Attenuation Relationships Research Articles

Empirical models for predicting lateral spreading considering the effect of regional seismicity

A revised empirical model has been developed for predicting liquefaction-induced lateral spreading displacement (LD) as a function of both response spectral acceleration derived from strong-motion attenuation models and geotechnical parameters from Youd’s LD data set (Youd website). This revised model is different from the model of Zhang and Zhao, which overcame some drawbacks of earlier models for predicting lateral spreading and was primarily used in Japan and the western U.S. The revised model can potentially be applied anywhere if ground shaking (in terms of 5% damped acceleration or displacement response spectra) can be estimated using local strong-motion attenuation relationships. The revised model is examined using data from Japan and the western U.S. and applied to Turkey and New Zealand, where the ground shaking is estimated using appropriate strong-motion attenuation relationships for each region. The accuracy of the revised model is evaluated by comparing its predicted lateral displacements with those measured in actual earthquakes. The results show that the revised model can account for the effects of local seismicity on lateral spreading displacements and is comparable with existing prediction models.

Analysis of earthquake parameters to generate hazard maps by integrating AHP and GIS for Küçükçekmece region

Abstract. Definition of an earthquake includes parameters with respect to region of interest. Each of those parameters has different weights on the earthquake ground motion and effect. This study examines the weight of common parameters that have an influence on the effects of earthquakes. The Analytic Hierarchy Process (AHP) is used for factor weighting of each parameter and Geographic Information Systems (GIS) are used for simulating the results of the AHP on a spatial environment. In this study, it is aimed to generate a hierarchical structure of the model for the simulation of an earthquake hazard map (EHM). The parameters of the EHM, which are selected by the criterion of non-correlated factors, are: topography, distance to epicenter, soil classification, liquefaction, and fault/focal mechanism. As a result of the study, weights of the parameters that affect the earthquake ground motion at the study area are determined and compared with a selected attenuation relation map.

Characterization of Grain Size and Yield Strength in AISI 301 Stainless Steel Using Ultrasonic Attenuation Measurements

AISI 301 stainless steel samples were annealed over the temperature range of 800–1200°C for 60 minutes to produce different grain sizes. These samples were characterized by ultrasonic immersion technique, tensile test, and optical microscopy. The attenuation of ultrasonic waves measured at a frequency of 20 MHz showed a good correlation with average grain size, hardness, and yield strength of AISI 301 stainless steel samples. A new equation was derived for calculation of yield strength on the basis of ultrasonic wave attenuation and Hall-Petch relation.

Significant Earthquakes on the Enriquillo Fault System, Hispaniola, 1500-2010: Implications for Seismic Hazard

Abstract Historical records indicate frequent seismic activity along the north‐east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. The intensity assignments and the attenuation relation are used in a grid search to find source locations and magnitudes that best fit the intensity assignments. Here we describe a sequence of devastating earthquakes on the Enriquillo fault system in the eighteenth century. An intensity magnitude M I 6.6 earthquake in 1701 occurred near the location of the 2010 Haiti earthquake, and the accounts of the shaking in the 1701 earthquake are similar to those of the 2010 earthquake. A series of large earthquakes migrating from east to west started with the 18 October 1751 M I 7.4–7.5 earthquake, probably located near the eastern end of the fault in the Dominican Republic, followed by the 21 November 1751 M I 6.6 earthquake near Port‐au‐Prince, Haiti, and the 3 June 1770 M I 7.5 earthquake west of the 2010 earthquake rupture. The 2010 Haiti earthquake may mark the beginning of a new cycle of large earthquakes on the Enriquillo fault system after 240 years of seismic quiescence. The entire Enriquillo fault system appears to be seismically active; Haiti and the Dominican Republic should prepare for future devastating earthquakes. Online Material: Table listing small earthquakes, and figures of intensity assignments and intensity magnitude estimates.

Regional Arias Intensity Attenuation Relationship for Taiwan Considering VS30

The Arias intensity is a measure of earthquake intensity arrived at through the integration of a square of the acceleration time history. It has been demonstrated to be an effective predictor of earthquake damage potential in relation to short-period structures, liquefaction, and seismic slope stability, and has begun to be considered as a ground-motion measure suitable for use in probabilistic seismic hazard analysis (PSHA), as well as earthquake loss estimation. A new empirical Arias intensity attenuation relationship for shallow crustal earthquakes is developed where both fault type and a continuous site variable VS30 are considered. The relationship is based on a large number of strong-motion records (6570) from a wide range of earth- quake magnitudes (3.9-7.6) from the Taiwan Strong Motion Instrument Program (TSMIP) network. Its functional form is modified from that of Travasarou et al. (2003), which is derived from a point-source model, and the coefficients are determined through nonlinear regression analyses using a mixed-effects model. The results show that the incorporation of VS30 can significantly reduce regression error. The Arias intensity value predicted in the present study is generally similar to that obtained by Travasarou et al. (2003), but is different in detail, being more suitable for usage in PSHA for a tectonically young orogenic belt like that in Taiwan or New Zealand.

Investigation on the Corrosion Behavior of Zn<sub>27</sub>Al<sub>3</sub>Cu Alloy in 3.5 wt.% NaCl Solution

The corrosion behavior of Zn27Al3Cu in 3.5 Wt.% NaCl solution is investigated through weight loss method. The morphology of corrosion products were observed and analyzed with optical microscopy (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The experimental results indicate that weight loss of the alloy with time follows the exponential attenuation relationship. Corrosion mechanism of Zn27Al3Cu alloy are intergranular corrosion and preferential corrosion in 3.5 Wt.% NaCl solution, the main corrosion products are compound oxide and chloride.

Updated PGA, PGV, and Spectral Acceleration Attenuation Relations for Iran

We have developed updated attenuation relations for peak ground acceleration (PGA), peak ground velocity (PGV), and acceleration response spectra with 5% damping on the basis of the data (78 earthquakes and 351 records) pertaining to strong ground motion in Iran. Moment magnitude, distance, fault mechanism, site class, and zone were the model parameters considered. A term for the saturation of the acceleration amplitude was also used in the model in order to improve the estimations in near-source regions. A nonlinear regression analysis was performed to obtain the coefficients. A comparison between the data set used in the current study for Iran and two next generation attenuation (NGA) models showed good correlation between our model and the Campbell-Bozorgnia NGA model. The model described is applicable for moment magnitudes from 5.0 to 7.3, distances from 15 to 135 km, and site classes with an average shear-wave velocity at a subsurface depth of 30 m (AVS30) of more than 175 m/s.

Probabilistic and Deterministic Seismic Hazard Assessment in Amol Center, a City in North of Iran

In this paper, the peak ground acceleration (PGA) over the bedrock is calculated by a probabilistic and deterministic seismic hazard assessment. An active fault map of the region is prepared. For this purpose, all active faults in a radius of 100 km from Amol city center are recognized and their seismic and rapture parameters are determined. Afterwards, for seismic hazard analysis, the seismic parameters of study region are determined and seismic classification zone is performed. Maximum earthquake, seismic parameters and also occurrence rate are determined. Seismic hazard analysis is performed using 3 different attenuation relationships resulted in seismic hazard curves for Amol city center. The peak ground acceleration (PGA) for design levels MCE, OBE and benefit life structure 50 and 100 years are presented. For the PGA quantity design levels operating base earthquake (OBE), maximum credible earthquake (MCE) for horizontal and vertical dimensions were equal to sequences of 0.33, 0.5 and 0.3, 0.53 g, respectively.

Historical perspective on seismic hazard to Hispaniola and the northeast Caribbean region

[1] We evaluate the long-term seismic activity of the North-American/Caribbean plate boundary from 500 years of historical earthquake damage reports. The 2010 Haiti earthquakes and other earthquakes were used to derive regional attenuation relationships between earthquake intensity, magnitude, and distance from the reported damage to the epicenter, for Hispaniola and for Puerto Rico and the Virgin Islands. The attenuation relationship for Hispaniola earthquakes and northern Lesser Antilles earthquakes is similar to that for California earthquakes, indicating a relatively rapid attenuation of damage intensity with distance. Intensities in Puerto Rico and the Virgin Islands decrease less rapidly with distance. We use the intensity-magnitude relationships to systematically search for the location and intensity magnitude MI which best fit all the reported damage for historical earthquakes. Many events occurred in the 20th-century along the plate-boundary segment from central Hispaniola to the NW tip of Puerto Rico, but earlier events from this segment were not identified. The remaining plate boundary to the east to Guadeloupe is probably not associated with M > 8 historical subduction-zone earthquakes. The May 2, 1787 earthquake, previously assigned an M 8–8.25, is probably only MI 6.9 and could be located north, west or SW of Puerto Rico. An MI 6.9 earthquake on July 11, 1785 was probably located north or east of the Virgin Islands. We located MI < 8 historical earthquakes on April 5, 1690, February 8, 1843, and October 8, 1974 in the northern Lesser Antilles within the arc. We speculate that the December 2, 1562 (MI 7.7) and May 7, 1842 (MI 7.6) earthquakes ruptured the Septentrional Fault in northern Hispaniola. If so, the recurrence interval on the central Septentrional Fault is ∼300 years, and only 170 years has elapsed since the last event. The recurrence interval of large earthquakes along the Hispaniola subduction segment is likely longer than the historical record. Intra-arc M ≥ 7.0 earthquakes may occur every 75–100 years in the 410-km-long segment between the Virgin Islands and Guadeloupe.

Directivity Effect on PGV Attenuation Relationships in Silakhor Earthquake (2006, Mw6.1)

Directivity Effect on PGV Attenuation Relationships in Silakhor Earthquake (2006, Mw6.1)

Robust attenuation relations for peak time-domain parameters of strong ground motions

This study presents new attenuation models for the estimation of peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) using a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The PGA, PGV, and PGD were formulated in terms of earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms. A worldwide database of strong ground motions released by Pacific Earthquake Engineering Research Center (PEER) was employed to establish the models. A traditional genetic programming analysis was performed to benchmark the proposed models. For more validity verification, the GP/SA models were employed to predict the ground-motion parameters of the Iranian plateau earthquakes. Sensitivity and parametric analyses were carried out and discussed. The results show that the GP/SA attenuation models can offer precise and efficient solutions for the prediction of estimates of the peak time-domain characteristics of strong ground motions. The performance of the proposed models is better than or comparable with the attenuation relationships found in the literature.

Simulation of strong ground motion in northern Iran using the specific barrier model

SUMMARY In this study, based upon the calibrated specific barrier model (SBM) against the latest available strong motion data, ground motion prediction equations for soil and rock sites in northern Iran are developed. The SBM may provide the most complete, simple and self-consistent description of the faulting process, which is applicable in both ‘near-fault’ and ‘far-field’ regions. Consequently, the SBM may provide consistent ground motion simulations over the entire necessary frequency range and for all distances of engineering interests. To determine source parameters in this study, we used 163 three-component records of 32 earthquakes with magnitude ranging from MW 4.9 to 7.4 in northern Iran. In the database, records with hypocentral distances less than 200 km are chosen and only earthquakes whose moment-magnitude estimates are available have been used. Furthermore, using the best available information, recording sites are classified into two main geologic categories: rock and soil. Because of the lack of site amplification information in the most regions of the world including Iran, we used the H/V ratio method for estimating the site amplification. Moreover, the Kappa factor that shows diminishing the high-frequency amplitude is determined. In this study, two data sets are considered for determining the source parameters (ΔσG and ΔσL) and the H/V ratio and the Kappa factor. Only S-wave part of signals is used in each analysis. Regression analysis is performed using ‘random effects’ method that considers both interseismic (event-to-event) and coseismic (within-event) variabilities to effectively deal with the problem of weighting observations from different earthquakes. The residuals are controlled against available northern Iranian strong ground motion data to verify that the model predictions are unbiased and that there are no significant residual trends with magnitude and distance. At first, it is assumed that no sign of self-similarity breakdown is observed between the source radius and its seismic moment. After controlling the results, the modified SBM should be used as some deviations have been observed. To verify the robustness of the results, the number of observations is changed by removing various randomly selected data sets from the original database, which results in unchanged results of the model. Stochastic simulations are then implemented to predict peak ground motion and response spectra parameters. The stochastic SBM predictions are in relatively good agreement with other available attenuation relationships proposed for Iran, Europe and Middle East. It has been shown that the proposed SBM of this study provides unbiased ground motion estimates over the entire frequency range of most engineering applications. It provides a reliable and physically realistic, yet computationally efficient, way to model strong ground motions.

Specificity of unenhanced CT for non-invasive diagnosis of hepatic steatosis: implications for the investigation of the natural history of incidental steatosis

To determine a highly specific liver attenuation threshold at unenhanced CT for biopsy-proven moderate to severe hepatic steatosis (≥30% at histology). 315 asymptomatic adults (mean age ± SD, 31.5 ± 10.1 years; 207 men, 108 women) underwent same-day unenhanced liver CT and ultrasound-guided liver biopsy. Blinded to biopsy results, CT liver attenuation was measured using standard region-of-interest methodology. Multiple linear regression analysis was used to assess the relationship of CT liver attenuation with patient age, gender, BMI, CT system, and hepatic fat and iron content. Thirty-nine subjects had moderate to severe steatosis and 276 had mild or no steatosis. A liver attenuation threshold of 48 HU was 100% specific (276/276) for moderate to severe steatosis, with no false-positives. Sensitivity, PPV and NPV at this HU threshold was 53.8%, 100% and 93.9%. Hepatic fat content was the overwhelming determinant of liver attenuation values, but CT system (P < 0.001), and hepatic iron (P = 0.035) also had a statistically significant independent association. Unenhanced CT liver attenuation alone is highly specific for moderate to severe hepatic steatosis, allowing for confident non-invasive identification of large retrospective/prospective cohorts for natural history evaluation of incidental non-alcoholic fatty liver disease. Low sensitivity, however, precludes effective population screening at this threshold. • Unenhanced CT liver attenuation is highly specific for diagnosing moderate/severe hepatic steatosis. • Unenhanced CT can identify large cohorts for epidemiological studies of incidental steatosis. • Unenhanced CT is not, however, effective for population screening for hepatic steatosis.

A new methodology to determine elastic displacement spectra in the near-fault region

The evaluation of the displacement demand especially at small distances from the causative fault, in the so-called near-source region, is a subject of particular interest for earthquake engineering design, in the light of the growing application of the displacement-based design philosophy. This study presents a new methodology to determine the elastic displacement spectra using a sample of near-fault records from small-to-moderate magnitude earthquakes, typical of the seismic activity in Europe. The displacement spectrum is developed using near-fault attenuation relationships available in literature for peak ground velocity that is less sensitive in the procedures applied to correct the accelerograms. Also, the distance from the causative fault and the type of directivity are taken into consideration. The prevailing period corresponds to the maxima of the displacement spectra for zero damping and is used to normalize the spectra, leading to significant decrease of the statistical dispersion. The average bi-normalized spectrum, in terms of the peak ground displacement d g, max and the dominant period T d-p , appears to be slightly affected by the soil category and earthquake magnitude. A correlation between the damping correction factor η and the normalized period T/ T d-p is detected and the applicability of several provisions of the current version of Eurocode 8 is examined, including characteristic periods and spectral amplitudes.

Role of attenuation relationship in shaping the seismic hazard

Attenuation relationships are commonly used for engineering studies to estimate the peak ground acceleration values. This paper presents the role of attenuation relationship in defining the seismic hazard in an area. It is seen that the seismic hazard in an area, which is calculated using attenuation relationships, is mostly controlled by the type of attenuation relationship used in the study. The present work aims to study the effect of attenuation relationship on seismic hazard study. In the present work, seismic hazard maps have been prepared in the seismically very active northeast Himalaya using the approach given by Joshi and Patel (Tectonophysics 283:289–310, 1997). The attenuation relationships of Jain et al. (2000), Sharma (2000), Joyner and Boore (Bull Seism Soc Am 71:2011–2038, 1981) and Abrahamson and Litehiser (Bull Seism Soc Am 79:549–580, 1989) have been considered in the present study. Among all considered attenuation relationships, the Abrahamson and Litehiser (Bull Seism Soc Am 79:549–580, 1989) attenuation relationship gives the least root mean square error between the recorded and calculated peak ground acceleration values. Therefore, the same has been used to define attenuation characteristic of the region. The mean and standard deviation of peak ground acceleration values at all the observation points due to above-mentioned attenuation relationships in the NE Himalayas are calculated. The study shows that the Zone III covers an area of 81,000 km2 and Zone II of 96,000 km2 in the map prepared using the mean peak ground acceleration values, whereas the area of Zone IV increases by 40,000 km2 when the map is prepared by adding the standard deviation values in the mean peak ground acceleration values, and only Zone II is left with 183,000 km2 when the standard deviation values are subtracted from the mean. This high standard deviation is due to the difference in the peak ground acceleration values obtained from different events. This study shows that a rigorous test needs to be done for selecting attenuation relationship for any hazard study in a given area.

Seismic hazard and site-specific ground motion for typical ports of Gujarat

Economic importance of major ports is well known, and if ports are located in seismically active regions, then site-specific seismic hazard studies are essential to mitigate the seismic risk of the ports. Seismic design of port sites and related structures can be accomplished in three steps that include assessment of regional seismicity, geotechnical hazards, and soil structure interaction analysis. In the present study, site-specific probabilistic seismic hazard analysis is performed to identify the seismic hazard associated with four typical port sites of Gujarat state (bounded by 20°–25.5°N and 68°–75°E) of India viz. Kandla, Mundra, Hazira, and Dahej ports. The primary aim of the study is to develop consistent seismic ground motion for the structures within the four port sites for different three levels of ground shaking, i.e., operating level earthquake (72 years return period), contingency level earthquake (CLE) (475 year return period), and maximum considered earthquake (2,475 year return period). The geotechnical characterization for each port site is carried out using available geotechnical data. Shear wave velocities of the soil profile are estimated from SPT blow counts using various empirical formulae. Seismicity of the Gujarat region is modeled through delineating the 40 fault sources based on the seismotectonic setting. The Gujarat state is divided into three regions, i.e., Kachchh, Saurashtra, and Mainland Gujarat, and regional recurrence relations are assigned in the form of Gutenberg-Richter parameters in order to calculate seismic hazard associated with each port site. The horizontal component of ground acceleration for three levels of ground shaking is estimated by using different ground motion attenuation relations (GMAR) including one country-specific GMAR for Peninsular India. Uncertainty in seismic hazard computations is handled by using logic tree approach to develop uniform hazard spectra for 5% damping which are consistent with the specified three levels of ground shaking. Using recorded acceleration time history of Bhuj 2001 earthquake as the input time motion, synthetic time histories are generated to match the developed designed response spectra to study site-specific responses of port sites during different levels of ground shaking. It is observed that the Mundra and Kandla port sites are most vulnerable sites for seismic hazard as estimated CLE ground motion is in order of 0.79 and 0.48 g for Mundra and Kandla port sites, respectively. Hazira and Dahej port sites have comparatively less hazard with estimated CLE ground motion of 0.17 and 0.11 g, respectively. The ground amplification factor is observed at all sites which ranges from 1.3 to 2.0 for the frequency range of 1.0–2.7 Hz. The obtained spectral accelerations for the three levels of ground motions and obtained transfer functions for each port sites are compared with provisions made in Indian seismic code IS:1893-Part 1 (2002). The outcome of present study is recommended for further performance-based design to evaluate the seismic response of the port structures with respect to various performance levels.

Seismology Based Ground Motion Attenuation Relationship for Sendai Area

For regions without adequate strong ground motion records, a method is developed to establish strong ground motion attenuation relationships, based on the stochastic method. Sendai area of Japan is selected as the target, since there are enough data from seismographic observation for calculation, and those from strong ground motion observation and some empirical relationships for result testing. Three parameters related to regional source and crustal medium are inversed by the micro-Genetic Algorithm. Total of 240 records from 77 small events, recorded by F-net, are adopted for the inversion. Fourier spectra are adopted as the objective function. These parameters are then taken into the stochastic method to estimate PGA. The regional ground motion attenuation relationships are compared with some strong ground motion records from K-NET and some empirical relationships to illustrate the reliability of this method.

Duration Characteristics of Ground Motion Based on Wenchuan Earthquake

Records from 56 stations on free-field within 150km to causative fault surface are used as database during the Mw7.9 Wenchuan earthquake in china. According to this study, the duration of ground motion is strongly affected by rupture distance, site conditions, fault rupture directory and thrust of hanging wall. Duration is obtained based on the time between 10 and 80 per cent of Arias intensity. A simple attenuation relation in terms of rupture distance is proposed and compared with some available predictions. The durations of tri-component ground motions on hanging wall are smaller than those on the foot wall in the same range of rupture distance. Durations of ground motions close to rupture fault resulting from directivity effects are significantly different between the forward and backward direction, and this difference reaches nearly 2 times on average.

Ground motion predictive modelling based on genetic algorithms

Abstract. This study aims to utilise genetic algorithms for the estimation of peak ground accelerations (PGA). A case study is carried out for the earthquake data from south-west Turkey. The input parameters used for the development of attenuation relationship are magnitude, depth of earthquake, epicentral distance, average shear wave velocity and slope height of the site. Earthquake database compiled by the Earthquake Research Institute of Turkey was used for model development. An important contribution to this study is the slope/hill data included into the dataset. Developed empirical model has a good correlation (R = 0.78 and 0.75 for the training and overall datasets) between measured and estimated PGA values. The proposed model is also compared with local empirical predictive models and its results are found to be reasonable. The slope-hill effect found to be an important parameter for the estimation of PGA.

Documenting Liquefaction and Lateral Spreading Triggered by the 12 January 2010 Haiti Earthquake

The 12 January 2010 Haiti earthquake (Mw 7.0) caused extensive damage to the Port-au-Prince region, including severe liquefaction failures along the Gulf of Gonâve coastline, along rivers north of Port-au-Prince draining into the Gulf, and a liquefaction-induced structural/bearing capacity failure of a three-story concrete hotel along the southern coast of the Gulf. During two reconnaissance missions, the authors documented ground conditions and performance at eight sites that liquefied and two sites that did not liquefy. Geotechnical characterization included surface mapping, dynamic cone penetration tests, hand auger borings, and laboratory index tests. The authors estimated median peak ground accelerations (PGAs) of approximately 0.17g to 0.48g at these sites using the Next Generation Attenuation (NGA) relations summarized by Power et. al. (2008) . These case histories are documented here so that they can be used to augment databases of level-ground/near level-ground liquefaction, lateral spreading, liquefaction flow failure, and liquefaction-induced bearing capacity failure.