Linfeng is the first CREEPer to cross the finish line!
On Friday June 29, 2018 at 11 a.m., Linfeng Ding carried out his defence to obtain the title “Doctor of Science” in the PhD subject Geology / Paleontology. His presentation, “Rheology and deformation of glass under extreme conditions”, took place at the Duesbergweg 10-14, room 00-236 in the Decanter of Chemistry, Pharmacy and Earth Sciences of the Johannes Gutenberg University of Mainz (JGU).
During the 30 minutes that university rules allow for the oral presentation, Linfeng clearly explained the experiments and models that he developed. He studied the volumetric relaxation of glass after high-pressure treatment above the glass transition region in Piston-cylinder apparatus and volume recovery measurements, the uniaxial deformation of glass under high pressure in Paterson press and the deviatoric torsional deformation of glass in high-pressure torsion apparatus. The main goal of the ESR5’s project was to measure experimentally, by deformation measurements, the effect of pressure on the viscosity and structural relaxation of glass in order to better quantify the viscous contribution to the rheology of glass. Linfeng showed his results to the audience, demonstrating the significance of studying the pressure dependence of the rheology of glass and how the experiments and models he presented can contribute to a better understanding of the rheology of glass under extreme conditions. Finally, he ended his presentation thanking the project CREEP and expressing his pleasure to be part of it.
Before the round of questions that followed his presentation, Linfeng was congratulated by the members of the tribunal for his nice presentation and especially by his supervisors, Clements Kunisch and Boris Kaus. Boris pointed out that Linfeng has been the first of his students to complete the doctoral thesis in less than three years.
Subsequently, only the members of the tribunal remained in the room to deliberate. Meanwhile, waiting outside, Linfeng, happy and more relaxed, received congratulations and support of his colleagues and friends. After a few minutes, Linfeng was invited to enter the room again to hear the tribunal’s decision.
When he left the room, we did not need to ask him anything to understand that it had been a success.
To celebrate the event, we went to another room to make a toast and have an apero. Following the German tradition, Doctor Ding received a hat made by his colleagues decorated with motifs related to his project and his stay in the city. Later, and to conclude the celebration, Linfeng invited us to a party in the garden outside the building of the institute, preparing Chinese Hot-Pot and Sichuan dishes and provided us with drinks, snacks and sweets.
As a present and a sign of the appreciation that the group has towards Linfeng, he received a small souvenir from Mainz and a ticket to go skydiving in the nice area of Miltenberg, Germany.
In May, Manuel Thieme did his academic secondment at the Montpellier Technology Center (MpTC), a center for wellbore and structural geology software connected to Schlumberger.
He spent most of his time learning and working with Poly3D, a modelling and research tool for fracture mechanics, earthquake studies and geomechanical analysis of fractured oil and gas reservoirs. Apart from the scientific points, Manuel spent many (long French) lunches discussing with colleagues to find out how an industry company works and in which areas the work-flow differs from academia. To his surprise, people were highly welcoming, proactive and integrating, offering perspective outside of work too.
To facilitate scientific outreach, Manuel presented his PhD topic and latest results to the team of the MpTC. Especially his high velocity friction experiments performed in cooperation with Durham University during his academic secondment found open ears and lead to a mutual benefiting discussion.
Seminar at the Dal Piaz LyceumESR4, Giacomo Pozzi, went to his former high school in his hometown Feltre (Italy) to give a seminar about his experiences in the academic world. He first presented an introduction to ‘the brittle behaviour of the Earth: faults and earthquakes’, in which he discussed the basic theory, but also covered interesting topics such as the recent earthquakes in the Apennines of Central Italy. During the seminar, Giacomo’s aim was not to scare the students with lots of math and equations, but to show the students what studying Geology is like. He also discussed the role of Universities in providing students the right background for a future career, but mentioned that a student’s own initiative is very important as well. The presentation was well received by the audience and Giacomo answered many questions. Most came from the students that wanted information about their future studies, especially on the subjects that research has to offer. Their interest in this non-conventional view of geology has been a pleasant surprise and a reward to Giacomo and he feels that sharing the science is one of the best delights of his job.
Outreach video as a part of the Italian ‘On the Rocks’ video contest
ESR6, Elenora van Rijsingen, made an outreach video about her PhD, in which she aims to explain the topic of her PhD in a simple way, understandable for the general audience. She starts with discussing what happens between the two plates in a subduction zone before, during and after an earthquake, after which she introduces her PhD topic and methods she uses to study the influence of seafloor topography on large megathrust earthquakes. The video did well in the contest and received the special award of the Honorary Committee. Elenora will travel to Sicily in september to attend the award ceremony of the contest, that takes place during the Congress of the Italian Geological Society in Catania on September 12, 2018.
Besides Linfeng’s brilliant performance, other results have been reached up to now. For instance, a list of latest publications is already available on the site but only authors and titles are indicated there. To explore better what has been done so far we prepared a short overview of some of them!
Manuel in “Thieme, M. et al 2018, Phys. Earth Planet. Int.”
During this work, Manuel and co. have studied the mechanical response and the evolution of correlated microstructure of fine-grained olivine aggregates subjected to incremental finite strains. They have observed a clear strain hardening of their samples but, despite that, no changes in texture and microstructure as a function of stress and finite strain have been detected. Strain hardening in olivine seems then to occur because of dislocation movements (with grain boundaries acting as dislocation sources), since they have found no confirmation that dislocation generation can be the cause for hardening during transient creep.
Giacomo in “Pozzi et al 2018, Geology.”
Giacomo’s paper points out a new interpretation of the so-called mirror-like surfaces, which are highly reflective, continuous smooth surfaces observed in experimental carbonate-hosted faults. After a series of experiments carried out in a rotary shear apparatus on calcite gouges, they ended up with a new explanation of what were considered before to be frictional principal slip planes. They noticed that sheared samples develop a thick principal slip layer (on a micrometer scale) within viscous flow is localized, and proposed that mirror-like surfaces should not be read anymore as simple slip planes but, instead, as a rheological boundary between coarse wall rocks and the much weaker core of the slip layer.
Gianluca in “Gerardi G. & Ribe N.M. 2018, Journal of Geophysical Research: Solid Earth.”
Turning to a larger scale, Gianluca explores here the dynamics of subduction using boundary-element method. He studied both the kinematics of subducting plate and the deformation of the overriding one. Even when the negative buoyancy of the downwelling slab is the only driving force, slab motion appears to be controlled by several parameters, such as its geometry and flexural stiffness, the width of the interface lubrification layer that separates the two plates, and the length of the plates. Concerning the deformation of the overring plate, it is compression-dominated close to the trench, bending-dominated along the remaining portion, and even extension-dominated in the back-arc portion, where the plate is positively buoyant. Finally, they applied their model to a real subduction zone, obtaining values of the interface layer viscosity significantly smaller than the mantle viscosity, as expected.
Elenora in ‘van Rijsingen et al. (2018). Geosys. Geochem. Geophys.”
To better understand what the role of subduction interface roughness on the occurrence of large megathrust earthquakes is, Elenora performed a global quantitative comparison between seafloor roughness seaward of the trenches and spatial rupture characteristics. Her results show that Mw ≥ 7.5 ruptures occur preferentially on smooth subducting seaﬂoor; this is especially clear for Mw> 8.5 events.
Wen in “Zhou W. & Paulssen, H. (2017). Geophys. Res. Lett.”
In his first paper, Wen focused on the Groningen Gas Reservoir in the Netherlands, the larger natural gas field in Europe. He derived P and S velocity structure from noise interferometry, a seismic interferometry that is used widely to get back information for imaging deep structures. Based on crosscorrelation of noise data from geophones placed in a 3 km depth borehole, he found that anthropogenic noise (traffic, in this case) can be used as signal in order to gain useful information, i.e. to determine the velocity structure of the gas field around the borehole .
Written by Beatriz Martinez Montesinos, Nicolò Sgreva and Elenora van Rijsingen