SM
Seismology

Laura Ermert

Laura is a PhD student at ETH Zürich in Switzerland. She is working on ambient noise source inversion with cross-correlation techniques. Her goal on the blog is to showcase PhD students' and young researchers' results, as well as recent seismological highlights. You can reach Laura at lermert att student.ethz.ch.

Harsher than reviewer 2?

Harsher than reviewer 2?

Have you ever wanted a reviewer who really tells it how it is? You should consider submitting a paper to the truly special publication ‘Frontiers for young minds’.

Frontiers for young minds  is a journal for students between ages 8 and 15 that are curious and passionate about science. However, what’s truly special about this journal is that it is also reviewed by students of the same age, assisted by a science mentor. The journal aims to communicate cutting edge science to young readers in a way that they find both understandable and interesting. Therefore, kids and teenage “young reviewers” are called upon to make sure that complex terms are explained or weeded out, basics are introduced at the beginning, and also that the article is an exciting read.

In going through this process, the young reviewers are supposed to learn about science and the process of peer review, while the scientists who wrote the article receive feedback about their science communication skills and how much their science appeals to an open-minded lay public. At the same time, the journal is building up a collection of texts that can be used by science teachers and interested lay persons – and that are hopefully more exciting and up-to-date than many schoolbooks can ever aim to be. Many reviews are actually performed by school classes who work on it together as a project.

The first articles were published in 2014; the journal is open-access and financially supported by the Jacobs foundation. This enables the journal to make submissions free for authors. Articles are subdivided into thematic groups. “Core concept” articles lay the foundation for young readers to understand the more current contributions, or “new discoveries”, based on recently published papers.

The journal for kids is the junior branch of a “grown up” series of open access journals called Frontiers. Frontiers is itself a young publication series, having started out in 2007. While several frontiers journals such as Frontiers in Neuroscience are widely known and highly ranked among the open access journals of their respective fields, Frontiers in Earth Science, which started out in 2013, has published only about 250 articles so far, and has yet to be assigned an impact factor. Thus, it is not surprising that most articles featured in Frontiers for young minds come from the fields of neuroscience and other medical research fields. Still, the section ‘Understanding the Earth and its resources’ features articles relating to geoscience, in particular environmental science. Who knows who will write and review the first contribution in seismology?

While the idea behind the journal is great – imagine how excited you would have been as a kid if the editor of National Geographic wrote to you to ask your opinion on the latest article about Polar Bears? – it obviously also provides a convenient platform for Frontiers to raise their visibility with a new generation of authors and/or their scientist parents. An open question for me is how well the young reviewers are made aware that peer review is not only a process that should embellish the language of articles and make them more readable, but is most importantly an instrument of critical and sometimes fierce scientific debate. It does not become quite clear either whether the young editors are granted the power to flatly reject a submission if they do not like it!

What is certain, though, is that school kids make the perfect reviewers. A blog associated to the publication lets us read some of the young reviewers’ comments on submitted manuscripts. While some politely draw attention to the fact that basic experimental procedures are undocumented –

“It would be helpful if they told us how they took the measurement of brains without actually having to remove the brain.”

others find more direct words about the quality of the manuscript:

“This seems important, but the way it is written is so boring I can’t even get to the end.”

Wouldn’t you have liked to write that under one review or the other…

We are excited to see who will be the first seismologist to brave the harsh review of a classroom full of nine-year-olds! You can have a look at the author guidelines here. Good luck! And let us know if you get published.


Edited by ECS representatives Laura Ermert and Matthew Agius.

Paper of the month — Signal apparition for wavefield separation

Paper of the month — Signal apparition for wavefield separation

Our paper of the month is  “Signal apparition for simultaneous source wavefield separation” (J. Robertsson et al., 2016) commented by Andreas Fichtner.

Andreas Fichtner is Assistant Professor for Computational Seismology at the Swiss Federal Institute of Technology (ETH) in Zurich. He received his PhD from the University of Munich for his work on Full Seismic Waveform Inversion for Structural and Source Parameters. During his postdoc at Utrecht University, Andreas worked on the development of resolution analysis and multi-scale methods for seismic waveform inversion.

His research interests include the development and application of methods for full seismic waveform inversion, resolution analysis in tomography, earthquake source inversion, seismic interferometry, and inverse theory. For his work, Andreas received the Keiiti Aki Award 2011 from the American Geophysical Union and the Early Career Scientist Award from the International Union of Geodesy and Geophysics.

In his paper of the month post, Andreas will present us a recently published paper by Robertsson et al. that describes a new approach to the magical art of source separation – or how to disentangle seismic signals from sources that acted at the same time!  Sounds impossible? Not for an exploration geophysicist!


“One of the most longstanding problems in exploration geophysics is the separation of two wavefields emitted by two different sources. Just imagine, for instance, that two sources are fired, emitting wavefields g(t) and h(t). A receiver records the sum of the wavefields, f(t)=g(t)+h(t). If one could separate g(t) and f(t) from their sum, the time needed for seismic acquisition could be reduced by 50 % because two sources could be fired simultaneously. This is just one of many possible applications of wavefield separation.

While most previous research on wavefield separation focused on temporal encoding of sources, Robertsson and co-workers introduce an entirely new concept that is wonderfully simple and elegant.

They start with the well-known observation that the f-k spectrum for a line of sources recorded at one receiver is restricted to a signal cone bounded by the slowest propagation speed of the medium, e.g. the propagation speed of water in a marine experiment. Thus, most of the f-k domain is empty.

Now you do a little modification to the experiment. Instead of firing all sources along the line in exactly the same way – as is usually done – all odd-numbered sources are fired with some freely chosen modified source signature, such as a filter. Magically, the signal from this modified subset of sources appears in the previously empty part of the f-k domain. From there it can be extracted without any pollution by the even-numbered sources. This ‘becoming visible’ of a wavefield is referred to as ‘signal apparition’ by the authors of the paper.

johansson_modified

While the authors limit their examples to seismic acquisition along a 2D line, many other applications could be envisioned. They include, for instance, the numerical forward simulation of seismic waves from a large number of earthquakes, as needed in waveform tomography.

I chose this paper not only because it offers a solution to a problem that has been studied for a long time, but also because of its beautiful simplicity. The approach works without any assumptions and does not require more than basic Fourier analysis to be fully understood.”


Reference: Robertsson, J. O., Amundsen, L., & Pedersen, Å. S. (2016). Signal apparition for simultaneous source wavefield separation. Geophysical Journal International206(2), 1301-1305.

Do you have questions, suggestions or comments? Please use the space below, or contact us on Facebook or Twitter @EGU_Seismo!

Are you an experienced seismologists and you want to be our next PoM author? Contact us at sm-ecs @ egu.eu

Edited by ECS representatives Laura Ermert, Matthew Agius, Lucia Gualtieri and Laura Parisi.

First Earthquakes, past and future

First Earthquakes, past and future

What was your first experience of an earthquake? Was it scary? Weird? Confusing?
The first earthquake I have consciously noticed was a magnitude 4.something on a small fault zone not far from my home town. The wave that shook our terraced house felt like a short burst of pressure, making me briefly worry, but then laugh as it prompted my mother to shout “Stop jumping off the wardrobe!” in a general upstairs direction. I didn’t figure out until hours later that an earthquake was what had happened.

I was reminded of that when recently arriving in Japan, probably a place of many ‘first earthquake’ experiences. Friends and colleagues got all giddy with “I felt a shaking last night!”. After all, there are many seismologists who work on earthquakes every day, yet have never consciously felt one!

But, being in Japan, we also came to realize what a huge national trauma an event like the 2011 one must mean, and that it is a matter of safety to stay earthquake-aware.

Take me as bad example: Wednesday morning, all sleepy pre-coffee, in my pyjama in a Tokyo hotel room. The building suddenly started shaking very noticeably and I barely had time to think “Wait! What was I supposed to do, again!?” before the motion, luckily, subsided. I don’t know what I was expecting – maybe a friendly border control officer saying “Please take a moment to visit our foreign visitors’ natural hazards awareness training room!”? But as it was, I came embarrassingly unprepared despite my previous earthquake experiences and stays in earthquake-prone regions. I thought, “I wouldn’t even recognize an early warning if I heard it on the radio.”

Another bad example! At xkcd.com.

Thus, today, I’d like to draw your attention to past and future first earthquake experiences! If anticipation is the way to prepare, then remembering is the way to refresh. Coming back to my first question – what was your first earthquake experience? We hope that some of you will share an earthquake story with us, in the comments or on facebook, be it confusing, sad or goofy.


And as a way to prepare: The Japan Meteorological Agency provides these informational videos. Of course, few countries operate elaborate early warning systems, but some of the information is generally useful.

MyShake – your phone as a seismic station

MyShake – your phone as a seismic station

Are you on Facebook or Twitter? Do you use Whatsapp regularly to communicate with friends and loved ones scattered across the globe or even just across the city? I’d be surprised if you answer ‘no’ to all of these questions. In fact, why not admit that you are just as addicted to that smartphone of yours as I am to mine? Being a seismologist, you might have played with one of the various ‘seismometer’ apps, placing your phone flat on its back and watching the accelerometer reading jump into cute little jiggles as you tapped on the table beside it.

 

These apps seemed of little more than educational use, but this could drastically change thanks to several research groups in California.  MyShake, developed by Qingkai Kong and colleagues at Seismolab of UC Berkeley, is available from Google play for Android phones since February. This app has the ambitious aim of turning all those accelerometers riding our pockets into a very densely instrumented Early Warning network. The app functions as data collector: once it is installed, your phone will report event triggerings and even event waveforms to a datacenter that evaluates the recordings from a crowd of phones concertedly. Seismology goes big data.

The perks you can imagine: While few areas of the world have densely instrumented seismic networks that broadcast data in real time, smartphones are present almost anywhere and their numbers are on the rise. Thus, the hope of the developers of MyShake is to complement existing networks with more data, but also to bring Earthquake Early warning to many more regions of the world.

In the future, existing EEW systems that use traditional seismic and geodetic networks could benefit from MyShake just as MyShake could benefit from integration of data from traditional networks. […] Finally, and perhaps most importantly, MyShake could deliver alerts in regions that have little in the way of traditional seismic networks. [1]

Of course, phone accelerometers are cheaper and lower quality than those used in seismic stations, meaning that they have a much higher noise level. Also, you may be wondering, what if I am out for a walk with my pet kangaroo when the Earthquake happens, with my phone tucked away in its pouch? This is where the capabilities of artificial intelligence, and the power of crowdsourcing come in. An artificial neural network within the MyShake app itself distinguishes a P-Wave from your favorite Samba move and other non-Earthquake signals on the basis of three continuously monitored triggering parameters. Once an event is triggered, the phone communicates these parameters to a data center, where they are evaluated in conjunction with triggers from other phones. If many phones report triggers in a seismic wave-like pattern, the algorithm will continuously update the Earthquake origin and try to infer the magnitude. Otherwise, your phone’s report will be quietly filed as “Ah, that guy with the marsupial again.” (Just kidding.)

What challenges are there? One is power consumption: As you can imagine, when the MyShake app continuously checks accelerometer readings, this does similar things to your battery as you continuously checking your twitter feed. The developers are working on this topic and assure on their website that power consumption should not drain your battery extraordinarily fast. What that means remains a little bit hazy.

Another issue is coupling versus sliding: In shaking-table experiments, smartphones lying on the tabletop started sliding at higher accelerations and frequencies, causing a magnitude saturation of the measurements. This is where the smartphone network could tremendously benefit from added information by ‘real’ seismic stations.

Are there privacy issues? I was wondering as I read about MyShake. After all, given an accelerometer taped to your body for large parts of the day, one may easily derive whether you are likely sleeping, running for a bus, or putting on those Samba moves (This has been quite successfully tried on rodents, although they weren’t caught dancing Samba). However, MyShake reports only when triggered. Thus, waveform data should only be transmitted for very short amounts of time, during which you should presumably have paused any activity to wonder whether to take to the nearest door frame.

What the project will benefit from is contributing smartphone users. After receiving widespread media coverage when released (e.g., BBC reported) 170,000 users have already downloaded MyShake to their phones. One especially exciting moment for the MyShake project must have been when a smartphone-seismic record section was produced from the Borrego Springs Earthquake.

This, I must admit, was also what caught my attention for the MyShake app: When I first saw that record section plot appear, guess where … on twitter.


Interested in becoming a crowdsource seismic station? If you want to help improve MyShake, this is your chance of doing so by installing the App if you own an android device. It is a small investment as your phone will have to be charged a little bit more frequently, but it might turn out to be a truly valuable contribution to Early Warning. Think about it!

Interested in other Crowdsourced Earthquake Detection Networks? The seismologists of the world want to turn you into an earthquake detector [2].

References
[1] Kong, Q., Allen, R. M., Schreier, L., & Kwon, Y. W. (2016). MyShake: A smartphone seismic network for earthquake early warning and beyond. Science advances, 2(2), e1501055.
[2] Deatrick, E. (2016), Crowdsourced seismology, Eos, 97, doi:10.1029/2016EO051335. Published on 26 April 2016.

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