EPOS-NL and EPOS-eNLarge improve the means, or “infrastructure”, for research into our subsurface. After five years of EPOS-NL, and one year into EPOS-eNLarge, it is time to reflect: What are the benefits of having such a national infrastructure? What hurdles do researchers encounter, in using it for their own research? We’ve asked Utrecht University postdoc researchers
Wen Zhou and Mark Jefferd.
What research are you involved in?
Wen: I work within the EPOS-eNLarge project, at the Tectonic modelling and High Pressure and Temperature laboratories of Utrecht University. I study acoustic emissions to look at fault behavior. Acoustic emissions are often considered as a lab analogue to earthquake-generated seismic waves.
Mark: I work on the DeepNL project “Integration” (PI: Juan Carlo Afonso). We combine geological, petrological, geomechanical and hydrological datasets, to develop a complete model for Groningen and the rest of the Netherlands.
Mark, you have a lab background yourself. Now you’re involved in modelling. Does that change your view on the requirements of lab research?
Mark: The challenge is that on the scale of subsurface models, the resolution is about 100 meters. Lab people often provide data on cm-scale. So how do you represent a 100 meter thick block of sandstone in a model? Before this project, I was working on another DeepNL project (Science4Steer, PI Jan Dirk Jansen). There were three lab scientists and two modelers in our team. It was interesting to see how it can be quite difficult to model our experiments. It was hard for us to come up with laws that modelers can use on a bigger scale.
Why?
Mark: First of all, we don’t have the parameters, and the exact response of the rock at every pressure and temperature condition, or every different minerology you can find in a field. On the other hand, if they were to create a model using the cm-scale that we work on, you need the biggest super-computer in the world.
Wen: If we upscale the sample, we still have to choose which sample we use. What we often see in labs are big blocks of perfect, homogeneous sandstone lying there (both laugh). If you look at core material at NAM, it has different layers at mm-cm scale.
Mark: Upscaling in complexity is perhaps a bigger problem than upscaling in space. Both experimentalists and modelers like to keep it simple. Maybe we need more field geologists… (both laugh again).
Wen, you work in the lab now, but before you worked on field-scale seismology. Do you see a difference in research?
Wen: A core question I have is: are seismic waves you see in the field, and acoustic emissions we measure in labs really analogue to each other? Acoustic emissions have much higher frequency than earthquakes do. If they’re the same, we should also have this very high frequency acoustic signal recorded in the field. I mean: with earthquakes you’d have many tiny acoustic emissions. This is a question that I have in my mind following the work on different scales. In the lab you know the stress and temperature conditions at which acoustic emissions occur exactly. You can see precursors before the earthquake really happens, and predict the earthquake in this way. In the field we never know which fault, or fault section is going to react. There you can often only listen.

What do you know about EPOS-eNLarge?
Wen: EPOS-eNLarge is a group of facilities for geoscientific research, with a focus on geomechanics, seismology or microscopy. It can support research for people from other institutes. This encourages collaboration.
Mark: It helps with answering questions about the subsurface, over a range in scales.
Do you see any hurdles, in using EPOS-eNLarge facilities for multi-scale research?
Mark: I think the main hurdle is that most people are hired within a research group that focusses one particular scale, or one particular problem, which forms the core of their research.
Wen: From a research point of view you dive into one point, and you want to dive deeper into it to understand this one point better. It’s easier for researchers to have this one focus.
Mark: It’s hard for any individual PhD or PostDoc become an expert in the small and big stuff. That’s quite a challenge.
Would this be easier in larger proposals, with multiple researchers?
Mark: Larger projects, that have multiple people involved can have a wider range in scales.
Wen: Taking the Delft Geothermal project as an example, there is one, clear research goal: safe and efficient energy provision from this site. There are both lab and large-scale monitoring facilities, and different people come there to study the same site, but with different perspectives, and research scales.
Mark: Going back to the Science4Steer program. With five PhDs and PostDocs we jointly tried to look at multiple scales. We were using the facilities that were part of EPOS-eNLarge.
If you were to write a research proposal right now, would you include multi-scale facilities, like those of EPOS-eNLarge?
Mark: If it were a small project, with one PhD, or PD, then it would be focused on 1, perhaps 2 scales, like rock deformation experiments, combined with microscopy. If it was to be a larger project, then you can include other people, who are experts at other disciplines, facilities and scales. This is a good point of EPOS-eNLarge: that people start to know each other better. Even if it starts where we have visiting researchers on EPOS-funded Facility Access projects. These last only 1-2 weeks, but it’s still building relations which can lead to bigger collaborations.
Wen: Having EPOS-eNLarge makes it easier to reach people with different expertise. Previously, I thought the TNO Rijswijk lab is somehow difficult to reach, but now I see that it’s part of EPOS-eNLarge and that you can also do research there. I didn’t know this before. I might go there now.