EGU 2014: The Landscape Detectives – Searching for prehistoric earthquakes

The 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.

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

Karsten 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 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

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

ICTP Earthquake Tectonics and Hazards on the Continents Workshop

During the last two weeks of June I had the good opportunity to attend the Earthquake Tectonics and Hazards on the Continents workshop at the International Centre for Theoretical Physics (ICTP) in Trieste, Italy.

The workshop was organised as part of the Earthquakes without Frontiers (EwF) project which is a large multidisciplinary project involving CGS academics in Leeds and other national and international collaborators.

James Jackson (University of Cambridge) introduced the workshop by highlighting the central theme for the event: Our understanding of earthquake hazards is directly related to our understanding of earthquakes.  In other words, the more we understand about earthquakes and their tectonic settings, the more we will understand the hazards they present.

Most cumulative deaths are from continental earthquakes between magnitudes 6.5-8.
Source: Roger Bilham

The workshop material was broadly split up into two week blocks, with the first week focused on the basics of continental tectonics and the techniques used to study the behaviour of the Earth. Topics covered included an introduction to earthquake source seismology, the relationship between active tectonics and lithospheric structure, earthquake/fault scaling laws, stress and strain, InSAR, focal mechanisms and the geomorphic expression of strike-slip, normal and reverse faults.

For me, the most important aspect of the first week was highlighted by Steve Wesnousky (University of Nevada) in his talk on earthquake scaling laws. The empirical scaling laws derived from basic observations indicate that there are (as Steve likes to put it), Rules of the Game. The general behaviour of faults and earthquakes can be estimated knowing certain parameters. For example, if we know the length and width of a fault  we can estimate the maximum magnitude earthquake that fault can generate. This is a very powerful concept and one that is central to our understanding of earthquake hazards.

One of the key learning goals for the first week was to be able to recognise active faults from aerial photos or satellite imagery.
Source: Steve Wesnousky

The second week consisted of detailed case studies of different regions and applications of the techniques studied in the previous week. The main focus was in regions along the Alpine-Himalayan mountain belt, central Asia, central and western America and the Afar region.

One of the main points from this week was that earthquakes are unpredictable! Some of the deadliest earthquakes in the past century occurred on faults we didn’t even know existed! This highlights the importance of identification and measurement of slip rates and recurrence intervals of known and unknown active faults.

CGS academic Tim Wright describing how InSAR can be used to study earthquake deformation.

It is understandable that due to the varied approaches at modelling and interpreting observations that some academics will not agree with the approach of others. Scientists by nature are critical people and this is an important aspect in the work we do. We had a brief glimpse of one such topic where it was clear some academics prefered interpreting GPS data using block models while others preferred a viscous modelling approach. I will not go into a discussion of their their relative pros and cons in this post.

The workshop ended with a day discussing how scientists can turn their science into policy which will directly affect people’s lives and livelihoods. We had some very inspiring case studies from Kyrgyzstan (by Kanatbek Abdrakhmatov), Tehran (by Morteza Talebian) and the recent L’Aquila case in Italy (by Giulio Selvaggi).

Many thanks to the organisers for bringing people from all around the world and from different backgrounds together to study this important subject. I think everyone will agree that it was a highly successful event.

All the teaching material from the workshop are available to download for free at: http://cdsagenda5.ictp.trieste.it/full_display.php?ida=a12186

This is a fantastic resource and one that hopefully many will make good use of.

Also read up on the workshop tweets at the event hashtag: #ICTPTectonics

Ekbal

Workshop group photo.

The mitigation …

“The mitigation of earthquake risk requires the knowledge of hazards to be delivered to the people that need it!”

Professor Roger Bilham

Earthquake hazard for Istanbul

Istanbul is an ancient and beautiful city with a long history at the centre of major empires including the Roman, Byzantine, Latin and Ottoman. It is a city inundated with rich culture and history. In 2010 it was named a European Capital of Culture making it the world’s tenth most popular tourist destination. Home to over 13 million people it is also one of the most densely populated cities in Turkey.

A building destroyed in the 1999 Izmit earthquake

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

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

It has been known for a while now that earthquakes on the fault tend to follow a successive sequence, i.e. an earthquake rupture will often occur in the section of the fault proceeding the last rupture. The current sequence started in 1939 with the magnitude 7.9 Erzincan earthquake and has been progressing to the west in a series of 12 large earthquakes.

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

Current westward progression of earthquakes along the North Anatolian Fault.

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

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

Is it too late?

This effectively means nearly 7 million buildings throughout Turkey will be rebuilt to current earthquake standards over the next two decades! This massive project is expected to generate over USD 500 billion worth of construction industry over the next decade. Only last month, (February 2013) work began in Istanbul.

A new rail line currently under construction which runs beneath the Bosphorus Sea and links the east and western parts of the city will also be able to withstand moderate to high intensity shaking.

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

For all our sake, I certainly hope so!

Ekbal

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