Seismic Microzonation in the Vienna Basin

Engineering Geology for Society and Territory - Volume 5, 2014

following the enactment of Italian Law 77, 2009, almost all the Italian regions have been funded to produce seismic microzonation studies, according to the three levels of detail provided by Instructions and Criteria for Seismic Microzonation, in municipalities where the PGA exceeds 0.125 g (recurrence time: 475y). In order to allow homogeneity both in terms of representation of themes that in terms of content of the studies, the "Standards of representation and computer storage" have been developed by the Technical Committee on Seismic microzonation. The Civil Protection Department, in support to the Committee, predisposed special investigative controls on seismic microzonation studies carried out, in order to verify compliance and correct application of mentioned standards. It is not possible however, for obvious reasons, to enter into technical and scientific quality of all the submitted studies. Some indications on the reliability may instead come from an analysis of investigations and elaborations performed as part of the studies. By virtue of the uniformity that characterizes all studies produced by the regions, it has been possible to develop a semi-automated system that allows to evaluate the products in terms of reliability of the content. This document describes which indicators are taken into account for assessing the reliability of the submitted studies and proposes a quantitative procedure for their qualification. The method is based on a series of theoretical and GIS-based criteria for assessing the reliability of seismic microzonation depending on its content, through several indexes, returning a series of themes developed in GIS environment which allows an immediate perception of results.

The earthquake record and the Code for design and construction in seismic regions in Bulgaria have shown that the territory of the Republic of Bulgaria is exposed to a high seismic risk due to local shallow and regional strong intermediate-depth seismic sources. The available strong motion database is quite limited, and therefore not representative at all of the real hazard. The application of the neo-deterministic seismic hazard assessment procedure for two main Bulgarian cities has been capable to supply a significant database of synthetic strong motions for the target sites, applicable for earthquake engineering purposes. The main advantage of the applied deterministic procedure is the possibility to take simultaneously and correctly into consideration the contribution to the earthquake ground motion at the target sites of the seismic source and of the seismic wave propagation in the crossed media. We discuss in this study the result of some recent applications of the neo-deterministic seismic microzonation procedure to the cities of Sofia and Russe. The validation of the theoretically modeled seismic input against Eurocode 8 and the few available records at these sites is discussed.

Earthquake Hazard, Risk and Disasters, 2014

This chapter is dedicated to understanding the role of seismic zonation and microzonation, as well as understanding seismic risk analysis and mitigation strategy. The merits and demerits of various approaches to estimating earthquake hazard are discussed in terms of whether it is probabilistic, deterministic, or neodeterministic. The importance of geotechnical, geomorphological, and geological databases for seismic microzonation has been highlighted along with various techniques available to characterize site conditions. A variety of tools currently in use illustrate the basic principles of microzonation mapping at different scales. The main parameters involved in earthquake loss assessments and evaluating the influence of soil conditions on these estimates are discussed using QLARM, an advanced seismic risk estimation tool, for a few case histories.

Soil Dynamics and Earthquake Engineering, 2007

The study of site effects and the microzonation of a part of the metropolitan Sofia, based on the modelling of seismic ground motion along three cross sections are performed. Realistic synthetic strong motion waveforms are computed for scenario earthquakes (M=7) applying a hybrid modelling method, based on the modal summation technique and finite differences scheme. The synthesized ground motion time histories are source and site specific. The site amplification is determined in terms of response spectra ratio (RSR). A suite of time histories and quantities of earthquake engineering interest are provided. The results of this study constitute a "database" that describes the ground shaking of the urban area. A case study of experiment-based assessment of vulnerability of a cast-in-situ single storey, industrial, reinforced concrete frame, designed according to Eurocodes 2 and 8 is presented. The main characteristics of damage index and story drift are discussed for the purposes of microzonation.

Engineering Geology, 2007

Noise measurements have been done in the urban area of Napoli (Italy), a densely and crowded populated city of southern Italy, with historical architectonic heritage often damaged by tectonic earthquakes. Noise has been recorded by Kinemetrics Q330 station with a 3 component Episensor broadband accelerometer. The H/V ratio between the mean of the Fourier spectra of the horizontal components and the spectrum of the vertical component has been computed for 20 s windows and averaged on about 150 windows of noise data.

Geoenvironmental Disasters

This study focuses on two weak points of the present procedure to carry out microzoning study in near-field areas: (1) the Ground Motion Prediction Equations (GMPEs), commonly used in the reference seismic hazard (RSH) assessment; (2) the ambient noise measurements to define the natural frequency of the near surface soils and the bedrock depth. The limitations of these approaches will be discussed throughout the paper based on the worldwide and Italian experiences performed after the 2009 L’Aquila earthquake and then confirmed by the most recent 2012 Emilia Romagna earthquake and the 2016–17 Central Italy seismic sequence. The critical issues faced are (A) the high variability of peak ground acceleration (PGA) values within the first 20–30 km far from the source which are not robustly interpolated by the GMPEs, (B) at the level 1 microzoning activity, the soil seismic response under strong motion shaking is characterized by microtremors’ horizontal to vertical spectral ratios (HVSR)...

Earthquake risk management represents a preventive measure the protection against earthquakes. To manage earthquake risk, it is necessary to perform seismic microzoning of urban areas threatened by catastrophic earthquakes, i.e. create hazard maps of distribution of peak ground acceleration upon the free surface, fundamental periods in elastic and plastic range of vibration of the soil deposit, and spectral amplitudes upon the free surface. For their elaboration, it is necessary to compute the uniform hazard at bedrock and the dynamic response of the soil deposit in the terrain of the urban city area. The uniform hazard is established for different probability definitions of seismic action as recommended by national or international regulations for seismic design according to types of structures. Presented as an example in this paper is the seismic microzoning of the urban area of the Skopje city (UPS) for the seismic action with a probability of exceedence of 10% for a time period of 50 years (annual probability of exceedence of 0.0021, or a referent return period of 475 years).

The string of earthquake in India has created a serious problem for engineers and administrators and even for people also. Metro cities and other big cities in India have experienced severe earthquake hazard problem. This is same for Himalayan region and even peninsular shield. On 26 jan 2001 , one of the greatest India has ever experienced strikes in Kachchh , a region of Gujrat. Magnitude of this earthquake was 7.7 (M W) .This earthquake spread a huge damage which was almost a radius of 400 Kms. This earthquake damaged major cities of Gujrat like Ahmedabad , Bhavnagar , Surat. No one can say no for same threat for Delhi , national capital of India from local and probable catastrophic earthquake due to central himalaya. There are many more other Indian cities which are sitting in thick sedimentry basins along Indo-Gangetic plane and Brahmaputra valley. They have also the same threat. To reduce the seismic hazard, it is now important to define a correct response in terms of peak ground acceleration and spectral amplification. Both are highly dependent on local site conditions and also dependent on source characterization of future expected earthquakes. Microzonation studies are now important for a detailed ground motion modelling for urban and semi-urban cities of India. This paper presents an overview of seismic microzonation. Steps required and methodology used for seismic microzoation is also discussed here.

2021

The development of the construction of high-rise residential buildings requires a separate approach, depending on the engineering and geological conditions of the site for seismic microzoning. There are not only engineering sectors but also large premises that will serve as business offices and technical centers in the underground part of high-rise buildings. In this regard, the foundation of the building goes to great depth. The influence of soil conditions at the level of abutment of the buildings' foundation can be determined with seismic microzoning. As a result, the task of clarifying the projected construction site in construction is currently relevant. It includes the refinement of the seismic intensity of the construction site during the construction of high-rise buildings, which are located in different multilayer soil types.

Arabian Journal for Science and Engineering, 2011

The main purpose of this study is to provide a high-resolution application of urban seismic microzonation. A probabilistic seismic hazard analysis was undertaken in the study area using Poisson probabilistic approaches. The resulting hazard is characterized by a 15% probability that a given level of acceleration will be exceeded in a 50-year period. Using deterministic seismic hazard analysis, the magnitudes were estimated by a quadruple rupture model (with three different fault lengths, 108, 119 and 174 km) of the North Anatolian Fault Zone in the Marmara Region. Using both analyses (deterministic and probabilistic), the magnitude of the design earthquake was taken as 7.6. From this design earthquake, accelerations were estimated for several distances (from 25 to 50 km) using several attenuation relationships. In the second phase of the study, soil amplification factors and site characteristic periods were determined and estimated by seismic measurements and Standard Penetration Test data for the Sisli area of central Istanbul. Microtremor and earthquake data were evaluated to compare the characteristic site period data obtained. According to Eurocode soil classifications, the study area mainly consists of B type soils. A small part of the study area has C and A type soils. Characteristic site periods obtained by seismic methods agree with strong (earthquake) and weak (ambient noise) motion spectral values in some parts of the study area. Finally, a seismic microzonation map was prepared for integrated use, incorporating all geophysical and geotechnical data.