Empirical Green's Functions Modified by Attenuation for Sources Located at Intermediate and Far Distances from the Original Source

We present a scheme to modify empirical Green's functions by attenuation considering: (1) geometrical spreading; (2) decay in high frequency; (3) regional attenuation; and (4) phase of the signal. The accelerograms computed with the proposed simulation method are compared, in time and frequency domains, with strong ground motions from subduction and intermediate-depth earthquakes recorded in Mexico. It is shown that this simple empirical Green's functions technique can synthesize both the shape and amplitude of the response spectra in the site, considering a postulated seismic source located at different distances from the original one.     

Attenuation Relationships for Iran

The purpose of this study is to derive the attenuation relationships for PGA, PGV, and EPA parameters for areas within the seismic zones of Zagros, Alborz and Central Iran with rock and soil substructures. In order to do so, at first the available scientific data including the methods used for deriving attenuation relationships and the parameters involved have been gathered. Afterwards, all the efforts have been focused on gathering a thorough catalogue of earthquakes occurred in Iran. In this regard, a majority of the available catalogs in Iran have been gathered and corrected through different methods and finally a set of 89 earthquake events including 307 earthquake records with reliable data was chosen.

Since in order to derive the attenuation relationships it is essential to extract the parameters from the acceleration records, a great effort was placed on gathering the earthquake acceleration records of Iran. This resulted in building a database of a majority of the earthquake records up to the year of 2004. Afterwards, correction methods applicable to earthquakes records of Iran considering the type of machines used and the ground type were examined which resulted in certain guidelines for correction of earthquake acceleration record data related to Iran.

In the next step the needed parameters were extracted from the earthquake acceleration record data which were consequently divided into two seismic zones of Zagros, and Alborz and Central Iran according to tectonic conditions. After examination of the parameters and choosing the most appropriate among them, the attenuation relationships were derived for such parameters.     

SEISMIC WAVE ATTENUATION FOR VRANCEA EVENTS REVISITED

New aspects of the frequency-dependent attenuation of the seismic waves travelling from Vrancea subcrustal sources toward NW (Transylvanian Basin) and SE (Romanian Plain) are evidenced by the recent experimental data made available by the CALIXTO'99 tomography experiment. The observations validate the previous theoretical computations performed for the assessment, by means of a deterministic approach, of the seismic hazard in Romania. They reveal an essential aspect of the seismic ground motion attenuation that has important implications on the probabilistic assessment of seismic hazard from Vrancea intermediate-depth earthquakes. The attenuation toward NW is shown to be a much stronger frequency-dependent effect than the attenuation toward SE and the seismic hazard computed by the deterministic approach fits satisfactorily well the observed ground motion distribution in the low-frequency band (<1Hz). The apparent contradiction with the historically-based intensity maps arises mainly from a systematic difference in the eigenperiods (type and size) of the buildings in the intra- and extra-Carpathians regions, thus the existing macroseismic data, based on buildings of small dimensions, i.e. with high eigenfrequency (5–10 Hz), can hardly be representative of the real hazard for new and large dimension, tall buildings, with eigenfrequency above 1 Hz.     

ATTENUATION RELATION FOR WEST EURASIA DETERMINED WITH RECENT NEAR-FAULT RECORDS FROM CALIFORNIA,JAPAN AND TURKEY

Strong ground motion close to a fault can be expected to be very large, so its estimation is essential for human safetv. Although a few strong-motion data exist for the west Eurasian region, we proposed in a previous work [Berge-Thierry et al., 2003] an attenuation relation for spectral acceleration using strong-motion data recorded in west Eurasia (mainly in Europe) and some in the western United States: this relationship was derived for the French Safety Rule, which is applied for seismic hazard assessment at nuclear power plants. In this study, we propose a constraining of the amplitude saturation term related to the proximity of the fault, and an adding of an amplitude saturation term in the regression model. We add, to the data-set previously used to derive the west Eurasian attenuation relationship strong-motions recorded during recent large earth-quakes: the 1995 Hyogo-ken Nanbu (Kobe) event in Japan and the 1999 Kocaeli (Izmit) event in Turkey. The regression analysis, adopted from Fukushima and Tanaka [1990], is non-linear, so an iterative procedure is applied. The determined regression coefficients lead to a prediction of a peak ground acceleration of about 0.7 g for soil site conditions at a fault distance of 0.5 km. The Q coefficient deduced, from the distance coefficient is in agreement with scattering Q models. The introduction of the saturation term leads to significantly lower predictions of average spectral accelerations at short distances as compared with using the Berge-Thierry et al. [2003] empirical model.     

Spectral Attenuation Relations at Soft Sites Based on Existing Attenuation Relations for Rock Sites

A simple and general method based on well-known random vibration theory is used to compute spectral attenuation relations at soft sites based on existing spectral attenuation relations at rock sites. The method consists of: (1) computation, for given magnitude and distance, of the expected Fourier amplitude spectrum associated with the median rock response spectrum computed with the attenuation relation; (2) inclusion of site effects characterized by a frequency-dependent, linear, or nonlinear transfer function; and (3) computation of the response spectrum at the soft site.     

Site Classification Assessment for Estimating Empirical Attenuation Relationships for Central-Northern Italy Earthquakes

The aim of this article is to investigate the ground motion attenuation of the most industrialized and populated regions of Italy, evaluating the capability of different approaches to estimate site dependent models. The 5.2 local magnitude earthquake on November 24, 2004 shocked the areas of Northern Italy producing damage of about 215 million euros. The data set, including 243 earthquakes of local magnitude up to 5.2, has been collected in the period December 2002–October 2005 by 30 three-component seismic stations managed by Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano (INGV-MI). Empirical attenuation relationships have been estimated for horizontal peak ground velocity (PGHV), acceleration (PGHA), displacement (PGHD), and for response spectral acceleration (SA) for periods between 0.1 and 1.5 s. To estimate suitable attenuation models, in particular for sites characterized by thick sedimentary geological formations, a soil discrimination based on EU8 code can lead to wrong evaluations. On the contrary, a classification based on H/V spectral ratios of seismic ambient noise (NHV) allows the models to fit better real and predicted data and to reduce the uncertainties of the process. For each receiver, NHV have been strengthened by additional H/V spectral ratio of earthquake data (EHV), calculated considering different portions of the analysed signals. In order to validate the PGHA attenuation relationship for greater magnitudes, accelerometric records, relative to Central-Northern Italy strong motions occurring in the last 30 years, have been collected and superimposed to our attenuation curves.     

PSHA for Broad-Band Strong Ground-Motion Hazards in the Saronikos Gulf,Greece, from Potential Earthquake with Synthetic Ground Motions

We perform a probabilistic seismic hazard analysis (PSHA) for broad-band strong ground motion within the Saronikos Gulf region, Greece, from potential earthquakes along the 30 km long Aigina fault in the northern part of the Gulf. We perform the PSHA utilizing empirical Green’s functions (EGFs) merged with synthetic Green’s functions (SGFs) along with models of finite rupture in place of standard “attenuation relations.” Our approach considers all significant magnitudes for PSHA and full broadband ground motion simulations. Calculations are source and site specific, and could reduce uncertainties in estimating standard engineering parameters. We use a range of rupture scenarios for all significant magnitude earthquakes along the fault. The hazard calculation is for frequencies 0.0– 15.0 Hz. Recordings of small earthquakes from an onshore/offshore local seismic array were used as EGFs for frequencies of 1.5–15.0 Hz, the finite difference code E3D was utilized to synthesize SGFs for frequencies 0.0–1.5 Hz, and an algorithm for merging the EGFs with SGFs was developed. The full-waveform calculations are important for non-linear dynamic analysis of structures in the coastal zone and potential hazard to long period structures. Results of proposed PSHA identify 2%, 10%, and 50% hazard at the selected sites of Saronikos Gulf.

Finally, we compare our PSHA results to those obtained by standard practice which involves prediction equations (GMPEs) recently developed in the Next Generation Attenuation (NGA) project and empirical predictive attenuation relations proposed for Greece. We believe that differences with the NGA results are due to site- and source-specific information utilized in this study, and incorporation of this information may significantly reduce the uncertainty in seismic hazard calculations.     

Local-scale turnpike roads in nineteenth-century Kentucky

This essay will examine, through a Kentucky case study, the process whereby states, county-level localities, and individuals undertook for themselves the responsibility for internal improvements, especially the construction of comprehensive road networks in the nineteenth century. Before the Kentucky legislature authorized state-funded road construction in the twentieth century, the state's best roads were a few toll turnpikes. Following other eastern states, Kentucky approved turnpike construction charters and subscribed to turnpike stock to underwrite construction. State statutes, based upon directives from trained engineers hired by the Board of Internal Improvement, required that turnpike construction follow complex procedures. A change in the state constitution in 1850 forced the state to withdraw from turnpike road investment and road construction oversight and finance devolved to counties and private investors. Local county road networks were largely the product of neighborhood turnpike companies chartered by the state. Primary documents record the local road-building process for a five-mile turnpike in a Bourbon County. With little direction or assistance from state engineers, the neighborhood residents, led by farmer John W. Jones, surveyed a route, arranged for right-of-way access through adjacent farms, hired Irish turnpike construction crews, built a tollhouse, and collected tolls. Formal state law and engineering directives became attenuated as amateur turnpike builders constructed a simplified version of the state's ideal road.     

SEISMIC DESIGN REGULATION CODES: CONTRIBUTION OF K-NET DATA TO SITE EFFECT EVALUATION

The purpose of this study is to compare the site effect section of building codes (EC8 and UBC97) with the set of data provided by the Kyoshin network. In order to obtain a set of site coefficients and spectral shapes, we have first deduced an attenuation law for both horizontal and vertical motion. Site conditions are represented by the shear velocity averaged over the upper 30 m (V _s ³⁰). Our site classification (4 categories similar to those proposed in the new ECS and the UBC97) is based on borehole investigations at every station. This classification has permitted to distinguish clearly four response spectra which demonstrates the efficiency of V _s ³⁰ as characterising site conditions. Our law is then used to test site coefficients and spectral shapes of building codes ECS and UBC97. Concerning spectral shapes and site coefficients, our results are found to be in good agreement with EC8 and UBC97 only if category B (400<V _s ³⁰<800 m/s) is taken as reference. We also conclude that a site which is characterised as “rock” on geological criteria can not generally be classified in category A (V _s ³⁰>800 m/s). This suggests that classification in category A should be based only on field measurements. Concerning vertical motion, our analysis of the K-NET data shows that the ratio av/ah (vertical peak ground acceleration over horizontal peak ground acceleration) is between 0.50 and 0.68.     

SEISMIC HAZARD IN GREECE BASED ON DIFFERENT STRONG GROUND MOTION PARAMETERS

The available Greek strong ground motion records to date are used in order to study the duration of strong-motion in Greece, covering magnitudes between 4.5 and 6.9 and distances from 1 km to 128 km. An attenuation relation of strong-motion duration is calculated and compared to earlier existing similar relations proposed for Greece and Japan. Furthermore, the seismic hazard for the area of Greece is assessed, using the strong-motion parameters of duration and peak ground acceleration. The results are presented in the form of a map according to which Greece is classified in four different categories of equal seismic hazard.