When continents collide: Active deformation and seismic hazard

Since 1900, 35 earthquakes worldwide have each killed at least 10,000 people. Of these, 26 were in the Alpine-Himalayan seismic belt – a broad “crumple zone” where the African, Arabian and Indian tectonic plates collide with Europe and Asia. Most of these deadly earthquakes were caused by the rupture of faults that had not previously been identified.

CGS scientist Tim Wright is Professor of Satellite Geodesy at the University of Leeds and Director of the Natural Environment Research Council’s Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET). His work has been at the forefront of developing the use of satellite radar for measuring tectonic and volcanic deformation.

Tim was recently invited to present a guest lecture at the Geological Society on his work trying to understand the nature of seismic hazard within the Alpine-Himalayan region.

You can follow Tim on twitter: @timwright_leeds

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EGU 2014: The Landscape Detectives – Searching for prehistoric earthquakes

20140429-103457.jpgThe annual European Geoscience Union meeting is the largest conference gathering of geoscientists in Europe. Held in the historic city of Vienna, the meeting brings together a diverse range of scientists, students and professionals to share and exchange their research and ideas.

Many CGS academics and students from the University of Leeds are attending this year’s event. For the next week or so I’ll be writing a few short posts about some of the talks that catch, my eye from the Natural Hazards sessions. The first in the EGU series of posts is about playing detective with the landscape and is based on a talk given by COMET+ scientist Richard Walker.

Earthquakes are caused by the sudden release of energy by movements along large fractures in the Earth called faults. These events release a lot of seismic energy that spreads away from the fault. These are what causes damage to buildings and the landscape. Earthquakes can be very destructive events, as we saw in 2010 when a magnitude 7.1earthquake in Haiti killed almost 230,000 people!

An earthquake rupture preserved in the landscape in Mongolia. Image courtesy of Richard Walker.

An earthquake rupture preserved in the landscape in Mongolia. Image courtesy of Richard Walker.

It is important to understand the history of earthquakes along large faults if we are to accurately understand its behaviour and be able to make reliable forecasts of the hazards it might pose. However, the historical record of past activity on large faults is very sparse. Particularly in regions around Central Asia where populations have historically been small and/or nomadic.

This is where the landscape detectives come in. Every large earthquake results in movements along faults. Very often these movements are preserved in the landscape. This might be in the form of an uplifted river terrace, a diverted stream, an offset hill etc.

The landscape detectives, or geomorphologist to use the technical term, hunt for these clues and gather evidence for past movements along faults and try to determine the size of the movements and when it occurred. Using these they can give an estimate of the size of the earthquake that caused the event and more importantly add constraints on how fast the fault is moving. All these are are vital if we are to understand the fault and forecasts it’s behaviour in the future.

If you would like more information be sure to send us an email. I will write a more detailed feature on the actual techniques used by geomorphologists to untangle the earthquake history from the landscape after the conference.

Ekbal

 

Guest Blog: Futurevolc – The Next Step in Volcano Monitoring

Exif_JPEG_PICTUREKarsten Spaans is a PhD student working in the Institute of Geophysics and tectonics at the University of Leeds. His research focuses on the monitoring of volcanoes using satellite radar. Today he writes about the aims and goals of the Futurevolc project.

The hazard of volcanoes stems as much from their economical consequences as from their potential to kill. Floods and pyroclastic flows take most casualties, while ash can severely disrupt air traffic over large areas, as happened during the 2010 Eyjafjallajökull eruption. Our limited understanding of the plumbing systems and processes beneath volcanoes mean that the only way to mitigate these hazards is to monitor them as closely as possible. Monitoring the volcanoes will give us the ability to give out early warning and track the evolution of eruptions, and communicate these observations and their interpretations to authorities and the general public. The observations will also help us gain a better understanding of what happens beneath the surface of the the volcanic systems. While there are certainly many scientists studying volcanoes, using many different techniques, an integrated approach, where different techniques are combined, is often lacking. Realising this, the idea for the FUTUREVOLC project was born, led by Prof. Freysteinn Sigmundsson at the University of Iceland.

futurevolc_logo_plainFUTUREVOLC is an EU funded project involving 26 partner institutions and SMEs (small and medium enterprises). The goal of FUTUREVOLC is to take the next step in volcano monitoring, through setting up an interdisciplinary monitoring system, development of new methods to evaluate volcanic events/crises and increasing the effectiveness of information flows to civil protection, authorities and the general public. The project is divided in several work packages, each focusing on a different aspects of monitoring volcanoes. There are work packages dealing with communication and the distribution of information, outreach of the project, and of course several packages aimed at improving the science. These include long term magma tracking, detecting imminent eruptive activity and early warning, and determining eruption parameters once eruptions are ongoing.

An ash covered Karsten after work in the field during the 2010 Eyjafjallajökull eruption

An ash covered Karsten after work in the field during the 2010 Eyjafjallajökull eruption

We, at the University of Leeds, are involved in the long term magma tracking package. I work on setting up processing techniques that allow us to rapidly extract surface deformation measurements from satellite radar images. By doing this in a fast way, and combining this with GPS and seismic data, we can track magma in near-real time. Tracking the magma in near-real time will provide valuable information on the likelihood of an impending eruption, and even after eruptions have started, it will give us hints on what might happen next. Civil protection and aviation authorities would then be able to base their decisions regarding evacuation and airspace closures based on the information provided by us, and other contributors to the projects.

 

More information:
[1] http://futurevolc.hi.is
[2] http://www.see.leeds.ac.uk/research/igt

Satellite Earth Observation: Understanding Natural Hazards

 

This is the first of two blogs on satellite Earth Observation. This article will focus on what can be achieved with this technology and the next will be on the strengths the University of Leeds’ School of Earth and Environment has in this field.

Recently I had the great opportunity to attend the European Space Agency (ESA)’s Living Planet Conference held this year in the historic city of Edinburgh. The conference brought together over 1900 people from all over the world with the common aim to share knowledge and expertise on how we use satellite earth observation data (particularly from European satellites) to better understand the world we live on.

In his talk at the plenary session ESA’s Director General Jean-Jacques Dordain pointed out that Earth Observation is by far the largest programme for ESA in terms of budget and that it is the scientists that fundamentally drive these missions.

Interfermoteric map of part of the Virunga Mountains, East Africa  (ESA). The colours can be used to determine the actively deforming regions.

Satellite radar map of part of the Virunga Mountains, East Africa. The colours can be used to determine the actively deforming regions.
(ESA)

Earth observer satellites play a pivotal role in providing data to better understand a multitude of 21st century societal challenges including but not limited to:

– Population growth and migration
– Food production and land use
– Energy
– Geohazards
– Climate change
– Weather, sea level and ocean currents
– Earth’s changing surface
– The Earth’s biomass
– The geomagnetic field and space weather

Rather than go into a lengthy discussion of all of these I will focus on how Earth observation has helped us to better understand geohazards and our climate.

The early satellites such as ERS-1 (1991), ERS-2 (1995) and ENVISAT (2002) paved the way for the satellite geodesy age. They’re almost two decades of constant monitoring of the Earth has provided a wealth of data for the scientific community which has been instrumental to improving our understanding of natural (and human induced) hazardous events. Even now, long after these satellites have been decommissioned, the archived data is used for ongoing research.

Synthetic interferogram for the 2003 Bam earthquake. The coloured fringes are essential contours of displacement during the earthquake. Source [1]

Synthetic interferogram for the 2003 Bam earthquake. The coloured fringes are essentially contours of displacement during the earthquake.
Source [1]

The extent of deformation from earthquake ruptures, for example, can often be misinterpreted from limited spatial data such as GPS and ground surveys. These satellites provided a means to determine the deformation from these events on large scales and at a high spatial resolution. Such studies led to the use of this data to measure the much smaller interseismic signals and the build-up of strain energy on locked faults. Even if these faults are not obvious in the landscape.

Parallel to this is the geodetic work to monitor active volcanoes. Satellite radar can be used to monitor to the uplift and subsidence of volcanoes which can be interpreted as inflation and deflation caused by the presence of magma. Such monitoring aided in providing early warning before the 2010 eruption of Mt Merapi in Indonesia and helped save thousands of lives.

The extent of floods and the potential for future flooding in a particular region can be assessed using space based geodetic monitoring. The location of landslides and the variation of surface motion can be monitored to determine the stability and likelihood that a landslide may be triggered by an incoming hurricane (which is also monitored using space based instruments).

Various gas concentrations (e.g. carbon-dioxide, sulphur dioxide, methane) in the atmosphere can be determined and their effects on the local and global climate studied. Such measurements are integral in adding boundary conditions to climate models which improve our estimates of the future effects of greenhouse gas emissions. Accurate weather reports rely on real-time satellite measurements of atmospheric pressure, humidity, temperature etc.

Sentinel-1, due to be launched early next year, will be the first dedicated Earth observation satellite for interferometry (i.e. mapping changes through time). Its long mission duration and systematic acquisitions will enable scientists to better understand the changing nature of the Earth’s surface through time. Such acquisitions will, for example, allow near-real time monitoring of volcanoes and and thus enable better and more accurate forecasting before these events. Also the detection of slow strain accumulation on large hazardous faults will be possible with only a few years worth of data.

Sentinel-1, due to be launched in march 2014. (ESA)

Sentinel-1, due to be launched in march 2014.
(ESA)

Four more Sentinel missions are planned for future years covering all the Earth observation topics such as biomass, sea level, atmospherics and land cover. ESA’s Open Access data policy also enables free access to all its mission data for both scientific and commercial use.

The next few years will certainly result in much greater efforts at understanding the workings of our little blue planet because after all, there is no alternative to planet Earth; we are here to stay.

Ekbal

 

More information:
    [1] Talebian et al., The 2003 Bam (Iran) earthquake: Rupture of a blind strike-slip fault, 2004, Geophysical Research Letters, vol. 31, L11611, doi:10.1029/2004GL020058
    [2] http://www.esa.int/Our_Activities/Observing_the_Earth

 

 

From Science to Action: Lessons learnt from Haiti

Eric Calais

Eric Calais


Recently we had our first joint Climate and Geohazard Services (CGS) and Institute of Geophysics and Tectonics (IGT) seminar at the University of Leeds.

Our invited speaker was Eric Calais who was the U.N.’s Geophysicist on the ground after the 2010 Haiti earthquake. This is a short summary of some of the topics discussed in his seminar.

Science and scientists are needed on the scene of disaster risk reduction – Eric Calais

Haiti and indeed all the Caribbean countries are exposed to many numerous hazards including earthquakes and hurricanes. Of these the most reliable are hurricanes which hit the region like clockwork every summer. However earthquakes are less regular and often occur after much longer time intervals. So when it comes to hazard mitigation hurricanes trump earthquakes!

Eric started his talk with an introduction to the tectonics of the Haiti region. The countries largest city, Port-au-Prince lies about 20 kilometres north of a major strike slip fault called the Enriquillo Fault. Eric, working in Haiti earlier in his career, had predicted the fault had a chance of storing enough energy which if released all at once will result in a magnitude 7.1 earthquake.

Earthquakes are not new to Haiti. There is abundant evidence for historic ruptures including one that was recorded by British colonist in the seventeen hundreds. However due to the long recurrence time of such events the human memory of these events gradually gets lost. Therefore, the inhabitants of Port-au-Prince were not prepared when a magnitude 7.0 earthquake shook the country on the 12th January 2010.

Shake and damage map of the 2010 earthquake. Source: BBC

Shake and damage map of the 2010 earthquake. Source: BBC

The resulting devastation took the lives of nearly nearly 316,000 people according to Haitian Prime Minister Jean-Max Bellerive and displaced nearly a million people from their homes.

The second part of Eric’s talk focused on his experiences working with the U.N. as the chief geophysicist on the ground immediately after the earthquake.

The first important lesson learnt from Haiti is that the impacts from natural disasters are amplified by socio-economical and political issues.

UN aid in Haiti. Source: www.telegraph.co.uk

UN aid in Haiti. Source: telegraph.co.uk

It is clear that a government needs to find a balance between the gains from increased mitigation with the costs needed to achieve such mitigation levels. The maximum mitigation achievable with the minimum cost is generally the prefered option, especially for developing countries. But these decisions need to made with due consideration to the types, expected magnitude and repeat interval of each individual hazard.

The U.N. is well aware that building resilience is the key to maintaining development and reducing loss from natural disasters.

An important goal for the U.N. is to offer advice and embed clear resilience and mitigation strategies into governmental policy and ensure that these policies are effectively enforced.

However much of the U.N. data on human exposure to natural disasters are not entirely accurate and often out of date. Worryingly there appears to be no clear procedure for updating this information. Improving resilience becomes much more difficult without knowing the nature of the hazards faced. It is clear that the U.N. needs to invest in resources to update key data tables such as exposure and vulnerability; combining information from industry, especially the re-insurance sector, and outputs from the scientific community.

Post earthquake. Source: manongeo.wordpress.com

Post earthquake. Source: manongeo.wordpress.com

Most of the U.N. members of staff are non-scientists. Therefore, many of the on-the-spot decisions during disasters are made without a proper understanding of the underlying science.

It is clear that the scientific community have not been paying enough attention! We as scientists need to be more involved with the issues of disaster risk reduction. Scientists understand the hazards, the risks involved and to some extent what needs to be done. We just need to step forward and be more involved.

Eric ended his talk with the following call to arms:

“The gap between science products and practitioners of risk reduction requires someone to make the first step; scientists are in the best position [to take this step].”

Further Reading:

[1] http://news.sciencemag.org/scienceinsider/2010/09/on-the-ground-with-eric-calais.html
[2] http://www.unfoundation.org/who-we-are/impact/our-impact/health-data-disaster-relief/haiti-earthquake-response.html
[3] http://www.britannica.com/blogs/2010/10/5-questions-for-geophysicist-eric-calais-on-the-newly-discovered-fault-in-haiti