Hazard and risk assessments for induced seismicity in Groningen

Earthquakes associated with gas production have been recorded in the northern part of the Netherlands since 1986. The Huizinge earthquake of 16 August 2012, the strongest so far with a magnitude of M L = 3.6, prompted reassessment of the seismicity induced by production from the Groningen gas field. An international research programme was initiated, with the participation of many Dutch and international universities, knowledge institutes and recognised experts. The prime aim of the programme was to assess the hazard and risk resulting from the induced seismicity. Classic probabilistic seismic hazard and risk assessment (PSHA) was implemented using a Monte Carlo method. The scope of the research programme extended from the cause (production of gas from the underground reservoir) to the effects (risk to people and damage to buildings). Data acquisition through field measurements and laboratory experiments was a substantial element of the research programme. The existing geophone and accelerometer monitoring network was extended, a new network of accelerometers in building foundations was installed, geophones were placed at reservoir level in deep wells, GPS stations were installed and a gravity survey was conducted. Results of the probabilistic seismic hazard and risk assessment have been published in production plans submitted to the Minister of Economic Affairs, Winningsplan Groningen 2013 and 2016 and several intermediate updates. The studies and data acquisition further constrained the uncertainties and resulted in a reduction of the initially assessed hazard and risk

Solid miscibility of common-anion lithium and sodium halides. Experimental determination of the region of demixing in lithium bromide + sodium bromide

The region of demixing of solid lithium bromide + sodium bromide mixtures has been measured by X-ray diffraction. The critical temperature of mixing corresponding to a thermodynamic fit of the experimental data is 513 K. Estimates are given of the regions of demixing in solid lithium chloride + sodium chloride and solid lithium iodide + sodium iodide

Monte Carlo Method for Probabilistic Hazard Assessment of Induced Seismicity due to Conventional Natural Gas Production

A Monte Carlo approach to probabilistic seismic‐hazard analysis is developed for a case of induced seismicity associated with a compacting gas reservoir. The geomechanical foundation for the method is the work of Kostrov (1974) and McGarr (1976) linking total strain to summed seismic moment in an earthquake catalog. Our Monte Carlo method simulates future seismic hazard consistent with historical seismic and compaction datasets by sampling probability distributions for total seismic moment, event locations and magnitudes, and resulting ground motions. Ground motions are aggregated over an ensemble of simulated catalogs to give a probabilistic representation of the ground‐motion hazard. This approach is particularly well suited to the specific nature of the time‐dependent induced seismicity considered. We demonstrate the method by applying it to seismicity induced by reservoir compaction following gas production from the Groningen gas field. A new ground‐motion prediction equation (GMPE) tailored to the Groningen field has been derived by calibrating an existing GMPE with local strong‐motion data. For 2013–2023, we find a 2% chance of exceeding a peak ground acceleration of 0.57g and a 2% chance of exceeding a peak ground velocity of 22  cm/s above the area of maximum compaction. Disaggregation shows that earthquakes of Mw 4–5, at the shortest hypocentral distances of 3 km, and ground motions two standard deviations above the median make the largest contributions to this hazard. Uncertainty in the hazard is primarily due to uncertainty about the future fraction of induced strains that will be seismogenic and how ground motion and its variability will scale to larger magnitudes

A regional site-response model for the Groningen gas field

A key element in the assessment of induced seismic hazard and risk due to induced earthquakes in the Groningen gas field is a model for the prediction of ground motions. Rather than use ground - motion prediction equations (GMPEs) with generic site amplifica tion factors conditioned on proxy parameters such as V S30 , a field - wide zonation of frequency - dependent non - linear amplification factors has been developed. Each amplification factor is associated with a measure of site - to - site variability that captures th e variation of V S profiles and hence amplification factors across each zone, as well as the influence of uncertainty in the modulus reduction and damping functions for each soil layer. This model can be used in conjunction with predictions of response spec tral accelerations at a reference rock horizon at a depth of about 80 0 m to calculate fully probabilistic estimates of the hazard in terms of ground shaking at the surface for a large region potentially affected by induced earthquakes

Framework for a ground-motion model for induced seismic hazard and risk analysis in the Groningen gas field, the Netherlands

The potential for building damage and personal injury due to induced earthquakes in the Groningen gas field is being modeled in order to inform risk management decisions. To facilitate the quantitative estimation of the induced seismic hazard and risk, a ground motion prediction model has been developed for response spectral accelerations and duration due to these earthquakes that originate within the reservoir at 3 km depth. The model is consistent with the motions recorded from small-magnitude events and captures the epistemic uncertainty associated with extrapolation to larger magnitudes. In order to reflect the conditions in the field, the model first predicts accelerations at a rock horizon some 800 m below the surface and then convolves these motions with frequency-dependent nonlinear amplification factors assigned to zones across the study area. The variability of the ground motions is modeled in all of its constituent parts at the rock and surface levels

An integrated shear-wave velocity model for the Groningen gas field, The Netherlands

A regional shear - wave velocity (V S ) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1,000 km 2 . The V S model, extending to a depth of almost 1 km, is an essential input to the modelling of hazard and risk due to induced earthquakes in the region. The detailed V S profiles are constructed from a novel combination of three data sets covering different, partially overlapping depth ranges. The uppermost 50 m of the V S profiles are obtained from a high - resolutio n geological model with representative V S values assigned to the sediments. Field measurements of V S were used to derive representative V S values for the different types of sediments. The profiles from 50 to 120 m are obtained from inversion of surface wav es recorded (as noise) during deep seismic reflection profiling of the gas reservoir. The deepest part of the profiles is obtained from sonic logging and V P - V S relationships based on measurements in deep boreholes. Criteria were established for the splicing of the three portions to generate continuous models over the entire depth range for use in site response calculations, for which an elastic half - space is ass umed to exist below a clear stratigraphic boundary and impedance contrast encountered at about 800 m depth. In order to facilitate fully probabilistic site response analyses, a scheme for the randomisation of the VS profiles is implemented