ALBERT

Description: Author(s): J. Murphy, C. P. Strehlow, K. Cho, M. A. Tanatar, N. Salovich, R. W. Giannetta, T. Kobayashi, S. Miyasaka, S. Tajima, and R. Prozorov Temperature-dependent London penetration depth λ ( T ) was measured in optimally doped x =0.35, as-grown [ T c ≈25 K, RRR= ρ (300 K)/ ρ ( T c )=4.5], and annealed ( T c ≈35 K, RRR=6.4) single crystals of SrFe 2 (As 1− x P x ) 2 iron-based superconductor. Annealing increases the residual resistivity ratio (RRR) and decreases... [Phys. Rev. B 87, 140505] Published Tue Apr 16, 2013

Description: Summary Aquifers are poroelastic bodies that respond to strain by changes in pore pressure. Crustal deformation due to volcanic processes induces pore pressure variations that are mirrored in well water levels. Here, we investigate water level changes in the Belham valley on Montserrat over the course of 2 yr (2004–2006). Using finite element analysis, we simulate crustal deformation due to different volcanic strain sources and the dynamic poroelastic aquifer response. While some additional hydrological drivers cannot be excluded, we suggest that a poroelastic strain response of the aquifer system in the Belham valley is a possible explanation for the observed water level changes. According to our simulations, the shallow Belham aquifer responds to a steadily increasing sediment load due to repeated lahar sedimentation in the valley with rising aquifer pressures. A wholesale dome collapse in May 2006 on the other hand induced dilatational strain and thereby a short-term water level drop in a deeper-seated aquifer, which caused groundwater leakage from the Belham aquifer and thereby induced a delayed water level fall in the wells. The system thus responded to both gradual and rapid transient strain associated with the eruption of Soufrière Hills Volcano (Montserrat). This case study gives field evidence for theoretical predictions on volcanic drivers behind hydrological transients, demonstrating the potential of hydrological data for volcano monitoring. Interrogation of such data can provide valuable constraints on stress evolution in volcanic systems and therefore complement other monitoring systems. The presented models and inferred results are conceptually applicable to volcanic areas worldwide.

Description: Well water level changes associated with magmatic unrest can be interpreted as a result of pore pressure changes in the aquifer due to crustal deformation, and so could provide constraints on the subsurface processes causing this strain. We use finite element analysis to demonstrate the response of aquifers to volumetric strain induced by pressurized magma reservoirs. Two different aquifers are invoked – an unconsolidated pyroclastic deposit and a vesicular lava flow – and embedded in an impermeable crust, overlying a magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pressurization and the resulting hydraulic head changes as well as flow through the porous aquifer, i.e. porous flow. The simulated strain leads to centimetres (pyroclastic aquifer) to metres (lava flow aquifer) of hydraulic head changes; both strain and hydraulic head change with time due to substantial porous flow in the hydrological system. Well level changes are particularly sensitive to chamber volume, shape and pressurization strength, followed by aquifer permeability and the phase of the pore fluid. The depths of chamber and aquifer, as well as the aquifer's Young's modulus also have significant influence on the hydraulic head signal. While source characteristics, the distance between chamber and aquifer and the elastic stratigraphy determine the strain field and its partitioning, flow and coupling parameters define how the aquifer responds to this strain and how signals change with time. We find that generic analytical models can fail to capture the complex pre-eruptive subsurface mechanics leading to strain-induced well level changes, due to aquifer pressure changes being sensitive to chamber shape and lithological heterogeneities. In addition, the presence of a pore fluid and its flow have a significant influence on the strain signal in the aquifer and are commonly neglected in analytical models. These findings highlight the need for numerical models for the interpretation of observed well level signals. However, simulated water table changes do indeed mirror volumetric strain, and wells are therefore a valuable addition to monitoring systems that could provide important insights into pre-eruptive dynamics.

Description: Well water level changes associated with magmatic unrest can be interpreted as a result of pore pressure changes in the aquifer due to crustal deformation, and so could provide constraints on the subsurface processes causing this strain. We use Finite Element Analysis to demonstrate the response of aquifers to volumetric strain induced by pressurised magma reservoirs. Two different aquifers are invoked – an unconsolidated pyroclastic deposit and a vesicular lava flow – and embedded in an impermeable crust, overlying a magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pressurisation and the resulting hydraulic head changes as well as porous flow in the aquifer. The simulated deformational strain leads to centimetres (pyroclastic aquifer) to meters (lava flow aquifer) of hydraulic head changes; both strain and hydraulic head change with time due to substantial porous flow in the hydrological system. Well level changes are particularly sensitive to chamber volume and shape, followed by chamber depth and the phase of the pore fluid. The Young's Modulus and permeability of the aquifer, as well as the strength of pressurisation also have significant influence on the hydraulic head signal. While source characteristics, the distance between chamber and aquifer and the elastic stratigraphy determine the strain field and its partitioning, flow and coupling parameters define how the aquifer responds to this strain and how signals change with time. We investigated a period of pre-eruptive head changes recorded at Usu volcano, Japan, where well data were interpreted using an analytical deformation model. We find that generic analytical models can fail to capture the complex pre-eruptive subsurface mechanics leading to well level changes, due to aquifer pressure changes being sensitive to chamber shape and lithological heterogeneities. In addition, the presence of a pore fluid and its flow have a significant influence on the strain signal in the aquifer and are commonly neglected in analytical models. These findings highlight the need for numerical models for the interpretation of observed well level signals. However, simulated water table changes do mirror volumetric strain and wells can therefore serve as comparatively cheap strain meters that could provide important insights into pre-eruptive dynamics.

Description: Forecasting and early warning systems are important investments to protect lives, properties and livelihood. While early warning systems are frequently used to predict the magnitude, location and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services or financial loss. Complementing early warning systems with impact forecasts has a two‐fold advantage: it would provide decision makers with richer information to take informed decisions about emergency measures, and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multi‐hazard early warning systems. This review discusses the state‐of‐the‐art in impact forecasting for a wide range of natural hazards. We outline the added value of impact‐based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe.

Description: Forschungsdrohnen ermöglichen einen völlig neuen Blick auf aktive Vulkane. Mit ihnen sind schnell hochauflösende Bilder direkt aus dem Krater und auch Daten aus anderen bisher unerreichbaren Zonen eines Vulkans zu beschaffen. Zugleich minimiert der Einsatz von Drohnen die Gefahren für Wissenschaftlerinnen und Wissenschaftler.

Description: Die meisten Vulkanausbrüche finden dort statt, wo wir sie nur schwer beobachten können: unter Wasser. Ein kleiner Einblick in die noch junge Forschungsdisziplin der Erkundung submariner Vulkane.

Description: Mit ihren katastrophalen Auswirkungen, die den ganzen Globus betreffen, stellen Supereruptionen alle geschichtlich dokumentierten Eruptionen in den Schatten.

Description: Supereruptions represent enormous natural disasters which potentially impact the whole planet. They are unlike any other known and documented eruption.

Description: Bei phreatischen Eruptionen fehlen häufig warnende Vorzeichen. Der plötzliche Ausbruch des japanischen Vulkans Ontake im Herbst 2014 traf viele unvorbereitet.

Description: Phreatic eruptions often occur without any forewarning. Many were unprepared for the sudden eruption of Ontake volcano, Japan in autumn 2014.