Riccardo Minetto, Agnès Helmstetter, Benjamin Edwards, Philippe Guéguen
In August 2019, a multistage hydraulic fracturing (HF) operation was carried out at Preston New Road, United Kingdom. HF caused abundant seismic activity that culminated with an ML 2.9 event. The seismic activity was recorded by a downhole array of 12 sensors located in a nearby monitoring well. About 55,556 events were detected and located in real time during the operation by a service company. In this study, we first improve the number of detections by applying template matching and later calculate the moment magnitude of the associated earthquakes. Then we show that by separately analyzing the periods during and immediately after injection, distinct patterns can be identified. We observe an increase in the delay and decrease in amplitude of peak seismicity during subsequent phases of injection. After injection, the seismicity decay can be described by the Omori–Utsu law. The decay rate tends to slow with each successive injection, in particular during the later injection stages. In addition, the frequency–magnitude distribution evolves from a tapered distribution (lack of large events) to a bilinear distribution (excess of large events). This evolution is gradual, with the corner magnitude increasing with each injection. We interpret these patterns as the result of the combined effect of two factors: (1) the stimulated volume becoming increasingly aseismic and (2) the gradual increase in its size, which increases the probability of triggered events on preexisting faults. More generally, these patterns suggest that seismic activity during injection is strongly influenced by the injection history and is modulated by local conditions such as stress state, fault structure, and permeability.
{"title":"How Injection History Can Affect Hydraulic Fracturing–Induced Seismicity: Insights from Downhole Monitoring at Preston New Road, United Kingdom","authors":"Riccardo Minetto, Agnès Helmstetter, Benjamin Edwards, Philippe Guéguen","doi":"10.1785/0120230147","DOIUrl":"https://doi.org/10.1785/0120230147","url":null,"abstract":"In August 2019, a multistage hydraulic fracturing (HF) operation was carried out at Preston New Road, United Kingdom. HF caused abundant seismic activity that culminated with an ML 2.9 event. The seismic activity was recorded by a downhole array of 12 sensors located in a nearby monitoring well. About 55,556 events were detected and located in real time during the operation by a service company. In this study, we first improve the number of detections by applying template matching and later calculate the moment magnitude of the associated earthquakes. Then we show that by separately analyzing the periods during and immediately after injection, distinct patterns can be identified. We observe an increase in the delay and decrease in amplitude of peak seismicity during subsequent phases of injection. After injection, the seismicity decay can be described by the Omori–Utsu law. The decay rate tends to slow with each successive injection, in particular during the later injection stages. In addition, the frequency–magnitude distribution evolves from a tapered distribution (lack of large events) to a bilinear distribution (excess of large events). This evolution is gradual, with the corner magnitude increasing with each injection. We interpret these patterns as the result of the combined effect of two factors: (1) the stimulated volume becoming increasingly aseismic and (2) the gradual increase in its size, which increases the probability of triggered events on preexisting faults. More generally, these patterns suggest that seismic activity during injection is strongly influenced by the injection history and is modulated by local conditions such as stress state, fault structure, and permeability.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"13 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140324050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthew C. Gerstenberger, Sanjay Bora, Brendon A. Bradley, Chris DiCaprio, Anna Kaiser, Elena F. Manea, Andy Nicol, Chris Rollins, Mark W. Stirling, Kiran K. S. Thingbaijam, Russ J. Van Dissen, Elizabeth R. Abbott, Gail M. Atkinson, Chris Chamberlain, Annemarie Christophersen, Kate Clark, Genevieve L. Coffey, Chris A. de la Torre, Susan M. Ellis, Jeff Fraser, Kenny Graham, Jonathan Griffin, Ian J. Hamling, Matt P. Hill, A. Howell, Anne Hulsey, Jessie Hutchinson, Pablo Iturrieta, Kaj M. Johnson, V. Oakley Jurgens, Rachel Kirkman, Rob M. Langridge, Robin L. Lee, Nicola J. Litchfield, Jeremy Maurer, Kevin R. Milner, Sepi Rastin, Mark S. Rattenbury, David A. Rhoades, John Ristau, Danijel Schorlemmer, Hannu Seebeck, Bruce E. Shaw, Peter J. Stafford, Andrew C. Stolte, John Townend, Pilar Villamor, Laura M. Wallace, Graeme Weatherill, Charles A. Williams, Liam M. Wotherspoon
The 2022 revision of Aotearoa New Zealand National Seismic Hazard Model (NZ NSHM 2022) has involved significant revision of all datasets and model components. In this article, we present a subset of many results from the model as well as an overview of the governance, scientific, and review processes followed by the NZ NSHM team. The calculated hazard from the NZ NSHM 2022 has increased for most of New Zealand when compared with the previous models. The NZ NSHM 2022 models and results are available online.
{"title":"The 2022 Aotearoa New Zealand National Seismic Hazard Model: Process, Overview, and Results","authors":"Matthew C. Gerstenberger, Sanjay Bora, Brendon A. Bradley, Chris DiCaprio, Anna Kaiser, Elena F. Manea, Andy Nicol, Chris Rollins, Mark W. Stirling, Kiran K. S. Thingbaijam, Russ J. Van Dissen, Elizabeth R. Abbott, Gail M. Atkinson, Chris Chamberlain, Annemarie Christophersen, Kate Clark, Genevieve L. Coffey, Chris A. de la Torre, Susan M. Ellis, Jeff Fraser, Kenny Graham, Jonathan Griffin, Ian J. Hamling, Matt P. Hill, A. Howell, Anne Hulsey, Jessie Hutchinson, Pablo Iturrieta, Kaj M. Johnson, V. Oakley Jurgens, Rachel Kirkman, Rob M. Langridge, Robin L. Lee, Nicola J. Litchfield, Jeremy Maurer, Kevin R. Milner, Sepi Rastin, Mark S. Rattenbury, David A. Rhoades, John Ristau, Danijel Schorlemmer, Hannu Seebeck, Bruce E. Shaw, Peter J. Stafford, Andrew C. Stolte, John Townend, Pilar Villamor, Laura M. Wallace, Graeme Weatherill, Charles A. Williams, Liam M. Wotherspoon","doi":"10.1785/0120230182","DOIUrl":"https://doi.org/10.1785/0120230182","url":null,"abstract":"The 2022 revision of Aotearoa New Zealand National Seismic Hazard Model (NZ NSHM 2022) has involved significant revision of all datasets and model components. In this article, we present a subset of many results from the model as well as an overview of the governance, scientific, and review processes followed by the NZ NSHM team. The calculated hazard from the NZ NSHM 2022 has increased for most of New Zealand when compared with the previous models. The NZ NSHM 2022 models and results are available online.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"63 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139580351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A ground‐motion model (GMM) that strikes a balance between empirical and simulation‐based approaches is developed in support of the 2022 update of the New Zealand National Seismic Hazard Model. The development follows the backbone approach, comprising a central model to express the median ground motions for earthquakes in New Zealand (NZ), along with upper and lower alternatives to describe its epistemic uncertainty. Aleatory variability of ground‐motion amplitudes about the median is also characterized. Separate GMMs are developed for crustal, interface, and in‐slab earthquakes. The approach taken is to perform a regression analysis of the NZ response spectra database employing a functional form, concepts, and constraints that are drawn from equivalent point‐source simulations. The model parameters that control the scaling of the GMM with magnitude and distance describe source effects (seismic moment and stress parameter), path effects (geometric and anelastic attenuation), and site effects (site shear‐wave velocity). The NZ database provides constraints on the model for M ∼ 4–7, for frequencies from 0.2 to 100 Hz, at distances to ∼400 km. Extension of the GMM to larger magnitudes (M 7–9) is constrained by the Hassani and Atkinson seismological model, which was developed for application to events of M 3–9 and validated in data‐rich regions (California for crustal earthquakes, Japan for interface and slab earthquakes).
{"title":"Backbone Ground‐Motion Models for Crustal, Interface, and Slab Earthquakes in New Zealand from Equivalent Point‐Source Concepts","authors":"Gail M. Atkinson","doi":"10.1785/0120230144","DOIUrl":"https://doi.org/10.1785/0120230144","url":null,"abstract":"A ground‐motion model (GMM) that strikes a balance between empirical and simulation‐based approaches is developed in support of the 2022 update of the New Zealand National Seismic Hazard Model. The development follows the backbone approach, comprising a central model to express the median ground motions for earthquakes in New Zealand (NZ), along with upper and lower alternatives to describe its epistemic uncertainty. Aleatory variability of ground‐motion amplitudes about the median is also characterized. Separate GMMs are developed for crustal, interface, and in‐slab earthquakes. The approach taken is to perform a regression analysis of the NZ response spectra database employing a functional form, concepts, and constraints that are drawn from equivalent point‐source simulations. The model parameters that control the scaling of the GMM with magnitude and distance describe source effects (seismic moment and stress parameter), path effects (geometric and anelastic attenuation), and site effects (site shear‐wave velocity). The NZ database provides constraints on the model for M ∼ 4–7, for frequencies from 0.2 to 100 Hz, at distances to ∼400 km. Extension of the GMM to larger magnitudes (M 7–9) is constrained by the Hassani and Atkinson seismological model, which was developed for application to events of M 3–9 and validated in data‐rich regions (California for crustal earthquakes, Japan for interface and slab earthquakes).","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"185 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139580482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Probabilistic seismic hazard analysis (PSHA) is a methodology with a long history and has been widely implemented. However, in the conventional PSHA and sequence‐based probabilistic seismic hazard analysis (SPSHA) approaches, the occurrence of mainshocks is modeled as the homogeneous Poisson process, which is unsuitable for large earthquakes. To account for the stationary occurrence of small‐to‐moderate (STM) mainshocks and the nonstationary behavior of large mainshocks, we propose a time‐dependent sequence‐based probabilistic seismic hazard analysis (TD‐SPSHA) approach by combining the time‐dependent mainshock probabilistic seismic hazard analysis (TD‐PSHA) and aftershock probabilistic seismic hazard analysis, consisting of four components: (1) STM mainshocks, (2) aftershocks associated with STM mainshocks, (3) large mainshocks, and (4) aftershocks associated with large mainshocks. The approach incorporates an exponential‐magnitude, exponential‐time model for STM mainshocks, and a renewal‐time, characteristic‐magnitude model for large mainshocks to assess the time‐dependent hazard for mainshocks. Then nonhomogeneous Poisson process is used to model the occurrence of associated aftershocks, in which the aftershock sequences can be modeled using the Reasenberg and Jones (RJ) model or the epidemic‐type aftershock sequence (ETAS) model. To demonstrate the proposed TD‐SPSHA approach, a representative site of the San Andreas fault is selected as a benchmark case, for which five time‐dependent recurrence models, including normal, lognormal, gamma, Weibull, and Brownian passage time (BPT) distributions, are chosen to determine the occurrence of large mainshocks. Then sensitivity tests are presented to show the effects on TD‐SPSHA, including (1) time‐dependent recurrence models, (2) mainshock magnitude, (3) rupture distance, (4) aftershock duration, (5) escaped time since the last event, and (6) future time interval. Furthermore, the bimodal hybrid renewal model is utilized by TD‐SPSHA for another case site. The comparison results illustrate that the sequence hazard analysis approach ignoring time‐varying properties of large earthquakes for long periods and the effects of associated aftershocks will result in a significantly underestimated hazard. The TD‐SPSHA‐based hazard curves using the ETAS model are larger than those of the RJ model. The proposed TD‐SPSHA approach may be of significant interest to the field of earthquake engineering, particularly in the context of structural design or seismic risk analysis for the long term.
{"title":"Time‐Dependent Probabilistic Seismic Hazard Analysis for Seismic Sequences Based on Hybrid Renewal Process Models","authors":"Ming‐Yang Xu, Da‐Gang Lu, Wei Zhou","doi":"10.1785/0120230074","DOIUrl":"https://doi.org/10.1785/0120230074","url":null,"abstract":"Probabilistic seismic hazard analysis (PSHA) is a methodology with a long history and has been widely implemented. However, in the conventional PSHA and sequence‐based probabilistic seismic hazard analysis (SPSHA) approaches, the occurrence of mainshocks is modeled as the homogeneous Poisson process, which is unsuitable for large earthquakes. To account for the stationary occurrence of small‐to‐moderate (STM) mainshocks and the nonstationary behavior of large mainshocks, we propose a time‐dependent sequence‐based probabilistic seismic hazard analysis (TD‐SPSHA) approach by combining the time‐dependent mainshock probabilistic seismic hazard analysis (TD‐PSHA) and aftershock probabilistic seismic hazard analysis, consisting of four components: (1) STM mainshocks, (2) aftershocks associated with STM mainshocks, (3) large mainshocks, and (4) aftershocks associated with large mainshocks. The approach incorporates an exponential‐magnitude, exponential‐time model for STM mainshocks, and a renewal‐time, characteristic‐magnitude model for large mainshocks to assess the time‐dependent hazard for mainshocks. Then nonhomogeneous Poisson process is used to model the occurrence of associated aftershocks, in which the aftershock sequences can be modeled using the Reasenberg and Jones (RJ) model or the epidemic‐type aftershock sequence (ETAS) model. To demonstrate the proposed TD‐SPSHA approach, a representative site of the San Andreas fault is selected as a benchmark case, for which five time‐dependent recurrence models, including normal, lognormal, gamma, Weibull, and Brownian passage time (BPT) distributions, are chosen to determine the occurrence of large mainshocks. Then sensitivity tests are presented to show the effects on TD‐SPSHA, including (1) time‐dependent recurrence models, (2) mainshock magnitude, (3) rupture distance, (4) aftershock duration, (5) escaped time since the last event, and (6) future time interval. Furthermore, the bimodal hybrid renewal model is utilized by TD‐SPSHA for another case site. The comparison results illustrate that the sequence hazard analysis approach ignoring time‐varying properties of large earthquakes for long periods and the effects of associated aftershocks will result in a significantly underestimated hazard. The TD‐SPSHA‐based hazard curves using the ETAS model are larger than those of the RJ model. The proposed TD‐SPSHA approach may be of significant interest to the field of earthquake engineering, particularly in the context of structural design or seismic risk analysis for the long term.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"31 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139580938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthew C. Gerstenberger, Allison L. Bent, P. Martin Mai, John Townend
The recent completion of a fundamental revision of the New Zealand National Seismic Hazard Model (New Zealand NSHM) provided the catalyst for a joint BSSA Special Issue and SRL Focus Section on seismic hazard models worldwide. The approaches to NSHMs in different locations are varied and driven by different expertise, different philosophies, different tectonic environments, and different needs of the local communities. Despite the large number of countries facing risks from earthquakes, the community of researchers working on NSHMs is small, and it is to our benefit as a community to learn from each other and to understand approaches other...
{"title":"Introduction to the BSSA Special Issue and SRL Focus Section on Seismic Hazard Models","authors":"Matthew C. Gerstenberger, Allison L. Bent, P. Martin Mai, John Townend","doi":"10.1785/0120230310","DOIUrl":"https://doi.org/10.1785/0120230310","url":null,"abstract":"The recent completion of a fundamental revision of the New Zealand National Seismic Hazard Model (New Zealand NSHM) provided the catalyst for a joint BSSA Special Issue and SRL Focus Section on seismic hazard models worldwide. The approaches to NSHMs in different locations are varied and driven by different expertise, different philosophies, different tectonic environments, and different needs of the local communities. Despite the large number of countries facing risks from earthquakes, the community of researchers working on NSHMs is small, and it is to our benefit as a community to learn from each other and to understand approaches other...","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"166 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139580483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Brendon A. Bradley, Sanjay S. Bora, Robin L. Lee, Elena F. Manea, Matthew C. Gerstenberger, Peter J. Stafford, Gail M. Atkinson, Graeme Weatherill, Jesse Hutchinson, Christopher A. de la Torre, Anne M. Hulsey, Anna E. Kaiser
This article summarizes the ground‐motion characterization (GMC) model component of the 2022 New Zealand National Seismic Hazard Model (2022 NZ NSHM). The model development process included establishing a NZ‐specific context through the creation of a new ground‐motion database, and consideration of alternative ground‐motion models (GMMs) that have been historically used in NZ or have been recently developed for global application with or without NZ‐specific regionalizations. Explicit attention was given to models employing state‐of‐the‐art approaches in terms of their ability to provide robust predictions when extrapolated beyond the predictor variable scenarios that are well constrained by empirical data alone. We adopted a “hybrid” logic tree that combined both a “weights‐on‐models” approach along with backbone models (i.e., metamodels), the former being the conventional approach to GMC logic tree modeling for NSHM applications using published models, and the latter being increasingly used in research literature and site‐specific studies. In this vein, two NZ‐specific GMMs were developed employing the backbone model construct. All of the adopted subduction GMMs in the logic tree were further modified from their published versions to include the effects of increased attenuation in the back‐arc region; and, all but one model was modified to account for the reduction in ground‐motion standard deviations as a result of nonlinear surficial site response. As well as being based on theoretical arguments, these adjustments were implemented as a result of hazard sensitivity analyses using models without these effects, which we consider gave unrealistically high hazard estimates.
{"title":"The Ground‐Motion Characterization Model for the 2022 New Zealand National Seismic Hazard Model","authors":"Brendon A. Bradley, Sanjay S. Bora, Robin L. Lee, Elena F. Manea, Matthew C. Gerstenberger, Peter J. Stafford, Gail M. Atkinson, Graeme Weatherill, Jesse Hutchinson, Christopher A. de la Torre, Anne M. Hulsey, Anna E. Kaiser","doi":"10.1785/0120230170","DOIUrl":"https://doi.org/10.1785/0120230170","url":null,"abstract":"This article summarizes the ground‐motion characterization (GMC) model component of the 2022 New Zealand National Seismic Hazard Model (2022 NZ NSHM). The model development process included establishing a NZ‐specific context through the creation of a new ground‐motion database, and consideration of alternative ground‐motion models (GMMs) that have been historically used in NZ or have been recently developed for global application with or without NZ‐specific regionalizations. Explicit attention was given to models employing state‐of‐the‐art approaches in terms of their ability to provide robust predictions when extrapolated beyond the predictor variable scenarios that are well constrained by empirical data alone. We adopted a “hybrid” logic tree that combined both a “weights‐on‐models” approach along with backbone models (i.e., metamodels), the former being the conventional approach to GMC logic tree modeling for NSHM applications using published models, and the latter being increasingly used in research literature and site‐specific studies. In this vein, two NZ‐specific GMMs were developed employing the backbone model construct. All of the adopted subduction GMMs in the logic tree were further modified from their published versions to include the effects of increased attenuation in the back‐arc region; and, all but one model was modified to account for the reduction in ground‐motion standard deviations as a result of nonlinear surficial site response. As well as being based on theoretical arguments, these adjustments were implemented as a result of hazard sensitivity analyses using models without these effects, which we consider gave unrealistically high hazard estimates.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"21 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139658235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pablo Iturrieta, Matthew C. Gerstenberger, Chris Rollins, Russ Van Dissen, Ting Wang, Danijel Schorlemmer
Seismicity usually exhibits a non‐Poisson spatiotemporal distribution and could undergo nonstationary processes. However, the Poisson assumption is still deeply rooted in current probabilistic seismic hazard analysis models, especially when input catalogs must be declustered to obtain a Poisson background rate. In addition, nonstationary behavior and scarce earthquake records in regions of low seismicity can bias hazard estimates that use stationary or spatially precise forecasts. In this work, we implement hazard formulations using forecasts that trade‐off spatial precision to account for overdispersion and nonstationarity of seismicity in the form of uniform rate zones (URZs), which describe rate variability using non‐Poisson probabilistic distributions of earthquake numbers. The impact of these forecasts in the hazard space is investigated by implementing a negative‐binomial formulation in the OpenQuake hazard software suite, which is adopted by the 2022 Aotearoa New Zealand National Seismic Hazard Model. For a 10% exceedance probability of peak ground acceleration (PGA) in 50 yr, forecasts that only reduce the spatial precision, that is, stationary Poisson URZ models, cause up to a twofold increase in hazard for low‐seismicity regions compared to spatially precise forecasts. Furthermore, the inclusion of non‐Poisson temporal processes in URZ models increases the expected PGA by up to three times in low‐seismicity regions, whereas the effect on high‐seismicity is minimal (∼5%). The hazard estimates presented here highlight the relevance, as well as the feasibility, of incorporating analytical formulations of seismicity that go beyond the inadequate stationary Poisson description of seismicity.
{"title":"Implementing Non‐Poissonian Forecasts of Distributed Seismicity into the 2022 Aotearoa New Zealand National Seismic Hazard Model","authors":"Pablo Iturrieta, Matthew C. Gerstenberger, Chris Rollins, Russ Van Dissen, Ting Wang, Danijel Schorlemmer","doi":"10.1785/0120230168","DOIUrl":"https://doi.org/10.1785/0120230168","url":null,"abstract":"Seismicity usually exhibits a non‐Poisson spatiotemporal distribution and could undergo nonstationary processes. However, the Poisson assumption is still deeply rooted in current probabilistic seismic hazard analysis models, especially when input catalogs must be declustered to obtain a Poisson background rate. In addition, nonstationary behavior and scarce earthquake records in regions of low seismicity can bias hazard estimates that use stationary or spatially precise forecasts. In this work, we implement hazard formulations using forecasts that trade‐off spatial precision to account for overdispersion and nonstationarity of seismicity in the form of uniform rate zones (URZs), which describe rate variability using non‐Poisson probabilistic distributions of earthquake numbers. The impact of these forecasts in the hazard space is investigated by implementing a negative‐binomial formulation in the OpenQuake hazard software suite, which is adopted by the 2022 Aotearoa New Zealand National Seismic Hazard Model. For a 10% exceedance probability of peak ground acceleration (PGA) in 50 yr, forecasts that only reduce the spatial precision, that is, stationary Poisson URZ models, cause up to a twofold increase in hazard for low‐seismicity regions compared to spatially precise forecasts. Furthermore, the inclusion of non‐Poisson temporal processes in URZ models increases the expected PGA by up to three times in low‐seismicity regions, whereas the effect on high‐seismicity is minimal (∼5%). The hazard estimates presented here highlight the relevance, as well as the feasibility, of incorporating analytical formulations of seismicity that go beyond the inadequate stationary Poisson description of seismicity.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"63 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139580766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Elizabeth Kaiser, Matt P. Hill, Chris de la Torre, Sanjay Bora, Elena Manea, Liam Wotherspoon, Gail M. Atkinson, Robin Lee, Brendon Bradley, Anne Hulsey, Andrew Stolte, Matt Gerstenberger
We provide an overview of the treatment of site effects in the New Zealand National Seismic Hazard Model (NZ NSHM), including a case study of basin effects in central Wellington. The NZ NSHM 2022 includes a change in site parameter from subsoil class (NZS class) to VS30. Poor NZ VS30 characterization is a major source of uncertainty in the NSHM; however, advanced site characterization in Wellington allows for in‐depth study. First, we construct a regional 3D shear‐wave velocity model and maps of site parameters (T0, NZS class, and VS30) for central Wellington. At central city soil sites, we find the ratios of NZ NSHM 2022 hazard spectra with respect to the current equivalent design spectra range from factors of ∼0.8–2.6 (median ∼1.5), depending on local site conditions and spectral period. Strong amplification peaks at 0.5–2 s are observed in central Wellington. Linear site‐specific amplifications from multiple methods are compared at 13 stations and are well‐defined by both site‐to‐site residuals and response spectral ratios relative to station POTS. At many deeper soft sites (VS30<300 m/s), strong amplification peaks occur around T0 that are underpredicted by mean ergodic ground‐motion model (GMM) predictions. This underprediction is slightly enhanced when using basin‐specific Z1.0 as an additional site parameter. Our study highlights outstanding challenges in modeling strong basin response within shallow basins in NSHMs, including the need to consider region‐ or basin‐specific modeling approaches as well as nonlinear effects at high shaking intensities that dominate the hazard. For New Zealand, in general, as illustrated in the Wellington case study, a priority is the further characterization of VS30 (and VS) for the seismic network to better isolate and quantify uncertainties in seismic hazard and allow useful exploration of regional–GMM adjustments and partially nonergodic approaches.
{"title":"Overview of Site Effects and the Application of the 2022 New Zealand NSHM in the Wellington Basin, New Zealand","authors":"Anna Elizabeth Kaiser, Matt P. Hill, Chris de la Torre, Sanjay Bora, Elena Manea, Liam Wotherspoon, Gail M. Atkinson, Robin Lee, Brendon Bradley, Anne Hulsey, Andrew Stolte, Matt Gerstenberger","doi":"10.1785/0120230189","DOIUrl":"https://doi.org/10.1785/0120230189","url":null,"abstract":"We provide an overview of the treatment of site effects in the New Zealand National Seismic Hazard Model (NZ NSHM), including a case study of basin effects in central Wellington. The NZ NSHM 2022 includes a change in site parameter from subsoil class (NZS class) to VS30. Poor NZ VS30 characterization is a major source of uncertainty in the NSHM; however, advanced site characterization in Wellington allows for in‐depth study. First, we construct a regional 3D shear‐wave velocity model and maps of site parameters (T0, NZS class, and VS30) for central Wellington. At central city soil sites, we find the ratios of NZ NSHM 2022 hazard spectra with respect to the current equivalent design spectra range from factors of ∼0.8–2.6 (median ∼1.5), depending on local site conditions and spectral period. Strong amplification peaks at 0.5–2 s are observed in central Wellington. Linear site‐specific amplifications from multiple methods are compared at 13 stations and are well‐defined by both site‐to‐site residuals and response spectral ratios relative to station POTS. At many deeper soft sites (VS30<300 m/s), strong amplification peaks occur around T0 that are underpredicted by mean ergodic ground‐motion model (GMM) predictions. This underprediction is slightly enhanced when using basin‐specific Z1.0 as an additional site parameter. Our study highlights outstanding challenges in modeling strong basin response within shallow basins in NSHMs, including the need to consider region‐ or basin‐specific modeling approaches as well as nonlinear effects at high shaking intensities that dominate the hazard. For New Zealand, in general, as illustrated in the Wellington case study, a priority is the further characterization of VS30 (and VS) for the seismic network to better isolate and quantify uncertainties in seismic hazard and allow useful exploration of regional–GMM adjustments and partially nonergodic approaches.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"116 6 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139647256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we present predictive models for significant ground-motion duration from interplate and intermediate-depth intraslab earthquakes at Mexico City for the horizontal components, the vertical component, and the vertical-to-horizontal ratio case. The considered sites are located over several zones in Mexico City, from rock to soft-soil sites. For the ground-motion duration models, the significant durations for ranges between 5% and 75%, 5% and 95%, and 2.5% and 97.5% of Arias intensity are considered for the analyses. The equations were developed as functions of magnitude, distance of the earthquake, and site period using 16 and 23 event recordings from interplate and intermediate-depth intraslab earthquakes at the hill, transition, and lakebed zones of the city using mixed-effect regression analyses. For the intraslab events, in particular, the new database includes recordings from two significant normal-faulting events that occurred in 2017. The models lead to differences with respect to the previous models. Therefore, predictive models for both considered focal mechanisms are proposed. The model is valid for interplate events at distances from 280 to 500 km and magnitude Mw from 6 to 8.1, for intraslab events at distances of 100 km up to about 650 km, magnitude Mw from 5 to 8.2, and focal depths from 40 km to over 120 km.
{"title":"Horizontal and Vertical Ground-Motion Duration Prediction Models from Interplate and Intermediate-Depth Intraslab Earthquakes in Mexico City","authors":"M. Jaimes, A. García-Soto, Gabriel Candia","doi":"10.1785/0120230153","DOIUrl":"https://doi.org/10.1785/0120230153","url":null,"abstract":"\u0000 In this study, we present predictive models for significant ground-motion duration from interplate and intermediate-depth intraslab earthquakes at Mexico City for the horizontal components, the vertical component, and the vertical-to-horizontal ratio case. The considered sites are located over several zones in Mexico City, from rock to soft-soil sites. For the ground-motion duration models, the significant durations for ranges between 5% and 75%, 5% and 95%, and 2.5% and 97.5% of Arias intensity are considered for the analyses. The equations were developed as functions of magnitude, distance of the earthquake, and site period using 16 and 23 event recordings from interplate and intermediate-depth intraslab earthquakes at the hill, transition, and lakebed zones of the city using mixed-effect regression analyses. For the intraslab events, in particular, the new database includes recordings from two significant normal-faulting events that occurred in 2017. The models lead to differences with respect to the previous models. Therefore, predictive models for both considered focal mechanisms are proposed. The model is valid for interplate events at distances from 280 to 500 km and magnitude Mw from 6 to 8.1, for intraslab events at distances of 100 km up to about 650 km, magnitude Mw from 5 to 8.2, and focal depths from 40 km to over 120 km.","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"47 46","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Erratum to Complex Crustal Deformation Controlled by the 3D Geometry of the Chile Subduction Zone","authors":"Marco T. Herrera, J. Crempien, José Cembrano","doi":"10.1785/0120230286","DOIUrl":"https://doi.org/10.1785/0120230286","url":null,"abstract":"","PeriodicalId":9444,"journal":{"name":"Bulletin of the Seismological Society of America","volume":"5 10","pages":""},"PeriodicalIF":3.0,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139445362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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