surface topography measurements – there are a number of benefits to a digital approach, the main one being that field data are automatically located using GPS or laser-based technology. This opens up a range of possibilities to map and study 3D structures that would be difficult and time-consuming, if not impossible, using more traditional approaches.

I certainly think that digital technologies will play an increasingly important role in geological mapping and research in the future, and the technology will inevitably become more fit-for-purpose and affordable. I recently taught a short workshop on digital mapping to a group of 4th year students in Otago; after a few days they were all quite confident using handheld computers and GPS devices to map, and I think they were impressed by the ease with which the digital data could be analysed to better understand the inherent complexities of geological structure.

Finally, will you be working on faults in the future or moving on to pastures new?

I think there are a lot of important research problems to tackle in fault zones, so it’s likely I’ll continue working on faults in a broad sense in the future. The devastating Tohoku-oki earthquake and tsunami in Japan in 2011 highlighted that our understanding of fault zones is far from complete. My post-doc experience has convinced me that integrating field and experimental work is a promising way to understand fault zone processes. At the moment I’m particularly interested in the very-small scale frictional processes that occur on fault surfaces during earthquakes, and I’m currently using some of the analytical equipment here in Otago to study experimental samples that were deformed under earthquake-like conditions.

If you’d like to suggest a scientist for an interview, please contact Sara Mynott.

People power

2 Apr

Seismic monitoring is critical in earthquake-prone areas such as Nepal, but limited resources mean limited monitoring. EGU Science Journalism Fellowship awardee Kate Ravilious reports back on how scientists are using social media to fill the gap. 

Data gathering needn’t always involve expensive instruments or exotic fieldtrips. Here in resource strapped Nepal, seismologists are tapping into the power of local people to collect information that could ultimately save many lives.

In places like California and Japan shake-maps, as they are known, are commonplace. Houses built on thick layers of sediment will be rattled much more than houses situated on granite bedrock for example. Detailed knowledge of local geology, plus dense arrays of instruments enable geologists to accurately predict which areas are going to wobble most when an earthquake arrives. This information ensures that funding can be targeted and spent in the areas which need it most. But here in Nepal the network of instruments is sparse and without these shake-maps it is very hard to know how best to spend the very limited funds and increase earthquake resilience in this earthquake-prone land.

The view over Kathmandu. (Credit: Katie Oven, Durham University/Earthquakes Without Frontiers).

Last week I visited Nepal’s National Seismological Centre in Kathmandu. Lok Bijaya Adhikari took me to see their accelerometer – an instrument that measures the acceleration produced by an earthquake and tells you literally how much the ground moved. I enjoyed making my own very mini earthquake by jumping up and down, and watching the light come on, registering that the ground had moved. Countries that can afford a good network of accelerometers can use the data gathered during small earthquakes to assess which parts of a city shake most. But Nepal has just seven accelerometers to cover the entire country – not nearly enough to gather the local detail required to produce a shake map.

Instead Adhikari and his colleagues are tapping into a much cheaper and more plentiful resource: gossip. When something exciting happens we all love to tell our version of events. Last year the National Seismological Centre added a ‘Did you feel it?’ button to their local earthquake reports webpage and Facebook site. People are invited to submit their experience of an earthquake – how intense the shaking felt, what kind of things fell over, how long the shaking went on for, and so on.

Obviously personal accounts are subjective and nowhere near as accurate as an accelerometer, but providing there are enough accounts the exaggerated answers are smoothed out. “We can gain some information on how the ground responds and estimate which local areas are most at risk,” Adhikari told me.

Given that Nepal experiences around five earthquakes of magnitude 4 or greater every month, there are plenty of opportunities for people to submit their experiences. And the explosive rise in mobile phone uptake and interest in social media in Nepal over the last five years or so suddenly make this a viable and very powerful method of gathering data. Now all Adhikari needs to do is spread the word…

By Kate Ravilious, Science Journalist (http://www.kateravilious.net)

An earlier version of this post was originally published on the Earthquakes Without Frontiers blog at http://ewf.nerc.ac.uk/2014/03/27/people-power/

Sniffing out signs of an earthquake

28 Mar

Last year Kate Ravilious was awarded an EGU Science Journalism Fellowship to follow scientists studying continental faults. Now she’s out in Nepal alongside researchers who are working out when the county’s next big quake will be…

Sometimes the best rocks are found in the worst locations. Yesterday I was reminded of this as I watched Paul Tapponnier, from the Earth Observatory of Singapore, and his team tracing one of the most dangerous earthquake faults in the world, right next to a dusty, noisy, dirty and busy main road in southern Nepal. Hooters were blaring, bells ringing and people shouting. Clouds of fine orange dust (from quarrying down the road) coated us from head to toe and under our feet lay the rubbish chucked out of bus and car windows. Glamourous it was not.

But Tapponnier and his team are prepared to hold their noses and get on with the job in hand. They know that these rocks are likely to hold the answers to the puzzle they are trying to solve, and that studying them could eventually help to save many lives.

Chasing charcoal – the key to dating faults. (Credit: Kate Ravilious)

Chasing charcoal – the key to dating faults. (Credit: Kate Ravilious)

In Nepal earthquakes are a fact of life. India is slamming into Asia at a rate of 4 cm per year (pushing up the mighty Himalayan mountain range) and the strain that accumulates in the underlying tectonic plates releases itself periodically in the form of earthquakes. Tremors of magnitude 4 or 5 happen more than ten times every year, but the real worry is the ‘great’ earthquakes – magnitude 8 or more – which Nepal encounters once every few decades.

The last great earthquake – a magnitude 8.4 – occurred in 1934. It  razed around one quarter of Nepal’s capital, Kathmandu, to the ground and killed 17,000 people across India and Nepal. Since then the population of Kathmandu has grown sevenfold and dangerous multi-story concrete buildings have sprung up everywhere. Kathmandu (which happens to be built on jelly-like ancient lake sediments) has risen to an unenviable first position in the world earthquake risk list and scientists estimate that up to one million people could be killed when the next big quake shakes the Himalayan region.

But when and where will this next big  earthquake be? For decades no-one could even locate the fault that caused the 1934 quake, let alone estimate when it might move again. But Tapponnier has an uncanny nose for sniffing out earthquake ruptures, and in 2008 he found the culprit, hidden underneath layers of Nepalese jungle down on the edge of the hot Terai plains in southern Nepal. Since then he has returned every year, to uncover the extent of this massive fault and learn more about how it operates.

Paul Tapponier searching for signs of earthquakes past. (Credit: Kate Ravilious)

Paul Tapponier searching for signs of earthquakes past. (Credit: Kate Ravilious)

And so it was that I ended up standing next to the busy road, near the small town of Bardibas, thanks to a travel grant awarded by the EGU, to learn about the work that Tapponnier and his team are doing.

This year much of the focus of the field trip has been to map out the shape of the land, using a sophisticated LIDAR (Light Detection and Ranging) technology. This sleek silver canister rotates and sends out 150,000 pulses of laser light every second. The reflections are used to build up a high resolution three-dimensional picture of the surface.

Sorvigenaleon Ildefonso, a LIDAR technician  from the Earth Observatory of Singapore, along with Aurélie Coudurier-Curveur and Çagil Karakaş, both post-doctoral researchers at the Earth Observatory of Singapore, have spent the last two weeks gathering as many measurements as possible, from a range of locations (many of which are beautiful and tranquil spots), often working until the light fades and they can no longer see what they are doing. The day I arrive they are hauling the LIDAR and associated equipment from location to location, ignoring the energy-sapping heat, blaring of horns, stink of rubbish and clouds of dust. While I am constantly distracted by what is going on around me, they are all completely focused, setting up their equipment with precision and great care, and recording their measurements meticulously.

Sorvigenaleon Ildefonso setting things up for LIDAR. (Credit: Kate Ravilious)

Sorvigenaleon Ildefonso setting things up for LIDAR. (Credit: Kate Ravilious)

What they are searching for is changes in gradient, not always visible to the naked eye under the thicket of vegetation. Much of the hillside has a step-like appearance, and each of those steps may represent one upward thrust of the earthquake. By using the LIDAR to map out these steps in detail they can work out how many times the fault has moved, and how much land it thrust upwards each time.

Meanwhile, down at the bottom of the hillside Tapponnier and his Nepalese colleague, Som Sapkota, from the Department of Mines and Geology in Kathmandu, are standing in a ditch, searching for miniscule pieces of charcoal in amongst the sand and cobbles of a small outcrop of rock. These incredibly precious fragments (often no bigger than a sesame seed) are the key to dating the timings of the fault movement and working out how often the fault moves on average.

In the pit, picking out charcoal and peering into the past. (Credit: Kate Ravilious)

In the pit, picking out charcoal and peering into the past. (Credit: Kate Ravilious)

It is hot, tiring and often tedious work, but for this group of scientists it is puzzle they refuse to leave unsolved. “We have to study these things, and do it quickly, before the next big earthquake strikes,” says Tapponnier.

By Kate Ravilious, Science Journalist (http://www.kateravilious.net)

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