Seismic Microzonation Maps Research Articles

Seismic Microzonation Mapping for Urban and Land Sustainable Planning in High Seismicity Areas (L’Aquila Municipality, Central Italy): The Contribution of 2D Modeling for the Evaluation of the Amplification Factors

Seismic Microzonation Mapping for Urban and Land Sustainable Planning in High Seismicity Areas (L’Aquila Municipality, Central Italy): The Contribution of 2D Modeling for the Evaluation of the Amplification Factors

Site Response Analysis Considering Site-Affects Leading to Seismic Microzonation Map of Lahore

Site Response Analysis Considering Site-Affects Leading to Seismic Microzonation Map of Lahore

Seismic microzonation mapping of Greater Vancouver based on various site classification metrics

The goal of the multi-year seismic microzonation mapping project for Greater Vancouver, British Columbia, Canada, is to produce seismic hazard maps inclusive of local site effects, in particular seismic hazard specific to one-dimensional site response and three-dimensional Georgia sedimentary basin amplification, as well as liquefaction and landslide hazard potential. We explore the variability in key seismic site characterization measures most often used for seismic microzonation mapping to evaluate the impact on mapping and communication of seismic microzonation of Greater Vancouver. This study focuses on the comparison of seismic microzonation maps of Greater Vancouver based on up to three seismic site term parameters and their associated classification schemes: 1) the time-averaged shear-wave velocity (Vs) of the upper 30 m (Vs30) and associated Canadian National Building Code (NBC) site class; 2) Vs30-based site classification proposed for the updated Eurocode 8; 3) site period (T0) determined from microtremor site amplification spectra; and 4) a hybrid site classification based on T0 and the average Vs and thickness of soil. 810 Vs30 and 2,200 T0 values are determined to evaluate sub-regional differences in these important seismic site parameters in Greater Vancouver. We find that the seismic microzonation of Greater Vancouver depends on the chosen seismic site parameter (Vs30, T0, or a combination of parameters) and that classification schemes with greater class divisions are beneficial to communicating the great variability in seismic site conditions in Greater Vancouver. We recommend that either one hybrid classification map or two classification maps of Vs30 and T0 together are required for effective communication of the seismic microzonation of Greater Vancouver.

The reconstruction process of the buildings damaged by the 2017 Ischia earthquake

The reconstruction process of the buildings damaged by the 2017 Ischia earthquake is currently ongoing and it is managed by the “Structure of the Commissioner” issued by Decree Law No. 109/2018. The Structure of the Commissioner adopted the Erikus-ric gis platform created by the Piemonte Region, Arpa Piemonte and the Civil Protection Department. The platform allows to acquire and manage all the information related to the technical surveys to assess the structural damage and usability of buildings as well as the data resulting from the intervention projects. In detail, data related to construction characteristics, damage to structural and non-structural components, and the usability ratings on about 2,000 buildings along with data from applications for funding, landslide and flood risk maps, seismic micro-zonation map, urban plans, short term countermeasures, and building amnesty have been collected and georeferenced.The paper focuses on statistics on the typological characteristics of Ischia's built environment, construction age, and on the damage detected to structural and nonstructural components. Conversion metrics are adopted to covert damage level to structural components to building damage state and vulnerability classes. The cross-correlation between DS and vulnerability class may allow to make a preliminary estimate of operational level, based on a quick inspection on the damaged residential building. This may help decision makers to define, in the chaotic time following a disaster, funding decisions on damaged buildings.

Probabilistic approach for seismic microzonation integrating 3D geological and geotechnical uncertainty

A novel probabilistic methodology for regional seismic site characterization is proposed and applied to a region with highly heterogeneous surficial geology and varying soil sediment thickness and stiffness. The method combines various sources of geological and geotechnical uncertainties to develop a three-dimensional (3D) shear-wave velocity ( Vs) model and evaluate the associated uncertainties. A 3D geological model of the unconsolidated deposits was developed using geostatistical interpolation and simulation methods. Sequential indicator simulations produced a quantitative geologic model that explicitly quantified geological uncertainties based on the likelihood of specific soil types occurring. In situ measurements and multivariate statistical analysis allowed the development of empirical correlations between Vs, geotechnical parameters, depth, and soil types. The resulting 3D Vs values were estimated on the basis of Vs-depth correlations and the probability of occurrence of each soil type. In this approach, the propagated uncertainty was also quantified by considering the combined variance. Seismic microzonation mapping was then conducted by transforming the 3D Vs model into two-dimensional (2D) maps that represent the spatial distributions of the time-averaged shear-wave velocity of the top 30 m ( Vs,30) and the fundamental site period ( T0), along with their respective uncertainties using Monte Carlo simulations. The results indicate that microzonation maps and their uncertainties are influenced by the thickness, occurrence probability, and geotechnical properties of soils. The proposed method can be used to assess the probabilistic seismic risk at local and regional scales in areas with geologically and geotechnically complex soil properties.

Seismic Microzonation Map for a Fixed-Jacket Platform in the Malay Basin

The existence of soft soil in offshore areas may lead to the amplification of vibration received from offshore facilities, especially from the existing fixed-jacket platforms, which were designed without provision to seismicity, as in Malaysian water. Therefore, this study was designed to develop a seismic microzonation map and a soil amplification factor map according to soil type; we propose horizontal response spectra and site coefficient values (Ca and Cv) for the Malay Basin. A one-dimensional nonlinear analysis of layered soil (NERA) was used in the ground response analysis for six selected seismic events under five return periods of 100, 200, 500, 1000, and 2500 years. Soil amplification factors for soil types D and E showed a decreasing trend from 100 years to 2500 years. Two designed horizontal response spectra are proposed (for soil type D and E) under average and envelope conditions; a comparison with ISO showed that the proposed spectra were higher, especially for soil type E. To summarize, the seismicity effect should be included in the development of offshore industries as findings indicated that soil amplification occurred in soil types D and E at the Malay Basin.

Seismic Microzonation of the Pompeii Archaeological Park (Southern Italy): Local Seismic Amplification Factors

Pompeii Archaeological Park is the best laboratory for the study of the seismic site effects on cultural heritage: the ancient site was destroyed and buried by the 79 AD Vesuvian eruption and, furthermore, it was also affected by the 62–63 AD strong earthquake. Large sectors of the city were reconstructed after this earthquake while other parts were still under reconstruction when the fall-out and pyroclastic density currents of the eruption buried the Roman city. In order to evaluate the distribution of the damage and reconstructions due to the earthquake, detailed mappings of the structures were carried out using multidisciplinary approaches. In addition, analyses of the topographical features, subsoil stratigraphies, and geophysical surveys, responsible for local seismic amplification (site effects), allow us to define the sectors of the ancient city where the Amplification Factors (AFs) were the main ones responsible for damage. Selected areas and examples of compromised and reconstructed buildings show that the ancient topography and subsoil features (both lithological and seismic) are the main AFs. In particular, the damages caused by the 62–63 AD earthquakes seem to be mainly due to topographical factors such as steep scarps and slopes, ridges, peaks, and terraces, as well as to the major thickness of the soft sediments (loose volcanoclastic layers, paleosols, weathered lavas, and anthropogenic infillings) located over the well-lithified lavas. It is not uncommon to also have the combination of these two factors. For the first time, this multidisciplinary approach allows us to draw a seismic microzonation map for one of the most important archaeological sites of the world.

Seismic microzoning of the Delhi metropolitan area, India—II: Hazard computation and zoning maps

AbstractWe present seismic microzonation maps of New Delhi, India, using the probabilistic seismic hazard analysis (PSHA) method with input seismic activity parameters estimated in Part‐I of this two‐part paper. Our calculations required three different attenuation equations for amplitude scaling of strong ground motion from three principal contributing sources: the National Capital Region (NCR), Northwestern Himalaya (NWH), and the Hindu Kush subduction (HKS). We show that uniform hazard spectral (UHS) amplitudes are dominated only by the local seismicity in the NCR at high frequencies beyond about 2 Hz. For intermediate and long periods, UHS amplitudes are dominated by contributions from the NWH and HKS earthquakes. Our results show that specifying strong motion amplitudes for use in engineering design by means of peak ground acceleration can lead to serious errors for buildings higher than four to five stories and hence should not be used. Our results also show that the shape of design spectra must depend on the nature of contributing earthquake sources, their relative activity, potential to create large magnitudes, and geographical placement relative to the site of interest, and thus a standard design‐spectrum shape cannot satisfy all these requirements. We use local geological site condition parameters directly in all calculations and present hazard maps for three different soil site conditions (“rock,” stiff soil sites, and deep soil sites). Thus, the user can extract the UHS amplitudes of pseudo relative velocity spectra at any site in the National Capital Territory by experimentally determining the local soil site conditions and then applying the corresponding maps shown in this paper.

Innovative Seismic Microzonation Maps of Urban Areas for the Management of Building Heritage: A Catania Case Study

Several urban areas in the Mediterranean have already been subjected to seismic microzonation studies aimed at determining the acceleration expected on the ground surface, therefore mitigating the associated seismic risks. These studies have been generally related to free-field conditions. The present paper shows innovative seismic microzonation maps based on a large-scale estimate of soil-structure interaction (SSI) effects on design accelerations for some areas characterized by a high seismic risk in Catania, Italy. The proposed procedure combined: (1) geotechnical characteristics; (2) building features; and (3) 1-D seismic response analyses in free-field conditions. The seismic hazard and site effects were evaluated using artificial inputs and inputs recorded recently in Catania. Structural fundamental periods and related spectral accelerations, considering both the fixed-base building configuration and flexible-base configuration, were mapped in the Google My Maps environment. These results showed that SSI often had a beneficial effect, but sometimes it had detrimental effects, especially for some masonry buildings. These maps provided important information for planning the seismic retrofitting of investigated buildings, which were based on more detailed analyses of SSI and the developed maps requiring them.

Multicriteria seismic hazard assessment in Puerto Vallarta metropolitan area, Mexico

Puerto Vallarta, a medium-size tourist city, located in the Pacific Coast of Mexico, in a similar way as many other coastal cities, combines human activity with the potential occurrence of natural hazard events. In this way, the use of new tools to evaluate the impact of such events seems imperative. Puerto Vallarta is located within a tectonic setting where the Rivera microplate subducts beneath the North American plate and is affected by seismic activity. We performed a seismic hazard assessment by implementing a GIS-based multicriteria evaluation model. The seismic microzonation map of Puerto Vallarta was performed using a criteria set of six thematic layers, i.e., peak ground acceleration values, soil, bedrock, slope gradient, curvature, and flow accumulation. We performed the integration of the criteria set by implementing the Analytical Hierarchy Process to assign a weight to each criterion according to its contribution to the seismic hazard, i.e., PGA (0.38), soil (0.25), rock (0.14), curvature (0.10), slope (0.08), and flow accumulation (0.07). The thematic maps were integrated using GIS according to the normalized weights. We classified the seismic hazard microzonation of Puerto Vallarta into five hazard levels, i.e., low (18%), low-medium (28%), medium (22%), medium–high (20%), and high (12%). The map shows heterogeneous distribution over the territory. However, the study area can be divided into three zones, i.e., the northern mountainous area, the Ameca River Valley, and the southern mountainous area. There is an overall increment of seismic hazard from south to north. However, the highest seismic hazard levels dominate the Rio Ameca Valley showing that it is more susceptible to deposits of soft sediment and thus can be affected in the occurrence of a major earthquake. The main objective of this paper was to implement a technique to quickly estimating seismic hazards levels using available data when there is no sophisticated geophysical and engineering analysis. Using the GIS-based multicriteria techniques in seismic hazard assessment allows to elucidated areas where factors influencing surface response to earthquakes interact and raise the soil amplification susceptibility.

Technical guidelines for the assessment of earthquake induced liquefaction hazard at urban scale

Microzonation for earthquake-induced liquefaction hazard is the subdivision of a territory at a municipal or submunicipal scale in areas characterized by the same probability of liquefaction manifestation for the occurrence of an earthquake of specified intensity. The liquefaction hazard at a site depends on the severity of expected ground shaking as well as on the susceptibility to liquefaction of that site. This in turn depends on geological, geomorphological, hydrogeological and geotechnical predisposing factors. Thus, liquefaction hazard implies the existence of territories characterized by a moderate to high level of intensity of expected ground shaking. Microzonation charts for ground shaking and liquefaction hazard play a key role for the mitigation of seismic risk of an urban centre as they provide a valuable tool for the implementation of prevention strategies and land use planning. The LIQUEFACT project fully addressed the problem of microzoning a territory for earthquake-induced liquefaction hazard in a specific work package. Four municipal testing areas were selected across Europe as peculiar case studies where to construct microzonation charts for earthquake-induced liquefaction hazard. They are located in Emilia-Romagna region (Italy), Lisbon metropolitan area (Portugal), Brežice territory (Slovenia) and Marmara region (Turkey). Their location was identified based on the following criteria: severity of expected seismic hazard, availability of geological and geotechnical data, presence of liquefiable soil deposits, documented cases of liquefaction manifestations occurred in historical earthquakes, representativeness of different geological settings, density of population in selected areas (exposure). This paper illustrates the general procedure developed in LIQUEFACT for the assessment of earthquake-induced liquefaction hazard at urban scale and presents the main achievements of the microzonation studies carried out at the four previously mentioned European testbeds. Since the microzonation studies have been carried out using a shared framework and methodology, this paper has the ambition to serve as technical guidelines for updating the standards and the operational criteria currently used in different countries worldwide to construct seismic microzonation maps of liquefaction hazard.

Correlating DYFI Data With Seismic Microzonation in the Region of Montreal

The Western Quebec seismic zone has moderate seismic activity with few historical damaging earthquakes. Nevertheless, recent risk analyses have shown that the combination of a high level of urbanization with soft soil deposits in the metropolitan area of Montreal could lead to significant damage and economic losses. Over the two decades, several projects have been completed to develop a seismic microzonation to identify zones where seismic waves could be amplified. During the same period, Natural Resources Canada developed an internet application to collect reports from the population after an earthquake and to convert them to the Modified Mercalli Intensity scale (MMI). This paper presents a first comparison of the MMI data compiled after eight recent earthquakes felt in Montreal area with the existing zonation in terms of soil classes. It shows that the MMI from individual reports increases when the observer is located in a soft soil zone. Statistics on average MMI over a regular grid confirms this trend. The numerous reports collected through the internet application, and future applications based on data collected from social media, could become a very useful source of information to complement seismic field measurements when developing and validating seismic microzonation maps.

Seismic hazard microzonation of ground response parameters in Bengkulu City, Indonesia

This paper presents the seismic hazard microzonation of ground motion parameters on the basis of earthquakes events in Bengkulu City. Geotechnical site investigation and geophysical survey were performed in Bengkulu City. Furthermore, data were used to observe the geological condition. The local seismic design code for soft soil was used to generate spectral acceleration, which was later used as the scaling factor to generate ground motion for earthquake simulation. One-dimensional seismic ground response analysis was conducted to simulate earthquake wave propagating through soil layers. Several parameters, such as peak ground acceleration (PGA), spectral accelerations (SA) at 0.2 s and 1 s, and seismic wave amplification factor were observed. Those parameters were also depicted in seismic microzonation maps and addressed to identify potential impact during the earthquake. The results showed that the possibility of structural building responses along coastal area of Bengkulu City is relatively high. Therefore, a local seismic design code is important to propose as the alternative for reliable seismic design code. In general, the results of this study could give a recommendation to local government to consider seismic resistance design for buildings in Bengkulu City.

Seismic micro-zonation framework for earthquake risk in Medan-North Sumatera Indonesia using geotechnical engineering survey

The micro zonation is very essential to identify the tectonic and geological formation in the study area, and still fundamental for determining the seismic source and establishing a realistic earthquake hazard model. Indonesia is located in the Pacific Ring of Fires, it is constantly at risk of earthquakes, tsunamis, and the eruption of volcanic. In this case, we focused to review the previous study of micro zonation in Indonesia and making the framework of micro-zonation for earthquake risk in Medan-North Sumatra, Indonesia. The goal of this study to illustrate the diversity of methodologies presently in use for the preparation of seismic hazard maps and to evaluate basic principles of zonation for different purposes and at different scales in new planning in Medan, North Sumatera. We select the micro zonation methods and looking for the opportunity for planning the micro zonation based on the literature review. The result of this review, the plan and framework of micro zonation in Medan, North Sumatera will be important and needed for mapping the seismic hazards. The output of seismic micro-zonation map based on the geotechnical engineering survey with the Multichannel Analysis of Surface Waves (MASW), Spatial Auto Correlation (SPAC) and Horizontal to Vertical Ratio (HVSR) for dominant period.

Overview of local site effects and seismic microzonation mapping in Metropolitan Vancouver, British Columbia, Canada

A multi-year seismic microzonation project to map local variations of site response across Metropolitan (Metro) Vancouver, British Columbia, Canada, is currently underway. This paper presents our progress in one-dimensional site amplification hazard mapping of Metro Vancouver following our first field campaign. We initiated our microzonation study by assembling relevant geological, geophysical and geotechnical datasets from online and private sources to develop a regional 3D geodatabase. We perform site characterization near 20 strong-motion stations located on soft and stiff sediments using multiple non-invasive in situ seismic methods, including surface wave array and microtremor horizontal-to-vertical spectral ratio (MHVSR) techniques, to retrieve shear-wave velocity (Vs) depth profiles. We also compile all available earthquake recordings from 6 events of moment magnitude (M) > 3.9 to assess earthquake site amplification across Metro Vancouver. Comparison of the limited earthquake horizontal-to-vertical spectral ratio (EHVSR) data with MHVSRs demonstrates consistent empirical site amplification, supporting the use of MHVSRs as a valid proxy for earthquake site amplification in British Columbia. Vertical array recordings in soft sediments from a M 4.7 earthquake further demonstrate consistency between these amplification measures. To achieve spatial coverage for regional microzonation mapping, the same Vs profiling methods are applied in available open areas and more than 1100 MHVSR measurements are collected in a 600-m resolution grid. Three additional field campaigns will target validation of our non-invasive seismic methods with co-located invasive testing and fill in any spatial gaps. This paper summarizes the developed and applied methodologies and challenges encountered in seismic amplification hazard mapping for the Metro Vancouver region.

Seismic microzonation based on large geotechnical database: Application to Lisbon

Historically, Portugal has suffered the effects of several strong earthquakes. In particular, Lisbon and the south and southwestern Portuguese coast were affected by the largest known European earthquake on November 1st, 1755.It is well known that the local ground conditions strongly affect the seismic ground motion, modifying the signal's amplitude, duration, and frequency content, which induces large variability in the motion induced to buildings and infrastructures.Aware of this situation, the Lisbon Municipality promoted the development of a project to elaborate a new seismic microzonation map, based on a large geotechnical database and geological data.The Eurocode 8 ground classification based on the VS30 parameter was adopted as reference. However, the geotechnical database has a very small number of geophysical logs and is mainly composed of borehole data and SPT blows number. An expedited methodology was applied to determine the N30 parameter, as a proxy of the VS30 parameter. Non-invasive field experiments (surface waves seismic profiles and HVSR performed with ambient vibrations) and data collected from independent geophysical reports were also used to check and validate the classification based on N30. Because the distribution of the classified profiles was not uniformly distributed, the final microzonation map was obtained from the combination of the profile classification and the surface geology.

Seismic microzonation and building vulnerability assessment based on site characteristic and geotechnical parameters by use of Fuzzy-AHP model (a case study for Kermanshah city)

ABSTRACT On 12th November 2017, an earthquake with a magnitude of 7.3 Richter scale in the town of Sarpol-e Zahab took place that caused lots of human casualties and devastation. After the incident, issues related to the probability of an earthquake with equal intensity and extents of similar building destruction were raised in Kermanshah city. Therefore, a seismic microzonation map of Kermanshah city has been prepared based on the geotechnical, geological, and geophysical data, and the data were analysed using Fuzzy analytic hierarchy process (AHP). In the next step, the vulnerability analysis of city buildings was carried out based on the ground-shaking map, vulnerability curves, and statistical data regarding the buildings. The results of the vulnerability rate of residential buildings indicate that 80% of residential buildings would be exposed to vulnerability from low to moderate. However, other buildings would suffer 2% fully destruction (D1), 7% very high destruction (D2) and 11% high destruction (D3), respectively. Finally, according to the obtained results, the proposed model is verified with the help of the data and observations from the Sarpol-e Zahab earthquake, which reveals that the model is in good agreement with the actual earthquake data.

On the realization of seismic microzonation of Almaty (Kazakhstan) in ground accelerations based on the “continual” approach

Seismic microzonation for Almaty city for the first time use probabilistic approach and hazard is expressed in terms of not only macroseismic intensity, but also Peak Ground Acceleration (PGA). To account for the effects of local soil conditions, the continual approach proposed by A.S. Aleshin [1, 2] was used, in which soil coefficients are a function of the continuously changing seismic rigidity. Soil coefficients were calculated using the new data of geological and geophysical surveys and findings of previous geotechnical studies. The used approach made it possible to avoid using soil categories and a jump change in characteristics of soil conditions and seismic impact. The developed seismic microzonation maps are prepared for further introduction into the normative documents of the Republic of Kazakhstan.

Nonlinear Deterministic Study of Seismic Microzoning of a City in North of Algeria

This paper presents also an overview of seismic microzonation studies of the city of Mohammadia-Algiers, which are important for a detailed ground movement modeling of urban cities. According to the seismic history of the city, one extraordinary earthquake event has been taken into consideration is Boumerdes earthquake (Algeria, May 21, 2003, magnitude Mw=6.5), that caused a huge damage. Thereby, the variability prediction of the seismic ground movement in a given built-up area, it is considered as an effective tool for planning appropriate urban development and understanding both seismic risk and damage pattern, caused by a strong movement event. We note that the shaking level is mainly described in terms of both maximum ground acceleration and visualized amplification by using response spectra. The study is carried out in two steps: - a detailed mapping of the geology and geotechnical properties of the area - numerical modeling of expected ground motions during earthquakes. A qualitative microzonation of the Mohammadia-Algiers city is presented, and it is discussed by comparing it to the historically reported damage of the 2003 Boumerdes earthquake. Finally, this study deals with the seismic microzonation map development, based on a SIG geological model.

Review of geological and seismotectonic investigations related to 1998 Mw5.6 and 2004 Mw5.2 earthquakes in Krn Mountains

A review of geological and seismotectonic investigations conducted in the two decades after the 12 April 1998 earthquake in Krn Mountains, according to its magnitude the strongest earthquake in Slovenia in the 20th century, is given. Many of these studies have wider scientific meaning than expected from the size of the earthquake. This was the first case in Slovenia that a strong earthquake was undoubtedly related to a particular fault. Seismotectonic studies of seismogenic Ravne fault revealed that it is an actively propagating strike-slip fault growing by interaction of individual right stepping fault segments and breaching of local transtensional step-over zones. Airborne laser scanning (LiDAR) of Idrija and Ravne faults, which resulted in high resolution bare earth digital elevation model, was in 2005 for the first time used to study surface expression of an active fault in Europe. Among the primary characteristics of the 1998 earthquake were extensive environmental effects expressed mainly as massive rockfalls. They were systematically documented and evaluated for intensity assessment using European Macroseismic Scale (EMS-98) and Environmental Seismic Intensity (ESI) scale introduced in 2007, because application of the data on damage to buildings was limited in sparsely populated high mountains epicentral area. These studies were pioneering due to novelty of both intensity scales, indicating their strong points and weaknesses. Large variations in damage to buildings in the upper Soča valley at similar epicentral distances pointed to strong site effects due to very heterogeneous glacial and fluvial deposits in sedimentary basins and valleys. Therefore, different seismic microzonation maps were prepared to evaluate the influence of soft sediments on seismic ground motion. Conducted studies fostered development of several earthquake geology research methods in Slovenia as tectonic geomorphology, evaluation of environmental seismic effects and seismotectonics. They had positive impact also on the university education in the fields of geophysics, seismology and structural geology.