251 results found
Bommer J, Montaldo-Falero V, Virtual fault ruptures in area source zones for PSHA: are they always needed?, Seismological Research Letters, ISSN: 0895-0695
Bommer J, Green RA, Stafford PJ, et al., Liquefaction hazard of the Groningen region of the Netherlands due to induced seismicity, Journal of Geotechnical and Geoenvironmental Engineering, ISSN: 0733-9410
The operator of the Groningen gas field is leading an effort to quantify the seismic hazard and riskof the region due to induced earthquakes, includingoverseeing one of the most comprehensive liquefaction hazard studies performedgloballyto date. Due tothe unique characteristics of the seismic hazard and the geologic deposits in Groningen, efforts first focused on developing relationships for a Groningen-specific liquefaction triggering model. The liquefaction hazard was then assessedusing a Monte Carlo method, wherein a range of credibleevent scenarios were considered in computingliquefaction damage-potentialhazard curves. Thiseffort entailed the use of a regional stochastic seismic source model,ground motion prediction equation,site response model,and geologic model that were developed as part of the broader regional seismic hazardassessment.“No-to-Minor Surficial Liquefaction Manifestations”arepredicted for mostsites across the study areafor a 75-year return period. The only sites where “Moderate Surficial Liquefaction Manifestations” are predicted are in the town of Zandeweer, with only some of the sites in the townbeing predicted to experience this severityof liquefactionfor thisreturn period.
Nievas CI, Bommer J, Crowley H, et al., A database of damaging small-to-medium magnitude earthquakes, Journal of Seismology, ISSN: 1383-4649
Interest in small-to-medium magnitude earthquakes and their potential consequences has increased significantly in recent years, mostly due to the occurrence of some unusually damaging small events, the development of seismic risk assessment methodologies for existing building stock, and the recognition of the potential risk of induced seismicity. As part of a clear ongoing effort of the earthquake engineering community to develop knowledge on the risk posed by smaller events, aglobal database of earthquakes withmomentmagnitudes in the range from 4.0 to 5.5 for which damage and/or casualties have been reportedhas been compiledand is made publicly available. Thetwo main purposeswereto facilitate studies onthe potential for earthquakes in thismagnitude range to cause material damage and to carry out a statistical study to characterise the frequency with which earthquakes of this size cause damage and/or casualties(published separately). The present paper describes the data sources and processfollowedfor the compilation of the database, whileproviding critical discussions on the challenges encounteredand decisions made, which are of relevance for itsinterpretation and use.The geographic, temporal and magnitude distributions of the 1,958 earthquakesthat make up the databaseare presented alongside thegeneral statistics on damage and casualties, noting that these stem from a variety of sources of differing reliability.Despite its inherent limitations, we believe it is an important contributionto the understanding of the extent of the consequences that may arise from earthquakes in the magnitude range of study.
Bommer J, NIevas CI, Helen C, et al., 2020, Global occurrence and impact of small-to-medium magnitude earthquakes: A statistical analysis, Bulletin of Earthquake Engineering, Vol: 18, Pages: 1-35, ISSN: 1570-761X
Despite their much smaller individual contribution to the global counts of casualties and damage than theirlarger counterparts, earthquakes with moment magnitudes Mw in the range 4.0-5.5 may dominate seismichazard and risk in areas of low overall seismicity, a statement that is particularly true for regions whereanthropogenically-induced earthquakes are predominant. With the risk posed by these earthquakescausing increasing alarm in certain areas of the globe, it is of interest to determine what proportion ofearthquakes in this magnitude range that occur sufficiently close to population or the built environment doactually result in damage and/or casualties. For this purpose, a global catalogue of potentially damagingevents—that is, earthquakes deemed as potentially capable of causing damage or casualties based on aseries of pre-defined criteria—has been generated and contrasted against a database of reportedlydamaging small-to-medium earthquakes compiled in parallel to this work. This paper discusses the criteriaand methodology followed to define such a set of potentially damaging events, from the issues inherent toearthquake catalogue compilation to the definition of criteria to establish how much potential exposure issufficient to consider each earthquake a threat. The resulting statistics show that, on average, around 2% ofall potentially-damaging shocks were actually reported as damaging, though the proportion variessignificantly in time as a consequence of the impact of accessibility to data on damage and seismicity ingeneral. Inspection of the years believed to be more complete suggests that a value of around 4 to 5%might be a more realistic figure.
Bahrampouri M, Rodriguez-Marek A, Bommer JJ, 2019, Mapping the uncertainty in modulus reduction and damping curves onto the uncertainty of site amplification functions, Soil Dynamics and Earthquake Engineering, Vol: 126, ISSN: 0267-7261
Probabilistic seismic hazard analysis often requires the use of site response analyses to calculate site amplification factors (AFs) that capture the effects of near-surface layers. The site response analyses must also be conducted in a probabilistic framework to quantify the variability in AFs resulting from variation in the rock input motions and uncertainty in the dynamic properties of the soil profile, including uncertainty in the shear-wave velocity and in the nonlinear behavior of the soil. In equivalent linear analyses, the latter is captured through modulus reduction and damping curves (MRD). The joint randomization of shear-wave velocity and MRD curves can result in large computational costs. The objective of this paper is to propose a procedure to separately calculate the contribution of uncertainty in the MRD curves to the total uncertainty in the AFs for a site. This procedure is illustrated in an application for a seismic hazard and risk assessment of the Groningen gas field in the Netherlands. The results show that the effect of uncertainty in MRD curves on the uncertainty in the AFs is highly dependent on the soil profile. This effect can be significant for soft soils and strong input motions. Results also indicate that the effects of MRD uncertainty can be correlated to elastic site properties.
Ntinalexis M, Bommer JJ, Ruigrok E, et al., 2019, Ground-motion networks in the Groningen field: usability and consistency of surface recordings, JOURNAL OF SEISMOLOGY, Vol: 23, Pages: 1233-1253, ISSN: 1383-4649
Several strong-motion networks have been installed in the Groningen gas field in the Netherlands to record ground motions associated with induced earthquakes. There are now more than 450 permanent surface accelerographs plus a mobile array of 450 instruments, which, in addition to many instrumented boreholes, yield a wealth of data. The database of recordings has been of fundamental importance to the development of ground-motion models that form a key element of the seismic hazard and risk estimations for the field. In order to maximise the benefit that can be derived from these recordings, this study evaluates the usability of the recordings from the different networks, in general terms and specifically with regards to the frequency ranges with acceptable signal-to-noise ratios. The study also explores the consistency among the recordings from the different networks, highlighting in particular how a configuration error was identified and resolved. The largest accelerograph network consists of instruments housed in buildings around the field, frequently installed on the lower parts of walls rather than on the floor. A series of experiments were conducted, using additional instruments installed adjacent to these buildings and replicating the installation configuration in full-scale shake table tests, to identify the degree to which structural response contaminated the recordings. The general finding of these efforts was that for PGV and oscillator periods above 0.1 s, the response spectral ordinates from these recordings can be used with confidence.
Green RA, Bommer JJ, Rodriguez-Marek A, et al., 2019, Addressing limitations in existing ‘simplified’ liquefaction triggering evaluation procedures: application to induced seismicity in the Groningen gas field, Bulletin of Earthquake Engineering, Vol: 17, Pages: 4539-4557, ISSN: 1570-761X
The Groningen gas field is one of the largest in the world and has produced over 2000 billion m3 of natural gas since the start of production in 1963. The first earthquakes linked to gas production in the Groningen field occurred in 1991, with the largest event to date being a local magnitude (ML) 3.6. As a result, the field operator is leading an effort to quantify the seismic hazard and risk resulting from the gas production operations, including the assessment of liquefaction hazard. However, due to the unique characteristics of both the seismic hazard and the geological subsurface, particularly the unconsolidated sediments, direct application of existing liquefaction evaluation procedures is deemed inappropriate in Groningen. Specifically, the depth-stress reduction factor (rd) and the magnitude scaling factor relationships inherent to existing variants of the simplified liquefaction evaluation procedure are considered unsuitable for use. Accordingly, efforts have first focused on developing a framework for evaluating the liquefaction potential of the region for moment magnitudes (M) ranging from 3.5 to 7.0. The limitations of existing liquefaction procedures for use in Groningen and the path being followed to overcome these shortcomings are presented in detail herein.
Green R, Bommer J, 2019, What is the smallest earthquake magnitude that needs to be considered in assessing liquefaction hazard?, Earthquake Spectra, Vol: 35, Pages: 1441-1464, ISSN: 8755-2930
Probabilistic assessments of the potential impact of earthquakes on the infrastructure entails the consideration of smaller magnitude events than those generally considered in deterministic hazard and risk assessments. In this context, it is useful to establish if there is a magnitude threshold below which the possibility of triggering liquefaction can be discounted because such a lower bound is required for probabilistic liquefaction hazard analyses. Based on field observations and a simple parametric study, we conclude that earthquakes as small as moment magnitude 4.5 can trigger liquefaction in extremely susceptible soil deposits. However, for soil profiles that are suitable for building structures, the minimum earthquake magnitude for the triggering of liquefaction is about 5. We therefore propose that in liquefaction hazard assessments of building sites magnitude 5.0 be adopted as the minimum earthquake size considered, while magnitudes as low as 4.5 may be appropriate for some other types of infrastructure.
Edwards B, Zurek B, van Dedem E, et al., 2019, Simulations for the development of a ground motion model for induced seismicity in the Groningen gas field, the Netherlands, Bulletin of Earthquake Engineering, Vol: 17, Pages: 4441-4456, ISSN: 1570-761X
We present simulations performed for the development of a ground motion model for induced earthquakes in the Groningen gas field. The largest recorded event, with M3.5, occurred in 2012 and, more recently, a M3.4 event in 2018 led to recorded ground accelerations exceeding 0.1 g. As part of an extensive hazard and risk study, it has been necessary to predict ground motions for scenario earthquakes up to M7. In order to achieve this, while accounting for the unique local geology, a range of simulations have been performed using both stochastic and full-waveform finite-difference simulations. Due to frequency limitations and lack of empirical calibration of the latter approach, input simulations for the ground motion model used in the hazard and risk analyses have been performed with a finite-fault stochastic method. However, in parallel, extensive studies using the finite-difference simulations have guided inputs and modelling considerations for these simulations. Three approaches are used: (1) the finite-fault stochastic method, (2) elastic point- and (3) finite-source 3D finite-difference simulations. We present a summary of the methods and their synthesis, including both amplitudes and durations within the context of the hazard and risk model. A unique form of wave-propagation with strong lateral focusing and defocusing is evident in both peak amplitudes and durations. The results clearly demonstrate the need for a locally derived ground motion model and the potential for reduction in aleatory variability in moving toward a path-specific fully non-ergodic model.
Stafford PJ, Zurek BD, Ntinalexis M, et al., 2019, Extensions to the Groningen ground-motion model for seismic risk calculations: component-to-component variability and spatial correlation, Bulletin of Earthquake Engineering, Vol: 17, Pages: 4417-4439, ISSN: 1573-1456
A bespoke ground-motion model has been developed for the prediction of response spectral accelerations, peak ground velocity and significant duration due to induced earthquakes in the Groningen gas field in the Netherlands. For applications to the calculation of risk to the exposed building stock, extensions to the model are required. The use of the geometric mean horizontal component in the ground-motion predictions and the arbitrary horizontal component for the building fragility functions requires the addition of component-to-component variability. A model for this variability has been developed that both reflects the strong horizontal polarisation of motions observed in many Groningen records obtained at short distances and the fact that the strong polarisation is unlikely to persist at larger magnitudes. The other extension of the model is the spatial correlation of ground motions for the calculation of aggregated risk, which can be approximated through simple rules for sampling the variance within site response zones. Making use of ground-motion recordings from several networks in the field and the results of finite difference waveform simulations, a Groningen-specific spatial correlation model has been developed. The new model also combines results from traditional variogram fitting approaches with a new method to infer spatial correlation lengths from observed variance reduction. The development of the new spatial correlation model relaxes the need to approximate spatial correlation through the sampling of site response, although the results obtained herein suggest that similar results could be obtained using either approach. The preliminary consideration of the numerical waveform modelling results in this study paves the way for significant extensions to be made for the modelling of spatial correlations and the decomposition of apparent spatial variability into systematic and random components within a fully non-ergodic framework .
van Elk J, Bourne SJ, Oates SJ, et al., 2019, A probabilistic model to evaluate options for mitigating induced seismic risk, Earthquake Spectra, Vol: 35, Pages: 537-564, ISSN: 8755-2930
Common responses to induced seismicity are based on control of the anthropogenic activity causing the earthquakes, like fluid injection or withdrawal, in order to limit either the magnitudes of the events or the level of ground motion to within established thresholds. An alternative risk mitigation option is seismic retrofitting of the more vulnerable buildings potentially exposed to the ground shaking in order to reduce the risk to acceptable levels. Optimal mitigation strategies may combine both production control and structural strengthening, for which a probabilistic risk model is required that can estimate the change in hazard due to production or injection variations and the changes in fragility resulting from structural interventions. Such a risk model has been developed for the Groningen gas field in the Netherlands. The framework for this risk model to inform decision-making regarding mitigation strategies can be adapted to other cases of anthropogenically-induced seismicity.
Dost B, Edwards B, Bommer JJ, Erratum The Relationship between M and ML: A Review and Application to Induced Seismicity in the Groningen Gas Field, The Netherlands, Seismological Research Letters, ISSN: 0895-0695
Verdon JP, Baptie BJ, Bommer J, 2019, An improved framework for discriminating seismicity induced by industrial activities from natural earthquakes, Seismological Research Letters, Vol: 90, Pages: 1592-1611, ISSN: 0895-0695
Heightened concerns regarding induced seismicity necessitate robust methods to assess whether detected earthquakes near industrial sites are natural or induced by the industrial activity. These assessments are required rapidly, which often precludes detailed modeling of fluid pressures and the geomechanical response of the reservoir and nearby faults. Simple question‐based assessment schemes in current use are a useful tool but suffer from several shortcomings: they do not specifically address questions regarding whether available evidence supports the case for natural seismicity; they give all questions equal weighting regardless of the relative influence of different factors; they are not formulated to account for ambiguous or uncertain evidence; and the final outcomes can be difficult to interpret. We propose a new framework that addresses these shortcomings by assigning numerical scores to each question, with positive values for answers that support induced seismicity and negative values for responses favoring natural seismicity. The score values available for each question reflect the relative importance of the different questions, and for each question the absolute value of the score is modulated according to the degree of uncertainty. The final outcome is a score, the induced assessment ratio, either positive or negative (or zero), that reflects whether events were induced or natural. A second score, the evidence strength ratio, is assigned that characterizes the strength of the available evidence, expressed as the ratio of the maximum score possible with the available evidence relative to the maximum score that could be obtained if all desired data were available at a site. We demonstrate this approach by application to two case studies in the United Kingdom, one widely regarded as a case of induced seismicity, and the other more likely to be a series of tectonic earthquakes.
de Almeida AAD, Assumpção M, Bommer JJ, et al., 2019, Probabilistic seismic hazard analysis for a nuclear power plant site in southeast Brazil, Journal of Seismology, Vol: 23, Pages: 1-23, ISSN: 1383-4649
A site-specific probabilistic seismic hazard analysis (PSHA) has been performed for the only nuclear power plant site in Brazil, located 130 km southwest of Rio de Janeiro at Angra dos Reis. Logic trees were developed for both the seismic source characterisation and ground-motion characterisation models, in both cases seeking to capture the appreciable ranges of epistemic uncertainty with relatively few branches. This logic-tree structure allowed the hazard calculations to be performed efficiently while obtaining results that reflect the inevitable uncertainty in long-term seismic hazard assessment in this tectonically stable region. An innovative feature of the study is an additional seismic source zone added to capture the potential contributions of characteristics earthquake associated with geological faults in the region surrounding the coastal site.
Ulmer KJ, Upadhyaya S, Green RA, et al., 2018, A Critique of b-Values Used for Computing Magnitude Scaling Factors, Geotechnical Earthquake Engineering and Soil Dynamics V, Pages: 112-121, ISSN: 0895-0563
© 2018 American Society of Civil Engineers. The objective of this paper is to explore the effects of relative density, effective confining stress, and liquefaction initiation criteria on the slope (or b-value) of the cyclic stress ratio versus number of uniform stress cycles to liquefaction curve in log-log space. The b-value is central to the computation of magnitude scaling factors (MSF) used in evaluating liquefaction potential and can be determined from cyclic laboratory tests such as cyclic triaxial (CTRX), cyclic simple shear (CSS), and cyclic torsional (CTS) tests. This paper provides a summary of b-values calculated from published test data representing multiple types of laboratory tests, sands, sample preparation methods, and liquefaction criteria. Trends between b-values and relative density are shown to be more ambiguous than is often assumed. Effective confining stresses and liquefaction criteria are also shown to have an effect on b-values.
Noorlandt R, Kruiver PP, de Kleine MPE, et al., 2018, Characterisation of ground motion recording stations in the Groningen gas field, Journal of Seismology, Vol: 22, Pages: 605-623, ISSN: 1383-4649
The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity (V S ). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ V S values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging. The offset SCPT, cross-hole tomography and common midpoint cross-correlation (CMPcc) processing of MASW data all revealed lateral variations on length scales of several to tens of metres in this geological setting. SCPTs resulted in very detailed V S profiles with depth, but represent point measurements in a heterogeneous environment. The MASW results represent V S information on a larger spatial scale and smooth some of the heterogeneity encountered at the sites. The combination of MASW and SCPT proved to be a powerful and cost-effective approach in determining representative V S profiles at the accelerograph station sites. The measured V S profiles correspond well with the modelled profiles and they significantly enhance the ground motion model derivation. The similarity between the theoretical transfer function from the V S profile and the observed amplification from vertical array stations is also excellent.
Dost B, Edwards B, Bommer JJ, 2018, The relationship between M and M<inf>L</inf>: A review and application to induced seismicity in the groningen gas field, the Netherlands, Seismological Research Letters, Vol: 89, Pages: 1062-1074, ISSN: 0895-0695
The use of local magnitude (M L ) in seismic hazard analyses is a topic of recent debate. In regions of weak or moderate seismicity, small earthquakes (characterized by M L ) are commonly used to determine frequency-magnitude distributions (FMDs) for probabilistic seismic hazard calculations. However, empirical and theoretical studies on the relation between moment magnitude (M) and M L for small earthquakes show a systematic difference between the two below a region-dependent magnitude threshold. This difference may introduce bias in the estimation of the frequency of larger events with given M, and consequently seismic hazard. For induced seismicity related to the Groningen gas field, this magnitude threshold is determined to be M ∼ 2, with equality between M and M L at higher magnitudes. A quadratic relation between M and M L is derived for 0:5 < M L < 2, in correspondence to recent theoretical studies. Although the seismic hazard analysis for Groningen is internally consistent when expressed in terms of M L (with the implicit assumption of equivalence between the two scales), a more physical interpretation of the seismicity model requires transformation of the earthquake catalog from local to moment magnitude, especially because the dataset currently used in estimating time-dependent hazard consists mainly of M L < 2:5 events. We show that measured station effects, derived from M calculations, correspond to predicted model calculations used to determine a ground-motion model for the region.
Bommer JJ, Dost B, Edwards B, The relationship between M and ML – a review and application to induced seismicity in the Groningen gas field, the Netherlands, Seismological Research Letters, ISSN: 0895-0695
The use of local magnitude (ML) in seismic hazard analyses is a topic of recent debate. In 2regions of weak-or moderate-seismicity, small earthquakes (characterized by ML) are 3commonly used to determine frequency-magnitude distributions (FMD) for probabilistic4seismic hazard calculations. However, empirical and theoretical studies on the relation 5between moment magnitude (M) and ML for small earthquakes show a systematic difference between the two below a region-dependent magnitude threshold. This difference may introduce bias in the estimation of the frequency of larger events with given M, and consequently seismic hazard. For induced seismicity related to the Groningen gas field, this magnitude threshold is determined to be M~ 2, with equality between Mand ML at higher magnitudes. A quadratic relation between M and ML is derived for 0.5 < ML < 2, in correspondence to recent theoretical studies. While the seismic hazard analysis for Groningen is internally consistent when expressed in terms of ML (with the implicit assumption of equivalence between the two scales), a more physical interpretation of theseismicity model requirestransformation of the earthquake catalogue from local to moment magnitude, especially since the dataset currently used in estimating time-dependent hazard consists mainly of ML< 2.5 events. We show that measured station effects, derived from Mcalculations, correspond to predicted model calculations used to determine a ground-motion model for the region.
Bommer JJ, Dost B, Edwards B, et al., 2018, Developing a model for the prediction of ground motions due to earthquakes in the Groningen gas field, NETHERLANDS JOURNAL OF GEOSCIENCES-GEOLOGIE EN MIJNBOUW, Vol: 96, Pages: S203-S213, ISSN: 0016-7746
Major efforts are being undertaken to quantify seismic hazard and risk due to production-induced earthquakes in the Groningen gas field as thebasis for rational decision-making about mitigation measures. An essential element is a model to estimate surface ground motions expected at anylocation for each earthquake originating within the gas reservoir. Taking advantage of the excellent geological and geophysical characterisationof thefield and a growing database of ground-motion recordings, models have been developed for predicting response spectral accelerations, peak groundvelocity and ground-motion durations for a wide range of magnitudes. The models reflect the unique source and travel path characteristics of theGroningen earthquakes, and account for the inevitable uncertainty in extrapolating from the small observed magnitudes to potential larger events.The predictions of ground-motion amplitudes include the effects of nonlinear site response of the relatively soft near-surface deposits throughoutthe field.
Green RA, Stafford P, Maurer BW, et al., Liquefaction hazard due to induced seismicity: Overview of the pilot study being performed for the Groningen region of the Netherlands, 11th U.S. National Conference on Earthquake Engineering, Publisher: Earthquake Engineering Research Institute
Bommer JJ, van Elk J, Doornhof D, et al., 2017, Hazard and risk assessments for induced seismicity in Groningen, Netherlands Journal of Geosciences, Vol: 96, Pages: 2259-s269, ISSN: 0016-7746
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.
Stafford PJ, Rodriguez-Marek A, Edwards B, et al., 2017, Scenario dependence of linear site effect factors for short-period response spectral ordinates, Bulletin of the Seismological Society of America, Vol: 107, Pages: 2859-2872, ISSN: 0037-1106
Ground‐motion models for response spectral ordinates commonly partition site‐response effects into linear and nonlinear components. The nonlinear components depend upon the earthquake scenario being considered implicitly through the use of the expected level of excitation at some reference horizon. The linear components are always assumed to be independent of the earthquake scenario. This article presents empirical and numerical evidence as well as a theoretical explanation for why the linear component of site response depends upon the magnitude and distance of the earthquake scenario. Although the impact is most pronounced for small‐magnitude scenarios, the finding has significant implications for a number of applications of more general interest including the development of site‐response terms within ground‐motion models, the estimation of ground‐motion variability components ϕS2SϕS2S and ϕSSϕSS , the construction of partially nonergodic models for site‐specific hazard assessments, and the validity of the convolution approach for computing surface hazard curves from those at a reference horizon, among others. All of these implications are discussed in the present article.
Rodriguez-Marek A, Kruiver PP, Meijers P, et al., 2017, A regional site-response model for the Groningen gas field, Bulletin of the Seismological Society of America, Vol: 107, Pages: 2067-2077, ISSN: 1943-3573
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 amplification factors conditioned on proxyparameters such as VS30, 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 the variation of VSprofiles 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 spectral accelerations at a reference rock horizon at a depthof about 800 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.
Bommer JJ, Crowley H, 2017, The purpose and definition of the minimum magnitude limit in PSHA calculations, Seismological Research Letters, Vol: 88, Pages: 1097-1106, ISSN: 0895-0695
A lower limit of magnitude Mmin is routinely defined for integrations of earthquake scenarios in probabilistic seismic‐hazard analysis but there is widespread misunderstanding of the technical bases for determining the value of this parameter. In this article, several misconceptions are identified and discarded prior to providing a clear and unambiguous definition of Mmin that points to the fact that seismic‐hazard assessment is always conditioned by the intended application of the outputs. We argue that Mmin is therefore an engineering parameter that is ultimately related to seismic risk rather than seismic hazard. The confusion surrounding this topic could be largely alleviated by defining lower limits on appropriate intensity measures rather than on magnitudes used as a proxy for shaking levels.
Bommer JJ, Stafford PJ, Edwards B, et al., 2017, Framework for a Ground-Motion Model for Induced Seismic Hazard and Risk Analysis in the Groningen Gas Field, The Netherlands, EARTHQUAKE SPECTRA, Vol: 33, Pages: 481-498, ISSN: 8755-2930
Bommer JJ, van Elk J, 2017, Comment on “The maximum possible and maximum expected earthquake magnitude for production-induced earthquakes at the gas field in Groningen, The Netherlands” by Gert Zöller and Matthias Holschneider, Bulletin of the Seismological Society of America, Vol: 107, ISSN: 1943-3573
Zöller and Holschneider (2016) propose estimates of the maximum magnitude of induced earthquakes resulting from gas production in the Groningen field in The Netherlands by applying the approach of Zöller and Holschneider (2014) to the earthquake catalog for the Groningen field. We wish neither to make any comment on the analytical approach that the authors propose, nor to comment on their results in this particular application. We do feel obliged to clarify for readers the context of the study by Zöller and Holschneider (2016) in relation to the March 2016 workshop to which they refer. In particular, the sentence in their Introduction stating that “this short note provides the results of those authors” (p. 2917) could be interpreted as implying that their paper presents the results from the workshop. The paper by Zöller and Holschneider (2016) summarizes one of the many inputs that contributed to the workshop, but not the final outcome of the workshop.
Kruiver PP, van Dedem E, Romijn R, et al., 2017, An integrated shear-wave velocity model for the Groningen gas field, The Netherlands, Bulletin of Earthquake Engineering, Vol: 15, Pages: 3555-3580, ISSN: 1570-761X
A regional shear-wave velocity (VS) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1000 km2. The VS 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 VS profiles are constructed from a novel combination of three data sets covering different, partially overlapping depth ranges. The uppermost 50 m of the VS profiles are obtained from a high-resolution geological model with representative VS values assigned to the sediments. Field measurements of VS were used to derive representative VS values for the different types of sediments. The profiles from 50 to 120 m are obtained from inversion of surface waves recorded (as noise) during deep seismic reflection profiling of the gas reservoir. The deepest part of the profiles is obtained from sonic logging and VP–VS 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 assumed 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.
Bommer JJ, Stafford PJ, Edwards B, et al., Framework for a ground-motion model for induced seismic hazard and risk analysis in the Groningen gas field, the Netherlands, Earthquake Spectra, ISSN: 8755-2930
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.
Bommer JJ, Dost B, Edwards B, et al., 2015, Developing an Application-Specific Ground-Motion Model for Induced Seismicity, Bulletin of the Seismological Society of America, Vol: 106, Pages: 158-173, ISSN: 1943-3573
A key element of quantifying both the hazard and risk due to inducedearthquakes is a suite of appropriate ground-motion prediction equations (GMPEs) thatencompass the possible shaking levels due to such events. Induced earthquakes arelikely to be of smaller magnitude and shallower focal depth than the tectonic earthquakesfor which most GMPEs are derived. Furthermore, whereas GMPEs formoderate-to-large magnitude earthquakes are usually derived to be transportable todifferent locations and applications, taking advantage of the limited regional dependenceobserved for such events, the characteristics of induced earthquakes warrant thedevelopment of application-specific models. A preliminary ground-motion model forinduced seismicity in the Groningen gas field in The Netherlands is presented as anillustration of a possible approach to the development of these equations. The GMPE iscalibrated to local recordings of small-magnitude events and captures the epistemicuncertainty in the extrapolation to larger magnitude considered in the assessment ofthe resulting hazard and risk.
Bourne SJ, Oates SJ, Bommer JJ, et al., 2015, Monte Carlo Method for Probabilistic Hazard Assessment of Induced Seismicity due to Conventional Natural Gas Production, Bulletin of the Seismological Society of America, Vol: 105, Pages: 1721-1738, ISSN: 0037-1106
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.
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