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GeoTalk: Matthew Agius on how online communication can help identify earthquake impact

8 Aug

In this edition of GeoTalk, we’re talking to Matthew Agius, a seismologist from the University of Malta and the Young Scientist Representative for the EGU’s Seismology Division. Matthew gave an enlightening talk during the EGU General Assembly on how communication on online platforms such as Facebook can help scientists assess the effect of earthquakes. Here he shares his findings and what wonders online data can reveal…

Before we get going, can you tell us a little about you’re area of research and what got you interested in using online communications to complement our understanding of earthquakes and their impact?

My area of research is the study of tectonic structures and dynamics using different seismic techniques. The regions I have studied the most are Tibet and the Central Mediterranean. During my student days many friends wondered about my research and I felt that there was a need to reach out for the public in order to eliminate misconceptions on how the Earth works, in particular about the seismic activity close to home – Malta. This led to the creation of a website with daily updates on the seismic activity in the Mediterranean. We set up an online questionnaire for people to report earthquake-related shaking. The questionnaire proved to be successful; hundreds of entries have been submitted following a number of earthquakes. This large dataset has valuable information because it gives an insight on the demographics in relation to earthquake hazard of the tiny nation.

How can social network sites such as Facebook and Twitter be used to assess the impact of earthquakes?

Nowadays the general public has access to smart phones connected to the internet, which have become readily available and affordable. This resulted in a rapid use of social websites. People increasingly tend to express themselves in ‘near’ real-time online. Furthermore, smartphones are equipped with various technologies such as a GPS receiver and an accelerometer – the basic set up of a seismic station – and also a camera. Altogether this has the potential to provide an unprecedented level of information about the local experience of an earthquake. Its immediate analysis can also supplement instrument-based estimates of early earthquake location and magnitude.

Out in the field – Matthew Aguis in the Grand Canyon. (Credit: Matthew Aguis)

Out in the field – Matthew Agius in the Grand Canyon. (Credit: Matthew Agius)

What sort of information can you gather from sites like Facebook or Twitter, and what can it tell you?

Users can post comments as well as photographs directly on a page, say a page dedicated to earthquakes. Such post are time stamped and can also have geolocation information. Although the posted information might seem too basic, the collective data from many users can be used to establish the local feeling in ‘real time’. Another way is to have a specific application that analyses the text expressed by social media users. Similar applications have already been considered in a number of regions such as USA and Italy, and have shown very interesting social sentiment expressed during and after an earthquake shake.

How do the earthquake sentiments relate to the geology? Can you see any patterns between what people say and share online and the intensity of the quake in a particular area?

This is a new area of research that is still being investigated. Earthquake intensity, shaking and damage in a local context, are known to vary from one place to another. These variations are primarily due to either the underlying geology, the seismic wave propagation complexities, or a combination of both. So far various mathematical models have been published for famous areas such as San Francisco Bay; soon scientists will have the opportunity to compare their models with information on people’s sentiment gathered in this new way. Such sentiment is expected to relate to the geology, to some extent.

And another shot of Matthew in the field – this time from Mount Etna. (Credit: Matthew Aguis)

And another shot of Matthew in the field – this time from Mount Etna. (Credit: Matthew Agius)

What are the difficulties of dealing with this sort of data, and how do you overcome them?

This type of data compilation is known as crowdsourcing. Although it is has powerful leads, one has to take careful measures on how to interpret the data. For example one must not assume that everyone has a public social profile on the internet where to posts his/her sentiment. One also has to consider that mobile phone coverage is sometimes limited to cities leaving out large, less inhabited areas without a network. Another limitation can be related to the list of specific keywords used during text analysis, a typical keyword could be ‘shake’; users might be using this term in a completely different context instead of when the ground is shaking! I think the best way to overcome such difficulties is to combine this data with current seismic monitoring systems; upon which an event is verified with the seismic data from across the investigated region.

During your talk you proposed other ideas for data analysis, how can it be used to support civil protection services and inform the public?

Until now social sentiment with regards to earthquakes has been studied through the use of Twitter or Facebook. But citizens are also making use of other online platforms such as news portals. All this information should ideally be retrieved and analysed in order to understand the earthquake sentiment of an area better. Furthermore, such studies must also be able to gather the sentiment in multiple languages and establish geolocation information from clues in the user’s text. I think it is time to implement a system to be used by civil protection services, whereby immediately after an earthquake has been established, an automatic alert is sent via a dedicated phone app and, at the same time, a web bot crawls the web to ‘read’ and analyse what people are expressing across multiple platforms. A felt map can then be generated in real time. This could be very useful for  civil protection services during a major disaster, helping them to redirect their salvage efforts as civilian phone calls become clogged.

Matthew also mans Seismoblog, a blog dedicated to the young seismologists of the European Geosciences Union – keep up with the latest seismology news and research on Seismoblog here.

Imaggeo on Mondays: Fuelling the clouds with fire

30 Jun

Wildfires frequently break out in the Californian summer. The grass is dry, the ground parched and a small spark can start a raging fire, but burning can begin even when water is about. Gabriele Stiller sets the scene for a blaze beside Mono Lake, exploring the events that got it going and what it may have started in the sky… 

While on shores of Mono Lake in the summer of 2012, I spotted something strange in the distance: a great blaze on the other side of the lake. We were on a trip through the southwestern states (a long tour through California, Nevada, Utah and Arizona). All the days before we had been continuously accompanied by thunderstorms that broke out during the afternoon. The photo was taken before the daily thunderstorm, and the large convective system already hinted to the next storm to come – and indeed it did, just a few hours later.

Desert fires close to Mono Lake, California. (Credit: Gabriele Stiller via imageo.egu.eu)

Desert fires close to Mono Lake, California. (Credit: Gabriele Stiller via imageo.egu.eu)

It was not clear if this convective cloud system was generated by uplift of heated air initiated by the fire, a process known as pyro-convection, or if it was simply a coincidence. After all, thunderstorms were a regular occurrence throughout our trip. This could have been the storm of the day, and the related convection could have transported the air and smoke from the fire upwards. Or a combination of both could have been behind it. The cumulus cloud was quite isolated, with clear sky surrounding it, but you can already see a small anvil developing (the area where ice is formed in the cloud) above the cauliflower-like cumulus – a hint towards a developing thunderstorm. Such a development would make the cloud into a cumulonimbus cloud.

So what caused the blaze? On 8 August 2012, the wildfire was started through lightning ignition by a thunderstorm coming from the Sierra Nevada, and it burned for several days on open grassland, far from human infrastructure. Due to these circumstances, firefighting was not particularly difficult for the authorities. However, more than 13000 acres were burned, and more than 500 people fought the fire. One of the priorities was to keep the amount of sage-grouse habitat burned to a minimum.

By Gabriele Stiller, Karlsruhe Institute of Technology, Karlsruhe, Germany

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Geosciences column: Shelter island – building a barrier to protect the coast

27 Jun

The latest Geosciences Column features recent research into tsunami hazards and explains how island building out to sea can help protect buildings on the shore…

Barrier reefs are well known for holding off the wrath of the ocean and sheltering the serene lagoons that stretch between them and the mainland. Barrier islands possess the same protective power, taking the impact of waves that have built up across the ocean and dissipating their energy before they break on the continent. Now, a team of Spanish and Columbian scientists have shown how this barrier island effect can be harnessed to protect communities from the worst of ocean waves – the tsunami.

Tsunamis are generated when vertical faults beneath the seabed slip, causing a large earthquake (over magnitude 5 on the Richter scale) and displacing a huge volume of water. They pose a greater hazard than earthquakes alone, and in seismically active coastal areas they are a significant concern. One such area is the seismic belt that shadows the coastline between Ecuador and Columbia, where the Nazca Plate subducts beneath the South American.  There have been six major quakes along the belt in the last century, the most recent of which was a magnitude 7.7 quake that resulted in a devastating tsunami and the destruction of an entire island within the Mira River Delta in 1979.

Spot the difference. Top: the island of El Guano prior to the 1979 tsunami; bottom: the same area following the tsunami. (Credit: Otero et al. 2014)

Spot the difference. Top: the island of El Guano prior to the 1979 tsunami; bottom: the same area following the tsunami. (Credit: Otero et al. 2014)

In the Columbian department of Nariño alone, the 1979 tsunami resulted in the loss of over 450 lives and 3080 homes. But the devastation would have been greater if it weren’t for El Guano, a sandy barrier island that was once present just off the country’s Pacific coast. By modelling tsunami as it happened, and how it would unfold if it occurred again today, Luis Otero and his colleagues from the University of Norte, Columbia, and the Environmental Hydraulics Institute IH Cantabria, Spain, showed just how good a barrier the island was – cutting the energy transferred to the island city of Tumaco by up to 60%.

It’s not the first time natural defences have been shown to protect the coast. Indeed, studies of the 2006 Boxing Day tsunami in Indonesia have shown that reefs, mangroves, beaches and dunes all provide the coast some protection by absorbing the tsunami’s initial impact and slowing the speed of the advancing wave.

How flooding would differ if El Guano island was present: (a) shows the current situation and (b) shows what would happen if the island was recreated. The white regions represent the areas that are not flooded and the black line shows the shoreline. (Credit: Otero et al. 2014)

What a difference an island makes: (a) shows the current situation and (b) shows what would happen if the island was present. The white regions represent the areas that are not flooded and the black line shows the shoreline. (adapted from Otero et al. 2014)

Tsunami hazard in this region is both high and likely, and the team show that rebuilding the island would be a worthwhile engineering effort if the government hopes to afford the area the same protection it had in ’79 in the future. Elongating the island would increase its protective potential even further, as would reshaping the it to form three similarly shaped barriers to cut the energy transferred to the Columbian coastline beyond.

Otero’s tsunami model showed such engineering would offer tremendous protection to Tumaco and the other inhabitants of the Mira River Delta in the event of a tsunami – particularly one that occurred at high tide. But because Tumaco is such a sizable coastal city, some unprotected areas would remain.

Currently, the government’s focus is on establishing a swift and effective early warning an evacuation strategy, but a barrier island could provide a big boost to the safety of the local population and the security of local infrastructure.

By Sara Mynott, EGU Communications Officer

Reference:

Otero, L. J., Restrepo, J. C., and Gonzalez, M.: Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection, Nat. Hazards Earth Syst. Sci., 14, 1155-1168, 2014.

Imaggeo on Mondays: Shaken, not stirred – sediment shows signs of past earthquakes

23 Jun

Nore Praet, a PhD student from Ghent University in Belgium, brings us this week’s Imaggeo on Mondays. She sets the scene for an investigation into past earthquakes and explains how peering through a lake’s icy surface and its murky waters, and into the sediment below can help scientists find out more about the impact of earthquakes in the future…

Early this year, I set off with a group of scientists (including Koen De Rycker, Maarten Van Daele and Philipp Kempf) from the Renard Centre of Marine Geology to conduct fieldwork in South-Central Alaska. The reason for our stay was the search for past megathrust earthquakes (earthquakes produced by the subduction of an oceanic tectonic plate under a continental plate), which had an unusually high magnitude and destructive power.

The most recent Alaskan megathrust earthquake was the Great Alaskan Earthquake in 1964, which represents the second largest earthquake ever instrumentally recorded (9.2 on the moment magnitude scale). In order to have an estimate when such a large earthquake may strike again, we need to study the recurrence pattern of past earthquakes. Since megathrust earthquakes typically have recurrence periods of several centuries, historical archives will not suffice. This is where natural archives, like lake sediments, come in. These records have the advantage of going much further back in time, and they are what brought us to Alaska’s Eklutna Lake.

Zooming in on some individual ice crystal aggregates (few centimeters across) and geometric frost patterns on the frozen surface of Eklutna Lake in Southern Alaska. (Credit: Nore Praet via imaggeo.egu.eu)

Zooming in on individual ice crystal aggregates (few centimeters across) and geometric frost patterns on the frozen surface of Eklutna Lake, Alaska. (Credit: Nore Praet via imaggeo.egu.eu)

Lake sediments can contain very distinct earthquake traces because seismic shaking produces underwater landslides that leave well-defined sediment deposits in the lake basin.

Long sediment cores, extending some 15 metres through these deposits, make it possible to construct a palaeoseismic record. From this we can make an estimate of the recurrence rate of megathrust earthquakes. This will be crucial for understanding seismic hazard in South-Central Alaska and, in particular, in the densely populated city of Anchorage.

This photo, taken in early February, captured the moment where we officially started the fieldwork, after checking the thickness of the ice and its stability.

The constant struggle with the almighty Alaskan cryosphere was the real common theme during the fieldwork. The freezing cold, together with ice formation on the coring equipment, seriously hampered the efficiency of the coring operation. It took some time to accept these conditions and adjust to the demanding laws of this harsh wilderness, but once you are willing to invest the energy into working here, every day nature surprises you with her astonishing beauty.

By Nore Praet, Ghent University

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

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