Flexible, Phase-Transfer Catalyzed Approaches to 4-Substituted Prolines

A range of 4-substituted prolines can be rapidly synthesized from a protected glycine Schiff base in only four steps and in 27–55% overall yield. Phase transfer catalysis allows direct access to both enantiomeric series, and the relative stereochemistry at the 4-position is readily controlled (>10:1 dr) through the choice of hydrogenation conditions

Semi-empirical relationships to assess the seismic performance of slopes from an updated version of the Italian seismic database

Funder: Dipartimento della Protezione Civile, Presidenza del Consiglio dei Ministri; doi: http://dx.doi.org/10.13039/100012783; Grant(s): ReLUIS research project - Working Pachage 16: Geotechnical Engineering - Task Group 2: Slope stabilityAbstractSeismic performance of slopes can be assessed through displacement-based procedures where earthquake-induced displacements are usually computed following Newmark-type calculations. These can be adopted to perform a parametric integration of earthquake records to evaluate permanent displacements for different slope characteristics and seismic input properties. Several semi-empirical relationships can be obtained for different purposes: obtaining site-specific displacement hazard curves following a fully-probabilistic approach, to assess the seismic risk associated with the slope; providing semi-empirical models within a deterministic framework, where the seismic-induced permanent displacement is compared with threshold values related to different levels of seismic performance; calibrating the seismic coefficient to be used in pseudo-static calculations, where a safety factor against limit conditions is computed. In this paper, semi-empirical relationships are obtained as a result of a parametric integration of an updated version of the Italian strong-motion database, that, in turn, is described and compared to older versions of the database and to well-known ground motion prediction equations. Permanent displacement is expressed as a function of either ground motion parameters, for a given yield seismic coefficient of the slope, or of both ground motion parameters and the seismic coefficient. The first are meant to be used as a tool to develop site-specific displacement hazard curves, while the last can be used to evaluate earthquake-induced slope displacements, as well as to calibrate the seismic coefficient to be used in a pseudo-static analysis. Influence of the vertical component of seismic motion on these semi-empirical relationships is also assessed.</jats:p

Exceedance of design actions in epicentral areas: insights from the ShakeMap envelopes for the 2016–2017 central Italy sequence

ShakeMap is the tool to evaluate the ground motion effect of earthquakes in vast areas. It is useful to delimit the zones where the shaking is expected to have been most significant, for civil defense rapid response. From the earthquake engineering point of view, it can be used to infer the seismic actions on the built environment to calibrate vulnerability models or to define the reconstruction policies based on observed damage vs shaking. In the case of long-lasting seismic sequences, it can be useful to develop ShakeMap envelopes, that is, maps of the largest ground intensity among those from the ShakeMap of (selected) events of a seismic sequence, to delimit areas where the effects of the whole sequence have been of structural engineering relevance. This study introduces ShakeMap envelopes and discusses them for the central Italy 2016–2017 seismic sequence. The specific goals of the study are: (i) to compare the envelopes and the ShakeMap of the main events of the sequence to make the case for sequence-based maps; (ii) to quantify the exceedance of design seismic actions based on the envelopes; (iii) to make envelopes available for further studies and the reconstruction planning; (iv) to gather insights on the (repeated) exceedance of design seismic actions at some sites. Results, which include considerations of uncertainty in ShakeMap, show that the sequence caused exceedance of design hazard in thousands of square kilometers. The most relevant effects of the sequence are, as expected, due to the mainshock, yet seismic actions larger than those enforced by the code for structural design are found also around the epicenters of the smaller magnitude events. At some locations, the succession of ground-shaking that has excited structures, provides insights on structural damage accumulation that has likely taken place; something that is not accounted for explicitly in modern seismic design. The envelopes developed are available as supplemental material

Methodology to identify the reference rock sites in regions of medium-to-high seismicity: an application in Central Italy

To evaluate the site response using both empirical approaches (e.g. standard spectral ratio, ground motion models (GMMs), generalized inversion techniques, etc.) and numerical 1-D/2-D analyses, the definition of the reference motion, that is the ground motion recorded at stations unaffected by site-effects due to topographic, stratigraphic or basin effects, is needed. The main objective of this work is to define a robust strategy to identify the seismic stations that can be considered as reference rock sites, using six proxies for the site response: three proxies are related to the analysis of geophysical and seismological data (the repeatable site term from the residual analysis, the resonance frequencies from horizontal-to-vertical spectral ratios on noise or earthquake signals, the average shear wave velocity in the first 30 m); the remaining ones concern geomorphological and installation features (outcropping rocks or stiff soils, fiat topography and absence of interaction with structures). We introduce a weighting scheme to take into account the availability and the quality of the site information, as well as the fulfillment of the criterion associated to each proxy. We also introduce a hierarchical index, to take into account the relevance of the proposed proxies in the description of the site effects, and an acceptance threshold for reference rock sites identification. The procedure is applied on a very large data set, composed by accelerometric and velocimetric waveforms, recorded in Central Italy in the period 2008-2018. This data set is composed by more than 30 000 waveforms relative to 450 earthquakes in the magnitude range 3.2-6.5 and recorded by more than 450 stations. A total of 36 out of 133 candidate stations are identified as reference sites: the majority of them are installed on rock with flat topography, but this condition is not sufficient to guarantee the absence of amplifications, especially at high frequencies. Seismological analyses are necessary to exclude stations affected by resonances. We test the impact of using these sites by calibrating a GMMs. The results show that for reference rock sites the median predictions are reduced down to about 45 per cent at short periods in comparison to the generic rock motions

Quantification of site effects in the Amatrice area (Central Italy): Insights from ground-motion recordings of the 2016–2017 seismic sequence

This work focuses on site response analyses in the Amatrice area (Central Italy), taking advantage of the 3A temporary seismic network, installed after the first shock (MW 6.0) of the 2016–2017 seismic sequence, and of a detailed site characterization. Classical empirical methods are applied on seismic signals to evaluate their capabilities to infer site response parameters. For about one-third of the stations, the H/V method fails in estimating the empirical SSR amplification function, as a consequence of the vertical amplification. Although the majority of sites belong to the EC8-B soil category, all the empirical methods show great variability in the site responses. For this reason, to find common features among the sites we perform a cluster analysis on SSR functions finding 5 clusters characterized by three site parameters: VS,30, f0 and Af0 (i.e microtremor H/V amplitude at f0). This result seems promising for site response estimation in Central Italy from velocity profiles and noise measurements

The engineering strong-motion database: A platform to access pan-European accelerometric data

This article describes the Engineering Strong-Motion Database (ESM), developed in the framework of the European project Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation (NERA, see Data and Resources). ESM is specifically designed to provide end users only with quality-checked, uniformly processed strong-motion data and relevant parameters and has done so since 1969 in the EuroMediterranean region. The database was designed for a large variety of stakeholders (expert seismologists, earthquake engineers, students, and professionals) with a user-friendly and straightforward web interface. Users can access earthquake and station information and download waveforms of events with magnitude ? 4:0 (unprocessed and processed acceleration, velocity, and displacement, and acceleration and displacement response spectra at 5% damping). Specific tools are also available to users to process strong-motion data and select ground-motion suites for codebased seismic structural analyses.Horizon 2020 Framework Programme, H2020: 67656

A non-parametric approach to site- and soil-specific probabilistic seismic hazard analysis

This study uses the large amount of data acquired during the 2009 L\u2019Aquila and 2016 Amatrice-Norcia seismic sequences in Central Italy to present a novel approach for site-specific seismic hazard assessment. Our approach applies the Generalized Inversion Technique (GIT) to a great number of recordings at several seismic stations, and incorporates the resulting station-specific amplification functions into the conventional procedure for Probabilistic Seismic Hazard Analysis. The scope of work is the definition of a probabilistic hazard map that incorporates site amplification for the site of L\u2019Aquila and surroundings. Results in terms of hazard curves and uniform hazard spectra will be also presented for a couple of sites

NESS v1.0: A worldwide collection of strong-motion data to investigate near source effects

The availability of high-quality waveforms recorded in epicentral areas of moderate-to-strong earthquakes is a key factor for investigating ground-motion characteristics close to the seismic source. In this study, near-source strong-motion waveforms (named NESS1) were collected from worldwide public archives with the aim of building a flat file of high-quality metadata and intensity measures (IMs) of engineering interest. Particular attention was paid to the retrieval of reliable information about event sources, such as geometries and rupture mechanisms that are necessary to model near-source effects for engineering seismology and earthquake engineering applications. The accelerometric records are manually and uniformly processed, and the associated information is fully traceable. NESS1 consists of about 800 three-component waveforms relative to 700 accelerometric stations, caused by 74 events with moment magnitude larger than 5.5 and hypocentral depth shallower than 40 km, with Joyner-Boore distance up to 140 km. Ground-motion data were selected to have a maximum source-to-site distance within one fault length, defined through seismological scaling relations. About 40 records exhibit peak acceleration or peak velocity exceeding 1g or 120 cm=s, and they represent some of the largest ground motion ever recorded. Evidence of near-source effects was recognized in the NESS1 dataset, such as velocity pulses, large vertical ground motions, directional and hanging-wall amplifications and fling step. In particular, around 30% of the records was found to exhibit pulse-like characteristics that are possibly due to forward rupture directivity. Electronic Supplement: Table listing the main features of the selected events, including the references of fault geometry parameters and Figures showing further metadata and intensity measures distributions of the NESS1 flat file