scholarly journals Vs30 Mapping and Soil Classification in The Southern Part of Kulon Progo Using Rayleigh Wave Ellipticity Inversion

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Bambang Sunardi
Keyword(s):  
Seismic Hazard ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Soil Type ◽  
Interpolation Method ◽  
Measurement Data ◽  
Ground Surface ◽  
Soft Rock ◽  
Soil Classification ◽  
Shear Wave Velocities

Shear wave velocity from the ground surface to a depth of 30 meters (Vs30) is a parameter to determine dynamic characteristics of the soil, which can be used to assess the level of seismic hazard. Thus, Vs30 mapping has an important role in seismic hazard mitigation efforts. Vs30 can be determined by Multichannel Analysis of Surface Waves (MASW) and Spatial Autocorrelation (SPAC) methods. A simpler alternative can be done by using Rayleigh wave ellipticity. The main objective of this research is to map Vs30 in the southern part of Kulon Progo using Rayleigh wave ellipticity inversion. In this study, Rayleigh wave ellipticity inversion was performed on 42 microtremor single measurement data, scattered in the southern part of Kulon Progo. The inversion results are used to estimate the value of Vs30 and classify the soil type at the measurement points, referring to SNI 1726:2012. A Vs30 distribution map and soil type classification are obtained by applying the geostatistical interpolation method. The mapping result showed that most of the southern part of Kulon Progo has a relatively low Vs30 value. These values are in the range of 180-342 m/s, which categorized as stiff soil (SD). In this region, some parts located in the hilly and transition zones have relatively high shear wave velocities in the range of 357-578 m/s and included in the category of very dense soil/ soft rock (SC) types

scholarly journals High-Velocity Surface Layer Effects on Rayleigh Waves: Recommendations for Improved Shear-Wave Velocity Modeling

2020 ◽  
Vol 110 (1) ◽  
pp. 279-287
Author(s):  
Gabriel Gribler ◽  
Lee M. Liberty ◽  
T. Dylan Mikesell
Keyword(s):  
Rayleigh Wave ◽  
Shear Wave ◽  
High Velocity ◽  
Site Response ◽  
Soil Classification ◽  
Cost Effective ◽  
Road Surface ◽  
Geologic Hazard ◽  
Soil Stiffness ◽  
Wave Inversion

ABSTRACT Soil stiffness estimates are critical to geologic hazard and risk assessment in urban centers. Multichannel analysis of surface-wave (MASW) data collection along city streets is now a standard, cost-effective, and noninvasive soil stiffness approximation tool. With this approach, shear-wave velocities (VS) are derived from Rayleigh-wave signals. Although the current MASW practice is to neglect the effect of a high-velocity road layer on soil VS estimates, our models show measurable impacts on Rayleigh-wave amplitudes and phase velocities when seismic data are acquired on a road surface. Here, we compare synthetic models with field MASW and downhole VS measurements. Our modeling indicates that a road layer attenuates Rayleigh-wave signals across all frequencies, introduces coherent higher-mode signals, and leads to overestimated VS and VS30 values. We show that VS30 can be overestimated by more than 7% when soft soils underlie a rigid road surface. Inaccurate VS estimates can lead to improper soil classification and bias earthquake site-response estimates. For road-based MASW data analysis, we recommend incorporating a surface road layer in the Rayleigh-wave inversion to improve VS estimate accuracy with depth.

scholarly journals GIS APPROACH GEOSPATIAL APPLICATION FOR SEISMIC MICROZONATION STUDY

2018 ◽  
Author(s):  
Г.П. Ганапатхи ◽  
В.Б. Заалишвили ◽  
Д.А. Мельков ◽  
В.Б. Свалова ◽  
А.В. Николаев
Keyword(s):  
Seismic Hazard ◽  
Shear Wave ◽  
Peak Ground Acceleration ◽  
Seismic Microzonation ◽  
Exceedance Probability ◽  
Ground Acceleration ◽  
Shear Wave Velocities ◽  
Gis Technique ◽  
Rock Depth ◽  
Chennai City

В работе представлен инструментарий в виде ГИС-технологий для составления карты сейсмического микрорайонирования. Рассмотрены методы и способы индийской и российской практики сейсмического микрорайонирования Реализована компиляция исходных данных в оперативную экспресс ГИС-методику. Построена карта сейсмического микрорайонирования первого уровня для города Ченнаи (Индия) с использованием ГИС-платформы на основе использования специфических информационных слоев в виде пикового ускорения грунта (PGA), скорости поперечной волны, геологического строения территории, уровня грунтовых вод и глубины кровли подстилающих коренных пород. Пиковое ускорение для сейсмических источников оценивалось на основе отношения затухания. При этом максимальное ускорение PGA для Ченнаи составило 0,176 g, а для Владикавказа – 0,2 g (для вероятности превышения 5%). Анализ сейсмической опасности включал матрицы данных (дискретные наборы данных из разных тем были преобразованы в сетки) для расчета окончательной матрицы сейсмической опасности путем интеграции и анализа веса исходных тематических слоев. Город Ченнай в процессе исследования был разделен на три обширные зоны: высокой, умеренной и низкой сейсмической опасности. Карта сейсмического микрорайонирования города Владикавказа была представлена в единицах шкалы MSK-64 и единицах ускорения. В обоих рассмотренных подходах скорости поперечных волн были одной из основных инструментальных основ для соответствующих расчетов. Используя в качестве исходных данных сценариев синтезированные расчетные записи с учетом характеристик неисправностей, учитывается трансформация исходных акселерограмм, обусловленных свойствами почвы на территории. In the paper GIS approach for seismic microzonation map compilation is presented. Approaches of Indian and Russian seismic microzonation practice are considered and compilated in express GIS technique. A first level seismic microzonation map of Chennai city has been produced with a GIS platform using the themes, viz, Peak Ground Acceleration (PGA), Shear wave velocity at 3 m, Geology, Ground water fluctuation and bed rock depth. The peak ground acceleration for these seismic sources were estimated based on the attenuation relationship and the maximum PGA for Chennai is 0.176 g and for Vladikavkaz 0.2 g (for 5% exceedance probability). The seismic microzonation analysis involved grid datasets (the discrete datasets from different themes were converted to grids) to compute the final seismic hazard grid through integration and weightage analysis of the source themes. The Chennai city has been classified into three broad zones, viz, High, Moderate and Low Seismic Hazard. Vladikavkaz city microzonation map was presented in MSK-64 scale. In both approaches shear wave velocities was one of the basic instrumental data. Using as initial data of the scenario synthesized records, taking into account the characteristics of faults, takes into account the transformation of the original accelerograms stipulated by soil properties of the territory.

Development of an NEHRP map for the Orleans suburb of Ottawa, Ontario

2008 ◽  
Vol 45 (8) ◽  
pp. 1180-1188 ◽  
Author(s):  
Dariush Motazedian ◽  
James Hunter
Keyword(s):  
Shear Wave ◽  
Ground Surface ◽  
Borehole Data ◽  
Glacial Sediments ◽  
Surface Reflection ◽  
Shear Wave Velocities ◽  
Reflection And Refraction ◽  
Wide Range ◽  
Average Shear ◽  
Geological Units

The average shear-wave velocity to a depth of 30 m (Vs30) has been obtained for 73 sites in the Orleans area in the northeast part of the City of Ottawa. Measurements of Vs30 were made using both ground surface reflection and refraction methods. In addition, borehole data was used to estimate Vs versus depth profiles using average Vs values assigned to distinct geological units. High values of Vs (>1500 m/s) were obtained in areas of thin surficial sediments overlying Paleozoic bedrock, and low Vs values (<180 m/s) were calculated in areas of thick late–post-glacial clay. The Vs30 values have been used to prepare an NEHRP map for the study area. Much of the suburb of Orleans is classified as NEHRP zone E, whereas the perimeter areas and some isolated central areas are classified as zones ranging from zone D to zone A. The presence of thick unconsolidated late–post-glacial sediments deposited in the Champlain Sea is the main contributing factor to the wide range of average shear-wave velocities in the study area.

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