Ground-Motion Prediction Equations for Central and Eastern North America (CENA)

First, a new path model, including the geometrical spreading and the quality factor functions, is developed for the New Madrid seismic zone (NMSZ) using recorded small and moderate earthquakes. The database consists of 500 broadband seismograms from 63 events of magnitude Mw 2.5 to 5.2. All the broadband stations are located within the Mississippi embayment. The vertical components of the records are processed and used to define the path effect term in the frequency range of 0.2 to 30 Hz. At distances less than 70 km, the spectral amplitudes decay as R-1; between 70 and 140 km, spectral amplitudes increase with distance and the geometric spreading is defined as R+0.25; beyond 140 km, the attenuation is described by R-0.5. The quality factor function is expressed as Q=614f0.32for frequencies greater than 1 Hz.Second, the horizontal-to-vertical component (H/V) spectral ratio is used as an estimation of the site response in the NMSZ. The observed average H/V ratios suggest site amplification between 2 and 4 in the low-frequency range (f\u3c5 Hz) for stations located on the lower shear-wave velocity deposits (Lowlands). The higher shear-wave velocity deposits (Uplands) indicate low-frequency amplification between 1.5 and 3 Hz. Comparison of the observed H/V ratios with the theoretical amplification factors suggest that the H/V ratios can be a first estimate of the site amplifications. Afterward, the variability of the H/V ratios with distance is examined and no discernible trends are found; therefore, the path effect model developed for the vertical ground motions in NMSZ using the database of this study is also applicable for the horizontal ground motions.Finally, a hybrid empirical method is used to develop a new ground-motion prediction equation (GMPE), for eastern North America (ENA), using five new GMPEs developed for western North America (WNA). A new GMPE is derived for a magnitude range of 5 to 8 and closest distances to the fault rupture up to 1000 km for hard-rock sites in ENA. The new GMPE is compared with two GMPEs used in the 2008 national seismic hazard maps as well as with available observed data for ENA

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Investigation of geometrical spreading and quality factor functions in the new madrid seismic zone

The accuracy and applicability of geometrical spreading and quality factor functions are investigated for the New Madrid seismic zone (NMSZ) using recorded small and moderate earthquakes. These functions represent the path effect in frequency domain. The database used in this study consists of 500 broadband seismograms from 63 events of magnitude Mw 2.5 to 5.2, recorded by the Center for Earthquake Research and Information (CERI) at the University of Memphis. The hypocentral distances range from 10 to 400 km. All the broadband stations are located within the Mississippi embayment with different site conditions. The vertical components of the records are processed and used to define the path effect term in frequency range of 0.2 to 30 Hz. A hinged-trilinear geometrical spreading and frequency-dependent quality factor functions are used to describe the path term. The regression analysis using a genetic algorithm (GA) indicates that at distances less than 70 km the spectral amplitudes decay as R-1; between 70 and 140 km spectral amplitudes increase with distance and the geometric spreading is defined as R++0.25; beyond 140 km, the attenuation is described by R-0.5. The quality factor function is expressed as Q = 614f0.32 for frequencies greater than 1 Hz after the regression analysis. For the broader range offrequency used in this study (0.2 to 30 Hz), the Q function is described by a third-degree polynomial described as log Q(f) = 2.898 - 0.464logf + 1.238(logf)2 - 0.540(logf)3. The results of this study are compared with those of Atkinson (2004) and Samiezade-Yazd et al. (1997). The path term obtained in this study can be used in the stochastic method to predict ground motions in the NMSZ and eastern North America (ENA)

A study of horizontal-to-vertical component spectral ratio in the New Madrid seismic zone

The horizontal-to-vertical component (H/V) spectral ratio of the small and moderate earthquake ground motions for the shear-wave window was used as an estimation of the site response in the New Madrid seismic zone (NMSZ). The database used in this study consisted of 500 broadband seismograms from 63 events of magnitude Mw 2.5 to 5.2, recorded on 11 stations operated by the University of Memphis Center for Earthquake Research and Information (CERI) at the University of Memphis. All the broadband stations were located within the Mississippi embayment. Soil deposits overlying the rock basement of the embayment strongly affected the amplitudes of the ground motions. The horizontal-to-vertical component ratios were evaluated for the frequency range of 0.2 to 20 Hz. The observed average H/V ratios suggested site amplification between 2 and 4 in the low-frequency range (f ≤ 5 Hz) for stations located on the lower shear-wave velocity deposits (lowlands). The higher shear-wave velocity deposits (uplands) indicated low-frequency amplification between 1.5 and 3 Hz. The observed average H/V ratios were also compared with the soil amplifications in the upper Mississippi embayment developed by Romero and Rix (2005) from the 1D (equivalent linear) method for generic regional profiles. The H/V ratios were also compared with the theoretical quarter-wavelength approximation. These comparisons suggested that the H/V ratios could be a first estimate of the site amplifications. Finally, the variability of the H/V ratios with distance was examined and no discernible trends were found; therefore, the path effect model developed by Zandieh and Pezeshk (2010) for the vertical ground motions in NMSZ using the database of this study was also applicable for the horizontal ground motions

Hybrid empirical ground-motion prediction equations for Eastern North America using NGA models and updated seismological parameters

In the field of earthquake engineering, ground-motion prediction modelsare frequently used to estimate the peak ground acceleration (PGA) and the pseudospectral acceleration (PSA). In regions of the world where ground-motion recordings are plentiful, such as western North America (WNA), the ground-motion prediction equations are obtained using empirical methods. In other regions, such as eastern North America (ENA), with insufficient ground-motion data, alternative methods must be used to develop ground-motion prediction equations (GMPEs). The hybrid empirical method is one such method used to develop ground-motion prediction equations in areas with sparse ground motions. This method employs the stochastic simulation method to adjust empirical GMPEs developed for a region with abundant strongmotion recordings in order to estimate strong-motion parameters in a region with a sparse database. The adjustments take into account differences in the earthquake source, wave propagation, and site-response characteristics between the two regions. In this study, a hybrid empirical method is used to develop a new GMPE for ENA, using five new ground-motion prediction models developed by the Pacific Earthquake Engineering Research Center (PEER) for WNA. A new ENA GMPE is derived for a magnitude range of 5 to 8 and closest distances to the fault rupture up to 1000 km. Ground-motion prediction equations are developed for the response spectra (pseudoacceleration, 5% damped) and the PGA for hard-rock sites in ENA. The resulting ground-motion prediction model developed in this study is compared with two ENA ground-motion models used in the 2008 national seismic hazard maps as well as with available observed data for ENA

Estimation of κ0 implied by the high-frequency shape of the NGA-west2 ground-motion prediction equations

The spectral-decay parameter κ0 is often used to account for the reduction of the high-frequency amplitude of ground motion caused by attenuation within the site profile. In this study, we used the inverse random vibration theory approach described by Al Atiket al.(2014) to calculate Fourier amplitude spectra from predicted values of response-spectral acceleration for all five Next Generation Attenuation (NGA)-West2 ground-motion prediction equations (GMPEs). We used these spectra to estimate κ0 using the spectral-decay method. Each GMPE was evaluated for a National Earthquake Hazard Reduction Program B/C site condition and for default estimates of depth to the top of rupture, hypocentral depth, and sediment (basin) depth. We derived estimates of κ0 for magnitudes ranging from 3.5 to 8.0 and distances ranging from 5 to 20 km and used a mixed-effects model to derive equations for these estimates as a function of magnitude. We also calculated κ0 from the geometric mean of the response-spectral accelerations of the GMPEs to check the sensitivity of the results to the two approaches and found that the values of κ0 derived in this study using a mixed-effects model are in good agreement with these estimates. The values of κ0 obtained in this study do not necessarily represent the physical high-frequency damping within the site profiles used to develop the NGA-West2 GMPEs. Instead, they are intended to represent the high-frequency shape of the median predicted spectral accelerations from the GMPEs. The κ0 model developed in this study can be used in inversions to develop stochastic models that are intended to mimic the predictions from the NGA-West2 GMPEs

A ground-motion model for the gulf coast region of the United States

In this study, the hybrid empirical method (HEM) was used to develop a new ground-motion model (GMM) for the Gulf Coast of the United States. We used five new empirical GMMs developed by the Pacific Earthquake Engineering Research Center for the Next Generation Attenuation-West2 project to estimate ground-motion intensity measures (GMIMs) in the host region. The new GMM is derived for the horizontal peak ground acceleration and response-spectral ordinates at periods ranging from 0.01 to 10 s, moment magnitudes ranging from M 3.5 to 8.0, and rupture distance (RRUP) as far as 1000 km from the site, although the GMMs are the best constrained for RRUP \u3c 300–400 km. The predicted GMIMs are for a reference site defined as the Gulf Coast region hard rock with VS30 3000 m/ s and κ0 0:006 s, in which VS30 is the time-averaged shear-wave velocity in the top 30 m of the site profile, and κ0 is the total attenuation of the ground motion as it propagates through the site profile. Seismological parameters used to derive the GMIM stochastic estimates in the Gulf Coast target region are adopted from the most recent research and published information for the region. The seismological parameters for the western North America host region are adopted from Zandieh et al. (2017). The proposed GMM is compared with the Pezeshk et al. (2018) model, which is also a HEM approach, and was developed for central North America and excluded the Gulf Coast region to show the differences between the regions

An equivalent point-source stochastic simulation of the NGA-west2 ground-motion prediction equations

In this study, we use a genetic algorithm to invert horizontal groundmotion intensity measures (GMIMs) predicted from the empirical Next Generation Attenuation-West2 (NGA-West2) ground-motion prediction equations (GMPEs) to estimate a consistent and correlated set of seismological parameters to use with an equivalent point-source stochastic model. The GMIMs are peak ground acceleration and pseudospectral acceleration evaluated over a wide range of magnitudes, distances, and frequencies. The inversion is performed for M 3:5-8:0, RRUP= 1-300 km, T = 0:01-10 s, and National Earthquake Hazard Reduction Program (NEHRP) B/C site conditions. Seismological parameters are obtained as a function of earthquake magnitude. The near-source geometric spreading was modeled as both magnitude-and frequency dependent to fit the empirical predictions. The agreement between the model and empirical predictions over all magnitudes and distances evaluated in this study is generally within 10%, with some local exceptions. The near-source geometric spreading is consistent with a distance decay of R−0:8to R−1:3at frequencies of f ≤ 1 Hz for Mranging from 3.5 to 8. Near 5 Hz, the distance decay is expressed as R−1:17, on average at short distances. At larger frequencies, the near-source distance decay varies from R−1:0to R−1:25. This stochasticmodel can be used for any application that requires a frequencydomain representation of the NGA-West2 GMPEs

Ground-motion prediction equations for central and eastern north America using the hybrid empirical method and NGA-west2 empirical ground-motion models

The hybrid empirical method (HEM) of simulating ground-motion intensity measures (GMIMs) in a target region uses stochastically simulated GMIMs in the host and target regions to develop adjustment factors that are applied to empirical GMIM predictions in the host region. In this study, the HEM approach was used to develop two new ground-motion prediction equations (GMPEs) for a target region defined as central and eastern North America (CENA), excluding the Gulf Coast region. The method uses five new empirical GMPEs developed by the Pacific Earthquake Engineering Research Center for the Next Generation Attenuation-West2 (NGA-West2) project to estimate GMIMs in the host region. The two new CENA GMPEs are derived for peak ground acceleration and response spectral ordinates at periods ranging from 0.01 to 10 s, moment magnitudes (M) ranging from 4.0 to 8.0, and rupture distance (Rrup) as far as 1000 km from the site, although the GMPEs are best constrained for Rrup \u3c 300–400 km. The predicted GMIMs are for a reference site defined as CENA hard rock with VS30 3000 m/s and κ0 0:006 s. The seismological parameters for the western North America host region were adopted from a point-source inversion of the median GMIM predictions from the NGA-West2 GMPEs for events and sites with M ≤ 6:0, Rrup ≤ 200 km, VS30 760 m/s, a generic (average of strike slip and reverse) style of faulting, and earthquake-depth and sediment-depth parameters equal to the default values recommended by the NGA-West2 developers. The two CENA GMPEs are based on two fundamentally different approaches to magnitude scaling at large magnitudes: (1) using the HEM approach to model magnitude scaling over the entire magnitude range and (2) using the HEM approach to model magnitude scaling for events with M ≤ 6:0 and using the magnitude scaling predicted by the NGA-West2 GMPEs for the larger events

A study of vertical-to-horizontal ratio of earthquake components in the Gulf Coast Region

A new ground-motion prediction model is developed for the response spectral ratio of vertical-to-horizontal (V/H) components of earthquakes for the Gulf Coast region. The proposed V/H response spectral ratio model has the advantage of considering the earthquake magnitude, source-to-site distance, and the shear-wave velocity of soil deposits in the upper 30 m of the site (VS30) for the peak ground acceleration, and a wide range of spectral periods (0.01–10.0 s). The model is based on a comprehensive set of regression analyses of the newly compiled Next Generation Attenuation-East database of available central and eastern North America recordings with the moment magnitudes M ≥3:4 and the rupture distances RRup \u3c 1000 km. The 50th percentile (or median) pseudospectral acceleration values computed from the orthogonal horizontal components of ground motions rotated through all possible nonredundant rotation angles, known as the RotD50 (Boore, 2010), is used along with the vertical component to perform regression using a nonlinear mixed-effects regression algorithm. The predicted V/H ratios from the proposed model are compared with the recently published V/H spectral ratio models for different regions. The derived V/H ratios can be used to develop the vertical response spectra for the sites located within the Gulf Coast region, which include the Mississippi embayment