Broadband Platform Research Articles

Dynamic near-field and far-field radiation manipulation using a reprogrammable guided-wave-excited metasurface

The dynamic and integrated control of near- and far-field electromagnetic waves is essential for advancing emerging intelligent information technology. Metasurfaces, distinguished by their low-profile design, cost-effectiveness, and ease of fabrication, have successfully revolutionized various electromagnetic functions. However, current research on the dynamic integrated manipulation of near-field and far-field electromagnetic waves using a single metasurface remains relatively constrained, due to the complexity of element-level control, restricted dynamic tuning range, and tuning speed. Herein, we propose an element-level controlled, versatile, compact, and broadband platform allowing for the real-time electronic reconstruction of desired near/far-field electromagnetic wavefronts. This concept is achieved by precisely regulating the 1-bit amplitude coding pattern across a guided-wave-excited metasurface aperture loaded with PIN diodes, following our binary-amplitude holographic theory and modified Gerchberg–Saxton (G–S) algorithm. Consistent findings across calculations, simulations, and experiments highlight the metasurface’s robust performance in 2D beam scanning, frequency scanning, dynamic focusing lens, dynamic holography display, and 3D multiplexing holography, even under 1-bit control. This simplified and innovative metasurface architecture holds the promise of substantially propelling forthcoming investigations and applications of highly integrated, multifunctional, and intelligent platforms.

Broadband Ground-Motion Synthesis via Generative Adversarial Neural Operators: Development and Validation

ABSTRACT We present a data-driven framework for ground-motion synthesis that generates three-component acceleration time histories conditioned on moment magnitude (M), rupture distance (Rrup), time-average shear-wave velocity at the top 30 m (VS30), and style of faulting. We use a Generative Adversarial Neural Operator (GANO)—a resolution invariant architecture that guarantees model training independent of the data sampling frequency. We first present the conditional ground-motion synthesis algorithm (cGM-GANO) and discuss its advantages compared to the previous work. We next train cGM-GANO on simulated ground motions generated by the Southern California Earthquake Center Broadband Platform (BBP) and on recorded the Kiban–Kyoshin network (KiK-net) data, and show that the model can learn the overall magnitude, distance, and VS30 scaling of effective amplitude spectra (EAS) ordinates and pseudospectral accelerations (PSA). Results specifically show that cGM-GANO produces consistent median scaling with the training data for the corresponding tectonic environments over a wide range of frequencies for scenarios with sufficient data coverage. For the BBP dataset, cGM-GANO cannot learn the ground-motion scaling of the stochastic frequency components (f > 1 Hz); for the KiK-net dataset, the largest misfit is observed at short distances (Rrup<50 km) and for soft-soil conditions (VS30<200 m/s) due to the scarcity of such data. Except for these conditions, the aleatory variability of EAS and PSA are captured reasonably well. Finally, cGM-GANO produces similar median scaling to traditional ground-motion models (GMMs) for frequencies greater than 1 Hz for both PSA and EAS but underestimates the aleatory variability of EAS. Discrepancies in the comparisons between the synthetic ground motions and GMMs are attributed to inconsistencies between the training dataset and the datasets used in GMM development. Our pilot study demonstrates GANO’s potential for efficient synthesis of broadband ground motions.

Plasmonic Bullseye Nanocavities for Broadband Light Localization and Multi‐Wavelength SERS

AbstractPlasmonic nanostructures capable of broadband light trapping and field enhancement have promising applications in a wide range of fields. This study presents a platform for broadband, polarization‐independent field enhancement in the visible regime through the use of width‐graded nanocavities in a bullseye configuration. The fabrication procedure utilizes electron beam lithography (EBL) to achieve fine control over the nanocavity geometry and template stripping to enable rapid and low‐cost production. The utility of these devices as substrates for multi‐wavelength surface enhanced Raman spectroscopy (SERS) is demonstrated through molecular detection in a 10 μM solution at two excitation wavelengths. The impact of bullseye geometry on both the broadband spectral response and multi‐wavelength SERS performance is examined. The measured SERS enhancement factor (EF) is shown to depend primarily on the plasmonically active surface area of the device, regardless of the local electromagnetic field strength within the nanocavities. These results highlight not only the utility of the width‐graded bullseye as a broadband platform for SERS and other applications but also provide design guidelines to optimize the enhancement factor and broadband performance of similar devices.

Regional Calibration of Hybrid Ground-Motion Simulations in Moderate Seismicity Areas: Application to the Upper Rhine Graben

ABSTRACTThis study presents the coupling of the spectral decomposition results for anelastic attenuation, stress drop, and site effects with the Graves-Pitarka (GP) hybrid ground-motion simulation methodology, as implemented on the Southern California Earthquake Center (SCEC) broadband platform (BBP). It is targeted to applications in the Upper Rhine graben (URG), which is among the seismically active areas in western Europe, yet a moderate seismicity area. Our development consists of three main steps: (1) calibration of regional high-frequency (HF) attenuation properties; (2) modification of the hybrid approach to add compressional waves in the HF computation and examine various strategies to evaluate site amplification factors in the Fourier domain (e.g., VS30-based or site-specific factors); (3) testing of the simulations using earthquake records from the URG (3.7<Mw<5). The validation process of the simulated time histories is performed first on rock sites, and, then subsequently at all stations, whatever their site conditions. The performance of the simulations for rock sites is assessed through the standard validation technique in the BBP (comparison of the waveforms, intensity measures, and estimation of the response spectra model bias). We additionally compare the Fourier amplitude spectrum of the simulations and observations, and compute their corresponding bias. The results show that the simulated ground motions match the general characteristics of the recorded motions, and that the model bias generally fluctuates around zero across the broadband frequency range. Hence, the hybrid ground-motion methodology implemented in the SCEC BBP can be successfully applied outside high-seismicity areas and outside those areas for which it had been generally calibrated. Our results also show that HF modification and calibration were necessary to improve the fits with the observation, and demonstrate the potential benefits of using site-specific amplification factors compared to VS30-based amplification factors.

Regional seismic ground‐motion simulation and observation with engineering applications

Regional seismic ground‐motion simulation and observation with engineering applications

Tall building performance‐based seismic design using SCEC broadband platform site‐specific ground motion simulations

AbstractThe scarcity of strong ground motion records presents a challenge for making reliable performance assessments of tall buildings whose seismic design is controlled by large‐magnitude and close‐distance earthquakes. This challenge can be addressed using broadband ground‐motion simulation methods to generate records with site‐specific characteristics of large‐magnitude events. In this paper, simulated site‐specific earthquake seismograms, developed through a related project that was organized through the Southern California Earthquake Center (SCEC) Ground Motion Simulation Validation (GMSV) Technical Activity Group, are used for nonlinear response history analyses of two archetype tall buildings for sites in San Francisco, Los Angeles, and San Bernardino. The SCEC GMSV team created the seismograms using the Broadband Platform (BBP) simulations for five site‐specific earthquake scenarios. The two buildings are evaluated using nonlinear dynamic analyses under comparable record suites selected from the simulated BBP catalog and recorded motions from the NGA‐West database. The collapse risks and structural response demands (maximum story drift ratio, peak floor acceleration, and maximum story shear) under the BBP and NGA suites are compared. In general, this study finds that use of the BBP simulations resolves concerns about estimation biases in structural response analysis which are caused by ground motion scaling, unrealistic spectral shapes, and overconservative spectral variations. While there are remaining concerns that strong coherence in some kinematic fault rupture models may lead to an overestimation of velocity pulse effects in the BBP simulations, the simulations are shown to generally yield realistic pulse‐like features of near‐fault ground motion records.

Sensitivity Analysis of the Interfrequency Correlation of Synthetic Ground Motions to Pseudodynamic Source Models

AbstractGiven the deficiency of recorded strong ground-motion data, it is important to understand the effects of earthquake rupture processes on near-source ground-motion characteristics and to develop physics-based ground-motion simulation methods for advanced seismic hazard assessments. Recently, the interfrequency correlation of ground motions has become an important element of ground-motion predictions. We investigate the effect of pseudodynamic source models on the interfrequency correlation of ground motions by simulating a number of ground-motion waveforms for the 1994 Northridge, California, earthquake, using the Southern California Earthquake Center Broadband Platform. We find that the cross correlation between earthquake source parameters in pseudodynamic source models significantly affects the interfrequency correlation of ground motions in the frequency around 0.5 Hz, whereas its effect is not visible in the other frequency ranges. Our understanding of the effects of earthquake sources on the characteristics of near-source ground motions, particularly the interfrequency correlation, may help develop advanced physics-based ground-motion simulation methods for advanced seismic hazard and risk assessments.

Ge-rich graded SiGe waveguides and interferometers from 5 to 11 µm wavelength range.

The mid-infrared (mid-IR) wavelength range hosts unique vibrational and rotational resonances of a broad variety of substances that can be used to unambiguously detect the molecular composition in a non-intrusive way. Mid-IR photonic-integrated circuits (PICs) are thus expected to have a major impact in many applications. Still, new challenges are posed by the large spectral width required to simultaneously identify many substances using the same photonic circuit. Ge-rich graded SiGe waveguides have been proposed as a broadband platform approach for mid-IR PICs. In this work, ultra-broadband waveguides are experimentally demonstrated within unprecedented wavelength range, efficiently guiding light from 5 to 11 µm. Interestingly, losses from 0.5 to 1.2 dB/cm are obtained between 5.1 and 8 µm wavelength, and values below 3 dB/cm are measured from 9.5 to 11.2 µm wavelength. An increase of propagation losses is seen between 8 and 9.5 µm; however, values stay below 4.6 dB/cm in the entire wavelength range. A detailed analysis of propagation losses is reported, supported by secondary ion mass spectrometry measurement, and different contributions are analyzed: silicon substrate absorption, oxygen impurities, free carrier absorption by residual doping, sidewall roughness and multiphonon absorption. Finally, Mach-Zehnder interferometers are characterized, and wideband operation is experimentally obtained from 5.5 to 10.5 µm wavelength.

Kinematic Source Modeling for the Synthesis of Broadband Ground Motion Using the f‐k Approach

Abstract A procedure for building a kinematic source model is proposed in this article for the synthesis of broadband ground motion based on the frequency–wavenumber Green’s function. The spatial distribution of slip on the rupture plane is generated by combining asperity slip with random slip. A set of scaling laws recently updated for the global and local parameters of seismic sources is adopted. To characterize the temporal evolution of slip on the rupture plane, different rupture velocities, and rise times are first generated by considering the correlation with slip, and a source time function obtained by rupture dynamics is selected for each subsource. Then, the entire rupture process is set as the object to jointly determine the rise time and rupture velocity for a given slip distribution under the selection criterion that the entire rupture process should radiate the closest seismic energy to the expected energy. To reduce uncertainty, 30 spatiotemporal rupture processes for an earthquake scenario are realized to select a mean source model. To demonstrate the feasibility of the proposed source modeling approach, two California earthquakes, the Whittier Narrows earthquake and the Loma Prieta earthquake, are chosen as case studies. The performance of the obtained source models shows that our modeling approach is advantageous for estimating the size of the rupture plane, emphasizing the effect of asperity, and considering the correlation between temporal rupture parameters and slip. The bias values between the observed and synthetic pseudospectral accelerations are relatively small compared to those for the methods on the Southern California Earthquake Center broadband platform. The synthetics are further compared with the estimates from regional ground‐motion prediction equations for four scenario earthquakes with moment magnitudes of 6.0, 6.5, 7.0, and 7.5. Finally, the sensitivity of the synthetic motion to various rupture parameters is analyzed.

Validation of the SCEC Broadband Platform simulations for tall building risk assessments considering spectral shape and duration of the ground motion

SummaryEarthquake simulation technologies are advancing to the stage of enabling realistic simulations of past earthquakes as well as characterizations of more extreme events, thus holding promise of yielding novel insights and data for earthquake engineering. With the goal of developing confidence in the engineering applications of simulated ground motions, this paper focuses on validation of simulations for response history analysis through comparative assessments of building performance obtained using sets of recorded and simulated motions. Simulated ground motions of past earthquakes, obtained through a larger validation study of the Southern California Earthquake Center Broadband Platform, are used for the case study. Two tall buildings, a 20‐story concrete frame and a 42‐story concrete core wall building, are analyzed under comparable sets of simulated and recorded motions at increasing levels of ground motion intensity, up to structural collapse, to check for statistically significant differences between the responses to simulated and recorded motions. Spectral shape and significant duration are explicitly considered when selecting ground motions. Considered demands include story drift ratios, floor accelerations, and collapse response. These comparisons not only yield similar results in most cases but also reveal instances where certain simulated ground motions can result in biased responses. The source of bias is traced to differences in correlations of spectral values in some of the stochastic ground motion simulations. When the differences in correlations are removed, simulated and recorded motions yield comparable results. This study highlights the utility of physics‐based simulations, and particularly the Southern California Earthquake Center Broadband Platform as a useful tool for engineering applications.

Alternative reliability-based methodology for evaluation of structures excited by earthquakes

In this paper, an alternative reliability-based methodology is developed and implemented on the safety evaluation of structures subjected to seismic loading. To effectively elaborate the approach, structures are represented by finite elements and seismic loading is applied in time domain. The accuracy of the proposed reliability-based methodology is verified using Monte Carlo Simulation. It is confirmed that the presented approach provides adequate accuracy in calculating structural reliability. The efficiency and robustness in problems related to performance-based seismic design are verified. A structure designed by experts satisfying all post-Northridge seismic design requirements is studied. Rigidities related to beam-to-column connections are incorporated. The structure is excited by three suites of ground motions representing three performance levels: immediate occupancy, life safety, and collapse prevention. Using this methodology, it is demonstrated that only hundreds of deterministic finite element analyses are required for extracting reliability information. Several advantages are documented with respect to Monte Carlo Simulation. To showcase an applicability extension of the proposed reliability-based methodology, structural risk is calculated using simulated ground motions generated via the broadband platform developed by the Southern California Earthquake Center. It is validated the accuracy of the broadband platform in terms of structural reliability. Based on the results documented in this paper, a very solid, sound, and precise reliability-based methodology is proved to be acceptable for safety evaluation of structures excited by seismic loading.

Stochastic Extended Simulation (EXSIM) of M<sub>w</sub> 7.0 Kumamoto-Shi earthquake on 15 April 2016 in the Southwest of Japan using the SCEC Broadband Platform (BBP)

Ground motions for Mw 7.0, 15 April 2016, Kumamoto-Shi earthquake of Japan are simulated employing Stochastic Extended Simulation (EXSIM) methodology within the Southern California Earthquake Centre (SCEC) Broadband Platform (BBP) version 15.3.0, utilizing the strong ground motion data from K-NET and KiK-net. Residuals [(ln(data/model)] are plotted as a function of hypocentral distance for a subset of eight periods. Trail simulations are run by varying stress drop until a better match of residuals is obtained. Validation exercise is run with a new data set to ascertain the accuracy of simulations. The results exhibit a close match between the recorded and predicted data. Adopting the validated seismological model of this study, ground motions are predicted at three important sites, which are devoid of strong-motion stations. These results can be used as inputs for conducting dynamic, response spectrum analysis of structures, liquefaction potential of soils, stability analysis and landslide runout estimation of slopes.

The Internet of Platforms and Two-Sided Markets: Legal and Regulatory Implications for Competition and Consumers

This article examines developments in the Internet marketplace that favor embedded intermediaries that have significant market power and the ability to install a platform that both upstream sources of content and applications as well as downstream consumers need to access. Ventures such as Amazon, Facebook and Google have exploited, “winner take all” networking externalities resulting in the creation of seemingly impenetrable barriers to market entry even by innovative companies. Courts and regulatory agencies recognize the substantial market shares these ventures have acquired, but refrain from imposing sanctions on grounds that consumers accrue ample benefits when platform operators use upstream revenues to subsidize downstream services. Consumers also benefit when platform intermediaries eschew short term profits in the quest for greater product diversity and “shelf space” in the Internet marketplace. Additionally, courts and regulators may over-estimate the opportunities for consumers to migrate to alternatives, but underestimate the harms to competition and consumers occurring on either or both sides of an intermediary’s platform. The article identifies four types of government responses to price and quality of service discrimination that exploits choke points within the Internet ecosystem where large volume of traffic has to traverse a single digital, broadband carrier’s network, or service provider’s platform. Governments can refrain from regulating access and accept aspects of market concentration as proper rewards to ventures offering desirable content and carriage services. Alternatively, they can impose access sanctions for antitrust violations, unfair trade practices, consumer harms and unreasonable access discrimination to offset market-driven concentration and dominance. Between these poles, governments can apply antitrust/competition policy remedies, or rely on expert regulatory agencies to respond to complaints. The article examines digital broadband platform operators with an eye toward assessing the aggregate benefits and costs to both upstream firms and downstream consumers. The article notes that in some instances, government-imposed, ex ante safeguards anticipate and attempt to resolve transitory, comparatively insignificant, or possibly nonexistent problems. In other instances, governments have stated an intention to rely on ex post remedies, but they never get around to refining procedures to reduce the potential for false negatives that ignore or underestimate significant marketplace harm. The article concludes that governments have failed to revise and recalibrate tools that examine potential marketplace distortions and assess the potential for damage to competition and consumers. The article demonstrates how the Justice Department, Federal Trade Commission and the Federal Communications Commission have relied on economic and legal doctrine ill-suited for digital broadband market assessments. These agencies have generated false positives, resulting in market intervention where not major problem exists and false negatives, where undetected major problems cause harm without remedy. Additionally these agencies appear to misallocate their resources and attention on insignificant matters when more compelling problems exists. The article recommends that courts and government agencies consider both sides of an intermediary’s market when assessing current and prospective harms, commit to more accurate estimates of the potential for consumers to change platform allegiances and consider the overall impact of two-sided market domination instead of simply dismissing market concentration as necessary and harmless.

Silicon-on-Insulator Waveguide Devices for Broadband Mid-Infrared Photonics

In this paper, we demonstrate silicon-on-insulator (SOI) channel waveguides with propagation loss and $r$ = 10 $\mu$ $\text{m}$ bends with bending loss as low as 2 dB/cm and 0.02 dB/90 $^{\circ }$ in the broad wavelength range of 3.68–3.88 $\mu$ $\text{m}$ . We also indicate the limitation of SOI waveguide loss in mid-infrared wavelength by analyzing loss mechanisms. Based on this high-performance mid-infrared waveguide, we systematically analyze the coupling efficiency of various directional couplers, which are critical and commonly used building blocks for on-chip light routing and power splitting. By varying coupling length and sweeping wavelength, the performance of directional coupler with various gap separations is meticulously investigated in 3.68–3.88 $\mu$ $\text{m}$ . A experimental database for directional coupler with any power splitting ratio is provided. Our results offer a promising broadband platform for dense wavelength division multiplexing (DWDM) and applications that require precise control of coupling such as racetrack resonator in the mid-infrared region.

Simulation of strong ground motion for the 25 April 2015 Nepal (Gorkha) Mw 7.8 earthquake using the SCEC broadband platform

The 25th April 2015 Nepal (Gorkha) earthquake has been introduced into the SCEC BBP v15.3, and validation simulations are run using EXSIM methodology with the strong ground motion data of the earthquake. Synthetic seismograms are generated along with the response spectra for engineering applications. Goodness-of-fit metrics have been computed from response spectra for 14 stations located in the Central Indo-Gangetic Plains (CIGP). Plots of residuals are made as a function of hypocentral distance for various time periods. Spatial distribution of residuals as well as average residuals for all stations for the horizontal components are computed. The results demonstrate that there was a good match between the actual data and synthetics generated by the broadband platform. Finally, four of the widely used ground motion prediction equations around the world are chosen to compare how they predict the synthetics for Gorkha earthquake in CIGP.

Validation of Duration Parameters from SCEC Broadband Platform Simulated Ground Motions

ABSTRACT We validate the duration of ground‐motion time series produced by simulation routines implemented on the Southern California Earthquake Center broadband platform. This validation is based on comparisons of median and standard deviation of simulated durations and their trends with magnitude and distance, with semiempirical ground‐motion prediction equations (GMPEs). The GMPEs selected from the present work are based on a large database that includes five target events from California considered in the simulations. The duration parameters used for this validation are significant durations for 5%–75%, 5%–95%, and 20%–80% of the normalized Arias intensity. Some misfits are observed in the median and dispersion of durations from simulated motions and their trend with magnitude and distance. Understanding the source of these misfits can help guide future improvements in the simulation routines.

Towards an Efficient Radio Network Planning of LTE and Beyond in Densely Populated Urban Areas

Long Term Evolution (LTE) is a fourth generation technology which is expected to be the mobile broadband platform for services in innovation for the foreseeable future. Going on with LTE radio network planning is a well-chosen challenge and a certain hot topic in the current research arena. Again, efficient radio network planning for a densely populated city adds to certain level of complexity in the overall work in terms of proper resource management and capacity requirement fulfillment. In this paper, a detailed LTE radio network planning procedure has been elaborately presented which concentrates on nominal and detailed planning considering possible network implementation in the most populated Indian city Mumbai.

SCEC Broadband Platform: System Architecture and Software Implementation

Online Material: Text‐based (BBP) input and output files and figures of goodness of fit; seismogram comparisons and source model illustrating the BBP validation of the Loma Prieta earthquake. The Southern California Earthquake Center (SCEC) Broadband Platform (BBP) is an open‐source software distribution that contains physics‐based ground‐motion models capable of calculating earthquake ground motions at frequencies above 10 Hz across regional distances. In addition, the BBP contains software tools for evaluating ground‐motion models and comparing simulation results to observed ground‐motion recordings and against ground‐motion prediction equations (GMPEs). The BBP also includes software utilities that help users run large numbers of ground‐motion simulations and manage the simulation results. Several of the ground‐motion simulation methods included in the BBP are described in related articles in this special focus issue. In this article, we describe how the BBP system architecture and software implementation support the scientific and engineering processes needed to assess ground‐motion models for use in engineering applications. The BBP design and development was initiated after a number of promising broadband ground‐motion simulation methods were developed (e.g., Atkinson and Boore, 2003; Boore and Atkinson, 2008; Graves and Pitarka, 2010; Mai et al. , 2010; Schmedes et al. , 2010). Researchers were interested in comparing ground‐motion simulation results between methods and in comparing simulation results to observations and to GMPEs. Such comparisons can be difficult because alternative methods often require different input parameters or specify input parameters in dissimilar formats. Fair comparisons between methods are only possible once multiple methods can input equivalent problem definitions and output comparable results. Based on previous experience evaluating simulation methods, seismologists and earthquake engineers recognized a need for a software tool to support the evaluation of the newly emerging broadband simulation methods. Drawing on discussions with both seismologists and engineers (e.g., Jordan and Maechling, 2003; Maechling …

The Composite Source Model for Broadband Simulations of Strong Ground Motions

My goal is to generate synthetic strong ground motions that are sufficiently realistic to be useful for engineering applications. The composite source model (CSM) uses a kinematic source model for rupture on a finite fault. This source is propagated to the station using a flat‐layered velocity model, scattering, and attenuation that can be measured from independent seismological observations. A key objective is to reproduce the wave propagation within the constraints of the measured velocity and Q structure. This article summarizes the CSM as implemented for the Southern California Earthquake Center (SCEC) Broadband Platform validation exercise (Goulet et al. , 2015). The CSM was first described by Yu (1994) and Zeng et al. (1994). Motivated by Frankel (1991), the model describes the source slip function as a superposition of overlapping circular subevents of random sizes, located randomly on the fault. Multiple source realizations naturally result in different seismograms. Zeng and Anderson (1996) and Zeng and Chen (2001) demonstrated that it is possible to find a specific realization of the CSM that reproduces the low‐frequency accelerograms in Northridge and Chi‐Chi earthquakes and that the slip functions resemble the slip function determined by other methods. Additional applications of the model include Khattri et al. (1994), Yu et al. (1995), Anderson and Yu (1996), and Su, Anderson, Ni, et al. (1998), Su, Anderson, Zeng (1998), and Hartzell et al. (2011). Variations of the original model have been proposed (e.g., Zeng et al. , 1991, 1995). For simplicity, the current implementation is close to the basic version, although some aspects of the Broadband platform implementation have not been described elsewhere. For this reason, this article gives a brief summary of the model on the Broadband Platform. ### Representation Theorem The theoretical basis for understanding ground motion from a finite fault is the representation theorem (e.g., …

Validation of the SCEC Broadband Platform V14.3 Simulation Methods Using Pseudospectral Acceleration Data

Online Material: Figures showing bias of PSA between data and simulations and between GMPEs and simulations for validation events and scenarios. This article summarizes the evaluation of ground‐motion simulation methods implemented on the Southern California Earthquake Center (SCEC) Broadband Platform (BBP), version 14.3 (as of March 2014). A seven‐member panel, the authorship of this article, was formed to evaluate those methods for the prediction of pseudospectral accelerations (PSAs) of ground motion. The panel’s mandate was to evaluate the methods using tools developed through the validation exercise (Goulet et al. , 2015) and to define validation metrics for the assessment of the methods’ performance. This article summarizes the evaluation process and conclusions from the panel. The five broadband, finite‐source simulation methods on the BBP include two deterministic approaches herein referred to as CSM (Anderson, 2015) and UCSB (Crempien and Archuleta, 2015); a band‐limited stochastic white noise method called EXSIM (Atkinson and Assatourians, 2015); and two hybrid approaches, referred to as G&P (Graves and Pitarka, 2015) and SDSU (Olsen and Takedatsu, 2015), which utilize a deterministic Green’s function approach for periods longer than 1 s and stochastic methods for periods shorter than 1 s. Two acceptance tests were defined to validate the broadband finite‐source ground‐motion simulation methods (Goulet et al. , 2015). Part A compared observed and simulated PSAs for periods from 0.01 to 10 s for 12 moderate‐to‐large earthquakes located in California, Japan, and the eastern United States. Part B compared the median simulated PSAs with published Next Generation Attenuation‐West 1 (NGA‐West 1) (Abrahamson and Silva, 2008; Boore and Atkinson, 2008; Campbell and Bozorgnia, 2008; Chiou and Youngs, 2008) ground‐motion prediction equations (GMPEs) for specific magnitude and distance cases, using a pass–fail criterion based on a defined acceptable range around the spectral shape of the GMPEs. For the initial part A and part …