Seismic slip on the west flank of the Upper Rhine Graben (France-Germany) : evidence from tectonic morphology and cataclastic deformation bands

Intraplate large and moderate earthquakes have occurred along the Upper Rhine Graben (URG) in the past but no coseismic surface faulting has been reported so far. We investigate the 25-km-long linear Riedseltz-Landau normal fault scarp affecting late Pleistocene and Holocene deposits of the western edge of the northern URG. The fault zone with cataclastic deformation textures is exposed in the Riedseltz quarry where it affects Pliocene and late Pleistocene (Wurm) units. Cataclasis is demonstrated by spalling and transgranular fractures in quartz grains concentrated in deformation bands with reduced grain size. The observed microstructures suggest multiple phases of deformation with cataclasis followed by emplacement of Fe-oxide matrix into deformation bands, and later emplacement of a clay-rick matrix into fractures. Previous studies along the fault show late Pleistocene (Wurm) loess deposits and early Holocene sand-silty deposits with 1.5 m and 0.7 m surface slip, respectively. New and previous results provide a minimum 0.15 mm/yr slip rate. A dislocation model suggests a minimum Mw 6.6 earthquake as a plausible scenario in the western edge of northern URG. Surface faulting in young sediments associated with cataclasis provides new evidence for assessing the occurrence of large earthquakes and seismic hazard assessment in the northern URG

Effective crustal permeability controls fault evolution: An integrated structural, mineralogical and isotopic study in granitic gneiss, Monte Rosa, Northern Italy

Two dextral faults within granitic gneiss in the Monte Rosa nappe, northern Italy reveal key differences in their evolution controlled by evolving permeability and water/rock reactions. The comparison reveals that identical host rock lithologies develop radically different mineralogies within the fault zones, resulting in fundamentally different deformation histories. Oxygen and hydrogen isotope analyses coupled to microstructural characterisation show that infiltration of meteoric water occurred into both fault zones. The smaller Virgin Fault shows evidence of periodic closed system behaviour, which promoted the growth of hydrothermal K-feldspar, whilst the more open system behaviour of the adjacent Ciao Ciao Fault generated a weaker muscovite-rich fault core, which promoted a step change in fault evolution. Effective crustal permeability is a vital control on fault evolution and, coupled to the temperature (i.e. depth) at which key mineral transformations occur, is probably a more significant factor than host rock strength in controlling fault development. The study suggests that whether a fault in granitic basement grows into a large structure may be largely controlled by the initial hydrological properties of the host rocks. Small faults exposed at the surface may therefore be evolutionary “dead-ends” that typically do not represent the early stages in the development of larger faults

Increasing the quality of seismic interpretation

Acknowledgments E. Macrae was funded by an NERC Open CASE Ph.D. award (NE/F013728/1) with Midland Valley Exploration Ltd. as the industry partner. We thank 763 geoscientists for their participation, and in particular, the REs who gave their time freely to the project. M. Scott (University of Glasgow, UK) is thanked for assisting with the statistical analysis. Four reviewers are thanked for their constructive comments that improved the manuscript.Peer reviewedPublisher PD

Fracking bad language – hydraulic fracturing and earthquake risks

We thank all conference and event organis- ers for supporting our work, as well as survey participants. We also thank Stella Pytharouli, James Verdon, and Stephen Hicks, for their insights into earthquake magnitudes and seismological terminology, and Juan Alcalde for comments about language nuance and trans- lation. We would also like to thank Brigitte Nerlich for the early discussion about the relevance of this work.Peer reviewedPublisher PD

Automated high accuracy, rapid beam hardening correction in X-Ray Computed Tomography of multi-mineral, heterogeneous core samples

X-ray Computed Tomography scanning is an innovative procedure that allows representing the internal structure of samples. Among its several purposes, X-ray CT is widely used for investigation of petrophysical properties of porous media. To provide accurate results, it is necessary to have high quality scan images, free of artefacts. One of the most problematic artefacts is beam hardening, which, in cylindrical shapes, increases the attenuation values with increasing distance from the centre. Until now, no automatic solution has been proposed for cylindrically-shaped cores that is both computationally feasible and applicable to all geological media. A new technique is here introduced for correcting beam hardening, using a linearization procedure of the beam hardening curve applied after the reconstruction process. We have developed an automated open source plug-in, running on ImageJ software, which does not require any a priori knowledge of the material, distance from the source or the scan conditions (current, energy), nor any segmentation of phases or calibration scan on phantom data. It is suitable for expert and non-expert use, alike. We have tested the technique on μCT scan images of a plastic rod, a sample of loose sand, several heterogeneous sandstone core samples (with near-cylindrical shapes), and finally, on an internal scan of a Berea sandstone core. The Berea core was also scanned using a medical X-ray CT scanner with a fan-beam geometry, as opposed to a cone beam geometry, showing that our algorithm is equally effective in both cases. Our correction technique successfully removes the beam hardening artefact in all cases, as well as removing the cupping effect common to internal scans. For a Berea Sandstone, with a porosity of 20%, porosity calculated using the corrected scan is 20.54%, which compares to a value of 14.24% using the software provided by the manufacturer

What Have We Learnt About CO2 Leakage in the Context of Commercial-Scale CCS?

The viability of Carbon Capture and Storage (CCS) depends on the reliable containment of injected CO2 in the subsurface. Robust and cost-effective approaches to measure monitor and verify CO2 containment are required to demonstrate that CO2 has not breached the reservoir, and to comply with CCS regulations. This includes capability to detect and quantify any potential leakage to surface. It is useful to consider the range of possible leak rates for potential CO2 leak pathways from an intended storage reservoir to surface to inform the design of effective monitoring approaches. However, in the absence of a portfolio of leakage from engineered CO2 stores we must instead learn from industrial and natural analogues, numerical models, and laboratory and field experiments that have intentionally released CO2 into the shallow subsurface to simulate a CO2 leak to surface. We collated a global dataset of measured or estimated CO2 flux (CO2 emission per unit area) and CO2 leak rate from industrial and natural analogues and field experiments. We then examined the dataset to compare emission and flux rates and seep style, and consider the measured emission rates in the context of commercial scale CCS operations. We find that natural and industrial analogues show very wide variation in the scale of CO2 emissions, and tend to be larger than leaks simulated by CO2 release experiments. For all analogue types (natural, industrial, or experiment) the emission rates show greater variation between sites than CO2 flux rates. Quantitation approaches are non-standardized, and that measuring and reporting both the CO2 flux and seep rate is rare as it remains challenging, particularly in marine environments. Finally, we observe that CO2 fluxes tend to be associated with particular emission characteristics (vent, diffuse, or water-associated). We propose that characteristics could inform the design and performance requirements for CO2 leak monitoring approaches tailored to detect specific emission styles

Independent Expert Scientific Panel – Report on Unconventional Oil and Gas

No abstract available

Reducing the environmental impact of hydraulic fracturing through design optimisation of positive displacement pumps

The current approach to hydraulic fracturing requires large amounts of industrial hardware to be transported, installed and operated in temporary locations. A significant proportion of this equipment is comprised of the fleet of pumps required to provide the high pressures and flows necessary for well stimulation. Studies have shown that over 90% of the emissions of CO2 and other pollutants that occur during a hydraulic fracturing operation are associated with these pumps. Pollution and transport concerns are of paramount importance for the emerging hydraulic fracturing industry in Europe, and so it is timely to consider these factors when assessing the design of high pressure pumps for the European resources. This paper gives an overview of the industrial plant required to carry out a hydraulic fracturing operation. This is followed by an analysis of the design space of the pump design that could result in improved pump efficiency. We find that reducing the plunge diameter and running the pump at higher speeds can increase the pump efficiency by up to 4.6%. Such changes to the pump’s parameters would results in several environmental benefits beyond the obvious economic gains of lower fuel consumption. The paper concludes with a case study that quantifies these benefits

Multiphase deformation, fluid flow and mineralization in epithermal systems : inferences from structures, vein textures and breccias of the Kestanelik epithermal Au-Ag deposit, NW Turkey

We investigate the multiphase deformation, fluid flow, and mineralization processes in epithermal systems by presenting a detailed study of vein textures and breccias of the Kestanelik epithermal Au-Ag deposit, NW Turkey. The mineralization in the deposit is associated with several quartz veins. Fault-hosted veins and mode I veins share many textural and breccia characteristics owing to (i) overprinting of tectonic breccias formed during coseismic rupturing by subsequent coseismic hydrothermal brecciation and (ii) reworking of earlier vein breccia phases by repeated rupturing and hydraulic fracturing events. The spatial distribution of breccias at fault-hosted veins proposes that power of coseismic hydrothermal brecciation is controlled by the distance to the level of boiling within a vein. The brecciation affects the entire vein proximal to the level of boiling; however, it is limited to the footwall contact of the vein more distally at the upper levels of a vein. Varying number of mineralization events for the veins suggests that any individual earthquake event reopened only one or more sealed vein, but not all at once. Fewer mineralization events in fault-hosted veins compared to the mode I veins is either linked to (i) focusing of high fluid flux into the conduits of mode I veins that accommodate more dilation or (ii) reopening of mode I veins owing to the driven of extensional failure under low differential stress. Although fault-hosted veins record fewer mineralization events, they have higher average Au grade (4.106 g/t) compared to that of mode I veins (2.736 g/t). On the other hand, fewer mineralization events in wall rock structures compared to the adjacent faults is attributed to (i) absence or poor development of the damage zone structures in earlier seismic events or (ii) deactivation of them after clogging due to the rotation of the optimum stress field or (iii) their formation as hydraulic extension fractures. This study emphasizes the importance of detailed studies of vein infill for understanding the internal structural evolution of the veins in epithermal deposits that is interest to the geologists within both industry and academic fields