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We develop seismic microzonation maps in Seoul employing a GIS-aided approach. We use extensive borehole database of Seoul, which include stratigraphical information and standard penetration test (SPT) results. Two outlier detection methods are used to remove unreliable data. VS profiles are developed empirically both from SPT blow counts where available and averaged values representative of geologic soil layers where only stratigraphical information are provided. The sites are classified using the Korean design system (KDS) and a revised site classification system of Aaqib et al. (Earthq Eng 26:8257–8279, 2022, DOI:10.1080/13632469.2021.1990164), (AEA22). It is revealed that the KDS system, which uses the bedrock depth and average VS of soil, is not effective in categorizing the sites, resulting in significant overlapping of site parameters for different classes. The site period dependent AEA22 system better captures the surface geologic variations in Seoul, producing cleaner yet more representative classification map. We further develop the surface spectral acceleration maps of Seoul subjected to a 2400-year return period earthquake. The seismic amplifications are calculated using three procedures, which are (1) simulation-based site amplification model of Aaqib et al. (Earthq Spec 37:1900–1930, 2021, DOI:10.1177/8755293020981984) developed for shallow bedrock sites of Korea, (2) KDS and (3) AEA22 amplification factors. The site amplification model is considered as the reference method. The KDS system produces unrealistic predictions, underestimating the short period accelerations while overestimating the mid-to-long period responses. The AEA22 system produces an enhanced predictions of the surface accelerations compared with the KDS system. We propose to utilize the site amplification model or the AEA22 system for estimation of the seismic hazard in Seoul. [ABSTRACT FROM AUTHOR]

Uttarakhand is one of the most seismically active states of India. In this study, the seismic hazard map of Uttarakhand has been developed through deterministic seismic hazard analysis approach. Seismotectonic map with various geological discontinuities has been prepared. A homogenous earthquake catalogue for moment magnitude has been prepared for the duration of 1953–2020 and the past seismic data have been checked for completeness with regard to time and magnitude. Maximum potential magnitude was then assessed for the seismic sources. Concept of logic tree with four different ground motion prediction models was employed for the assessment of hazards. For developing the microzonation map, the state was divided into several grid points (0.1°×0.1°), and the seismic hazard was estimated in terms of peak ground acceleration (PGA) for each of the grid points. The estimated PGA values were found to be varying from 0.12 g to as high as 0.70 g. For northern regions, Main Central Thrust, Sundernagar and Ropar faults are critical, whereas for southern regions, thrusts TT18, TT23, TT19, TT23 and faults F37, F36, and F31 are significant. It has also been observed that the current Indian standard underestimates the response spectrum values for most regions of the state. [ABSTRACT FROM AUTHOR]

This paper evaluates the amplification factors at different locations of a tuff cliff subjected to seismic loading. We present a 1D and 2D modelling of a cliff located in the Sorrento Peninsula, a major Quaternary morpho-structural unit of the western flank of Southern Apennines. The geometry of our model is represented by a tuff cliff of 30 m height, with sand deposits at its base, covered by a 7-m-thick volcanoclastic layer. The geotechnical and geophysical parameters used for the analysis have been estimated via field measurements and laboratory tests. We selected seven scaled seismic events as input motions for the analysis, and the linear equivalent assumption was used in both 1D and 2D modelling. The general trend showed that in the cliff edge area, the amplification factor reaches a maximum value of 10 with a period of 0.11 s, while in other areas, its value decreases down to 2.90 seaside and 4.0 landside. The comparison of the 1D and 2D modelling highlights the importance of the topographic effects connected with a cliff. The average amplification factors (AF) for the 1D and the 2D models, have been computed within different time ranges, consistent with the ones adopted in the Italian microzonation studies (0.1–0.5 s, 0.4–0.8 s, 0.7–1.1 s). [ABSTRACT FROM AUTHOR]

Kyrgyzstan is an earthquake-prone country at the border of the Pamir Thrust, north of the active shortening structure of the Pamir Mountains and the intra-continental mountain belt of the Tian Shan further north. The region has had several M7 + damaging earthquakes, which have killed thousands of people. In the West, the country is cut through by the 700-km-long NW–SE Talas-Fergana active strike-slip fault system, where no major earthquakes have been observed in the last 250 years even though paleoseismic studies show the potential to produce M7.0 + events. This study is the second part of a project to estimate the potential damage and losses on residential buildings as well as critical infrastructures in the case of a large earthquake in the two mining towns of Kadamjay and Aidarken in the SW of Kyrgyzstan. Microtremors were recorded on 82 sites and analyzed with the Horizontal-to-Vertical Spectral Ratio (HVSR) method. For each site, we estimate the average frequency of the clearest peak and its amplitude in the HVSR spectra to produce microzonation maps, in terms of response frequency. We further used these data for the calculation of ground shaking using a set of six seismic scenarios based on the known faults around the two towns. This approach has proved to be efficient in a country where the resources and available data are limited and when the time of investigation is short. The Kadamjay and Aidarken cities have been divided into different zones with specific predominant resonance frequency ranges, which information is useful for risk analysis, mitigation and buildings retrofit. In Kadamjay, three regions dominate which are related to the history of alluvial deposition in a series of terraces. The more elevated terrace could be the place of seismic site amplification. Aidarkan is much more homogenous in terms of thickness and type of alluvial deposits. [ABSTRACT FROM AUTHOR]

The geotechnical industry has widely adopted the refraction microtremor shear-wave velocity measurement technique, which is accepted by building authorities for evaluation of seismic site class around the world. Clark County and the City of Henderson, Nevada, populated their Earthquake Parcel Map with over 10,000 site measurements for building code enforcement, made over a 3-year period. 2D refraction microtremor analysis now allows engineers to image lateral shear-wave velocity variations and do passive subsurface imaging. Along with experience at a basic level, the ability to identify the "no energy area" and the "minimum-velocity envelope" on the slowness-frequency (p-f) image helps practitioners to assess the quality of their ReMi data and analysis. Guides for grading (p-f) image quality, and for estimating depth sensitivity, velocity-depth tradeoffs, and depth and velocity resolution also assist practitioners in deciding whether their refraction microtremor data will meet their investigation objectives. Commercial refraction microtremor surveys use linear arrays, and a new criterion of 2.2% minimum microtremor energy in the array direction allows users to assess the likelihood of correct results. Unfortunately, any useful and popular measurement technique can be abused. Practitioners must follow correct data collection, analysis, interpretation, and measurement procedures, or the results cannot be labeled "refraction microtremor" or "ReMi" results. We present some of the common mistakes and provide solutions with the objective of establishing a "best practices" template for getting consistent, reliable models from refraction microtremor measurements. [ABSTRACT FROM AUTHOR]

A general methodological approach is here discussed to integrate geological and geophysical information in seismic microzonation studies. In particular, the methodology aims at maximizing the exploitation of low-cost data for an extensive preliminary assessment of ground motion amplification phenomena induced by the local seismo-stratigraphical configuration. Three main steps are delineated: (a) the combination of geological/geomorphological analyses to develop an Engineering-Geological Model of the study area; (b) targeted geophysical prospecting to provide an Engineering-Geological/Geophysical Model; (c) evaluating effectiveness of Engineering-Geological/Geophysical Model by estimating expected ground motion amplification phenomena by the use of suitable computational tools. The workflow is illustrated by a case-study based on a set of villages in the Umbro-Marchean Apennine (Central Italy) damaged during the Seismic sequence that occurred in Central Italy during 2016–2017. [ABSTRACT FROM AUTHOR]

The possibility is here explored to use an 'equivalent' homogeneous configuration to simulate 1D seismic response of heterogeneous engineering-geological bodies when relatively weak seismic impedance contrasts internal to the bodies (it was assumed a shear wave velocity variation between the alternating layers equal to 150 m/s) only exist above the seismic bedrock. This equivalent configuration is obtained by considering an equivalent Vs value the harmonic average of the actual Vs values and a linear combination of G/G0 and D curves relative to the lithotechnical components present in the actual configuration. To evaluate feasibility of this approach, a wide set of numerical simulations was carried out by randomly generating subsoil layering including sequences of alternating thin layers of geotechnical units (e.g. sands and clays) each characterized by a characteristic nonlinear curve. Outcomes of these simulations are compared with those provided by considering a single homogeneous layer characterized by equivalent nonlinear curves obtained as a weighted average of the original curves. By comparing the heterogeneous and the homogeneous columns seismic response in terms of amplification factors and fundamental period, the results confirm the possibility to model a 1D column characterized by a generic lithostratigraphic succession with an equivalent one without introducing significative errors that, at least for the studied cases, do not exceed the 6%. This conclusion is substantially confirmed by extending the comparison to a real case, i.e., the 113 m-thick heterogeneous soil profile at Mirandola site (Northern Italy), presented in the last part. [ABSTRACT FROM AUTHOR]

A seismic microzonation study was conducted to refine the seismic hazard model for the city of Saguenay, Canada. The Quaternary geology underlying Saguenay shows complex glacial and post-glacial stratigraphy with a number of buried valleys filled with fluvioglacial and glaciomarine sediments. High impedance contrast between rock formations and surficial sediments is prone to seismic amplification. To evaluate their applicability, advantages and limitations in capturing the geological specificity of the study area, four site classification methods were applied: the current National Building Code of Canada (NBCC) and Eurocode 8, both mainly based on the average shear-wave velocity for the surficial sediments (VS,avg) and for the top 30 m (VS,30); a method based on the fundamental site period (T0); and a hybrid method based on the combination of VS,30, T0 and VS,avg. The study specifically aimed to evaluate the importance of the site classification parameters on the resulting microzonation maps. VS,30 is capable to present the geological and geotechnical site conditions, however, the results may be further improved by considering Vs,avg in shallow and T0 in thick layers of soil sediments as secondary parameters. The T0 method gives also satisfactory results with T0 showing a better correlation to Vs,30 than to Vs,avg. The versatile hybrid method may be challenging to apply in certain cases with its nine different site categories and parameters. [ABSTRACT FROM AUTHOR]

The impacts of Iran's recent and destructive earthquake of Mw 7.3 November 12 2017, and its important subsequent events are investigated at Sarpol-e-zahab by means of 1D-equivalent linear site response analyses. Local damages at Sarpol-e-zahab highlighted the role of seismic microzonation in seismic risk reduction and damage prevention plans for future events. Hence, the main goals of this study are set to provide maps for amplification factors and shaking levels of the city as well as validating design-basis earthquake loads for buildings and structures of the national code of IRSt2800. This is achieved by deconvolution of the strong motions recorded by ISMN-SPZ as the closest station to the epicenter of Mw 7.3 earthquake and finding the two horizontal bedrock motions and subsequently, convolution of the horizontal bedrock motions to find the ground motions at 38 points across the city. The results of seismic site response analyses have provided very instructive information for rehabilitation of the existing buildings and future constructions as well as seismic vulnerability assessment of buildings during earthquakes. Furthermore, it provides an unprecedented research in Iran of a complete seismic microzonation at urban scale after an earthquake and a successful application of seismic microzonation at urban area with inadequate number of strong motion recording stations. [ABSTRACT FROM AUTHOR]

The organizations in different countries involved in seismic zoning modify the maps in response to various seismic events. The predictive ground motion is used in the analyses which may not be estimated using a single attenuation relation, because it is established on theoretical basis not with the actual ones and hence always errors are included in the analysis. However, the impact of faults is not considered in many of such seismic zoning efforts in several countries. An earthquake is generally triggered along the fault line; magnitude of generated earthquake depends on many factors, mainly the fault characteristics. Hence, the fault is the basic source of seismic activity and its presence and importance directly influences the seismic status of a region. In the present study a new term "fault importance index (FII)" is proposed which is a numeric value estimated from fault characteristics. The FII value for each of linear feature is calculated and relation is derived between the FII with earthquake intensity. The generated polynomial equations relate the past intensity spread with FII. The seismic risk zone map is then generated on the basis of FII. The developed seismic risk map has been compared to few earlier seismic maps and it can be used for design of buildings especially near the earthquake source. [ABSTRACT FROM AUTHOR]

Seismic microzonation represents a basic tool for local administrations in the developing of cost-effective risk reduction strategies and emergency planning. In recent years, the Italian scientific community has been deeply involved in implementing best-practices and tools to make seismic microzonation studies affordable by allowing its widespread application. Specific guidelines were provided that are representative of the international state of the art in this field. Moreover, the national Center for Seismic Microzonation and its applications (CentroMS) was established, which includes the most important Italian scientific institutions involved in seismic microzonation studies during last years. One of the purposes of this Center is supporting local Authorities and professionals in the field practice. Effectiveness of this organization has been tested during most recent seismic sequences, where the Center was charged to support the development of reconstruction plans. In this review paper the main features of these activities are addressed by focusing on experiences gained in the seismic microzonation studies carried out at 138 Municipalities in the area of Central Italy damaged by the 2016–2017 seismic sequence. [ABSTRACT FROM AUTHOR]

This paper describes the seismological analyses performed within the framework of the seismic microzonation study for the reconstruction of 138 municipalities damaged by the 2016–2017 sequence in Central Italy. Many waveforms were recorded over approximately 15 years at approximately 180 instrumented sites equipped with permanent or temporary stations in an area that includes all the damaged localities. Site response was assessed using earthquake and noise recordings at the selected stations through different parameters, such as spectral amplification curves, fundamental resonance frequencies, site-specific response spectra, and average amplification factors. The present study was a collaboration of many different institutions under the coordination of the Italian Center for Seismic Microzonation and its applications. The results were homogenized and gathered into site-specific forms, which represent the main deliverable for the benefit of Italian Civil Protection. It is remarkable that the bulk of this study was performed in a very short period (approximately 2 months) to provide quantitative information for detailed microzonation and future reconstruction of the damaged municipalities. [ABSTRACT FROM AUTHOR]

The paper presents the results of 5 case studies on complex site effects selected within the project for the level 3 seismic microzonation of several municipalities of Central Italy damaged by the 2016 seismic sequence. The case studies are characterized by different geological and morphological configurations: Monte San Martino is located along a hill slope, Montedinove and Arquata del Tronto villages are located at ridge top whereas Capitignano and Norcia lie in correspondence of sediment-filled valleys. Peculiarities of the sites are constituted by the presence of weathered/jointed rock mass, fault zone, shear wave velocity inversion, complex surface and buried morphologies. These factors make the definition of the subsoil model and the evaluation of the local response particularly complex and difficult to ascertain. For each site, after the discussion of the subsoil model, the results of site response numerical analyses are presented in terms of amplification factors and acceleration response spectra in selected points. The physical phenomena governing the site response have also been investigated at each site by comparing 1D and 2D numerical analyses. Implications are deduced for seismic microzonation studies in similar geological and morphological conditions. [ABSTRACT FROM AUTHOR]

A comprehensive treatment of seismic risk requires a reliable seismic hazard assessment. For this purpose, authors propose here the application of a synthetic damage-constrained parameter (named as HSM) which establishes, in three chosen vibration period ranges of engineering interest, an absolute ranking of seismic hazard. It includes the regional seismic hazard and the amplification due to the geological and geophysical setting of such areas of the Italian territory where the results of seismic microzonation studies are available. The purpose behind the application of this new parameter is providing new elements for effective implementation of seismic risk prevention and mitigation policies. In particular, a methodology is defined for individuating the thresholds values of the HSM parameter that classify the territory according to an increasing hazard scale, coupling with a theoretical expected average damage. In order to enhance the robustness of this methodology, a tempt of validation using experimental data is described in Appendix 1. The aforementioned scale of representation is applied on the dataset of the seismic microzonation studies conducted in 137 municipalities in Central Italy after the Mw 6.0 earthquake of 24 August 2016, providing for these centers realistic estimates of the overall seismic hazard. As future perspectives, it is shown how the inclusion of this parameter in urban planning and seismic design may help reaching different outcomes. In particular, in this paper it is discussed the effective contribution of HSM at: (i) helping decision makers to highlight priority intervention areas; (ii) defining best practices for existing structures, such as specific response studies, where higher overall seismic hazard values are expected. [ABSTRACT FROM AUTHOR]

This work describes the analysis of the strong-motion data from the Engineering Strong Motion database (ESM, http://esm.mi.ingv.it), aimed at: (1) extract a dataset of accelerometric waveforms recorded during the 2016–2017 Central Italy seismic sequence; (2) identify the recording stations to be used as reference sites for further seismological analysis; (3) select the records to be used as input for seismic microzonation of higher level at 137 municipalities. Firstly, a residual analysis is carried out on the extracted dataset to perform: (1) the quality check of the waveforms recorded by temporary networks installed soon after the occurrence of the first main shock (M 6.0, 24 August 2016); (2) the estimation of the site-to-site residual term for each recording station with the aim of recognising potential reference rock sites. Finally, the software REXELite, integrated within the ESM website, is adopted to select suites of spectrum-compatible accelerograms, that will be used as input for calculating site amplifications through 1D and 2D simulations at sites which suffered the greatest damage. The results of this work demonstrate the success of the synergy among Italian institutions. The setup of key infrastructures, such as emergency networks and data repositories, together with the knowledge developed during national projects, turned out to be successful in terms of timely intervention during the emergency phase and the planning of the post-emergency. [ABSTRACT FROM AUTHOR]

The Seismic Microzonation of level 3 (SM3) is nowadays a world-wide accepted tool for the mitigation of seismic risk. The SM3 is a complex process involving different disciplines ranging from Geology and Applied Seismology to Structural and Geotechnical Engineering. The outcome of a SM3 is presented on a zoning map in terms of a selected ground shaking intensity parameter and susceptibility to main ground instability (soil liquefaction, settlements, landslides, fault ruptures). In an advanced SM3 study for a given area, four main interdisciplinary steps can be recognized: (1) definition of the reference input motions, (2) construction of the subsoil model, (3) performing of numerical analyses and computing of amplification factors, (4) identification of zones with different geotechnical hazard potential and drawing up of the SM3 map. After the 2016–2017 Central Italy seismic sequence, intensive studies have been performed to obtain SM3 maps in 137 municipalities most damaged by the earthquakes. The aim of these studies has been to obtain a clear background on site effects to perform a correct reconstruction of the municipalities. In the paper, main results and critical issues of the above-mentioned steps of SM3 procedure are discussed together with some remarks on the use of SM3 output in supporting seismic design for reconstruction. [ABSTRACT FROM AUTHOR]

Scenarios of earthquake-induced landslides are necessary for seismic microzonation (SM) studies since they must be integrated with the mapping of instability areas. The PARSIFAL (Probabilistic Approach to pRovide Scenarios of earthquake‐Induced slope FAiLures) approach provides extensive analyses, over tens to thousands of square kilometers, and is designed as a fully comprehensive methodology to output expected scenarios which depend on seismic input and saturation conditions. This allows to attribute a rating, in terms of severity level, to the landslide-prone slope areas in view of future engineering studies and designs. PARSIFAL takes into account first-time rock- and earth-slides as well as re-activations of existing landslides performing slope stability analyses of different failure mechanisms. The results consist of mapping earthquake-induced landslide scenarios in terms of exceedance probability of critical threshold values of co-seismic displacements (P[D ≥ Dc|a(t),ay]). PARSIFAL was applied in the framework of level 3 SM studies over the municipality area of Accumoli (Rieti, Italy), strongly struck by the 2016 seismic sequence of Central Apennines. The use of the PARSIFAL was tested for the first time to screen the Susceptibility Zones (ZSFR) from the Attention Zones (ZAFR) in the category of the unstable areas, according to the guidelines by Italian Civil Protection. The results obtained were in a GIS-based mapping representing the possibility for a landslide to be induced by an earthquake (with a return period of 475 years) in three different saturation scenarios (i.e. dry, average, full). Only 41% of the landslide-prone areas in the Municipality of Accumoli are existing events, while the remaining 59% is characterized by first-time earth- or rock-slides. In dry conditions, unstable conditions or P[D ≥ Dc|a(t),ay] > 0 were for 54% of existing landslides, 17% of first-time rock-slides and 1% of first-time earth-slides. In full saturation conditions, the findings are much more severe since unstable conditions or P[D ≥ Dc|a(t),ay] > 0 were found for 58% of the existing landslides and for more than 80% of first-time rock- and earth-slides. Moreover, comparison of the total area of the ZAFR versus ZSFR, resulted in PARSIFAL screening reducing of 22% of the mapped ZAFR. [ABSTRACT FROM AUTHOR]

We present the results of seismological and geophysical investigations performed by the "Istituto Nazionale di Geofisica e Vulcanologia" team operating in Amatrice village (Central Italy), in the emergency phases following the Mw 6.0 event of August 24th 2016, that caused severe damage in downtown and surrounding areas. Data from seven seismic stations equipped with both weak and strong motion sensors are analyzed in terms of standard spectral ratio to empirically define amplification function using a bedrock reference site. Ambient vibration spectral ratios between horizontal and vertical component of motion are also evaluated in a large number of sites, spread out in the investigated area, to recover the resonance frequency of the soft soil outcropping layers and to generalize the results obtained by earthquake data. Ambient noise vibration are also used for applying a 2D array approach based on surface waves techniques in order to define the near-surface velocity model and to verify its lateral variation. The results allows to better understand the amplification factors in the investigated area, showing spatial variation of site effects despite of the homogeneous shallow geological condition indicated by the microzonation studies available at moment of the described field campaign. The analysis reveals a diffuse amplification effect which reaches its maximum values in downtown area with a resonant frequency of about 2 Hz. The obtained results were used to integrate the microzonation studies and they can be used for urban planning and reconstruction activities. [ABSTRACT FROM AUTHOR]

Dhanbad is the largest producer of coal in the state of Jharkhand, India, and hence, it is one of the most important cities in the country. Considering the present-day importance and future growth of the city, assessment of seismic hazard is extremely needed, especially for the mining authorities and the city planners. The prime objective of this study is to develop seismic hazard map of Dhanbad City for the bedrock level following the deterministic approach. In view of the absence of the region-specific Ground Motion Prediction Equations, the concept of logic tree comprising four different attenuation models is adopted. It is observed that the Peak Ground Acceleration in the range of 0.10–0.26 g may be expected in the city. Specifically, southern blocks of the city such as Baghmara, Jharia and Baliapur are found to be most vulnerable to the seismic hazard. Besides, developed seismic hazard map is divided into four zones and smooth acceleration response spectrums are proposed for the zones as per the expected seismicity in different parts of the city. [ABSTRACT FROM AUTHOR]

This paper presents a scenario for the spatial variation of the fundamental frequency of the sediment deposits above the basement and the corresponding amplification as well as the average spectral amplification in different frequency bandwidths for the National Capital Territory Delhi (the capital of India). The exposed central quartzite ridge and the Yamuna River channel are responsible for very large spatial variations of the fundamental frequency in the eastern part of the National Capital Territory Delhi. At 20% of the considered sites, a good match is obtained between the fundamental frequency computed numerically using available S-wave velocities to a certain depth and their extrapolation and that obtained experimentally. The computed fundamental and dominant frequencies reveal that both medium-rise (5–10 storey) and high-rise (> 10 storey) buildings in the western part and medium-rise buildings lying in the localities east of or very near to the Yamuna River may suffer heavy to very heavy damage due to the occurrence of the double resonance phenomenon. Furthermore, 1–2-storey buildings lying on the weathered exposed quartzite rock may also suffer heavy damage during local earthquakes because of the occurrence of double resonance. The possible reasons behind the lack of earthquake damage to the Qutab Minar, the tallest brick masonry minaret in the world, over the last 800 years may be the nonoccurrence of double resonance and almost no amplification in the low frequency range. There are two localities in the western part of the National Capital Territory Delhi, namely Kanganheri-Chhawla and Buradi, wherein all sorts of buildings are highly vulnerable to earthquake damage. For the closed Chhatarpur Basin and a semiclosed basin to its northeast, formed due to exposed quartzite rock, three-dimensional (3D) simulations are required to predict the characteristics of basin-generated surface waves and their focusing effects in the Chhatarpur Basin. The average spectral amplification map developed for the 0–10 Hz bandwidth depicts a range of 2.25–4.82 in the National Capital Territory Delhi and may be directly used to transfer the estimated seismic hazard at basement to the free surface. [ABSTRACT FROM AUTHOR]

To allow a widespread application of seismic microzonation studies in Italy, simplified cost effective procedures are required. To this purpose, regional abacuses allowing the evaluation of 1D litho-stratigraphical amplification phenomena based on a small set of cheap surface measurements have been proposed. These abacuses were initially elaborated by extensive one-dimensional numerical simulations of a wide set of representative seismo-stratigraphic configurations testified in the study area. In order to test effectiveness of the abacuses in use in the Marche Region (Central Italy), seismic amplification estimates deduced from this tool have been compared with outcomes of detailed seismic response studies carried out at a number of sites included in the area affected by the 2016–2017 seismic sequence in Central Italy. This analysis indicated that abacuses provide reliable estimates in the most part of the area except a specific geological domain where available subsoil information was not exhaustive when abacuses were initially formulated. Then, abacuses where partially reformulated by obtaining outcomes in line with independent observations. This in general, testifies the accuracy of the simplified approach but also the requirement for accurate field-testing before their widespread application. [ABSTRACT FROM AUTHOR]

Three levels of seismic microzonation are considered in the Italian guidelines: 1st level allows to qualitatively recognise those areas characterised by the same seismic performance, while 2nd and 3rd levels quantify the modification of the reference signal due to the specific site conditions. The paper summarises and compares the results of 2nd and 3rd level seismic microzonation studies for the Dovadola urban area (Emilia-Romagna, Italy). The site was selected due to the availability of in situ and laboratory investigations for the definition of a detailed geotechnical seismic model of the subsoil. The 2nd level study was conducted adopting the regional charts for the quantification of the stratigraphic amplification phenomena and the regional procedures for assessing the influence of topography. The 3rd level analysis was developed through mono- and two-dimensional seismic site response analyses adopting a numerical non-linear approach. Amplification factors for the peak ground acceleration and for the velocity spectrum intensity (i.e. the integral of the pseudo-spectral velocity of a ground motion from 0.1–0.5 to 0.5–0.1 s) were determined along two geotechnical sections of the site, both characterised by a central large and surficial valley bordered by irregular topography. The study indicates a general satisfactory match between the results of the simplified regional approach and the advanced numerical tool, especially when one-dimensional seismic site conditions prevail. Further comparative studies are encouraged to validate the 2nd level microzonation as a reliable tool for seismic risk mitigation. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard analysis (PSHA) encompasses quantitative estimation of seismic hazard at a site by considering all plausible earthquake scenarios. The outcome of a PSHA is often reported as the mean rate of exceeding a specific ground motion intensity measure at a given site. This study attempts to perform PSHA for the western area of the city Naples (southern Italy) by employing the most advanced methods and new databases; namely, DISS3.2 (Database of Individual Seismogenic Sources) and CPTI15 (Parametric Catalogue of Italian Earthquakes). Seismogenic models include individual seismogenic structures/faults liable to generating major earthquakes with magnitude greater than 5.5, and background areal source model to evaluate the effect of earthquakes with magnitude less than 5.5. The PSHA is built up based on the long-term earthquake recurrence on seismogenic tectonic faults and the spatial distribution of historical earthquakes. Site amplification is considered based on seismic microzonation maps derived for the western area of Naples. The microzonation maps delineate expected levels of ground motion amplification based on reliable geological and geotechnical subsoil models. Hazard maps are derived for a number of return periods for ground-shaking in terms of peak ground acceleration and 5%-damped pseudo-spectral acceleration at a range of periods that are representative of the existing construction within the area. Detailed comparisons of the PSHA results with Italian national hazard maps and the code-based design spectra emphasize the importance of performing site-specific PSHA with explicit consideration of site effects. [ABSTRACT FROM AUTHOR]

This paper shows the results of a multidisciplinary research aimed at defining the seismic microzonation of the district Bagnoli–Fuorigrotta in the Western part of Naples metropolitan area, which is subjected to a significant urban requalification project. The area is located in a complex geological setting within an active volcanic field and seismic hazard is characterized by both tectonic and volcanic seismicity, which frequently affected the urban setting. Following the recommendations of National and International Guidelines, the microzonation of the area was carried out adopting a multi-level approach. The maps obtained by applying Grade I and II approaches were the starting points for the numerical prediction of the site response carried out within the Grade III approach. The results of linear and non-linear dynamic analyses were synthesized in terms of amplification factors of peak ground acceleration at surface, PGA, and Housner Intensity, this latter computed through two different period ranges, i.e. 0.1–0.5 s and 0.7–2 s. The above factors were finally mapped adopting a rational approach to extend the local values of the surface amplification to broader areas. The results of the dynamic analyses highlighted that the seismic response of the whole area is highly affected by soil non-linearity and that the amplification of the ground motion mainly depends on the depth of the seismic bedrock, rather than on the local variability of shallow soil layering. [ABSTRACT FROM AUTHOR]

The town of Adra (Almeria Province, South-Eastern Spain) has been seriously affected by historical damaging earthquakes in 1487, 1522, two in 1804 and in 1910 with epicentres offshore in the Alboran Sea that reached onshore an estimated maximum intensity of VIII, IX, VIII, VIII-IX and VII-VIII, respectively. Additionally, in the instrumental period, several seismic series near the city affected it with moderate structural damages like the recent one of 1993-1994, when two main earthquakes of magnitude 5.0 and 4.9 cause serious damage in mid-rise reinforced concrete buildings sited on soft soils. Consequently, the town can be affected by moderate to destructive earthquakes, so this paper provides an initial assessment of the potential impact and the consequences (in terms of structural damage, economic and human losses) if the 1910 Adra earthquake hit the city again. The results point out that buildings damage are mainly concentrated in the soft soils areas of the city and that the non-engineered buildings, especially the oldest one, have the highest vulnerability, and therefore, the structural damage is higher, while seismically designed structures show a better behaviour showing less damage. Additionally, mid- and high-rise buildings have more extensive damage than low-rise buildings. Besides, the reinforced concrete buildings with waffled-slab floors, built previously to the first Spanish seismic code (NCSE-94), show, also, important damage. In summary, we have obtained that 474 ± 160 and 973 ± 78 buildings will be affected by complete and extensive damage, respectively, that is around 40% of the buildings in the city. [ABSTRACT FROM AUTHOR]

The ground layer response to seismic loading is analyzed in the paper. Two approaches to the site profile behavior are considered: elastic (linear) and viscoelastic (equivalent linear modeling). Four typical soil profiles are taken into account; input peak values are within the range from 0.1 to 0.6g. In all profiles, when ignoring the nonlinear behavior, the calculated impacts are still within the standard response spectrum. When the nonlinearity is taken into account, the pattern is completely different. The standard spectrum is abundantly conservative for high frequencies; meanwhile, it substantially underestimates the level of hazard at low frequencies. Therefore, the shape of standard spectra as a whole does not adequately describe a seismic hazard, especially when the input signal is higher than 0.2g. [ABSTRACT FROM AUTHOR]

Functional dependencies are established for the characteristics of seismic transients recorded at various points of a studied site, which are used to propose a new approach to seismic microzonation (SMZ) that enables the creation of new SMZ maps of strong seismic motion, with due regard for dynamic parameters of recorded transients during weak earthquakes. [ABSTRACT FROM AUTHOR]

The identification of natural hazard prone areas for future planning requires an efficient decision support tool to provide the appropriate weights for the various topographical, geological, and seismological factors responsible for the expected hazards. In the present study, an analytical hierarchy process (AHP) with six earthquake hazard parameters (EHPs) was used as a decision support system for the identification of earthquake triggered hazards in the Al-Madinah region of the Kingdom of Saudi Arabia. The pairwise comparison matrix and the final weights for all the EHPs during the implementation of AHP were calculated with an acceptable limit of consistency ratio. A GIS-based integrated analysis was carried out on all the selected attributes to generate the final hazard and microzonation map. From the analysis, it was observed that 15 % of the region fall under a very high or high hazard category. The very high seismic hazard zone is located in the northwestern region of Al-Madinah province, while the eastern and southern regions show low to very low hazard. The result of the study may be used as a first-level hazard and reliability map in selecting the appropriate earthquake resistant sites in designing the forthcoming new buildings against the potential seismic hazard of the province. [ABSTRACT FROM AUTHOR]

The microzonation map of any region is important to plan proper design of building, especially in seismic prone region. This paper discusses the use of remote sensing data and digital elevation model (DEM) in evaluating the site-specific conditions for microzonation map of Syria. We have made efforts to quantify the dynamic properties of surface soil for Syrian territory in terms of shear velocity $$V_{\text{S}}^{30}$$ and predominant period $$T_{S_0}^{30}$$ and have prepared a microzonation map that divides the surface soil into various classes according to Syrian building code. In the present study, we have used ASTER satellite DEM of high resolution (30 × 30 m pixel size) to produce slope map of the Syrian territory. The slope-velocity $$V_{\text{S}}^{30}$$ model is used to generate the base velocity map. The map of predominant period is also created. We present microzonation maps with respect to dynamic properties of soil ( $$V_{\text{S}}^{30}$$ , $$T_{S_0}^{30}$$ ) that show four classes. The used slope-velocity model failed to characterize the sites which have velocities lower or higher than the assigned range bounds. The present results show that the value of $$V_{\text{S}}^{30}$$ varies in the range 180-760 m/s and fits the geological, tectonic, geomorphological and topographic settings of Syria. The results indicate that the predominant period of surface soil varies in the range of 0.1578-0.667 s. A quick review on general amplification factor ' F' is presented which varies in the range 1.381-5.83 for Syrian territory $$\left( {\bar{F} = 3.66} \right)$$ . The produced site-class characterization maps are very much required by Syrian anti-seismic design code. [ABSTRACT FROM AUTHOR]

Seismic site coefficients (Fs) for Imphal city have been estimated based on 700 synthetically generated earthquake time histories through stochastic finite fault method, considering various combinations of magnitudes and fault distances that may affect Imphal city. Seismic hazard curves and Uniform Hazard Response Spectra (UHRS) are presented for Imphal city. Fs have been estimated based on site response analyses through SHAKE-91 for a period range of engineering interest (PGA to 3.0 s), for 5% damping. Fs were multiplied by UHRS values to obtain surface level spectral acceleration with 2 and 10% probability of exceedance in 50 year (~2500 and ~500 year) return period. Comparison between predicted mean surface level response spectra and IS-1893 code shows that spectral acceleration value is higher for longer periods (i.e., > 1.0 s), for ~500 year return period, and lower for periods shorter than 0.2 s for ~2500 year return period. [ABSTRACT FROM AUTHOR]

The development of seismic microzonation maps is now a prerequisite for performing advanced seismic hazards and seismic risk assessments in urban areas. Current microzonation procedures are based on classifying site response in soil categories based on $$\hbox {V}_\mathrm{S30}$$ . In many practical cases, information on shear wave velocity is sparse and analysts must resort to other sources of information to develop zonation maps over large regions. For Montreal, Canada, a geostatistical approach combining a large dataset of boreholes, $$\hbox {f}_{0}$$ data from the H/V method, and a limited number of shear wave velocity measurements is proposed. Predictive equations are developed with the different types of information and partly used to create three different $$\hbox {V}_\mathrm{s30}$$ models: A first model based on the total thickness of soft soil deposits (One Layer Model), a second model based on stratigraphy obtained from borehole data (Four Layers Model) and a third model (Composite Model) that combines data from the previous two models with data from seismic surveys. Variability and uncertainty associated with the choice of the models are described and estimated using a second moment analysis. The composite model which combines borehole, $$\hbox {f}_{0}$$ and Vs data is shown to be the most accurate compared to models derived only from borehole and Vs data (an average reduction of 40 % of the squared error) and shows good agreement with the geological map for clay and sand locations with soils classes C and D (54 % agreement on average). This approach opens new perspectives for $$\hbox {V}_\mathrm{s30}$$ microzonation in urban areas when budgets for Vs surveys are limited. [ABSTRACT FROM AUTHOR]

The paper summarizes the results of a multidisciplinary study aimed at seismic microzonation of the Central Archeological Area of Rome including the Palatine hill, Roman Forum and Coliseum. A large amount of subsoil data, available mainly from adjacent subway lines and from the archaeological superintendence, were collected and used to plan new multidisciplinary investigations, carried out in 2010-2011. First, the paper describes the integrated subsoil model aimed at numerical modeling of site effects. The results of equivalent linear 2D site response analyses carried out on seven representative cross-sections of the area are then presented and discussed. Ground motion amplification factors defined in terms of Housner Intensity were computed in different ranges of period, covering the different fundamental vibration periods pertaining to the monuments and structures. The contouring of amplification factor values from all the numerical simulations, based on morphological and geological constrains, eventually allowed to create microzonation maps. Finally, a sensitivity study was carried out to investigate the effects of uncertainties of input parameters and soil heterogeneity on microzonation. [ABSTRACT FROM AUTHOR]

A reliable litho-technical model for seismic microzonation requires a robust understanding of the subsoil architecture, that is essential to extrapolate in the space geognostic data that are often sparse. This paper presents the application to the level 1 seismic microzonation of the Central Archaeological Area of Rome of a complete methodological approach implementing physical stratigraphy concepts into an integrated analysis of a subsurface dataset. Particular emphasis has been placed on the reconstruction of buried geometries, distribution of lithofacies, and stacking pattern of geological bodies, which can control local seismic response. The spatial distribution of paleovalley infill and interfluves domains in the subsoil was reconstructed, which in virtue of their peculiar stratigraphy and morphology may determine 1D and 2D resonance effects. The summation of amplification effects due to the thick anthropogenic layer allowed to outline five stable zones prone to ground motion amplification, of which the most critical coincide with the narrow and deep infill of recent valleys. Potentially less prone to valley effects is the Middle Pleistocene paleovalley infill in the subsurface of the northern and eastern Palatine hill. Finally, the less hazardous zones correspond to the ancient, multilayered volcano-sedimentary interfluves separating the paleovalleys. [ABSTRACT FROM AUTHOR]

This paper presents the ground motion amplification scenario along with fundamental frequency ( F) of sedimentary deposit for the seismic microzonation of Kolkata City, situated on the world's largest delta island with very soft soil deposit. A 4th order accurate SH-wave viscoelastic finite-difference algorithm is used for computation of response of 1D model for each borehole location. Different maps, such as for F, amplification at F, average spectral amplification (ASA) in the different frequency bandwidth of earthquake engineering interest are developed for a variety of end-users communities. The obtained ASA of the order of 3-6 at most of the borehole locations in a frequency range of 0.25-10.0 Hz reveals that Kolkata City may suffer severe damage even during a moderate earthquake. Further, unexpected severe damage to collapse of multi-storey buildings may occur in localities near Hoogly River and Salt Lake area due to double resonance effects during distant large earthquakes. [ABSTRACT FROM AUTHOR]

Site characterization was carried out for Muscat region using the ambient noise measurements applying the horizontal-to-vertical spectral ratio (HVSR) technique and using active seismic survey utilizing the multichannel analysis of surface waves (MASW) of survey data. Microtremors measurements were carried out at 459 sites using short-period sensors. This extensive survey allowed the fundamental resonance frequency of the soft soil to be mapped and areas prone to site amplification to be identified. The results indicate a progressive decrease in the fundamental resonance frequencies from the southern and eastern parts, where the bedrock outcrops, toward the northern coast where a thickness of sedimentary cover is present. Shear wave velocity (Vs) was evaluated using the 2-D MASW at carefully selected 99 representative sites in Muscat. These 99 sites were investigated with survey lines of 52 m length. 1-D and interpolated 2-D profiles were generated up to a depth range 20–40 m. The vertical Vs soundings were used in the SHAKE91 software in combination with suitable seismic input strong motion records to obtain the soil effect. Most of the study area has amplification values less than 2.0 for all the considered spectral periods. The estimated fundamental frequencies obtained using the H/V spectral ratio method and using SHAKE91 are found to be in a relatively good agreement. Maps of spectral amplification, earthquake characteristics on the ground surface for peak ground and spectral accelerations at 0.1, 0.2, 0.3, 1.0, and 2.0 s, for 475 years return period are produced. The surface ground motion maps show that the hazard level is moderate with expected PGA in the range 0.059–0.145 g for 475 years return period. [ABSTRACT FROM AUTHOR]

Fundamental frequency map of site amplification at different sites in Doon valley, Uttarakhand, India is prepared from microtremor (ground ambient noise) using Horizontal to Vertical Spectral Ratio (HVSR) technique. The fan deposited alluvium filled synclinal valley of Doon lies between Main Boundary Thrust (MFT) and Himalayan Frontal Thrust (HFT) in the Himalayan active seismic belt and experienced many earthquakes in the past. The HVSR at different sites in the Doon valley ranges between the predominant frequencies 0.13 and 12.77 Hz. The HVSR in lower frequencies indicates that the site has either thick sediment covers or less compact rocks with fractures. Based on information on fundamental frequency and soft soil thickness, site classification map is generated. Results indicate that degree of compactness of rock types and presences of sediments vary significantly, which may play a major role in seismic hazard. The use of microtremor, therefore, constitutes an effective and inexpensive approach to site response and soft soil thickness estimation for preliminary microzonation. [ABSTRACT FROM AUTHOR]

A methodology to model seismic microzonation maps is required in the hazard mitigation decision plans of the earthquake prone areas. The stage of disaster preparedness for new residential places is of great importance for detailed seismic microzonation models. The effects of local geological and geotechnical site conditions were considered in order to establish site characterization as the initial stage of the models in this study. Dynamic soil properties based on the empirical correlations between shear wave velocity ( V) and standard penetration test blow counts were taken into account in order to define representative soil profiles extending down to the engineering bedrock. One-dimensional site response analyses were performed to analyze earthquake characteristics on the ground surface. The layers for soil classification, geology, depth to groundwater level, amplification, distance to fault, slope and aspect, and liquefaction-induced ground deformation potential of the study area were prepared in seismic microzonation models. The study area, Erbaa, is placed along the seismically active North Anatolian Fault Zone. Final seismic microzonation map of the study area was evaluated applying different GIS-based Multi-Criteria Decision Analysis (MCDA) techniques. Two of the MCDA techniques, simple additive weighting and analytical hierarchical process (AHP), are considered during the evaluation step of the final seismic microzonation map. The comparison is made in order to distinguish two different maps based on these MCDA techniques. Eventually, AHP-based seismic microzonation map is more preferable for the seismic design purposes in this study. [ABSTRACT FROM AUTHOR]

Seismic microzonation is one of the most important measures to mitigate earthquake hazards in urban areas. Because the ground motion varies significantly with the subsurface geology, it is needed for microzonation to account as much as possible for the local soil conditions. Noteworthy is that nonlinear deformation properties of soil play essential roles in amplification of strong ground motion. It is desired furthermore to focus on the expected damage extent in addition to the calculated maximum acceleration and/or velocity. The present study first developed a computer code for one-dimensional response analysis of ground that reasonably takes into account nonlinear dynamic soil properties. Second, correlations between the calculated ground motion and damage extent were obtained by examining seismic damages during the past earthquakes. By combining these two issues, seismic microzonation was carried out, and detailed damage distribution was assessed. The product of this study covers not only the damage caused by ground shaking but also liquefaction problem and lifeline damage. [ABSTRACT FROM AUTHOR]

In this paper we present a site effects analysis carried out in Málaga city's historical centre (Southern Spain). Two different methodologies have been used: an experimental technique using ambient noise measurements and a 1D numerical method. Soil fundamental frequencies have been obtained from the first technique, and soil transfer functions have been calculated from the numerical methodology. In order to use these results in vulnerability studies, intensity increments for each type of soil have also been estimated. From this information, a seismic microzonation has been proposed for the city centre, classified in six types of soils. Soil fundamental frequencies vary between above 5.0Hz at the hills of the city (where rock arises on the surface), and 1.0Hz near Guadalmedina river. The results show regions with high intensity increments (ΔI = +1.5) corresponding to areas which suffered heavy damage in the 1680 earthquake (I = VIII-IX). Moreover, most of the monuments and historical buildings in the city are located in these high risk areas. Results underline the importance of this kind of studies for seismic risk mitigation, historical preservation and emergency planning in the main cities' historical centres. [ABSTRACT FROM AUTHOR]

An attempt was made to estimate seismic microzonation in Marsa Alam city, Egypt based on the analysis of seismic microtremor observations. Observations were carried out at 140 sites in the study region. Analysis and processing of microtremor were divided into two steps; the first one is to measure the horizontal-to-vertical spectral ratios (HVSR) for each site and picked predominant frequency and its amplitude for each site. The second step is to measure the average shear wave velocity in the upper 30 m (Vs30) of subsoil using inversion of HVSR technique. The results show well matching of theoretical HVSR and observed HVSR for body waves in all sites. The Vs30 parameter was used to classify subsoil into classes of soil properties converted to the slandered European soil code (Eurocode-8 (2002)) as follows; Vs < 180(class D), 180 ≤ Vs < 360 (class C), 360 ≤ Vs < 800 (class B) and Vs ≥ 800 m/s (class A). Our study exhibits that most of Marsa Alam city were covered by B and C classes with small portions of class D close to the shoreline and class A at the northeastern part of the region. The developed classification soil map of the study area was correlated with the distribution of the predominant frequency in view of the surface geology and given a good matching. The results of this study will be useful for planning the Marsa Alam region to be the future tourist dream for Egypt. The method used in assessment of seismic microzonation in Marsa Alam city could be the fast and inexpensive technique to measure the Vs30 based on the HVSR of microtremor and would be applied in many other areas in Egypt. [ABSTRACT FROM AUTHOR]

Kolkata, one of the oldest cities of India, is situated over the thick alluvium of the Bengal Basin, where it lies at the boundary of the zone III and zone IV of the seismic zonation map of India. An example of the study of site effects of the metropolitan Kolkata is presented based on theoretical modeling. Full synthetic strong motion waveforms have been computed using a hybrid method that combines the modal summation and finite difference techniques. The 1964 Calcutta earthquake, which was located at the southern part of Kolkata, is taken as the source region, with the focal mechanism parameters of dip = 32°, strike = 232° and rake = 56°. Four profiles are considered for the computation of the synthetic seismograms from which the maximum ground acceleration ( A) is obtained. Response spectra ratios (RSR) are then computed using a bedrock reference model to estimate local amplifications effects. The A varies from 0.05 to 0.17 g and the comparison of the A with the different intensity scales (MM, MSK, RF and MCS) shows that the expected intensity is in the range from VII to X (MCS) for an earthquake of magnitude 6.5 at an epicentral distance of about 100 km. This theoretical result matches with the empirical (historical and recent) intensity observations in Kolkata. The RSR, as a function of frequency, reaches the largest values (largest amplification) in the frequency range from 1.0 to 2.0 Hz. The largest site amplification is observed at the top of loose soil. [ABSTRACT FROM AUTHOR]

The earthquake of April 6th, 2009 in the L'Aquila area is one of the largest seismic events of the last years in Italy. The event, that caused significant damage in a large area of the Abruzzo region (cental Italy) and site amplification phenomena which were recorded even at large distances from the epicentre. After the emergency period, a detailed study of the surface effects was necessary for the post-earthquake reconstruction, but in a way it should be carried out rapidly enough to give instructions to urban planners, codes to public administrators and information to engineers. A team of surveyors were trained to collect field information such as geologic and geomorphologic features and geotechnical or geophysical information. The seismic inputs, for the numerical analyses, were provided, and the collected information were analyzed with the aid of dynamic codes to calculate the possible local site effects. The results are presented as acceleration response spectra, amplification coefficients (FA, FV and FH) and microzonation maps, aimed to urban planning and project design. In particular the more dangerous areas, affected by the higher amplification effects, were identified. Finally a comparison between the results obtained by the numerical analyses and the results derived from an experimental field analysis, measuring both earthquake weak motion and ambient noise, were performed. In this paper we present the results for one of the most severely damaged area (up to IX-X MCS), the Paganica-Tempera-Onna-San Gregorio area, located 6 to 10 km east of the April 6th main shock. [ABSTRACT FROM AUTHOR]

The technique of ground ambient noise (micro tremor) measurement and analysis has been successful for site characterization in many places around the world. This technique has the advantage of being a fast and easy way to estimate the effect of ground motion characteristics due to an earthquake. Single station ground ambient noise (micro tremor) measurements were carried out at 136 sites in the municipal limit of Jammu city, NW Himalaya. This extensive survey allows the estimation of fundamental resonance frequencies (0.432 to 7 Hz) of the region and identifies the areas prone to site amplification. The thickness of the soft sediments has been derived using empirical relationship that comes out to be 14 to 295 mts above the bedrock. The results are in good agreement with the 1-D profile derived using MASW measurements from representative sites. The resonance frequency and sediment thickness is in good agreement with the geological distribution of sedimentary units, indicating a progressive decrease of the fundamental resonance frequencies from the northeastern part (where the bedrock outcrops is exposed) to the southwestern and southern side where a thick sedimentary cover is estimated. [ABSTRACT FROM AUTHOR]

The populated and expanding city of Chandigarh is located in the foothills of Himalaya, near the potentially active Main Frontal Thrust (MFT). A hazard assessment for this city is consequently of major importance. Thick sediments underlies the city and that can potentially amplify the earthquake shaking and contribute to an earthquake disaster in the city. The present study applies the Horizontal to Vertical Spectral Ratio (HVSR) ambient noise methodology to estimate the resonance frequency of the soft sediments and to obtain a first order estimate of sediment thickness. The study indicates that the soil thickness range from 30 to 270 m and that the resonance frequencies vary from 0.236 to 1.479 Hz. A smooth correlation function between soil thickness and resonance frequency is found, indicating relatively homogeneous soil. [ABSTRACT FROM AUTHOR]

This article presents a geographical information system (GIS) which manages geotechnical data obtained from detailed geotechnical surveys as well as from in situ observations in Athens, Greece. Thoroughly examined data from more than 2,000 exploratory boreholes and trial pits located in the wider area of Athens have been incorporated using a relational database system. From the analysis of these results, thematic maps are compiled to illustrate the distribution of engineering geological information (e.g. the depth of the “Athens schist” head). In addition, a methodology for an automated GIS-aided seismic microzonation study is outlined and is being employed taking into account the aforementioned geotechnical and engineering geological information, as well as existing seismological data to estimate the variability of seismic ground motion for the southern part of Athens. [ABSTRACT FROM AUTHOR]

The damages caused by recent earthquakes in India have been a wake up call for people to take proper mitigation measures, especially the major cities that lie in the high seismic hazard zones. Kolkata City, with thick sediment deposit (∼12 km), one of the earliest cities of India, is an area of great concern as it lies over the Bengal Basin and lies at the boundary of the seismic zones III and IV of the zonation map of India. Kolkata has been affected by the 1897 Shillong earthquake, the 1906 Calcutta earthquake, and the 1964 Calcutta earthquake. An analysis on the maximum magnitude and b-value for Kolkata City region is carried out after the preparation of earthquake catalog from various sources. Based on the tectonic set-up and seismicity of the region, five seismic zones are delineated, which can pose a threat to Kolkata in the event of an earthquake. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3: Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ), and Zone 5: Shield Zone (SZ). The maximum magnitude ( m max) for Zones 1, 2, 3, 4, and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. A probability of 10% exceedance value in 50 years is used for each zone. The probabilities of occurrences of earthquakes of different magnitudes for return periods of 50 and 100 years are computed for the five seismic zones. The Peak Ground Acceleration (PGA) obtained for Kolkata City varies from 0.34 to 0.10 g. [ABSTRACT FROM AUTHOR]

The seismic microzonation of the Bengal Basin, Haldia region, India is carried out using the Analytical Hierarchy Process (AHP) on the Geographic Information System (GIS). Three themes are used for the seismic microzonation, namely Peak Ground Acceleration (PGA), predominant frequency and elevation map. An analysis of the maximum magnitude ( m max) and the b value is carried out after preparing the earthquake catalogue from various sources. On the basis of the tectonic set up and seismicity of the region, five seismic zones are delineated which can be a threat to Haldia. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3: Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ) and Zone 5: Shield Zone (SZ). The m max for Zones 1, 2, 3, 4 and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. The PGA value is computed for Haldia following the attenuation relationship taking the m max of each source zone. The expected PGA at Haldia varies from 0.09–0.19 g. The predominant frequency of Haldia is also calculated using the H/V ratio with a frequency ranging from 0.1–3.0 Hz. The elevation map of Haldia is also generated using the Shuttle Radar Topography Mission (STRM) data. A first-order seismic microzonation map of Haldia is prepared in which four zones of hazard have been broadly classified for Haldia as very high seismic hazard zone, high seismic hazard zone, moderate seismic hazard zone and less seismic hazard zone. The very high seismic hazard zone is observed along the southern part of Haldia where there are major industrial and port facilities. The PGA for the four hazard zones are: 0.09–0.13 g for low hazard zone, > 0.13–0.15 g for moderate hazard zone, > 0.15–0.16 g for high hazard zone and > 0.16–0.19 g for very high hazard zone. [ABSTRACT FROM AUTHOR]

A first order seismic microzonation map of Delhi is prepared using five thematic layers viz., Peak Ground Acceleration (PGA) contour, different soil types at 6 m depth, geology, groundwater fluctuation and bedrock depth, integrated on GIS platform. The integration is performed following a pair-wise comparison of Analytical Hierarchy Process (AHP), wherein each thematic map is assigned weight in the 5-1 scale: depending on its contribution towards the seismic hazard. Following the AHP, the weightage assigned to each theme are: PGA (0.333), soil (0.266), geology (0.20), groundwater (0.133) and bedrock depth (0.066). The thematic vector layers are overlaid and integrated using GIS. On the microzonation theme, the Delhi region has been classified into four broad zones of vulnerability to the seismic hazard. They are very high (> 52%), high (38–52%), moderate (23–38%) and less ( < 23%) zones of seismic hazard. The “very high” seismic hazard zone is observed where the maximum PGA varies from 140 to 210 gal for a finite source model of Mw 8.5 in the central seismic gap. A site amplification study from local and regional earthquakes for Delhi region using Delhi Telemetry Network data shows a steeper site response gradient in the eastern side of the Yamuna fluvial deposits at 1.5 Hz. The ‘high’ seismic hazard zone occupies most of the study area where the PGA value ranges from 90 to 140 gal. The ‘moderate’ seismic hazard zone occurs on either side of the Delhi ridge with PGA value varying from 60 to 90 gal. The ‘less’ seismic hazard zone occurs in small patches distributed along the study area with the PGA value less than 60 gal. Site response studies, PGA distribution and destruction pattern of the Chamoli earthquake greatly corroborate the seismic hazard zones estimated through microzonation on GIS platform and also establishes the methodology incorporated in this study. [ABSTRACT FROM AUTHOR]

This paper presents a study of the ambient seismic noise features in Motril City. The predominant resonant period at each site was determined using the Horizontal to Vertical Noise Ratio (HVNR) of the microtremors records; it was applied to 91 points which cover the city and we present the distribution of the periods over a map which shows important characteristics requiring consideration in a study focussing on the mitigation of the seismic risk. Using these results, two zones can be distinguished: north of the GG’ profile with predominant periods smaller than 0.25 sec which corresponds with a hard soil, and south of GG’ with periods ranging from 0.25 to 0.6 indicating a medium-soft soil. Microtremors are a preliminary useful tool that compensates for the lack of seismic recorded data, and that can complement other valuable information (borehole logs, geology, etc.) to evaluate the seismic risk on places as Motril City where some of this information is unavailable. Through the predominant period the HVNR indicates the kind of soil we are dealing with. [ABSTRACT FROM AUTHOR]