Thea K Hincks

Eruptive history of an alkali basaltic diatreme from Elie Ness, Fife, Scotland

The Elie Ness diatreme (Fife, Scotland) is an ideal place to study the internal architecture and emplacement processes of diatremes. Elie Ness is one of approximately 100 alkali basaltic diatremes and intrusions in the East Fife area, emplaced during Upper Carboniferous to Early Permian times into an extensive rift system in the northern Variscan foreland. Within the diatreme, seven lithofacies and three lithofacies associations (LFAs 1–3) are recognised. Field, petrographic and geochemical studies demonstrate that the diatreme experienced a protracted history of eruption and infill, initially driven by volatile expansion and later by magma–water interaction. Massive lapilli tuffs of LFA 1 contain abundant highly vesicular juvenile scoria and magma-coated clasts, which are best explained by a magmatic origin for the early explosive eruptions. On a large-scale, the tuffs are well mixed and locally exhibit small-scale degassing structures attributed to fluidisation processes occurring within the diatreme fill. The occurrence of abundant volcaniclastic autoliths and megablocks within LFA 1 can be explained by subsidence of volcaniclastic strata from the maar crater and upper diatreme during emplacement. Pyroclastic density current deposits of LFA 2 form a series of continuous sheets across the diatreme, some of which may have originated from phreatomagmatic explosions in a neighbouring vent. We attribute the overall bedding pattern to a combination of primary volcanic processes and post-depositional folding related to movement along an adjacent fault. Minor steeply inclined breccias and tuffs of LFA 3 cross-cut the LFA 2 succession and are interpreted as late-stage volcaniclastic dykes and conduits, signalling the final phase of eruptive activity at Elie Ness. The study offers new insights into the volcanic evolution of diatremes fed by low viscosity, alkali-rich magmas.

Risk and uncertainty assessment of volcanic hazards

List of contributors Preface 1. Risk and uncertainty assessment in natural hazards L. J. Hill, R. S. J. Sparks and J. C. Rougier 2. Quantifying natural hazard risk J. C. Rougier 3. Model limitations: the sources and implications of epistemic uncertainty J. C. Rougier and K. J. Beven 4. Expert elicitation and judgment W. P. Aspinall and R. M. Cooke 5. Risk and uncertainty in hydrometeorological hazards T. L. Edwards and P. G. Challenor 6. Hydrometeorological hazards under future climate change T. L. Edwards and P. G. Challenor 7. Hydrological flood uncertainty and risk research J. Freer, K. J. Beven, J. Neal, G. Schumann, J. Hall and P. Bates 8. Uncertainties in probabilistic seismic hazard assessment W. P. Aspinall 9. Landslide and avalanche hazards T. K. Hincks, W. P. Aspinall, R. S. J. Sparks, E. A. Holcombe and M. Kern 10. Tsunami hazard and risk T. K. Hincks, R. S. J. Sparks and W. P. Aspinall 11. Risk and uncertainty assessment of volcanic hazards R. S. J. Sparks, W. P. Aspinall, H. S. Crosweller and T. K. Hincks 12. Risk assessment and management of wildfires T. K. Hincks, B. D. Malamud, R. S. J. Sparks, M. J. Wooster and T. J. Lynham 13. Technological facilities, infrastructure and hazardous materials, including some notes on space weather R. S. J. Sparks, W. P. Aspinall, N. A. Chapman, B. E. Hill, D. J. Kerridge, J. Pooley and C. A. Taylor 14. Statistical aspects of risk characterization in ecotoxicology G. L. Hickey and A. Hart 15. Social science perspectives on natural hazards risk and uncertainty S. Cornell and M. Jackson 16. Human responses to natural hazard risk: considerations for improving the effectiveness of risk management systems H. S. Crosweller and J. Wilmshurst Index.

Oklahoma's induced seismicity strongly linked to wastewater injection depth

Injection depth matters for induced earthquakes Wastewater injection has induced earthquakes in Oklahoma, but the relative importance of operational and geologic parameters in triggering such earthquakes is unclear. Hincks et al. developed an advanced Bayesian network to determine the interplay between these parameters in Oklahoma. The injection depth above the crystalline basement was the most important parameter when considering the potential for release of seismic energy. This modeling strategy may provide a way to improve forecasts of the impact of proposed regulatory changes on induced seismicity. Science, this issue p. 1251 A Bayesian network approach implicates well depth as the most important operational factor for induced earthquakes. The sharp rise in Oklahoma seismicity since 2009 is due to wastewater injection. The role of injection depth is an open, complex issue, yet critical for hazard assessment and regulation. We developed an advanced Bayesian network to model joint conditional dependencies between spatial, operational, and seismicity parameters. We found that injection depth relative to crystalline basement most strongly correlates with seismic moment release. The joint effects of depth and volume are critical, as injection rate becomes more influential near the basement interface. Restricting injection depths to 200 to 500 meters above basement could reduce annual seismic moment release by a factor of 1.4 to 2.8. Our approach enables identification of subregions where targeted regulation may mitigate effects of induced earthquakes, aiding operators and regulators in wastewater disposal regions.