When the science meets art – a report from the creation of comics about Earthquakes and Geomagnetic field

<p>As science communicators we are confronted with little attention paid to the understanding of the Earth inner processes in the educational system of the Czech Republic. For that reason, we thought about ways how to explain basic principles of the Earth dynamics in accessible way to the school students and high school youth. We saw comics as an attractive way that would overcome the gap between knowledge and the need to entertain the young readers. We also thought that in the comics we should not be tell all everything with lot of explanatory text, but rather to try to provoke the reader to look for information and answers and hence to start the passion for science. So, we are trying to explain by graphics.</p><p>The presented experience covers the collaboration among three researches, graphic designer and writer in the process of creation of two short comic books about earthquake origin and inner structure of the Earth and origin of the Earth magnetic field.</p><p>We believe that such collaboration – to be effective – needs to be founded on several principles. The base of the comics, the storyboard, needs to be the result of discussions and collective effort of all participants. The artists need to be given creative freedom and the researchers should explain how the processes work inside the Earth rather than to try to push forward their views of artistic expression of them. Also, mainly the researches need to accept the equality of roles during the creative process. Last but not least the friendly atmosphere helps a lot.</p><p>The first comics “When the Earth Quakes” was created during second half of year 2019 and first months of year 2020 so the work was mostly based on personal meetings. The second comics is in production during diverse lockdowns and thus most of the communication is realized online. Therefore, different types of communication will be reflected based on our experience.   </p><p>The comics “When the Earth Quakes” and related board game is published under the Creative Commons license: https://www.ig.cas.cz/en/outreach/comics-seismic-wave/</p>

Relative Timing of the Eocene Global Reorganization of Plate Motions: New Results for Pacific Plate Hotspot Tracks

<p><span> </span><span>To improve</span><span> </span><span>modeling of</span><span> deep-earth dynamics </span><span>it is i</span><span>mportant</span><span> to understand</span><span> changes in the arrangements of plate boundaries, especially trenches accommodating subduction, </span><span>and </span><span>major </span><span>changes</span><span> in tectonic plate motion. </span><span>Here</span><span> we focus on </span><span>the sequence of </span><span>key surface events in </span><span>Eocene </span><span>time that </span><span>likely coincide with changes in </span><span>deep-earth dynamics. In particular, we </span><span>develop </span><span>methods of analysis of seamount locations and age dates using a small number of adjustable parameters (10 per chain)</span><span> on the Pacific plate </span><span>with a focus on the </span><span>timing of the </span><span>Hawaiian-Emperor bend </span><span>relative to the timing of other </span><span>major Eocene tectonic changes</span><span>. </span></p><p><span> </span><span>We find that motion between hotspots differs insignificantly from zero with rates of 2</span><span>±</span><span>4 mm/a (±2</span><span>σ</span><span>) for 0-48 Ma and 26±34 mm/a (±2σ) for 48-80 Ma. Relative to a mean Pacific hotspot reference frame, </span><span>nominal rates of </span><span>motion of the Hawaii, Louisville, and Rurutu hotspots are </span><span>~</span><span>5</span><span> mm/a and </span><span>differ insignificantly from zero</span><span>. We conclude that plumes underlying these Pacific hotspots are more stable in a convecting mantle than previously inferred.</span></p><p><span> We estimate the locations and ages (with uncertainties) of bends in Pacific hotspot chains using a novel inversion method. The location of the ~60° change in trend at the Hawaiian-Emperor bend is well constrained within ~50-80 km (=2σ), but the location of the bends in the Louisville and Rurutu hotspots are more uncertain. If the uncertainty in the location of the bend in the Louisville chain is included, we find no significant difference in age between the bends of different Pacific hotspot chains. The best-fitting assumed-coeval age for the bends is 47.4±1.0 Ma (±2σ), which is indistinguishable from the age of the C21o geomagnetic reversal. The age of the bend is younger than the initiation of subduction in the Western Pacific, but approximately coeval with changes in Pacific and circum-Pacific relative plate motion. Changes to the tectonic system near the age of the bend are not limited to the Pacific basin. The smooth-rough transition flanking the Carlsberg Ridge records a threshold in the decreasing spreading rate between India and Africa, thought to record the onset of the collision of India with Eurasia, and is constrained to be between C21y and C20o (46 Ma and 43 Ma) in age. Nearly simultaneously, South America and Australia began to diverge more rapidly from Antarctica. The Eocene bend in Pacific hotspot chains may be the most evident feature recording a global re-organization of plate motions and mantle circulation possibly caused by the earlier collision of India and Eurasia or initiation of western Pacific subduction.</span></p>

Nonlinear Climate Dynamics: from Deterministic Behavior to Stochastic Excitability and Chaos

<p>Glacial-interglacial cycles are global climatic changes which have characterised the last 3 million years. The eight latest<br>glacial-interglacial cycles represent changes in sea level over 100 m, and their average duration was around 100 000 years. There is a<br>long tradition of modelling glacial-interglacial cycles with low-order dynamical systems. In one view, the cyclic phenomenon is caused by<br>non-linear interactions between components of the climate system: The dynamical system model which represents Earth dynamics has a limit cycle. In an another view, the variations in ice volume and ice sheet extent are caused by changes in Earth's orbit, possibly amplified by feedbacks.<br>This response and internal feedbacks need to be non-linear to explain the asymmetric character of glacial-interglacial cycles and their duration. A third view sees glacial-interglacial cycles as a limit cycle synchronised on the orbital forcing.</p><p>The purpose of the present contribution is to pay specific attention to the effects of stochastic forcing. Indeed, the trajectories<br>obtained in presence of noise are not necessarily noised-up versions of the deterministic trajectories. They may follow pathways which<br>have no analogue in the deterministic version of the model.  Our purpose is to<br>demonstrate the mechanisms by which stochastic excitation may generate such large-scale oscillations and induce intermittency. To this end, we<br>consider a series of models previously introduced in the literature, starting by autonomous models with two variables, and then three<br>variables. The properties of stochastic trajectories are understood by reference to the bifurcation diagram, the vector field, and a<br>method called stochastic sensitivity analysis.  We then introduce models accounting for the orbital forcing, and distinguish forced and<br>synchronised ice-age scenarios, and show again how noise may generate trajectories which have no immediate analogue in the determinstic model. </p>

Estimating the changes in the Moho interface beneath the Tibetan Plateau based on GRACE data

<p>         The Tibetan Plateau (TP) experiences complex mass transfer and redistribution due to the effects from internal earth dynamics and external climate change, such as, land water change, crustal uplift, surface denudation, and Moho interface change. These phenomenas are accompanied by the gravity field change and could be observed by the Gravity Recovery and Climate Experiment (GRACE). This study applies GRACE data to estimate the corresponding mass changes expressed by water equivalent height (EWH) anomaly of the TP. In addition, we use ICESat data and hydrological models to estimate the effects of hydrological factors (lake, glaciers, snow, soil moisture, and groundwater), to separate them from the comprehensive mass field to obtain the tectonic information. The total hydrological contribution to the average EWH change is -0.30±0.21 cm/yr. We further estimate the rates of tectonic uplift and denudation based on GNSS and denudation, with results of 0.71±0.46 mm/yr and 0.38±0.10 mm/yr, respectively. Removing the effects of hydrological change, surface displacements and GIA from the GRACE data, we obtain the EWH change contributed from interior mass change of 0.21±0.27 cm/yr, which is equivalent to a mean Moho interface uplift rate of 3.63±4.32 mm/yr. Final results show that the crustal thickness of the northern TP is thinning because of the upwelling of Moho interface and the southern TP is thickening along with Moho deepening, coinciding with the tomographic results.</p><p>Key words: the Tibetan plateau, mass transfer, land water change, Moho interface change, GRACE</p>

A non-extensive statistical physics view in Earth Physics: Geodynamic properties in terms of Complexity theory .

<p>Boltzmann-Gibbs (BG) statistical physics is one of the cornerstones of contemporary physics. It establishes a remarkably useful bridge between the mechanical microscopic laws and macroscopic description using classical thermodynamics. If long-range interactions, non-markovian microscopic memory, multifractal boundary conditions and multifractal structures are present then another type of statistical mechanics, than BG, seems appropriate to describe nature (Tsallis, 2001).</p><p>To overcome at least some of these anomalies that seem to violate BG statistical mechanics, non-extensive statistical physics (NESP) was proposed by Tsallis  (Tsallis, 1988) that recovers the extensive BG as a particular case. The associated generalized entropic form controlled by the entropic index  q that represents a measure of non-additivity of a system. S<sub>q</sub> recovers S<sub>BG</sub> in the limit q→1. For a variable X with a probability distribution p(X), as that of seismic moment , inter-event times  or distances between the successive earthquakes or the length of faults in a given region, using terms of NESP, we obtain the physical probability which expressed by a q-exponential function as defined in Tsallis, (2009).  Another type of distributions that are deeply connected to statistical physics is that of the squared variable X<sup>2</sup>. In BG statistical physics, the distribution of X<sup>2</sup> corresponds to the well-known Gaussian distribution. If we optimize S<sub>q</sub> for X<sup>2</sup>, we obtain a generalization of the normal Gaussian that is known as q-Gaussian distribution (Tsallis, 2009). In the limit q→1, the normal Gaussian distribution, recovered. For q> 1, the q-Gaussian distribution has power-law tails with slope -2/(q-1), thus enhancing the probability of the extreme values.</p><p>In the present work we review a collection of Earth physics problems such as a) NESP pathways in earthquake size distribution, b) The effect of mega-earthquakes, c) Spatiotemporal description of Seismicity, d) the plate tectonics as a case of non-extensive thermodynamics e) laboratory seismology and fracture, f) the non-extensive nature of earth’s ambient noise, and g) evidence of non-extensivity in eartquakes’ coda wave. The aforementioned cases cover the most of the problems in Earth Physics indicated that non extensive statistical physics could be the underline interpretation tool to understand earth's evolution and dynamics.</p><p>We can state that the study of the non-extensive statistical physics of earth dynamics remains wide-open with many significant discoveries to be made. The results of the analysis in the cases described previously indicate that the ideas of NESP can be used to express the non-linear dynamics that control the evolution of the earth dynamics at different scales. The key scientific challenge is to understand in a unified way, using NESP principles, the physical mechanisms that drive the evolution of fractures ensembles in laboratory and global scale and how we can use measures of evolution that will forecast the extreme fracture event rigorously and with consistency.</p><p><strong> </strong><strong>Acknowledgments. </strong>We acknowledge support by the project “HELPOS – Hellenic System for Lithosphere Monitoring” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece & European Union (ERDF).</p><p><strong> </strong></p>

On the permanent tide and the Earth dynamical ellipticity

<p>As other relevant quantities related to the Earth dynamics, the Earth dynamical ellipticity is influenced by tidal effects. In particular, it is affected by the permanent tide due to the time independent part of the Earth redistribution tidal potential. Hence, it is necessary to distinguish between its tide-free and non tide-free values (e.g., Burša 1995) when determining it from observations (e.g., Marchenko & Lopushanskyi 2018). This question is seldom considered in Earth rotation studies. For example, neither IAU2000/AIU2006 nutation/precession model nor IERS Conventions specify explicitly whether the dynamical ellipticity is a zero-tide parameter or not. However, current accuracy goals might be sensitive to that difference.</p><p>Within the framework of a Hamiltonian approach (Baenas, Escapa, & Ferrándiz 2019), we present a consistent treatment of the influence of the permanent tide on the dynamical ellipticity. In particular, we develop an analytical expression of the redistribution tidal potential based on Andoyer canonical variables and a semi-analytical theory of the orbital motions of the Moon and the Sun, following the same procedure as that given in Kinoshita (1977).</p><p>This method allows obtaining an expression of the zero frequency term of the redistribution tidal potential that updates that of Zadro & Marussi (1973), usually employed in reporting parameters of common relevance to Astronomy, Geodesy, & Geodynamics (e.g., Burša 1995, Groten 2004). In addition, it clarifies the procedure that must be followed in order that the dynamical ellipticity, fitted to the observations, contains the effects of the permanent tide avoiding in this way potential inconsistencies.</p>

3-D numerical modelling of crustal polydiapirs with volume-of-fluid methods

SUMMARY Gravitational instabilities exert a crucial role on the Earth dynamics and in particular on its differentiation. The Earth’s crust can be considered as a multilayered fluid with different densities and viscosities, which may become unstable in particular with variations in temperature. With the specific aim to quantify crustal scale polydiapiric instabilities, we test here two codes, JADIM and OpenFOAM, which use a volume-of-fluid (VOF) method without interface reconstruction, and compare them with the geodynamics community code ASPECT, which uses a tracking algorithm based on compositional fields. The VOF method is well-known to preserve strongly deforming interfaces. Both JADIM and OpenFOAM are first tested against documented two and three-layer Rayleigh–Taylor instability configurations in 2-D and 3-D. 2-D and 3-D results show diapiric growth rates that fit the analytical theory and are found to be slightly more accurate than those obtained with ASPECT. We subsequently compare the results from VOF simulations with previously published Rayleigh–Bénard analogue and numerical experiments. We show that the VOF method is a robust method adapted to the study of diapirism and convection in the Earth’s crust, although it is not computationally as fast as ASPECT. OpenFOAM is found to run faster than, and conserve mass as well as JADIM. Finally, we provide a preliminary application to the polydiapiric dynamics of the orogenic crust of Naxos Island (Greece) at about 16 Myr, and propose a two-stages scenario of convection and diapirism. The timing and dimensions of the modelled gravitational instabilities not only corroborate previous estimates of timing and dimensions associated to the dynamics of this hot crustal domain, but also bring preliminary insight on its rheological and tectonic contexts.

10 years with planet Earth essence in the primary school children drawings

10 years with Planet Earth is the title of the 2016 INGV calendar for primary schools resulting from the review of a project conceived to support and complement 15 years of INGV dissemination activities with schools. We made 10 calendars together with and for primary schools, every year with a different subject related to a world in constant evolution. We have launched competitions asking children to send drawings on the themes chosen, to stimulate learning about Earth Sciences and Planet Earth dynamics. We intended to raise awareness on water resources availability, prevention of natural disasters and planet sustainability. For each competition, we chose the most significant drawings to be included in the yearly calendar about the Earth. The authors of drawings were awarded by scientists, journalists, artists and science communicators and even by a minister. Beyond the competitions, the drawings reflect impressions and thoughts, providing an opportunity to illustrate the children's point of view. From drawings arise a great sensitivity, consideration, responsiveness and respect for the Planet and positive feeling for Science. The project was made possible thanks to the teachers and to the wonderful students of more than 200 schools. We received about 10 000 drawings that have intrigued, touched, enchanted, and surprised us. We are grateful for all they have chosen to share with us.