EMPIRICAL EVALUATION OF THE HORIZONTAL-TO-VERTICAL SPECTRAL RATIO TECHNIQUE: RESULTS FROM THE “SESAME” PROJECT

In order to empirically evaluate the horizontal-to-vertical (H/V) spectral ratio technique, ambient noise measurements performed in about two hundred sites mainly in Europe where weak or/and strong motion data was recorded. Standard Information Sheets (SIS) and earthquake information data were included in the SESAME [Site EffectS assessment using AMbient Excitations] project database, specially designed to facilitate data selection. All noise recordings were processed with JSESAME software to calculate (H/V) spectral ratio, whereas weak and strong motion earthquake recordings were processed with a similarly standardized procedure. For the latter, (H/V) receiver function for all sites were calculated. Experimental site transfer functions obtained from earthquake recordings were compared with the (H/V) spectral ratios from noise recordings in terms of fundamental frequency, amplification bandwidth and amplification level. Similarities and differences between (H/V) spectral ratio of noise and earthquake recordings are presented and discussed. In addition, a dense grid of noise measurements were performed within urban environment of cities affected by strong earthquake (Greece: Thessaloniki, Kalamata, Italy: Palermo). It seems that the (H/V) spectral ratio may satisfactorily indicate areas favorable to the occurrence of higher damage in urban environment. However, quantitative correlation between (H/V) spectral ratio properties and damage distribution (macroseismic intensity, damage grades) in some cases, is difficult to be established given the complexity of parameters involved

Sesame Project - Deliverable D08-02 - WP02 H/V technique : experimental conditions - Final report on Measurement Guidelines

In the following we report the final results for WP02-Measurement Guidelines. This work was conducted under the framework of the SESAME Project (Site Effects Assessment Using Ambient Excitations, EC-RGD, Project No. EVG1-CT-2000-00026 SESAME), Task A (H/V technique), Work Package 02 (WP02 – Measurement Guidelines).European Commission – Research General Directorate Project No. EVG1-CT-2000-00026 SESAMEPublished4.1. Metodologie sismologiche per l'ingegneria sismicaope

Development of site-specific elastic design spectra for future building codes, Part 1: an updated classification of empirical amplification functions

This report illustrates the data collection, processing and elaborations carried out in the framework of strategy 1 (“An updated classification of empirical amplification functions”) of the project “Development of site-specific elastic design spectra for future building codes”. This strategy aims at reconstructing a set of site-specific uniform hazard spectra (UHS), based on seismic hazard inputs representative of the Swiss hazard scenario and comprehensive of local amplification effects. We consider site amplification for a variety of subsurface soil configurations. These site-specific UHSs are sorted according to the characteristics of the corresponding subsoil, and collated with the elastic design spectra from the present building codes. The input empirical data set is constituted by the recordings of the Japanese KiK-net strong motion network, including approximately 700 sites, each instrumented with a downhole reference seismometer (generally encased within the seismic bedrock) coupled with a receiver placed at the soil surface. This instrumental configuration is ideal for the study of site amplification phenomena. Earthquake waveforms from KiK-net stations were processed to derive Fourier amplification functions at each site of the network; these functions are then referred to a common seismic bedrock condition (the same as in the Swiss hazard maps) and finally translated to the response spectral domain, so to express the site amplification in terms of spectral acceleration. In this process, the relevance of non- linear soil behavior is also discussed. At the last processing step, the empirically derived response spectral amplification functions are finally superimposed to seismic hazard inputs characteristic for the Swiss hazard scenario, yielding site-specific UHSs, which are compared with elastic design spectra from the present building code. The obtained results have evidenced the need for an improved site-condition classification and changes in the definition of normative spectra that would take into consideration site-amplification effects, in particular resonances. Conservative and simplified solutions are proposed for the case when only indirect or poor information is available for the considered site; vice versa, in case of well-constrained site characterization, a more specific and complex approach should be preferred. --> This report illustrates the data collection, processing and elaborations carried out in the framework ofstrategy 1 (“An updated classification of empirical amplification functions”) of the project“Development of site-specific elastic design spectra for future building codes”.This strategy aims at reconstructing a set of site-specific uniform hazard spectra (UHS), based on seismichazard inputs representative of the Swiss hazard scenario and comprehensive of local amplificationeffects. We consider site amplification for a variety of subsurface soil configurations. These site-specificUHSs are sorted according to the characteristics of the corresponding subsoil, and collated with theelastic design spectra from the present building codes.The input empirical data set is constituted by the recordings of the Japanese KiK-net strong motionnetwork, including approximately 700 sites, each instrumented with a downhole reference seismometer(generally encased within the seismic bedrock) coupled with a receiver placed at the soil surface. Thisinstrumental configuration is ideal for the study of site amplification phenomena.Earthquake waveforms from KiK-net stations were processed to derive Fourier amplification functionsat each site of the network; these functions are then referred to a common seismic bedrock condition(the same as in the Swiss hazard maps) and finally translated to the response spectral domain, so toexpress the site amplification in terms of spectral acceleration. In this process, the relevance of non-linear soil behavior is also discussed.At the last processing step, the empirically derived response spectral amplification functions are finallysuperimposed to seismic hazard inputs characteristic for the Swiss hazard scenario, yielding site-specificUHSs, which are compared with elastic design spectra from the present building code.The obtained results have evidenced the need for an improved site-condition classification and changesin the definition of normative spectra that would take into consideration site-amplification effects, inparticular resonances. Conservative and simplified solutions are proposed for the case when onlyindirect or poor information is available for the considered site; vice versa, in case of well-constrainedsite characterization, a more specific and complex approach should be preferred

The false Basel earthquake of May 12, 1021

ISSN:1383-4649ISSN:1573-157

Estimating Geophysical Bedrock Depth Using Single Station Analysis and Geophysical Data in the Extra-Carpathian Area of Romania

Local site evaluation is an essential step in understanding the amplification of seismic motion induced by the complex geological structure and their estimation for future strong earthquakes in urban regions. One of the critical parameters on evaluating amplification effects is the depth of the geophysical bedrock, whose interface to soft sediments is responsible for the development of destructive resonance phenomena. The present study is focused on the estimation of the geophysical bedrock depth along the extra-Carpathian area of Romania (Moesian Platform and surroundings) by correlating and interpolating the results obtained from single station measurements with the available geological/geophysical data. Each site was investigated through the computation of horizontal-to-vertical (H/V) spectral ratios from three-component single station measurements of ambient vibrations. The geophysical bedrock depth was computed using a two-step inversion scheme, based on the retrieval of the Rayleigh-wave ellipticity peak at each seismic station using a regional generic velocity profile. The fundamental frequency of resonance reaches the lowest value in the deepest side (0.07 Hz) and is rising to 13 Hz in the South of the Moesian Platform, where a shallow bedrock is present. The computed bedrock depths (from 30 to ~ 3100 m) show a dipping tendency towards the Southern Carpathians and complex features such as local outcrops and lateral depth variations superpose this gradually dipping trend. In the Carpathian foreland, the bedrock is interpreted as the transition between different sediment layers of Neogene, while outside this area as the Neogene—Cretaceous transition. © 2020, Springer Nature Switzerland AG.ISSN:0033-4553ISSN:1420-9136ISSN:1557-736

Toward New Single-Station Sigma Models

Single-station sigma values for more than 600 stations have been computed using the same method for all records and datasets from different tectonic regions (California, Taiwan, Japan, Turkey, Mexico, Switzerland and France). This work has been driven by the need to develop better estimates of standard deviation for non-ergodic probabilistic seismic hazard assessment in Switzerland (PEGASOS Refinement Project), and for new ground motion models being developed for eastern North America (NGA-east) and western North America (NGA-west2). The results show that the average single-station standard deviations are lower than the ergodic values of standard deviation. Moreover, the single-station withinevent standard deviations appear to have little variability across different tectonic regions. However, there is significant variability between stations and, in some instances, values of single-station standard deviation are higher than their ergodic counterpart. This variability seems to be (on the first order) controlled by path effects, and it can be modelled by probability distribution functions. Our results also show that the Vs30 dependency is weak, while a reduction of the withinevent standard deviation is apparent with increasing distance (and magnitude). We finally amalgamate all within-event residuals from the different tectonic regions in order to propose and test several within-event single-station sigma models (constant, distance-dependent, distance and magnitude-dependent)

Sesame Project - Deliverable D08-02 - WP02 H/V technique : experimental conditions - Final report on Measurement Guidelines

In the following we report the final results for WP02-Measurement Guidelines. This work was conducted under the framework of the SESAME Project (Site Effects Assessment Using Ambient Excitations, EC-RGD, Project No. EVG1-CT-2000-00026 SESAME), Task A (H/V technique), Work Package 02 (WP02 – Measurement Guidelines)

Sesame Project - Deliverable D04-04 - Report of the WP04 H/V Technique : Empirical Evaluation - Homogeneous Data Set of Noise and Earthquake Recordings at Many Sites

In this Report the homogeneous data set of earthquake and noise recordings at many sites that is generated under the framework of the SESAME Project (Site Effects Assessment Using Ambient Excitations, EC- RGD, Project No. EVG1-CT-2000-00026 SESAME), Task A (H/V technique), Work Package 04 (WP04– H/V Technique: Empirical Evaluation), is presented. Three main topics are included in the Report: (a) The Standard Information Sheet (SIS) structure, (b) The SESAME Ascii Format (SAF) files, and (c) The SESAME SIS-database. The SIS compiled in this sub-task and SAF format adopted for all data, constitute a homogeneous data set to be processed for further scientific results in the framework of the WP04. In addition, the SIS-database is going to facilitate data selection and management