Pseudoprospective Evaluation of UCERF3-ETAS Forecasts during the 2019 Ridgecrest Sequence

ABSTRACT The 2019 Ridgecrest sequence provides the first opportunity to evaluate Uniform California Earthquake Rupture Forecast v.3 with epidemic-type aftershock sequences (UCERF3-ETAS) in a pseudoprospective sense. For comparison, we include a version of the model without explicit faults more closely mimicking traditional ETAS models (UCERF3-NoFaults). We evaluate the forecasts with new metrics developed within the Collaboratory for the Study of Earthquake Predictability (CSEP). The metrics consider synthetic catalogs simulated by the models rather than synoptic probability maps, thereby relaxing the Poisson assumption of previous CSEP tests. Our approach compares statistics from the synthetic catalogs directly against observations, providing a flexible approach that can account for dependencies and uncertainties encoded in the models. We find that, to the first order, both UCERF3-ETAS and UCERF3-NoFaults approximately capture the spatiotemporal evolution of the Ridgecrest sequence, adding to the growing body of evidence that ETAS models can be informative forecasting tools. However, we also find that both models mildly overpredict the seismicity rate, on average, aggregated over the evaluation period. More severe testing indicates the overpredictions occur too often for observations to be statistically indistinguishable from the model. Magnitude tests indicate that the models do not include enough variability in forecasted magnitude-number distributions to match the data. Spatial tests highlight discrepancies between the forecasts and observations, but the greatest differences between the two models appear when aftershocks occur on modeled UCERF3-ETAS faults. Therefore, any predictability associated with embedding earthquake triggering on the (modeled) fault network may only crystalize during the presumably rare sequences with aftershocks on these faults. Accounting for uncertainty in the model parameters could improve test results during future experiments.

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ETAS-Approach Accounting for Short-Term Incompleteness of Earthquake Catalogs

Bulletin of the Seismological Society of America ◽

10.1785/0120210146 ◽

2021 ◽

Author(s):

Sebastian Hainzl

Keyword(s):

Aftershock Sequence ◽

Additional Parameter ◽

Spatiotemporal Evolution ◽

Short Term ◽

Seismicity Rate ◽

Detection Algorithms ◽

Estimated Parameters ◽

Epidemic Type Aftershock Sequence ◽

Aftershock Sequences ◽

Completeness Magnitude

ABSTRACT The epidemic-type aftershock sequence (ETAS) model is a powerful statistical model to explain and forecast the spatiotemporal evolution of seismicity. However, its parameter estimation can be strongly biased by catalog deficiencies, particularly short-term incompleteness related to missing events in phases of high-seismic activity. Recent studies have shown that these short-term fluctuations of the completeness magnitude can be explained by the blindness of detection algorithms after earthquakes, preventing the detection of events with a smaller magnitude. Based on this assumption, I derive a direct relation between the true and detectable seismicity rate and magnitude distributions, respectively. These relations only include one additional parameter, the so-called blind time Tb, and lead to a closed-form maximum-likelihood formulation to estimate the ETAS parameters directly accounting for varying completeness. Tests using synthetic simulations show that the true parameters can be resolved from incomplete catalogs. Finally, I apply the new model to California’s most prominent mainshock–aftershock sequences in the last decades. The results show that the model leads to superior fits with Tb decreasing with time, indicating improved detection algorithms. The estimated parameters significantly differ from the estimation with the standard approach, indicating higher b-values and larger trigger potentials than previously thought.

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In-Plane Flexible Ring Tire Model—Part 1: Modeling and Parameter Identification

Tire Science and Technology ◽

10.2346/tire.18.460303 ◽

2018 ◽

Vol 46 (3) ◽

pp. 174-219 ◽

Cited By ~ 2

Author(s):

Bin Li ◽

Xiaobo Yang ◽

James Yang ◽

Yunqing Zhang ◽

Zeyu Ma

Keyword(s):

Static Load ◽

Model Parameters ◽

Tire Model ◽

Test Results ◽

Lumped Mass ◽

Virtual Test ◽

Proposed Model ◽

Particle Swarm Method ◽

Vehicle Dynamic Simulation ◽

Flexible Ring

ABSTRACT The tire model is essential for accurate and efficient vehicle dynamic simulation. In this article, an in-plane flexible ring tire model is proposed, in which the tire is composed of a rigid rim, a number of discretized lumped mass belt points, and numerous massless tread blocks attached on the belt. One set of tire model parameters is identified by approaching the predicted results with ADAMS® FTire virtual test results for one particular cleat test through the particle swarm method using MATLAB®. Based on the identified parameters, the tire model is further validated by comparing the predicted results with FTire for the static load-deflection tests and other cleat tests. Finally, several important aspects regarding the proposed model are discussed.

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Investigating the vibrational behaviour of a rotating two-blade propeller by using a self-tracking method

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406218764514 ◽

2018 ◽

Vol 233 (3) ◽

pp. 835-847 ◽

Cited By ~ 1

Author(s):

Mohammad-Reza Ashory ◽

Farhad Talebi ◽

Heydar R Ghadikolaei ◽

Morad Karimpour

Keyword(s):

Natural Frequency ◽

Measurement Errors ◽

Mode Shapes ◽

Model Parameters ◽

Test Results ◽

Modal Assurance Criterion ◽

Tracking Method ◽

Strong Resemblance ◽

Test Scenarios ◽

Good Agreement

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

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Identification of Optimized Cranial Bone Constitutive Model Parameters at High Strain Rate Using Polymeric Split Hopkinson Pressure Bar Test Results

10.1007/978-3-030-86446-0_3 ◽

2021 ◽

pp. 19-26

Author(s):

Shiri Seddik ◽

Halgrin Julien

Keyword(s):

Constitutive Model ◽

High Strain Rate ◽

Split Hopkinson Pressure Bar ◽

Cranial Bone ◽

Model Parameters ◽

Test Results ◽

Hopkinson Pressure Bar ◽

Split Hopkinson ◽

Bar Test ◽

Pressure Bar

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Operational Earthquake Forecasting during the 2019 Ridgecrest, California, Earthquake Sequence with the UCERF3-ETAS Model

Seismological Research Letters ◽

10.1785/0220190294 ◽

2020 ◽

Vol 91 (3) ◽

pp. 1567-1578 ◽

Cited By ~ 3

Author(s):

Kevin R. Milner ◽

Edward H. Field ◽

William H. Savran ◽

Morgan T. Page ◽

Thomas H. Jordan

Keyword(s):

High Performance ◽

Aftershock Sequence ◽

Lessons Learned ◽

Ease Of Use ◽

Earthquake Forecasting ◽

Earthquake Rupture ◽

Etas Model ◽

Epidemic Type Aftershock Sequence ◽

Aftershock Sequences ◽

High Performance Computing Cluster

Abstract The first Uniform California Earthquake Rupture Forecast, Version 3–epidemic-type aftershock sequence (UCERF3-ETAS) aftershock simulations were running on a high-performance computing cluster within 33 min of the 4 July 2019 M 6.4 Searles Valley earthquake. UCERF3-ETAS, an extension of the third Uniform California Earthquake Rupture Forecast (UCERF3), is the first comprehensive, fault-based, epidemic-type aftershock sequence (ETAS) model. It produces ensembles of synthetic aftershock sequences both on and off explicitly modeled UCERF3 faults to answer a key question repeatedly asked during the Ridgecrest sequence: What are the chances that the earthquake that just occurred will turn out to be the foreshock of an even bigger event? As the sequence unfolded—including one such larger event, the 5 July 2019 M 7.1 Ridgecrest earthquake almost 34 hr later—we updated the model with observed aftershocks, finite-rupture estimates, sequence-specific parameters, and alternative UCERF3-ETAS variants. Although configuring and running UCERF3-ETAS at the time of the earthquake was not fully automated, considerable effort had been focused in 2018 on improving model documentation and ease of use with a public GitHub repository, command line tools, and flexible configuration files. These efforts allowed us to quickly respond and efficiently configure new simulations as the sequence evolved. Here, we discuss lessons learned during the Ridgecrest sequence, including sensitivities of fault triggering probabilities to poorly constrained finite-rupture estimates and model assumptions, as well as implications for UCERF3-ETAS operationalization.

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Maximum Earthquake Size and Seismicity Rate from an ETAS Model with Slip Budget

Bulletin of the Seismological Society of America ◽

10.1785/0120190196 ◽

2020 ◽

Vol 110 (2) ◽

pp. 874-885

Author(s):

David Marsan ◽

Yen Joe Tan

Keyword(s):

Seismic Moment ◽

Aftershock Sequence ◽

Physical Parameters ◽

Model Parameters ◽

Seismicity Rate ◽

Omori Law ◽

Epidemic Type Aftershock Sequence ◽

Earthquake Size ◽

Maximum Earthquake ◽

Seismicity Model

ABSTRACT We define a seismicity model based on (1) the epidemic-type aftershock sequence model that accounts for earthquake clustering, and (2) a closed slip budget at long timescale. This is achieved by not permitting an earthquake to have a seismic moment greater than the current seismic moment deficit. This causes the Gutenberg–Richter law to be modulated by a smooth upper cutoff, the location of which can be predicted from the model parameters. We investigate the various regimes of this model that more particularly include a regime in which the activity does not die off even with a vanishingly small spontaneous (i.e., background) earthquake rate and one that bears strong statistical similarities with repeating earthquake time series. Finally, this model relates the earthquake rate and the geodetic moment rate and, therefore, allows to make sense of this relationship in terms of fundamental empirical law (the Gutenberg–Richter law, the productivity law, and the Omori law) and physical parameters (seismic coupling, tectonic loading rate).

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The statistical impact of experimental result scatter of asphalt mixtures on their numerical modelling

MATEC Web of Conferences ◽

10.1051/matecconf/201926205014 ◽

2019 ◽

Vol 262 ◽

pp. 05014 ◽

Cited By ~ 1

Author(s):

Cezary Szydłowski ◽

Jarosław Górski ◽

Marcin Stienss ◽

Łukasz Smakosz

Keyword(s):

Numerical Models ◽

Asphalt Mixture ◽

Experimental Result ◽

Model Parameters ◽

Test Results ◽

Mean Values ◽

Estimated Parameters ◽

The Mean ◽

Parameter Values ◽

Test Outcomes

The paper presents selected test results of asphalt mixture conducted in low temperatures. The obtained parameters are highly diverse. It concerns ultimate breaking loads, stiffness parameters related to Young's modulus but also the fracture course. Statistical analysis upon the results makes it possible to relevantly estimate the material-defining parameter values. Such a random approach leads to the mean values of breaking and fracture-triggering loads, dealing with their dispersion too. The estimated parameters allow to form appropriate numerical models of asphalt mixture specimens. This type of analysis supports the laboratory tests. The paper presents the authors' simplified model considering non-uniform material features. The results reflect the scatter of real laboratory test outcomes. In order to do so an algorithm to calibrate the numerical model parameters was created.

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Accuracy of performance-test linking based on a many-facet Rasch model

Behavior Research Methods ◽

10.3758/s13428-020-01498-x ◽

2020 ◽

Author(s):

Masaki Uto

Keyword(s):

Performance Test ◽

Performance Assessments ◽

Task Characteristics ◽

Model Parameters ◽

Test Results ◽

Irt Models ◽

Test Linking ◽

Rater Severity ◽

Task Parameters ◽

And Task

Abstract Performance assessments, in which human raters assess examinee performance in practical tasks, have attracted much attention in various assessment contexts involving measurement of higher-order abilities. However, difficulty persists in that ability measurement accuracy strongly depends on rater and task characteristics such as rater severity and task difficulty. To resolve this problem, various item response theory (IRT) models incorporating rater and task parameters, including many-facet Rasch models (MFRMs), have been proposed. When applying such IRT models to datasets comprising results of multiple performance tests administered to different examinees, test linking is needed to unify the scale for model parameters estimated from individual test results. In test linking, test administrators generally need to design multiple tests such that raters and tasks partially overlap. The accuracy of linking under this design is highly reliant on the numbers of common raters and tasks. However, the numbers of common raters and tasks required to ensure high accuracy in test linking remain unclear, making it difficult to determine appropriate test designs. We therefore empirically evaluate the accuracy of IRT-based performance-test linking under common rater and task designs. Concretely, we conduct evaluations through simulation experiments that examine linking accuracy based on a MFRM while changing numbers of common raters and tasks with various factors that possibly affect linking accuracy.

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A Novel Fatigue Damage Model of Rock considering Temperature Effects

Advances in Civil Engineering ◽

10.1155/2020/8838335 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Yaoliang Zhu ◽

Jin Yu ◽

Yanyan Cai ◽

Xin Tang ◽

Wei Yao ◽

...

Keyword(s):

Fatigue Damage ◽

Stress Ratio ◽

Damage Model ◽

Model Parameters ◽

Test Results ◽

Rock Fatigue ◽

Proposed Model ◽

Different Temperatures ◽

Effects Of Temperature ◽

Cyclic Damage

The deformation rules and failure types of rock fatigue damage at different temperatures are quite different, and existing constitutive theory cannot describe them quantitatively. A novel rock fatigue damage model considering the effects of temperature was presented based on phenomenology. In this model, the residual strain method was used to define the fatigue damage, and the Harris attenuation function was introduced to characterize the cyclic damage evolution. The proposed model has considered the influence of the initial damage and temperature, and the model parameters can be easily calculated. The accuracy of the model was verified by comparing the calculated values of cyclic upper strain and fatigue life with previous test results. The physical significance of the model parameters shows that parameter a is related to fatigue stress ratio and lithology, while parameter b is related to temperature. The study has some reference values for the fatigue damage model of rock considering the influence of temperature.

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Suitability of Several Statistical Models to Simulate Observed Distribution of Sample Test Results in Inspections of Aflatoxin-Contaminated Peanut Lots

Journal of AOAC International ◽

10.1093/jaoac/79.4.981 ◽

1996 ◽

Vol 79 (4) ◽

pp. 981-988 ◽

Cited By ~ 7

Author(s):

Thomas Whitaker ◽

Francis Giesbrecht ◽

Jeremy Wu

Keyword(s):

Parameter Estimation ◽

Negative Binomial Distribution ◽

Binomial Distribution ◽

Statistical Models ◽

Negative Binomial ◽

Estimation Method ◽

Likelihood Method ◽

Model Parameters ◽

Test Results ◽

Parameter Estimation Method

Abstract The acceptability of 10 theoretical distributions to simulate observed distribution of sample aflatoxin test results was evaluated by using 2 parameter estimation methods and 3 goodness of fit (GOF) tests. All theoretical distributions were compared with 120 observed distributions of aflatoxin test results of farmers' stock peanuts. For a given parameter estimation method and GOF test, the negative binomial distribution had the highest percentage of statistically acceptable fits. The log normal and Poisson-gamma (gamma shape parameter = 0.5) distributions had slightly fewer but an almost equal percentage of acceptable fits. For the 3 most acceptable statistical models, the negative binomial had the greatest percentage of best or closest fits. Both the parameter estimation method and the GOF test had an influence on which theoretical distribution had the largest number of acceptable fits. All theoretical distributions, except the negative binomial distribution, had more acceptable fits when model parameters were determined by the maximum likelihood method. The negative binomial had slightly more acceptable fits when model parameters were estimated by the method of moments. The results also demonstrated the importance of using the same GOF test for comparing the acceptability of several theoretical distributions.

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