Mastodawn

EGU Geodynamics Division Apr 14, 2023

This week, Professor Monica Sanders discusses the need for democratising climate information 🌍

https://blogs.egu.eu/divisions/gd/2023/04/12/democratising-climate-information/

Democratising Climate Information

How can we ensure a greener and more equitable future for everyone in the forthcoming years? In this week’s blog, Professor Monica Sanders from Georgetown University and Tulane University shares her thoughts on how and why we need to democratise climate information towards the general public and primarily to the divested communities that are being impacted the most by this global climate crisis. Climate change is an existential threat that has been affecting the planet for several years, and its impacts have only intensified in recent times. The adverse effects of climate change are felt by everyone, but it is the divested communities in low-income countries who are most vulnerable to its effects. These communities often lack the necessary resources and access to information to adequately address and adapt to climate change. Therefore, democratising climate change information is crucial to ensure that everyone, including those in low-income countries, has access to the knowledge needed to mitigate and adapt to the effects of climate change. Firstly, democratising climate change information is essential because it empowers divested communities in low-income countries to take necessary action against climate change. These communities are most vulnerable to climate change’s impacts, including rising sea levels, extreme weather events, and prolonged droughts, among others. Yet, they often lack the necessary information and resources to adapt to these changes. When these communities have access to climate change information, they can better understand the changes taking place, assess their vulnerability, and identify ways to mitigate the risks. For example, farmers in low-income countries can use weather forecasts to plan their crop cycles and mitigate losses due to drought or floods. Figure 1: Post-hurricane destruction in Puerto Rico (photo: Monica Sanders). Secondly, democratising climate change information helps to address the global climate crisis. Climate change is a global phenomenon that affects everyone on the planet, regardless of their location or economic status. Therefore, it is critical that everyone has access to accurate and up-to-date climate change information. For instance, climate change mitigation efforts such as reducing greenhouse gas emissions and investing in renewable energy sources require collective action from individuals, businesses, and governments worldwide. With access to climate change information, individuals and communities can take action and demand accountability from their governments and businesses to mitigate climate change’s effects. Thirdly, democratising climate change information promotes social justice and equity. In many cases, divested communities in low-income countries are the most affected by climate change but have the least access to information and resources to address it. This creates social injustice and perpetuates the cycle of poverty and vulnerability. By democratising climate change information, we can bridge the gap between those who have access to the necessary resources and those who do not. This helps to ensure that everyone, regardless of their economic status or location, has access to the information and resources needed to mitigate and adapt to climate change. Figure 2: A young man in Baltimore stabilising a WIFI node by himself (photo: Monica Sanders). Furthermore, democratising climate change information can contribute to sustainable development. Sustainable development is the concept of meeting the present needs of society without compromising the ability of future generations to meet their own needs. Democratising climate change information is a crucial step towards achieving sustainable development goals. By providing access to climate change information, we can encourage individuals and communities to adopt sustainable practices and lifestyles, such as investing in renewable energy sources, reducing waste, and conserving natural resources. This, in turn, can contribute to sustainable economic growth and development. In conclusion, democratising climate change information is essential to ensure that everyone, including divested communities in low-income countries, has access to the information needed to mitigate and adapt to climate change’s effects. By democratising climate change information, we can empower individuals and communities to take necessary action against climate change, address the global climate crisis, promote social justice and equity, and contribute to sustainable development. Governments, businesses, and civil society organisations all have a role to play in democratising climate change information. They can do this by investing in climate change education programmes, ensuring access to climate change information and data, and supporting the development of technologies that facilitate the sharing of climate change information. Ultimately, democratising climate change information is a crucial step towards building a sustainable and equitable future for all. References Butler, K. A., Jackson, L. A., Kruk, M. C., Merati, N., & Vance, T. C. (2022, December 15). Editorial: Democratising data: Environmental data access and its future. Frontiers. Retrieved March 9, 2023, from https://www.frontiersin.org/articles/10.3389/fclim.2022.1081021/full Falcon, E. (2021, January 12). The FCC and states must ban digital redlining. Electronic Frontier Foundation. Retrieved March 9, 2023, from https://www.eff.org/deeplinks/2021/01/fcc-and-states-must-ban-digital-redlining National Academies of Sciences, Engineering, and Medicine. 2021. Motivating Local Climate Adaptation and Strengthening Resilience: Making Local Data Trusted, Useful, and Used. Washington, DC: The National Academies Press. https://doi.org/10.17226/26261. Sanders, M. C. (2023, February 28). Using a digital justice framework to improve disaster preparation and response. Day One Project. Retrieved March 9, 2023, from https://www.dayoneproject.org/ideas/using-a-digital-justice-framework-to-improve-disaster-preparation-and-response/#footnotes

Geodynamics

EGU Geodynamics Division Apr 11, 2023

EGU23 is fast approaching! Make the most of the conference by attending the networking events organized by the Geodynamics Division:

https://blogs.egu.eu/divisions/gd/2023/04/05/the-geodynamics-division-egu23/

The Geodynamics Division @ EGU23

With the EGU General Assembly (GA) less than a month away, it’s time for attendees to start planning their schedule to get the most out of the week. In today’s blog, Geodynamics (GD) Division Early Career Scientist (ECS) representative Megan Holdt highlights the networking events for the GD Division, provides an overview of key events at the GA and gives some tips for first-time attendees. Networking Events: Geodynamics Division What: ECS Pre-GA Icebreaker When: 15:00-16:30 Sunday 23 April Where: Copa Beach This Icebreaker event is designed for Early Career Scientists to meet before the start of the General Assembly. We’ll be meeting at Copa Beach from 3pm . It’s the perfect opportunity to get to know other attendees from the Geodynamics, Seismology and Geodesy Divisions. Bring your own drinks and snacks for a relaxing afternoon on the banks of the Danube. What: Geodynamics ECS Lunch When: 12: 45 – 1 4 :00 Tuesday 2 5 April Where: G Terrace On Tuesday, we’ll have a geodynamics lunch for Early Career Scientists. Bring your lunch and join us on G Terrace. Get to know other ECS researchers within the Geodynamics Division and learn more about the activities of the Geodynamics ECS team. What: Division meeting for Geodynamics When: 12:45-13:45 Wednesday 26 April Where: Room D2 We encourage all geodynamicists to come along to the annual Geodynamics Division meeting. This meeting will provide a summary of this years activities and will also share forward plans. This is the primary forum for the geodynamics community to share their thoughts and ideas on the direction of our division. Lunch will be provided. What: Geodynamics ECS Dinner When: 18:30-20:00 Thursday 27 April Where: G igerl restaurant @ 19:00 ; m eet in front of the conference center @ 18:30 The Geodynamics ECS Dinner is a great opportunity to connect with other geodynamicists from across the world. We’ll meet in front of t he conference center at 18:30 and make our way to Gigerl restaurant . It is essential to sign-up to this dinner as pl aces are limited. To attend, register via this form. Geodynamics Award Lectures The Augustus Love Medal Lecture by Thorsten W. Becker & GD Division Outstanding ECS Award Lecture by Ágnes Király will be hel d on Monday 24 Apr, 19:00–20:00 (CEST). Ágnes Király will present on “ Mantle flow around subduction zones: evolution through time ” while Thorsten Becker will present “ On convective memory. ” Great Debates Great Debates have been a regular feature of the EGU programme since 2005. These forums provide an opportunity to tackle a topical issue in a lively and entertaining format. This year, the Great Debate include: GDB5 – Is social media outreach? Mon, 24 April, 14:00 – 15:45 (CEST) GDB2 – As climate change impacts accelerate, are we sleepwalking into the inferno…? Mon, 24 April, 16:15 – 18:00 (CEST) GDB3 – The Science activist: should science get Political? Tue, 25 April, 10:45 – 12:30 (CEST) GDB6 – Open access publishing: national strategies, challenges and solutions Thu, 27 April, 8:30 – 10:15 (CEST) GDB4 – Scientific Neocolonialism: tools and mechanisms to advocate and amplify the voices, knowledge and recognition of local knowledge in geoscience research – Thu, 27 Apr, 08:30–10:15 (CEST) GDB1 – The thrills and dangers of extending human impact beyond our planetary boundaries Thu, 27 Apr, 14:00–15:45 (CEST) Short Courses EGU23 will host over 50 short courses throughout the duration of the GA. Aimed at providing an interactive forum for participants, these short courses cover many topics and offer something for everyone: Expand your knowledge of other disciplines ( Geodesy 101, Geology 101, Seismology 101, Geodynamics 101: Numerical modelling). Improve your communication skills ( ‘How do I make my geoscience communication publishable? – A drop-in ‘clinic’ with the Geoscience Communication editors, Creative collaboration: working with artists to communicate science ). Develop your networking skills ( How to build and grow your scientific network ). For a complete list of all short courses, visit the EGU website. First time attendees: making the most of EGU23 If this is your first EGU, consider signing up to the Mentoring Programme. This programme is specifically designed to help first-time conference attendees and assists them with developing connections with other researchers. To participate, register by 7 April 2023. Another helpful resource is the Short Course SC1.1 How to navigate EGU: tips and tricks. Scheduled on Monday morning, this course will share advice on how to make the most of EGU. Finally, before you arrive, take some time to review the scientific programme and plan which presentations, short courses and networking events you would like to attend. The communications team recently released a blog focusing on creating your own personal program to schedule the week. Share your EGU23 experience The official hashtag for Geodynamics Division at the GA is # EGU23_GD. If you tag the GD twitter (@EGU_GD) in your tweet, your content will be shared with the community.

Geodynamics

EGU Geodynamics Division Mar 29, 2023

Wednesday is #blogday for the Geodynamics Division 🙌 In this week's #EGUblog, Dr. Nevena Andrić-Tomašević and Dr. Alexander Koptev share their exciting research on the dynamics of subducting plates. Check out their research below 👇

https://blogs.egu.eu/divisions/gd/2023/03/29/how-does-slab-tearing-evolve/

How does slab tearing evolve?

TT Prof. Dr. Nevena Andrić-Tomašević, Institute of Applied Geosciences, Karlsruhe Institute of Technology (KIT), Germany Slab tearing refers to the gradual propagation of the break-off of a subducting plate. As observed in numerous modern and ancient convergent tectonic settings, the growth of the tear “window” in the downgoing plate has strongly influenced various geologic and geodynamic processes, such as depocenter migration of foreland basins, uplift rates in mountain ranges, earthquakes, volcanism, and flow patterns in the upper mantle. However, our understanding of the dynamics of slab break-off and tearing, especially in non-collisional environments, is still limited. This week, Nevena Andrić-Tomašević, Tenure-track Professor at the Institute of Applied Geosciences, Karlsruhe Institute of Technology (KIT), and Alexander Koptev, a postdoctoral researcher at the German Research Centre for Geosciences (GFZ Potsdam), report on their recent work on slab tearing in the context of oblique oceanic subduction. ( Andrić-Tomašević et al., 2023). The concept of slab tearing emerged several decades ago from seismic topography models of the 3D velocity structure of the upper mantle in the Mediterranean-Carpathian region as an explanation for detached fragments of subducting plate in the upper and lower mantle (Spakman, 1990; Wortel and Spakman, 1992, 2000; Hafkenscheid et al., 2006). The slab tearing is thus considered as lateral or vertical propagation of rupture in the subducting slab, producing a gap (or “window”) in the downgoing lithosphere whose gradual growth (or “opening”) significantly affects mantle flow patterns (e.g., Govers and Wortel, 2005; Duretz et al., 2014). Other consequences include thermal perturbations, anomalous magmatic activity, acceleration of trench retreat and rotation, and extension within overriding plate (e.g., Rosenbaum et al., 2008; Burkett and Billen, 2010; Menant et al., 2016). Dr. Alexander Koptev, postdoctoral researcher at the German Research Centre for Geosciences (GFZ Potsdam) The first 3D thermo-mechanical models of slab break-off (Burkett and Billen, 2010; van Hunen and Allen, 2011) have demonstrated that in the case of a laterally symmetric and homogeneous subducting plate, detachment occurs almost simultaneously along the entire length of the slab. In contrast, the presence of lateral heterogeneities in the incoming subducting plate (mid-ocean ridges or continental blocks) leads to horizontally propagating rupture of the slab (or slab tearing). Inspired by these findings, subsequent modelling studies (Li et al., 2013; Duretz et al., 2014; Sternai et al., 2014; Menant et al., 2016) explored the dynamics of the continental corner (i.e., the lateral transition between continents and oceans) during simultaneous oceanic subduction and continental collision and showed that the subducting plate first detaches beneath the collided continents and then propagates toward the adjacent region of continuous ocean-continent subduction. Combined with geodynamic and geologic data and reconstructions, numerical modelling has revealed that heterogeneities within the incoming oceanic lithosphere, such as along strike variable slab ages, asymmetric mantle flow in oblique subduction settings or the arrival of terranes (e.g., oceanic plateaus, island arcs, seamounts, submarine ridges, continental fragments), can not only result in variable roll-back velocities along the active margin (e.g., Balazs et al., 2021) but also appear to be the main factor controlling the process of slab tearing (e.g., Rosenbaum et al., 2008). Although tomographic imaging has captured slab tearing in numerous subduction zones worldwide, such as Izu-Bonin-Marianas (Stern et al., 2004; Miller et al., 2006; Zhang et al., 2019), Tonga (Bevis et al., 1995; Martin, 2014), Mexico (Rogers et al., 2002), and Sunda (Curray, 1989; Widiyantoro and van der Hilst, 1996), the process of slab rupture has not yet been investigated in non-collisional settings with continuous ocean-continent or ocean-ocean subduction. Here, we focus our modeling study on examining the effects of subduction obliquity on the dynamics of slab break-off and tearing. To do so, we have performed a series of 3D thermo-mechanical experiments for oblique subduction (i.e., subduction where the convergence vector and trench are not perpendicular to each other) using the viscous-plastic code I3ELVIS (Gerya and Yuen, 2007; Gerya, 2019). In our work, we analyzed the impact of three key parameters: (1) subduction obliquity angle, (2) age of the oceanic slab, and (3) partitioning of boundary velocities (i.e., the ratio between subduction component and overriding plate advance in the overall convergence). In our simulations, we find that as the subducting slab retreats, the fore-arc and back-arc lithosphere becomes thinner because the hot asthenosphere rises from the underlying mantle wedge, decoupling the overriding plate from the subducting slab. As a result of the initial obliquity of the active plate margin, the velocity of the slab roll-back varies progressively along the trench. Coevally with the gradual rotation of the trench, the decoupling front between the overriding and downgoing plates, along with predicted magmatic activity and topographic uplift, migrates in a horizontal direction. Figure. 1) Compositional field of the initial model setup with oblique subduction. Both cross (left panel) and plan views (right panel) are shown. 2) The breakoff initiates first in the back side of the model domain and propagates (i.e., tearing) towards frontal side. The tearing is associated with differential trench retreat velocities causing counter clockwise trench rotation. 3) 3D configuration of the subducting plate showing the slab window resulting from progressive horizontal tear propagation transforming into vertical tearing. Our models indicate that in subduction zones with low angles of subduction obliquity (< 15◦), relatively old subducting plates (> 50 Ma), and in the absence of the subduction component in the total shortening, slab detachment occurs either simultaneously along the entire length of the subduction zone or not at all. In contrast, with higher subduction obliquity (≥ 15◦), younger slabs (≤ 50 Ma), and in the presence of a boundary push on the oceanic side, the initial slab break-off is followed by the gradual growth of the tear “window” in the direction opposite to the migration path of the previously established plates decoupling. The sharp contrast in trench retreat rates between subduction zone segments affected and unaffected by slab detachment results in the arcuate shape of the trench (Fig. 1. 1-2). Furthermore, the direction of slab tearing may change from horizontal to vertical, eventually leading to the formation of a transform fault on the subducting plate (Fig. 1. 3). In contrast to previous studies (Burkett and Billen, 2010; Li et al., 2013; Cui and Li, 2022), we show for the first time that even with a homogeneous oceanic plate and laterally unchanging constant boundary velocities, the obliquity of the active margin appears to be a sufficient factor to cause horizontal and vertical slab tearing. Remarkably, our results demonstrate striking similarities with several characteristic features, such as trench curvature, subduction zone segmentation, magmatic production, lithospheric stress/deformation fields, and associated topographic changes, observed in many real-world subduction zones (e.g., Marianas, New Hebrides, Mexico, and Calabrian). Therefore, our modelling may provide valuable insights to explain arcuate trench configurations and segmented subduction boundaries on length scales up to 1500 km. In addition, we reveal that horizontal and vertical slab tearing are temporally and spatially coupled processes that represent district phases in the dynamic evolution of the lithosphere-mantle system. References: Andrić-Tomašević, N., Koptev, A., Maiti, G., Gerya, T., & Ehlers, T. A. (2023). Slab tearing in non-collisional settings: Insights from thermo-mechanical modelling of oblique subduction. Earth and Planetary Science Letters, 610. https://doi.org/10.1016/j.epsl.2023.118097 Balázs, A., Faccenna, C., Ueda, K., Funiciello, F., Boutoux, A., Blanc, E.J.-P., Gerya, T., 2021. Oblique subduction and mantle flow control on upper plate deformation: 3D geodynamic modeling. Earth Planet. Sci. Lett. 569, 117056. Bevis, M., et al., 1995. Geodetic observations of very rapid convergence and back-arc extension at the Tonga arc. Nature 374 (6519), 249–251. Burkett, E.R., Billen, M.I., 2010. Three-dimensionality of slab detachment due to ridge-trench collision: laterally simultaneous boudinage versus tear propagation. Geochem. Geophys. Geosyst. 11 (11), Q11012. Cui, Q., Li, Z.H., 2022. Along-strike variation of convergence rate and pre-existing weakness contribute to Indian slab tearing beneath Tibetan Plateau. Geophys. Res. Lett. 49 (4), e2022GL098019. Curray, J.R., 1989. The Sunda Arc: a model for oblique plate convergence. Neth. J. Sea Res. 24 (2–3), 131–140 Duretz, T., Gerya, T.V., Spakman, W., 2014. Slab detachment in laterally varying subduction zones: 3-D numerical modeling. Geophys. Res. Lett. 41, 1951–1956. https://doi.org/10.1002/2014GL059472. Gerya, T., 2019. Introduction to Numerical Geodynamic Modelling, 2nd edition. Cambridge University Press, p. 471 Gerya, T.V., Yuen, D.A., 2007. Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Phys. Earth Planet. Inter. 163 (1–4), 83–105. https://doi.org/10.1016/j.pepi.2007.04.015. Govers, R., Wortel, M.J.R., 2005. Lithosphere tearing at STEP faults: response to edges of subduction zones. Earth Planet. Sci. Lett. 236 (1–2), 505–523. https://doi.org/10.1016/j.epsl.2005.03.022 Hafkenscheid, E., Wortel, M.J.R., Spakman, W., 2006. Subduction history of the Tethyan region derived from seismic tomography and tectonic reconstructions. J. Geophys. Res., Solid Earth 111 (B8), B08401 Li, Z.H., Xu, Z., Gerya, T., Burg, J.P., 2013. Collision of continental corner from 3-D numerical modeling. Earth Planet. Sci. Lett. 380, 98–111. Martin, A.K., 2014. Concave slab out board of the Tonga subduction zone caused by opposite toroidal flows under the North Fiji Basin. Tectonophysics 622, 56–61. Menant, A., Sternai, P., Jolivet, L., Guillou-Frottier, L., Gerya, T., 2016. 3D numerical modeling of mantle flow, crustal dynamics and magma genesis associated with slab roll-back and tearing: the eastern Mediterranean case. Earth Planet. Sci. Lett. 442, 93–107. Miller, M.S., Kennett, B.L.N., Toy, V.G., 2006. Spatial and temporal evolution of the subducting Pacific plate structure along the western Pacific margin. J. Geophys. Res. 111, B02401. https://doi.org/10.1029/2005JB003705 Rogers, R., Karason, H., van der Hilst, R., 2002. Epeirogenic uplift above a detached slab in northern Central America. Geology 30, 1031–1034. Stern, R.J., Fouch, M.J., Klemperer, S.L., 2004. An overview of the Izu-Bonin-Mariana subduction factory. In: Eiler, J. (Ed.), Inside the Subduction Factory. Sternai, P., Jolivet, L., Menant, A., Gerya, T., 2014. Driving the upper plate surface deformation by slab rollback and mantle flow. Earth Planet. Sci. Lett. 405, 110–118. Van Hunen, J., Allen, M.B., 2011. Continental collision and slab break-off: a comparison of 3-D numerical models with observations. Earth Planet. Sci. Lett. 302, 27–37 Widiyantoro, S., van der Hilst, R., 1996. Structure and evolution of lithospheric slab beneath the Sunda arc, Indonesia. Science 271 (5255), 1566–1570. Wortel, M.J.R., Spakman, W., 2000. Geophysics – subduction and slab detachment in the Mediterranean-Carpathian region. Science 290 (5498), 1910–1917. Zhang, H., Wang, F., Myhill, R., et al., 2019. Slab morphology and deformation beneath Izu-Bonin. Nat. Commun. 10, 1310. https://doi.org/10.1038/s41467-019-09279-7.

Geodynamics

EGU Geodynamics Division Feb 24, 2023

Did you know that background vibrations, from sources like ocean waves, can reveal information about Earth's interior? 🌏🌊 In this week's #blog, Rajani Shrestha discusses the ambient seismic wavefield:

https://blogs.egu.eu/divisions/gd/2023/02/23/ambient-seismic-wavefield-how-noise-can-be-a-signal/

Ambient seismic wavefield: how noise can be a signal

Every now and then, the surface of our planet shakes violently during earthquakes like the recent magnitudes 7.8 and 7.5 Kahramanmaraş Earthquake Sequence in Türkiye. These vibrations are recorded by instruments called seismometers and are then processed and analyzed by seismologists to study the earthquake processes themselves as well as other deep Earth structures. Interestingly, seismometers also record vibrations during the relatively “quiet” intervals when we do not have earthquakes. These background vibrations result from a variety of sources including ocean waves and wind. Termed the ambient seismic wavefield, this background noise is very useful to probe the subsurface structure of the Earth at regions with little seismic activity as it helps us venture beyond the limitations of requiring earthquakes at the “right” location (Shapiro et al., 2005). Broadly, ambient seismic noise may be short period (0.1-1 s), intermediate period (1-30 s) or long period (30-500 s) (McNamara & Boaz, 2019). Short period noise is generally cultural and produced due to automobiles or industrial activities. The intermediate period noise consists primarily of the microseisms generated due to oceanic waves and storm swells. The oceanic microseism has two distinct peaks around the periods of 7 s and 14 s, referred to as the primary microseism and the secondary microseism respectively (McNamara & Boaz, 2019). The long period noise is due to ocean surface waves called infragravity waves (Bertin et al., 2018). Although generally considered a hindrance that makes it harder to see actual earthquakes, if we cross-correlate the record of “noise” between two stations, we obtain a meaningful parameter called the Green’s function (Wapenaar et al., 2010). The Green’s function is an impulse function that describes the response of the Earth between two stations, considering one station to be the source and the other to be the receiver (Wapenaar et al., 2010). By obtaining the Green’s function through techniques of seismic interferometry, the seemingly useless ambient noise can be utilized for applications ranging from monitoring volcanic activity (De Plaen et al., 2016) to investigating the response of man-made structures to earthquakes (Snieder & Şafak, 2006). References: Bertin, X., de Bakker, A., van Dongeren, A., Coco, G., André, G., Ardhuin, F., Bonneton, P., Bouchette, F., Castelle, B., Crawford, W. C., Davidson, M., Deen, M., Dodet, G., Guérin, T., Inch, K., Leckler, F., McCall, R., Muller, H., Olabarrieta, M., … Tissier, M. (2018). Infragravity waves: From driving mechanisms to impacts. Earth-Science Reviews, 177, 774–799. https://doi.org/10.1016/j.earscirev.2018.01.002 De Plaen, R. S. M., Lecocq, T., Caudron, C., Ferrazzini, V., & Francis, O. (2016). Single-station monitoring of volcanoes using seismic ambient noise. Geophysical Research Letters, 43(16), 8511–8518. https://doi.org/10.1002/2016GL070078 McNamara, Daniel E, D. E., & Boaz, R. I. (2019). Visualization of the Seismic Ambient Noise Spectrum. In N. Nakata, L. Gualtieri and A. Fichtner (Eds), Seismic Ambient Noise (pp. 1-27). Cambridge University Press. Shapiro, N. M., Campillo, M., Stehly, L., & Ritzwoller, M. H. (2005). High-Resolution Surface-Wave Tomography from Ambient Seismic Noise. Science, 307(5715), 1615–1618. https://doi.org/10.1126/science.1108339 Snieder, R., & Şafak, E. (2006). Extracting the Building Response Using Seismic Interferometry: Theory and Application to the Millikan Library in Pasadena, California. Bulletin of the Seismological Society of America, 96(2), 586–598. https://doi.org/10.1785/0120050109 Wapenaar, K., Draganov, D., Snieder, R., Campman, X., & Verdel, A. (2010). Tutorial on seismic interferometry: Part 1 — Basic principles and applications. GEOPHYSICS, 75(5), 75A195-75A209. https://doi.org/10.1190/1.3457445

Geodynamics

EGU Geodynamics Division Feb 16, 2023

Join Dr. Frank Zwaan on his voyage as he navigates the transition from analogue to numerical tectonic modeling! Discover the strengths of both approaches and the beauty of combining them in his latest blog post 🌍💻 #geodynamics #EGUblogs

https://blogs.egu.eu/divisions/gd/2023/02/15/a-voyage-between-different-tectonic-modelling-worlds-from-sandbox-to-supercomputer/

A voyage between different tectonic modelling worlds: from sandbox to supercomputer

A voyage between different tectonic modelling worlds: from sandbox to supercomputer On this day after Saint Valentine’s Day, let’s take a moment to talk about the love-hate relationship between analogue and numerical modelling. These two approaches to tectonic modelling may seem different, but they complement each other perfectly, each bringing their own unique strengths. In this blog, Dr. Frank Zwaan shares his journey as he navigates the transition from analogue to numerical modelling and reflects on the beauty of combining the two approaches. Into the sandbox world Dr. Frank Zwaan is a postdoctoral researcher at GFZ Potsdam working on the simulation of mantle exhumation during rifting and basin inversion by means of numerical models. In this blog post, he shares his experiences as he navigates the transition from analogue to numerical geodynamic modelling, including any challenges he has encountered along the way. If my name rings a bell at all, people probably recognise me as that tall (and possibly loud) guy who enjoys putting “sandboxes” in CT-scanners for fun (Fig. 1). It is indeed great fun to play with these “sandboxes”, which are in fact fascinating analogue tectonic models that allow researchers to simulate large-scale tectonic processes that take millions of years to unfold and cover vast areas of the Earth’s surface within a matter of hours or days in a laboratory the size of a living room. Such analogue models provide us with invaluable and direct insights into the dynamics of plate tectonic processes, and allow us to test the influence of different parameters on the evolution of a tectonic system in a unique way. Important challenges in this tectonic modelling endeavour are the choice of the right materials, building a suitable set-up for your specific research question, and the correct application of model scaling. When done correctly, you may be able to see spectacular tectonic features like the Himalayas develop in front of your eyes, especially when making physical cross-sections by cutting the model apart to reveal its internal secrets (Fig. 1b). . (a) (b) (c) (d) Fig. 1. (a) The author of this little novella in his former natural habitat, i.e., the Tectonic Lab University of Bern in Switzerland, explaining the viewer (it’s a still from a short video)* all about the analogue modelling capabilities in Bern. (b) Cross-section of one of the rifting models presented in pane, revealing its internal structures. (c) A model run in the CT-scanner and (d) a 3D depiction of a CT-scanned lithospheric-scale rifting model from a recent study (Zwaan & Schreurs, 2023). The practical aspects of analogue modelling, where simple materials such as sand and clay combined with some creative tinkering can help us to reveal the mysteries of tectonic systems, has captivated me from the moment I first saw a demonstration at the Vrije Universiteit Amsterdam. Growing up in a small fishing village along the Dutch coast, my childhood involved long days on its sandy beaches. In addition to sailing and fishing on the North Sea’s waves, these days were often spent building sand castles and waterworks to contain the flow of the tides as they swept in and out the gullies and sandbars between the surf and the sandy dunes. Yet, all small boys need to grow up, so I went to study Earth Sciences in Amsterdam (with plenty of fieldwork adventures abroad since the muddy territory of the Netherlands is largely devoid of proper rock outcrops). While keeping a broad interest in anything related to earth sciences, I got fascinated by structural geology and the titanic tectonic processes and massive timescales involved. The revelation that sand can be used to simulate tectonic processes has inspired large parts of my subsequent scientific career with of a number of cool projects at various tectonic labs throughout Europe. Drifting to the dark side At this point, attentive readers may wonder why on Earth I ended up in the Geodynamic Modelling group at GFZ Potsdam. After all, those geodynamic modellers have no proper tectonic laboratory at all! Worse still, they must actively avoid being around such labs, the dusty nature of which being positively detrimental to the computers they use for their “models”! Indeed, these people run numerical tectonic simulations instead, where they just feed some data into a black box they call a “code”, while pretending that the shiny imagery they generate is remotely related to real-world geology!? So, what am I doing on that dark side of the modelling world? Dear reader, allow me to explain! The preceding paragraph describes the (somewhat exaggerated) views an analogue modeller may have on these numerical modelling “upstarts”. Analogue modelling has after all been around since the dawn of geology as a science, with the first experiments done by the great Sir James Hall in 1815 (Hall, 1815). The methods involved have vastly improved over the centuries, evolving from a qualitative to a highly quantitative approach though the use of techniques such as (surface) strain analysis on time lapse imagery, topography reconstruction from stereoscopic pictures, CT-scanning, and keeps on providing us with exciting new insights. By contrast, computer modellers are rather new on the block, using numerical codes to directly calculate physical processes. Even so, the results derived from numerical modelling can be directly plotted and are truly impressive. An honest observer must (hesitantly) admit that numerical models are in a number of cases superior to the good old analogue models. As an analogue modeller, I am well-aware of the strengths and limitations of our methods. For instance, analogue models are great for studying detailed fault evolution and are highly intuitive as you can see them and literally touch them, making them excellent for both high-end research and general teaching / public outreach purposes. However, analogue modellers face major challenges when trying to incorporate factors such as thermal effects, phase changes and surface processes and their models are generally less suitable for large-scale (lithospheric-scale) modelling. Such factors are however much more easily incorporated into numerical models, which are overall better adapted to large-scale processes as well. Yet, numerical models have some drawbacks such as the a relatively low model resolution, high costs of simulating tectonics in 3D and the trust one must have in the numerical code, all issues that do not apply in analogue models. As such, we need to understand that although analogue and numerical models have significant overlap in applicability, both approaches have their specific strengths and weaknesses. Combining these approaches to get the best of both worlds would be the way forward, but unfortunately there are only few researchers who have a good grasp on both sides of the “tectonic modelling divide”. Thus, learning more about numerical modelling was a major reason for me to join the geodynamicists at GFZ Potsdam. Into the world of the supercomputer About a year ago left behind the cosy lab at the University of Bern located in the hilly foreland of the glorious Swiss Alps for Potsdam in the middle of the flat and windy North German Plain. I was lucky enough to have been awarded a GFZ Discovery Fellowship for a project on mantle exhumation during rifting and subsequent basin inversion, and was ready to kick off on my numerical modelling voyage. And so far It has been quite a voyage indeed! Next to the challenges of once more moving to a new country (amidst the ongoing covid pandemic), I quickly realised my relative lack of computer skills and had to scramble in a determined attempt to catch up. Indeed, it may be that most analogue modellers are basically structural geologists by trade, who somewhat lost their way and ended up in a dusty tectonic lab (while still feeling the need for fieldwork and hammering rocks)**. By contrast, numerical modellers seem to bring with them a much stronger technical and/or IT background, and tend to have somewhat more sophisticated wardrobe as they do not have to worry about getting dirty in lab or field. This “tectonic modelling divide” may indeed reflect an interesting difference in character between both these groups who I am probably simultaneously offending right now… Apart from me trying to patch up my computer skills, I also had to rearrange my deepest modelling instincts. I found I had no real clue about many practical aspects related to the model code, and it took a long time to “get these into my system”. Unlike working with analogue modelling set-ups, you cannot simply physically intervene by loosening a screw or scraping away some sand, and directly observe the result. Instead, you needs to painstakingly program things using mouse and keyboard, filter out typos and errors in the model parameter files. Generating numerical modelling results can take hours or even days after sending the “job” to a supercomputer, before you can download them for visualisation to find out you made an error. Indeed, these days I get a lot less exercise sitting behind a desk, instead of running through the lab carrying bags of sand around and preparing silicone mixtures for the upcoming experiment (Fig. 2). How times change! However, getting some insight into the notorious “black box” that numerical models may seem to be to outsiders is incredibly interesting, especially when you start to see how small details and issues may influence the model results, which is somewhat similar to the issues and boundary effects we may encounter in analogue models. Perhaps it is blasphemous to propose, but analogue and numerical modellers may not be that different after all…? (a) (b) Fig. 2. (a) The author of this little novella in his new and still somewhat unfamiliar habitat, i.e., the second floor of Haus A46 on the Albert-Einstein-Straße where the Geodynamic Modelling section of GFZ Potsdam is based, slightly suffering and despairing behind his many screens. (b) Yet, he is slowly but steadily acclimatising to his new surroundings, and is already producing some (at least) nice-looking modelling results of exhuming mantle. Some final reflections Trying my hand on numerical modelling also made me realise again that people who are new to analogue modelling probably have very similar issues when they first start working in the lab. As someone with several years of experience I may easily overlooks how confusing all the little practical details that I now know by heart can be for a newcomer. As such, this was a highly insightful but also humbling experience: one easily forgets how arduous previous steps in a study or career may have been, making it a challenge to put oneself into another person’s shoes. “I am but an egg” to quote Robert Heinlein’s human envoy from Mars, and “I have still so much to learn” would be a fitting life motto. Nevertheless, I am greatly enjoying my time GFZ and I am gradually getting the hang of things. We are now getting some cool modelling results, which I am planning to present at EGU this year. So, keep an eye out! And for those who may fear that I am forever and totally lost to the good old analogue modelling community: please don’t worry, I am still involved in some analogue projects, and I am regularly visiting the outstanding GFZ HelTec lab*** to “touch sand” when the overload of numerical stimuli becomes a bit too much. The END Notes * You can watch this ca. 5 min long, semi-professionally produced piece of analogue modeling propaganda on the EPOS Multi-scale Laboratories (MSL) YouTube channel (where also recordings of the MSL seminars is made avaiable): https://www.youtube.com/watch?v=ysb47SDMYTM&list=PLdv1BAYFyLsOtDa5knUhN5pQq6JvwlcGX. More info on the Bern lab can be found here: https://www.geo.unibe.ch/research/tectonics___structural_geology/laboratories/tectonic_modelling_laboratory/index_eng.html ** In fact, it seems that geologists/earth scientists actively distrust computers and electronic gadgets, as students were encouraged to solemnly swear to “never (blindly) trust a computer result” during a lively Saint Barbara Fest at Universität Potsdam. Saint Barbara being the Christian patron saint of those with dangerous trades involving fire and explosives (such as gunsmiths, cannoneers, miners [and by extension geologists]), the earth sciences students at Universität Potsdam organize a yearly feast in her honor. More info on the holy Barbara herself: https://en.wikipedia.org/wiki/Saint_Barbara *** HelTec - Helmholtz Laboratory for Tectonic Modelling: https://www.gfz-potsdam.de/en/section/lithosphere-dynamics/infrastructure/heltec References Hall, J., 1815. II. On the Vertical Position and Convolutions of certain Strata, and their relation with Granite. Earth and Environmental Science Transactions of The Royal Society of Edinburgh 7, 79–108. https://doi.org/10.1017/S0080456800019268 Zwaan, F., & Schreurs, G. (2023). Analogue models of lithospheric-scale rifting monitored in an X-ray CT scanner. Tectonics, 41, e2022TC007291. https://doi.org/10.1029/2022TC007291

Geodynamics

EGU Geodynamics Division Feb 16, 2023

Hello everyone! The EGU Geodynamics Division is excited to join Mastodon! Follow us here to get the latest news on all things related to #EGU, #geodynamics and# EarthScience