Tarje Nissen-Meyer

I (he/him) am a geophysicist at the Department of Earth Sciences, and a Fellow of Wolfson College, University of Oxford. Research-wise, I’m primarily interested in wave phenomena, as related to earthquakes and other sources, planetary interiors, numerical methods and machine learning. My group is (and always strives to become more) diverse in gender, academic, ethnic, and geographic backgrounds, and in our research themes ranging from the Earth’s deep interior, elephants, nuclear monitoring, Mars to ocean noise. Do these themes sound a bit bizarre, otherworldly or inaccessible but still spark your curiosity? Let’s talk about it some more! I am keen to share the passion for our science with an ever broader audience and range of (potential) students. Especially as a global geophysicist and human being, I collaborate beyond any geographical, cultural, political borders and warmly welcome interest from any background and place on this pristine planet that we strive to understand and protect.

My research is concerned with understanding, modeling, deciphering and infering from waves. Why? Well, as the most efficient mode of information transfer for most physical systems anywhere between the big bang and bats, propagating waves vibrate the Earth, oceans and atmosphere constantly across vast ranges of scales, and carry unique information about their origin and traveled path. How does the Earth’s core interact with its overlain mantle? Where to subducted slabs end up? What’s inside Mars? Do elephants use seismic waves to actively communicate? Can we reliably distinguish nuclear explosions in the presence of topography? Can seismology help in monitoring Antarctic ice depletion? Can deep learning/artificial intelligence replace conventional numerical methods for wave propagation, for instance for seismic hazard assessment? To address such questions, we work on novel techniques for modeling realistic wave propagation to address fundamental questions on Earth’s interior between sedimentary basins and the core, from Mars to icy worlds, from earthquakes to elephants, nuclear monitoring to earthquake hazard and ocean storms. We have developed the axisymmetric spectral-element method AxiSEM, as well as AxiSEM-based database methods instaseis and syngine, and the link to seismic tomography via MCKernel. These methods are used in research and teaching around the world. More recently, we (mostly Kuangdai Leng) introduced AxiSEM3D, a comprehensive, modern method to solve wave propagation very efficiently by exploiting wavefield smoothness, and can be applied to a range of complexities (asteroids, Mars, bathymetric oceans, deep mantle, tomography, exploration geophysics). We also embark on physics-informed deep learning for wave propagation and inversion, and on hybrid modeling as well as first-order scattering methods. Each method has a realm and limit of validity, and is thus tailored for specific applications. Altogether, our methodological portfolio can address many applications in seismology and related disciplines.

Wavefield simulation with AxiSEM3D by Kuangdai Leng

A particular research focal point has been the core-mantle boundary region: its multi-scale structures are crucial to determine Earth’s heat budget, core dynamics and tectonics. We illuminate this remote region from various angles using waveform tomography, high-resolution 3D modeling, modern signal processing and Bayesian inference. Further projects exist on the nature of seismic scattering regimes and wavefield complexity, global tomography, seismic hazard assessment, elephant communication through seismic waves, ocean-noise generation, nuclear monitoring, scattering on Mars and Moon. My research is fundamentally cross-disciplinary, and directly connected with aspects of geophysics, applied mathematics, machine learning, continuum mechanics, optics, signal processing, Bayesian statistics, zoology, medical imaging, optimisation theory, civil engineering, high-performance computing, complexity theory, psychology, as well as with exploration, re-insurance, artificial intelligence (Noble.AI), software and hardware industries, wildlife conservation charities (Save the Elephants) and (inter-)government agencies such as the CTBTO.

I’d be a disconnected puzzle piece if it weren’t for the joy to collaborate with students and postdocs, as well as many colleagues, groups and institutions around the world. My research projects are mostly funded by Oxford University, NERC, ARCHER supercomputer, STFC, and a donation, but many more research proposals have unfortunately been rejected by some funding agencies too (e.g. ERC, Leverhulme Trust, NERC), on sometimes reasonable, yet sometimes bizarre grounds (if any are given!). I am a proponent of reproducibility and transparency in scientific output, open {access, data, software, science} where reasonable, and open communication on decision-making and judgment in scientific communities to reduce any prevailing bias. I’m conversely skeptical about the usability, objectivity or quantifiability underlying some metrics used in academia to judge peers, proposals and (to a lesser extent) papers, such as citation metrics, the (impossible?) task of judging content filtered through a linguistic lense. I act as topical editor of open-access journal Solid Earth. If you need a copy of any of my publications and can’t find them online without paywall, please contact me.

Teaching. At Oxford, I regularly teach third-year undergraduates in Vector Calculus and Quantitative Seismology, 4th-years in Plate Tectonics & Mantle Convection, and incoming students in Earthquakes and Seismology (as part of the course Planet Earth). Previously I taught Mathematics for Materials anesed Earth Sciences at Oxford, and Seismology of the spherical Earth at ETH. I have also taught various lectures, workshops, shortcourses and tutorials in Denmark, Italy, Germany, France, Japan, Russia and USA, mostly at postgraduate research level (e.g. on numerical methods, inverse theory, Earth imaging, wavefields and scattering).

Want to join/collaborate/communicate with us? Please read on before getting in touch.

I warmly welcome interest in collaborations or joining our group. Funding for positions unfortunately does not exist by default unless announced here, but various routes for finding financial support can be discussed. Please note that we do not offer any (un)funded summer internships. Researchers in our discipline gain a strong and diverse background in quantitative seismology, applied mathematics, numerical methods, supercomputing, machine learning, signal processing of noisy data, inverse theory, and multidisciplinary reasoning. I am particularly keen on diversifying Earth sciences, and especially welcome interest from colleagues from underrepresented groups and locations around the planet. Oxford and academia at large might well seem like scary, pompous places… but as we’re all made of the same molecules, please don’t hesitate to get in touch.

Postdocs: It is wise to plan a postdoctoral stint at least one year prior to any intended start date, as the process of finding financial support and entry visa can be lengthy. If no particular project is announced here or on mailing lists, the best routes for funding postdoctoral positions are: Junior Research Fellowships at Oxford Colleges, Royal Society, NERC/EPSRC/STFC independent fellowships, EU schemes such as Marie Skłodowska-Curie, or researcher exchange schemes (e.g. SNF/Switzerland, DFG/Germany, NSF/USA, CSC/China). Please get in touch if interested, and peruse the various deadlines well in advance.

PhD students: Interested students should possess a strong background in applied mathematics, (geo)physics, engineering or computer science, combined with some experience in programming (C++, Python, Fortran90) and enthusiasm, curiosity, drive and passion to delve into quantitative Earth Sciences and fundamental research in general. Oxford PhD (entitled “DPhil”) admissions are centralised through graduate admissions with a deadline each January to start in October. A number of funded PhD positions exist every year through the Doctoral Training Programme in Environmental Sciences; please get in touch well before the deadline if you are interested in applying to this scheme to work with me. If we have other sources of funding available, they will be announced below. Note that, very unfortunately and frustratingly, for applicants from outside of UK/EU there are only limited and thus very competitive opportunities (such as the Clarendon fellowship) available at this time to cover international postgraduate student tuitions. It is therefore always suggested to consider exernal funding for PhD applicants from abroad (which now sadly includes applicants from the EU).

Available PhD projects (all of these can be done from within the DTP):

1. Seismic and multi-modal information transfer by savanna wildlife
2. other topics (seismic hazard, numerical methods, inverse theory) can be discussed

Media relations & outreach: Communicating science, uncertainties and evidence-based factual reasoning to public and decision-making bodies are of utmost importance for resolving societies’ most complex and urgent problems, ever more so in times of divisive populism. In this vein and aware of the privilege and luck of being an academic in such venerable institutions as Oxford, I very much enjoy interactions with non-specialists (without claiming much skill in communication), including primary/secondary schools (especially in deprived areas), public lectures (such as our TEDWomen talk), and media interviews. Please do get in touch if you believe I can provide any useful insight based on my experiences as described on these pages. For media publications, I insist on having sufficient time (e.g. a few days) to give a response, and to have a glance at the final version before publication due to negative experiences with quotes being taken out of context or wrongly attributed.

Media coverage (not always precisely correct nor reflecting my view!): BBC, BBC Newsbeat, New York Times, BBC Swahili, Science Friday, Reuters, National Geographic, NatGeo Romania, Le Monde, CBC (Quirks and Quarks), RTE (Mooney goes wild), Physics World, Wissenschaft.de, AAAS / EurekAlert!, EOS, Kopalnia Wiedzy, Česká Televize (Věda 24), Tekniikan Maailma, Financial Express (Bangladesh), Kenya Elephant Forum, ZME Science, EuropaPress (Espanol), Swara East Africa, Daily Express

Group:
Group webpage
Oxford seismology youtube channel

Our open-source methods (please get in touch if interested in other methods):
AxiSEM (also on CIG ): Axisymmestric spectral element method for global wave propagation
Instaseis: instantaneous seismograms from precomputed AxiSEM databases
Syngine : Instaseis-based web interface at IRIS for a number of available 1D Earth models
AxiSEM3D: Novel and very fast solver for 3D wave propagation in solid-fluid, anisotropic, viscoelastic 3D media with undulating interfaces & topography, for global or truncated domains

My whereabouts (click here for curriculum vitae, June 2020):
2020…………. Cox Visiting Professor (sabbatical), Dept of Geophysics, Stanford University, USA
2013-………… Associate Professor of Geophysics, Fellow at Wolfson College, University of Oxford, UK
2013-………… Adjunct Scientist, Lamont-Doherty Observatory, Columbia University, USA
2010-2013…. Senior research scientist, ETH Zurich, Switzerland
2008-2010… Postdoctoral Research Associate, Princeton University, USA
2007-2008… Postdoctoral Scholar in Geophysics, California Institute of Technology, USA
2007…………. Ph.D., Princeton University, USA
2001………….. M.Sc & B.Sc. (“Diplom”), Ludwig-Maximilians-University, Germany
1999………….. Visiting student, McGill University, Canada