Investigation on directional effects of Vrancea subcrustal earthquakes

This paper evaluates possible directional effects from strong ground motions recorded during the last four significant subcrustal earthquakes produced in the Vrancea seismic zone(Romania) in August 1986(M_w=7.1),May 1990(M_w=6.9 and 6.4) and October 2004(M_w=6.0).Several measures of the horizontal component of the ground motion given in the literature(Boore et al.,2006;Boore,2010) are computed and are related to the geometric mean of the as-recorded horizontal components.ANOVA method is applied in order to quantify the influence of the earthquake magnitude and of the soil class on some strong ground motion parameters(e.g.Arias intensity,PGV/PGA,or mean period T_M).The study of the directional effects is performed using the distribution of I_(JMA) and of the rotation angle corresponding to a measure of the horizontal component of the ground motion(RotD 100) and the results reveal a visible directional pattern for I_(JMA),while in the case of RotD100 the directional patterns are less visible.     

A study of residuals for strong ground motions in Adapazari basin,NW Turkey,by ground motion prediction equations (GMPEs)

The city of Adapazarı — located in the Marmara Region of northwest Turkey — is situated on a deep sedimentary basin and was the city most heavily damaged by the strong ground motion of the 17 August 1999 Kocaeli earthquake (moment magnitude M_w = 7.4). This study determines site amplifications of the attenuation relationships for shallow earthquakes in the Adapazarı basin by using the previous ground motion prediction equations (GMPEs) and the traditional spectral ratio method. The site amplifications are determined empirically by averaging the residuals between the observed and predicted peak ground acceleration (PGA) and spectral acceleration (SA) values for various periods. Residuals are significantly correlated with the known characteristics of geological units. A new attenuation model has also been developed for 5% damped spectral acceleration to determine the dependence of strong ground motions on frequency.     

Towards a new reference ground motion prediction equation for Italy: update of the Sabetta–Pugliese (1996)

A revised Italian strong motion archive has become available since July 2007, including all the records of the strongest events occurred from 1972 to 2004. It contains the uncorrected and corrected accelerograms and the metadata relevant to seismic events, recording stations and instruments added after a careful revision. The availability of this archive allowed us to perform a first step towards an update of the reference ground motion prediction equations for Italy, which were evaluated by Sabetta and Pugliese in (Bull Seismol Soc Am 77:1491–1513, 1987), for peak ground acceleration and velocity, and subsequently extended to the 5% damped pseudovelocity response spectra in 1996. A subset with the 27 major earthquakes occurred in Italy from 1972 to 2002, in the magnitude range 4.6–6.9, was extracted and 235 good quality waveforms were selected, recorded at distances up to 183 km. The goodness of fit of the Sabetta and Pugliese (Bull Seismol Soc Am 86:337–352, 1996) model was explored using two independent statistical approaches (Spudich et al. Bull Seismol Soc Am 89:1156–1170, 1999 and Scherbaum et al. Bull Seismol Soc Am 94:2164–2185, 2004). The results obtained show that the Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987) does not adequately fit the new strong-motion data set, for its small standard deviation and its non-zero bias. In particular, the most noteworthy result is that the Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987) over-predicts peak ground acceleration and velocity at rock sites. New coefficients for the prediction of horizontal peak ground acceleration, peak ground velocity and acceleration response spectra, adopting the same functional form in Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987), were then evaluated in order to fit the new data set. This paper illustrates the steps made to update the existing ground motion prediction equations for Italy, discusses their limitations and provides the basis for future developments.     

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 atte...     

Critical evaluation of strong motion in Kocaeli and Düzce (Turkey) earthquakes

Turkey was struck by two major events on August 17th and November 12th, 1999. Named Kocaeli (M_w=7.4) and Düzce (M_w=7.2) earthquakes, respectively, the two earthquakes provided the most extensive strong ground motion data set ever recorded in Turkey. The strong motion stations operated by the General Directorate of Disaster Affairs, the Kandilli Observatory and Earthquake Research Institute of Bogazici University and Istanbul Technical University have produced at least 27 strong motion records for the Kocaeli earthquake within 200 km of the fault. Kocaeli earthquake has generated six motions within 20 km of the fault adding significantly to the near-field database of ground motions for M_w>=7.0 strike–slip earthquakes. The paper discusses available strong motion data, studies their attenuation characteristics, analyses time domain, as well as spectral properties such as spectral accelerations with special emphasis on fault normal and fault parallel components and the elastic attenuation parameter, kappa. A simulation of the Kocaeli earthquake using code FINSIM is also presented.     

Ground motion models for the Molise region (Southern Italy)

The aim of this paper is to evaluate empirical attenuation relationships in order to validate peak values and pseudo-velocity spectra to calibrate shaking scenarios for the Molise area, which was struck by two earthquakes of M_w=5.7 (INGV-Harvard European-Mediterranean Regional Centroid-Moment tensor project) on October 31st and November 1st, 2002. Before the earthquake occurrence this region was classified as not hazardous, according to the former Italian seismic code. After the main-shocks, felt in many towns of the Molise and Puglia regions, a strong motion and a seismic temporary network were installed in the epicentral area and surrounding regions. This allowed the collection of a large data set, useful to characterize this area. The joint velocity-acceleration data set has been used to derive ground motion models for peak ground acceleration, peak ground velocity, and pseudo-velocity response spectra for both maximum horizontal and vertical components of the motion.The results obtained for the Molise area have been compared with the attenuation pattern of the Umbria-Marche region (central Italy) and the Italian territory. Remarkable differences have been observed leading to a discussion of the possible regional dependence of ground motion.     

Empirical equations for the prediction of PGA and pseudo spectral accelerations using Iranian strong-motion data

A recently compiled, comprehensive, and good-quality strong-motion database of the Iranian earthquakes has been used to develop local empirical equations for the prediction of peak ground acceleration (PGA) and 5%-damped pseudo-spectral accelerations (PSA) up to 4.0 s. The equations account for style of faulting and four site classes and use the horizontal distance from the surface projection of the rupture plane as a distance measure. The model predicts the geometric mean of horizontal components and the vertical-to-horizontal ratio. A total of 1551 free-field acceleration time histories recorded at distances of up to 200 km from 200 shallow earthquakes (depth < 30 km) with moment magnitudes ranging from M_w 4.0 to 7.3 are used to perform regression analysis using the random effects algorithm of Abrahamson and Youngs (Bull Seism Soc Am 82:505–510, 1992), which considers between-events as well as within-events errors. Due to the limited data used in the development of previous Iranian ground motion prediction equations (GMPEs) and strong trade-offs between different terms of GMPEs, it is likely that the previously determined models might have less precision on their coefficients in comparison to the current study. The richer database of the current study allows improving on prior works by considering additional variables that could not previously be adequately constrained. Here, a functional form used by Boore and Atkinson (Earthquake Spect 24:99–138, 2008) and Bindi et al. (Bull Seism Soc Am 9:1899–1920, 2011) has been adopted that allows accounting for the saturation of ground motions at close distances. A regression has been also performed for the V/H in order to retrieve vertical components by scaling horizontal spectra. In order to take into account epistemic uncertainty, the new model can be used along with other appropriate GMPEs through a logic tree framework for seismic hazard assessment in Iran and Middle East region.     

An empirical attenuation relationship for Northwestern Turkey ground motion using a random effects approach

Using a random effects model that takes into consideration the correlation of data recorded by a single seismic event, a database consisting of 195 recordings from 17 recent events is employed to develop empirical attenuation relationships for the geometric mean of horizontal peak ground acceleration and 5-percent damped spectral acceleration (S_a). The recordings employed are obtained from strong motion stations operating in Northwestern Turkey and resulted from events that include the Kocaeli (M_w=7.4) and the Düzce (M_w=7.1) earthquakes and their aftershocks as well as other events. By studying differences in standard errors, the random effects model is compared with a fixed effects model that does not account for distinctions between intra- and inter-event variability. Effects of local site conditions are included in the empirical relationships developed. The dependence on frequency of the various model parameters is also studied. Frequency-dependent attenuation coefficients for the proposed random effects models developed are summarized in tables to facilitate their use.     

Ground motion directionality inferred from a survey of minaret damage during the 1999 Kocaeli and Düzce, Turkey earthquakes

Directionality of ground motions has been discussed in near-source groundmotion study. This is interesting from the point of structural response.Dominance of the fault normal (FN) component has been reported inrelation to fault rupture direction based on the observation recordsobtained in the source area (e.g.. Somerville et al., 1996). The authorsperformed the damage survey of the two Turkey earthquakes in 1999, theKocaeli and the Düzce earthquake, and realized that minaret is a goodtarget to investigate the ground motion directionality, because a minaret isa simple cantilever structure without structural directionality. This paperdescribes the ground motion directionality based on the survey of minaretdamages during the two earthquakes in Turkey. From the damage survey,it is found that the fault normal direction was dominant with a certaindistance from the fault, say, less than 1km. While, at the region withshorter distances, the damage direction was not fault normal but about40^° from the fault strike. Discussion is addressed for the specificdamage direction inferred from the minaret damage near the fault.     

A SIMPLIFIED METHOD FOR PREDICTION OF KINEMATIC SOIL–FOUNDATION INTERACTION EFFECTS ON PEAK HORIZONTAL ACCELERATION OF A RIGID FOUNDATION

The kinematic soil–foundation interaction changes the free field ground motion to a different motion at the foundation of a structure. This interaction effect may be expressed by the ratio of the peak horizontal acceleration of a rigid and relatively lightweight foundation to the peak horizontal acceleration at the ground surface in the free field. It is found that the interaction effect can be defined by a simple function of the ratio of the peak horizontal ground velocity and ground acceleration in the free field, the length of the foundation and the shear wave velocity in the soil. Predictive equations for the kinematic soil foundation effect are derived using 350 strong motion records generated by 114 earthquakes world-wide. At the same time, an attenuation relationship is derived for the ratio of the peak horizontal ground velocity and acceleration from the same set of data. Ten case histories are studied; the interaction effects are calculated by using the predictive equations and then compared with measured field values. The results of the comparison illustrate the degree of predictive capability of the method when the foundation mass and the inertial soil–foundation interaction are not considered.     

欧洲中小震基岩水平向地震动衰减关系研究

大震与中小震之间的地震动衰减规律有所不同.本文使用了132条欧洲基岩水平向记录研究中小震地震动衰减规律.震级范围在地方震级4～6级,距离在震源距70km以内.本文得到了峰值加速度和5%阻尼比、周期0.04～4.00秒之间的加速度反应谱的衰减关系.通过与欧洲和美国西部地震动衰减关系对比,分析了在地震活动性不同的地区内,大震与中小震之间存在的差异有何不同.     

Seismic ground motion relationships in southern China based on stochastic finite-fault model

The characteristics of seismic ground motions in southern China are difficult to determine statistically due to a lack of strong ground motion data. In this study, a stochastic finite-fault ground motion model was adopted to simulate the seismic ground motions at bedrock for southern China, based on parameters derived from small and medium earthquakes that have occurred in the region. From these, the response spectra was estimated. A set of ground motion attenuation relationships was then developed based on simulated peak ground motions and response spectral parameters through regression, which would be applicable for use in engineering practice. Through comparisons, it was demonstrated that the proposed ground motion relationships are generally consistent with those obtained from other reported ground motion attenuation models for southern China.     

Seismic ground motion relationship in southern China based on stochastic finite-fault model

The characteristics of seismic ground motions in southern China are difficult to determine statistically due to a lack of strong ground motion data. In this study, a stochastic finite-fault ground motion model was adopted to simulate the seismic ground motions at bedrock for southern China, based on parameters derived from small and medium earthquakes that have occurred in the region. From these, the response spectra was estimated. A set of ground motion attenuation relations hipswas then developed based on simulated peak ground motions and response spectral parameters through regression, which would be applicable for use in engineering practice. Through comparisons, it was demonstrated that the proposed ground motion relationships are generally consistent with those obtained from other reported ground motion attenuation models for southern China.     

近断层竖向与水平向加速度反应谱比值特征

显著的竖向地震动是近断层地震动区别于远场地震动的重要特征之一,为更合理地确定竖向地震动作用,研究了近断层区域竖向地震动的反应谱特征及其与水平向反应谱比值的影响因素.首先,选取1952—1999年世界范围内震级在M5.4—7.6之间的18次地震的地震动记录,研究竖向地震加速度反应谱及其与水平向加速度反应谱比值特征;然后统计分析了断层距、场地条件、震级以及断层机制对竖向与水平向加速度反应谱比的影响.结果表明,一般情况下竖向加速度具有更丰富的短周期分量,并且竖向加速度反应谱衰减较慢;断层距在20km以内的近断层区域、软弱土层场地、中等震级地震和逆断层大震级中长周期范围等条件下,具有较大的竖向与水平向加速度反应谱比值;在近断层区域的结构抗震设计中应充分考虑竖向地震动的影响.     

Behaviour of near-source vertical and horizontal response spectra at smart-1 array,Taiwan

Over 700 accelerograms recorded from 12 earthquakes in northeast Taiwan have been analysed for investigating the behaviour of the vertical and horizontal peak and spectral ground motion in the near-source region. Pseudo-relative spectral velocities (PSV), at 5 per cent critical damping for 23 frequencies in the range of engineering interest have been subjected to non-linear regression procedures in terms of magnitude and hypocentral distance. Predicted response spectra for several discrete distances and magnitudes are presented. The results show that the shape of response spectra for both vertical and horizontal components of ground motion is magnitude- as well as distance-dependent. The 2/3 ratio of vertical to horizontal ground motion, commonly used in engineering applications, appears unconservative in the very near field for high frequency ground motion. However, it falls below 1/2 at distances greater than 50 km. The same ratio for peak ground velocity (PGV) and peak ground displacement (PGD) tends to increase with distance—the latter at a faster rate.     

A probabilistic seismic hazard assessment for the Turkish territory—part I: the area source model

The seismic zoning map of Turkey that is used in connection with the national seismic design code (versions issued both in 1997 and 2007) is based on a probabilistic seismic hazard assessment study conducted more than 20 years ago (Gülkan et al. in En son verilere göre haz?rlanan Türkiye deprem bölgeleri haritas?, Report No: METU/EERC 93-1, 1993). In line with the efforts for the update of the seismic design code, the need aroused for an updated seismic hazard map, incorporating recent data and state-of-the-art methodologies and providing ground motion parameters required for the construction of the design spectra stipulated by the new Turkish Earthquake Design Code. Supported by AFAD (Disaster and Emergency Management Authority of Turkey), a project has been conducted for the country scale assessment of the seismic hazard by probabilistic methods. The present paper describes the probabilistic seismic hazard assessment study conducted in connection with this project, incorporating in an area source model, all recently compiled data on seismicity and active faulting, and using a set of recently developed ground motion prediction equations, for both active shallow crustal and subduction regimes, evaluated as adequately representing the ground motion characteristics in the region. The area sources delineated in the model are fully parameterized in terms of maximum magnitude, depth distribution, predominant strike and dip angles and mechanism of possible ruptures. Resulting ground motion distributions are quantified and presented for PGA and 5 % damped spectral accelerations at T = 0.2 and 1.0 s, associated with return periods of 475 and 2475 years. The full set of seismic hazard curves was also made available for the hazard computation sites. The second part of the study, which is based on a fault source and smoothed seismicity model is covered in Demircioglu et al. in Bull Earthq Eng, (2016).     

Characteristics of horizontal ground motion measures along principal directions

<正>Ground motion records are often used to develop ground motion prediction equations(GMPEs) for a randomly oriented horizontal component,and to assess the principal directions of ground motions based on the Arias intensity tensor or the orientation of the major response axis.The former is needed for seismic hazard assessment,whereas the latter can be important for assessing structural responses under multi-directional excitations.However,a comprehensive investigation of the pseudo-spectral acceleration(PSA) and of GMPEs conditioned on different axes is currently lacking.This study investigates the principal directions of strong ground motions and their relation to the orientation of the major response axis, statistics of the PSA along the principal directions on the horizontal plane,and correlation of the PSA along the principal directions on the horizontal plane.For these,three sets of strong ground motion records,including intraplate California earthquakes,inslab Mexican earthquakes,and interface Mexican earthquakes,are used.The results indicate that one of the principal directions could be considered as quasi-vertical.By focusing on seismic excitations on the horizontal plane,the statistics of the angles between the major response axis and the major principal axis are obtained;GMPEs along the principal axes are provided and compared with those obtained for a randomly oriented horizontal component;and statistical analysis of residuals associated with GMPEs along the principal directions is carried out.     

用于核工程地震安全性评价的中小地震水平向加速度反应谱衰减关系研究

利用美国西部的中小地震记录对基岩场地条件下的中小地震水平向地震动多阻尼加速度反应谱的衰减关系进行了初步研究,并分析了震级与距离对中小地震水平向地震动加速度反应谱衰减规律的影响.     

山西原平4．2级地震山西数字强震动记录分析

对2009年3月28日山西原平4．2级地震山西数字强震动台网7个台的地震加速度记录进行了处理和分析,包括对加速度波形数据的基线校正、滤波、水平分向矢量合成以及部分台站速度计算（包括水平向速度矢量合成）和加速度付氏谱、反应谱计算。结果表明：记录的最大单分向（水平）加速度峰值为27．5cm／s^2,水平合成最大加速度PGAn为28．5cm／s^2,其折合地震烈度为5度。多数台站的垂直向加速度峰值大约为水平向的1／2。最大速度峰值PGVH为0．51cm／s。原平台加速度记录的谱分析表明,对于4～5级这样强度的地震,因为震源本身产生的地震波中的长周期成分很少,所以,厚覆盖土层对长周期地震波的影响在工程的意义上可以忽略。     

地震动输入能量衰减规律的研究

对所收集到的266条强震记录，将其按场地条件分类，计算了不同场地条件、不同延性系数下的“绝对”和“相对”输入能量反应谱，然后利用两步回归法，得出了不同场地条件下地震动“绝对”和“相对”两种输入能量的衰减规律，分析了场地条件、延性系数、震级及距离等参数对地震动能量谱的影响，并对两种输入能量衰减规律进行了比较。