scholarly journals Horizontal UHS Amplitudes for Regions with Deep Soil Atop Deep Geological Sediments—An Example of Osijek, Croatia

2021 ◽  
Vol 11 (14) ◽  
pp. 6296
Author(s):  
Borko Đ. Bulajić ◽  
Marijana Hadzima-Nyarko ◽  
Gordana Pavić
Keyword(s):  
Pannonian Basin ◽  
Strong Motion ◽  
Response Spectra ◽  
Eurocode 8 ◽  
Deep Soil ◽  
Regional Seismicity ◽  
South Central ◽  
Local Soil ◽  
Short Period ◽  
Deep Soils

In this paper, we demonstrate how UHS-based seismic microzonation can be applied in low-to-medium seismicity areas with deep local soil and deep geological deposits under the local soil. The case study area surrounds the city of Osijek, Croatia, which is in the south–central region of the Pannonian Basin. New frequency-dependent scaling equations are derived, and the empirical response spectra are compared to the spectra of real strong motions in the surrounding region. Empirical calculations for deep soil atop deep geological strata show a 37% reduction in short-period spectral amplitudes when compared to rock locations. This demonstrates that local soil amplification is mitigated by energy dissipation in deep soils. For vibration periods longer than 0.3 s, spectral amplitudes are being amplified. This amplification goes up to 2.37 times for vibration periods around 0.5 s. UHS spectra for Osijek are computed using regional seismicity estimates, data on local soil and deeper geological surroundings, and newly created regional empirical equations for scaling various spectral amplitudes. UHS amplitudes for Osijek are also compared to the Eurocode 8 spectra for ground type C. The results show that ratios of the maximum UHS amplitudes to PGA values are up to 46% larger than the corresponding 2.5 factor that is recommended by Eurocode 8 for horizontal spectra. The UHS results might be viewed as preliminary for Osijek and regions with similar seismicity and local soil and deep geology conditions. When the number of regional strong-motion records grows many times beyond what it is currently, it will be feasible to properly calibrate the scaling equations, resulting in more reliable and long-term UHS estimations for the area under consideration.

scholarly journals Vertical to Horizontal UHS Ratios for Low to Medium Seismicity Regions with Deep Soil atop Deep Geological Sediments—An Example of the City of Osijek, Croatia

2021 ◽  
Vol 11 (15) ◽  
pp. 6782
Author(s):  
Borko Đ. Bulajić ◽  
Marijana Hadzima-Nyarko ◽  
Gordana Pavić
Keyword(s):  
Ground Motions ◽  
Spectral Amplitude ◽  
Eurocode 8 ◽  
Uniform Hazard Spectra ◽  
Study Region ◽  
Spectral Estimates ◽  
Local Soil ◽  
The Impact ◽  
Deep Soils ◽  
The City

The severity of vertical seismic ground motions is often factored into design regulations as a component of their horizontal counterparts. Furthermore, most design codes, including Eurocode 8, ignore the impact of local soil on vertical spectra. This paper investigates vertical pseudo-absolute acceleration spectral estimates, as well as the ratios of spectral estimates for strong motion in vertical and horizontal directions, for low to medium seismicity regions with deep local soil and deep geological sediments beneath the local soil. The case study region encompasses the city of Osijek in Croatia. New regional frequency-dependent empirical scaling equations are derived for the vertical spectra. According to these equations, for a 0.3 s spectral amplitude at deep soils atop deep geological sediments compared to the rock sites, the maximum amplification is 1.48 times. The spectra of vertical components of various real strong motions recorded in the surrounding region are compared to the empirical vertical response spectra. The new empirical equations are used to construct a Uniform Hazard Spectra for Osijek. The ratios of vertical to horizontal Uniform Hazard Spectra are generated, examined, and compared to Eurocode 8 recommendations. All the results show that local soil and deep geology conditions have a significant impact on vertical ground motions. The results also show that for deep soils atop deep geological strata, Eurocode 8 can underestimate the vertical to horizontal spectral ratios by a factor of three for Type 2 spectra while overestimating them by a factor of two for Type 1 spectra.

Strong motion accelerograph records from the 1993 Napierville earthquake

1995 ◽  
Vol 22 (1) ◽  
pp. 190-196
Author(s):  
René Tinawi ◽  
André Filiatrault ◽  
Pierre Léger
Keyword(s):  
Ground Motion ◽  
Energy Content ◽  
Strong Motion ◽  
Response Spectra ◽  
High Energy ◽  
Period Range ◽  
Attenuation Relationships ◽  
Acceleration Time Histories ◽  
Short Period ◽  
Time Histories

An earthquake of magnitude ML = 4.3 occurred near Napierville, Quebec, on November 16, 1993. An accelerograph at the liquefaction, storage, and regasification plant of Gaz Metropolitain in Montreal, about 55 km from the epicentre, recorded the ground motion. Although the maximum accelerations and velocities from this event are small, the acceleration time histories do confirm the high energy content in the very short period range. The recorded ground motion and corresponding absolute acceleration response spectra are presented and various attenuation relationships, proposed for eastern North America, are utilized to compare the measured and predicted ground motion parameters. Key words: Napierville earthquake, attenuation relationships, acceleration spectra, strong motion records.

scholarly journals Towards preparation of design spectra for Serbian National Annex to Eurocode 8: Part I: spectral shapes and regional empirical equations for scaling pseudo-acceleration spectra

2012 ◽  
Vol 10 (2) ◽  
pp. 131-154
Author(s):  
Borko Bulajic ◽  
Miodrag Manic ◽  
Djordje Ladjinovic
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Strong Motion ◽  
Soil Conditions ◽  
Eurocode 8 ◽  
Empirical Equations ◽  
Strong Motion Data ◽  
Motion Data ◽  
Local Soil ◽  
Spectral Shapes

Eurocode 8 allows that any country can use its own shape of the elastic response spectrum after it defines it in the National Annex. Having in mind that such country-specific spectra are to be derived through analysis of the strong motion data recorded in the considered seismo-tectonic region, in this Paper we discuss the existing and a set of new empirical equations for scaling pseudo-acceleration spectra in Serbia and the whole region of north-western Balkans. We then compare the presented spectra to those proposed by Eurocode 8. Results show that the indiscriminate use of the strong motion data from different seismo-tectonic regions, improper classification of the local soil conditions, and neglect of the effects of deep geology, may all lead to unreliable scaling equations and to extremely biased ground motion estimates. Moreover, only two spectral shapes that are defined for wide magnitude ranges and scaled by a single PGA value, are not able to adequately represent all important features of real strong ground motion, and instead of using such normalized spectra one should rather employ the direct scaling of spectral amplitudes that is based on the analysis of regionally gathered and processed strong motion data.

Seismic analysis of short-period structures subjected to the 1988 Saguenay earthquake

1992 ◽  
Vol 19 (3) ◽  
pp. 510-520 ◽  
Author(s):  
Pierre Léger ◽  
Angelo Romano
Keyword(s):  
Seismic Design ◽  
Seismic Analysis ◽  
Strong Motion ◽  
Response Spectra ◽  
Base Shear ◽  
Ductility Demand ◽  
Short Period ◽  
Modification Factor ◽  
Energy Dissipation Capacity ◽  
Design Earthquake

This paper presents elastic and inelastic response spectra of strong motion accelerograms recorded during the 1988 Saguenay earthquake. Comparisons are made with the National Building Code of Canada (NBC) 1990 lateral forces requirements for the seismic resistant design of short-period structures. The use of a period-dependent force modification factor is proposed to take advantage of the energy dissipation capacity of short-period structures on a more rational basis. The seismic response of a typical low-rise steel building designed according to the NBC 1990 and CAN3-S16.1-M89 is then investigated. It is shown that to obtain a realistic picture of the ductility demand of low-rise buildings, the structural overstrength, that is, the supplied strength in excess of the seismic design base shear, should be explicitly considered in the design process. Key words: seismic design, earthquake, low-rise structures, code.

Estimation of ground motion at deep-soil sites in eastern North America

1991 ◽  
Vol 81 (6) ◽  
pp. 2167-2185 ◽  
Author(s):  
David M. Boore ◽  
William B. Joyner
Keyword(s):  
North America ◽  
Ground Motion ◽  
Soil Column ◽  
Response Spectra ◽  
Building Codes ◽  
Eastern North America ◽  
Deep Soil ◽  
Period Range ◽  
First Time ◽  
Deep Soils

Abstract The stochastic model used previously to estimate motions at hard-rock sites in eastern North America has been modified to include the effect of deep soils. We simulated motions for a number of distances and magnitudes for a representative soil column and used these motions to derive equations giving ground motion as a simple function of magnitude and distance. These new equations are intended for use in building codes and those engineering applications that do not require detailed site evaluations. The ground motions for which we derived equations include 5%-damped response spectra at 13 periods ranging from 0.05 to 4 sec, peak acceleration and the maximum pseudovelocity and maximum pseudoacceleration responses. The latter two quantities are introduced here for the first time. They represent the maxima over the period range 0.1 to 4 sec for a given magnitude and distance, and they may be useful as a basis for determining the seismic coefficient in building codes.

scholarly journals Preliminary Evaluation of the Impact of Eurocode 8 Draft Revision on the Seismic Zonation of Romania

2022 ◽  
Vol 12 (2) ◽  
pp. 649
Author(s):  
Florin Pavel ◽  
Radu Vacareanu ◽  
Kyriazis Pitilakis
Keyword(s):  
Control Period ◽  
Response Spectra ◽  
Eurocode 8 ◽  
Preliminary Evaluation ◽  
Seismic Zonation ◽  
Seismic Safety ◽  
Seismic Code ◽  
Local Soil ◽  
The Impact ◽  
Maximum Design

This study is focused on the impact of the Eurocode 8 draft revision on the seismic zonation of Romania, one of the countries with the highest hazard levels in Europe. In this study, the design response spectra are evaluated for a number of sites in Romania for which both shear wave velocity profiles and ground motion recordings are available. The impact of the proposed changes on the structural design for structures situated in the southern part of Romania is also discussed. The results show considerable differences between the design response spectra computed according to the Eurocode 8 draft revision and the design response spectra from the current Romanian seismic code P100-1/2013. The differences are larger in the case of the sites situated in the southern part of Romania and those which have large design values for the control period TC. In Bucharest, for instance, it was found that the maximum design spectral accelerations would correspond to those from the 2006 version of the code while the maximum design spectral displacements would be significantly smaller than the levels produced by the 1981 or 1992 versions of the code. The results presented herein show that the differences in the seismic hazard and design ground motions are mainly due to the effects of local soil and site conditions and the associated site amplification proposed in the current Romanian seismic code and EC8 draft revision. Moreover, it has been shown that more analyses are needed to apply the seismic actions proposed in Eurocode 8 revision specifically for the sites in Romania under the influence of Vrancea intermediate-depth earthquakes so as to ensure an increased level of seismic safety for structures designed and built in the future.

scholarly journals Case Study of a Heavily Damaged Building during the 2016 MW 7.8 Ecuador Earthquake: Directionality Effects in Seismic Actions and Damage Assessment

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 74
Author(s):  
Luis A. Pinzón ◽  
Luis G. Pujades ◽  
Irving Medranda ◽  
Rodrigo E. Alva
Keyword(s):  
Damage Assessment ◽  
Strong Motion ◽  
Response Spectra ◽  
Seismic Action ◽  
Damage State ◽  
Ground Acceleration ◽  
Intensity Measures ◽  
Capacity Curves ◽  
Building Orientation

In this work, the directionality effects during the MW 7.8 earthquake, which occurred in Muisne (Ecuador) on 16 April 2016, were analyzed under two perspectives. The first one deals with the influence of these effects on seismic intensity measures (IMs), while the second refers to the assessment of the expected damage of a specific building located in Manta city, Ecuador, as a function of its azimuthal orientation. The records of strong motion in 21 accelerometric stations were used to analyze directionality in seismic actions. At the closest station to the epicenter (RRup = 20 km), the peak ground acceleration was 1380 cm/s2 (EW component of the APED station). A detailed study of the response spectra ratifies the importance of directionality and confirms the need to consider these effects in seismic hazard studies. Differences between IMs values that consider the directionality and those obtained from the as-recorded accelerograms are significant and they agree with studies carried out in other regions. Concerning the variation of the expected damage with respect to the building orientation, a reinforced concrete building, which was seriously affected by the earthquake, was taken as a case study. For this analysis, the accelerograms recorded at a nearby station and detailed structural documentation were used. The ETABS software was used for the structural analysis. Modal and pushover analyses were performed, obtaining capacity curves and capacity spectra in the two main axes of the building. Two advanced methods for damage assessment were used to obtain fragility and mean damage state curves. The performance points were obtained through the linear equivalent approximation. This allows estimation and analysis of the expected mean damage state and the probability of complete damage as functions of the building orientation. Results show that the actual probability of complete damage is close to 60%. This fact is mainly due to the greater severity of the seismic action in one of the two main axes of the building. The results are in accordance with the damage produced by the earthquake in the building and confirm the need to consider the directionality effects in damage and seismic risk assessments.

Late Pleistocene chronology and paleoclimate of Vancouver Island determined from cave deposits

1981 ◽  
Vol 18 (11) ◽  
pp. 1643-1652 ◽  
Author(s):  
M. Gascoyne ◽  
D. C. Ford ◽  
H. P. Schwarcz
Keyword(s):  
Late Pleistocene ◽  
Growth Period ◽  
Vancouver Island ◽  
Isotopic Equilibrium ◽  
South Central ◽  
Cave Deposits ◽  
Short Period ◽  
Thermal Buffering

Speleothems from four caves in south-central Vancouver Island have been analysed by the 230Th/234U method. Only speleothems from one cave, Cascade Cave, near Port Alberni, contained sufficient uranium for them to be dated. Twenty-seven ages determined for seven speleothems were found to cluster in two periods: 67–28 ka, corresponding to the Olympia interstadial, and <23–10 ka (or <15 ka if corrected for detrital thorium contamination), corresponding to the Fraser (late Wisconsin) deglaciation and Holocene periods. Two speleothems were found to be deposited in isotopic equilibrium with their seepage waters. Profiles of variations in δ18O of the calcite (δ18Oc) of each of the two deposits show a decrease of 1.3‰ over the growth period, 64–28 ka. At all times, δ18Oc was less than δ18O of modern calcite in the cave. Using modern cave temperature and the variation of δ18O of seawater over the dated period, the profiles of δ18Oc are interpreted in terms of a paleotemperature record for the Olympia interstadial in Vancouver Island. The results show a gradual cooling from 4 °C at 64 ka, to 0 °C between 35 and 28 ka. These results are consistent with conditions necessary for speleothem growth and with published work on surficial Wisconsin deposits in the area. No distinct, short-period warming or cooling events are seen in the record, probably due to thermal buffering by the adjacent ocean.

Concurrent Design Forces in Structures under Three-Component Orthotropic Seismic Excitation

2002 ◽  
Vol 18 (1) ◽  
pp. 1-17 ◽  
Author(s):  
K. Anastassiadis ◽  
I. E. Avramidis ◽  
P. Panetsos
Keyword(s):  
Ground Motion ◽  
Design Procedure ◽  
Strong Motion ◽  
Response Spectra ◽  
Concurrent Design ◽  
Motion Model ◽  
Specific Point ◽  
Extreme Stress ◽  
Seismic Motion

According to the model of Penzien and Watabe, the three translational ground motion components on a specific point of the ground are statistically noncorrelated along a well-defined orthogonal system of axes p, w, and v, whose orientation remains reasonably stable over time during the strong motion phase of an earthquake. This orthotropic ground motion is described by three generally independent response spectra Sa, Sb, and Sc, respectively. The paper presents an antiseismic design procedure for structures according to the above seismic motion model. This design includes a) determination of the critical orientation of the seismic input, i.e., the orientation that gives the largest response, b) calculation of the maximum and the minimum values of any response quantity, and c) application of either the Extreme Stress Method or the Extreme Force Method for determining the most unfavorable combinations of several stress resultants (or sectional forces) acting concurrently at a specified section of a structural member.

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