On the Correlation of Seismic Intensity with Fourier Amplitude Spectra

1998 ◽  
Vol 14 (4) ◽  
pp. 679-694 ◽  
Author(s):  
V. Yu Sokolov ◽  
Yu K. Chernov

This paper presents a method for estimating the seismic intensity (MMI or MSK scale) using Fourier amplitude spectra of ground acceleration. The method implies that the severity of earthquake ground motion is determined by spectral amplitudes in a relatively narrow frequency band: so-called “representative frequencies”, at decreasing frequencies (from 7-8 Hz for small intensities to 0.7-1.0 Hz for MMI=VIII-IX) with increasing intensity level. It is examined through estimation of probable intensity at a site using recordings of recent earthquakes in several seismic regions, and prediction of intensity distribution patterns for the Coalinga, California earthquake of May 2, 1983, and the Spitak, Armenia earthquake of December 7, 1988. Seismic hazard maps, in terms of intensity levels based upon the proposed approach, should describe regional features of seismic waves excitation and propagation, as well as local ground conditions.

Author(s):  
Tomiya Takatani ◽  
Hayato Nishikawa

3-D collapsing process analysis of an old Japanese-style one-story wooden structure under two strong earthquake ground motions with a seismic intensity level was car-ried out in order to investigate the seismic performance of this one-story wooden structure without/with seismic retrofit. As a result, this wooden structure collapsed against a strong earthquake ground motion with the JMA seismic intensity “6 upper” level.


1976 ◽  
Vol 66 (4) ◽  
pp. 1343-1373 ◽  
Author(s):  
M. D. Trifunac

abstract An empirical model for scaling Fourier Amplitude Spectra of strong earthquake ground acceleration in terms of magnitude, M, epicentral distance, R, and recording site conditions has been presented. The analysis based on this model implies that: It has been shown that the uncertainties which are associated with the forecasting of Fourier amplitude spectra in terms of magnitude, epicentral distance, site conditions, and component direction are considerable and lead to the range of spectral amplitudes which for an 80 per cent confidence interval exceed one order of magnitude. A model has been presented which empirically approximates the distribution of Fourier spectrum amplitudes and enables one to estimate the spectral shapes which are not exceeded by the presently available data more than 100 (1 - p) per cent of time where p represents the desired confidence level (0 < p <1).


Author(s):  
Ф.Ф. Аптикаев

Задание сейсмических воздействий в отечественных строительных нормах практически не меняется в течение последних 60 лет. Накопленные эмпирические данные по сильным движениям позволяют коренным образом усовершенствовать методику расчета зданий и сооружений на сейсмостойкость. Ожидается снижение погрешностей расчета примерно вдвое. Цель работы. В последнее время много внимания уделяется проблемам построения карт сейсмической опасности в ускорениях. Однако по традиции в нашей стране такие карты оценивают сейсмическую опасность в баллах шкалы сейсмической интенсивности. В большинстве стран сейсмическая опасность оценивается именно в ускорениях. Строились такие карты и в нашей стране. В частности, карты ОСР-97 и ОСР-2012 имели вариант и в ускорениях. Построение карт сейсмической опасности в ускорениях не имеет принципиальных трудностей. Проблема в том, что ускорения не являются адекватной мерой сейсмических воздействий. Более половины века тому назад американские ученые на эмпирическом материале показали, что связь ускорений с баллами, а, следовательно, и с повреждаемостью зданий неоднозначна: шкалы сейсмической интенсивности различны для разных расстояний и грунтов. Ошибка в оценке последствий землетрясения по ускорениям грунта может достигать 2 баллов. Следовательно, расчет ожидаемых воздействий следует производить с учетом других характеристик сейсмических волн. К тому же, попытки построения карт сейсмической опасности строились без учета данных инженерной сейсмологии и с нарушениями правил теории вероятностей и поэтому обладают не только определенными достоинствами, но и серьезными недостатками. Некоторые исследователи считают, что скорости колебаний лучше коррелируются с повреждениями сооружений, по крайней мере, многоэтажных зданий и подземных трубопроводов. Методы работы. Однако анализ эмпирических данных показал, что использование ускорений, скоростей и смещений характеризуется примерно одинаковой точностью. Рассмотрены способы построения карт общего сейсмического районирования. В действующей шкале сейсмической интенсивности ГОСТ Р 57546.2017 приведены оценки корреляции повреждаемости зданий с различными параметрами сейсмических колебаний: ускорениями, скоростями, смещениями, мощностью колебаний грунта. Оценено влияние продолжительности колебаний. Результаты работы. Показано, что дальнейшее повышение надежности расчетов объектов на сейсмостойкость связана с представлением сейсмических воздействий не с амплитудами колебаний, а с энергетическими характеристиками сейсмических волн The specification of seismic effects in domestic building codes has remained practically unchanged over the past 60 years. The accumulated empirical data on strong ground notions make it possible to radically improve the methodology for calculating buildings and other structures for seismic resistance. It is expected that the calculation errors will be reduced by about half. Aim. Recently, much attention has been paid to the problems of developing seismic hazard maps in accelerations. However, by tradition in our country, such maps assess the seismic hazard in terms of the seismic intensity scale. In most countries, seismic hazard is assessed in terms of accelerations. Such maps were also built in our country. In particular, OSR-97 maps also had a variant in acceleration. The construction of seismic hazard maps in accelerations has no fundamental difficulties. The problem is that accelerations are not an adequate measure of seismic effects. More than half a century ago, American scientists, using empirical material, showed that the relationship between accelerations and points, and, consequently, with the damage to buildings, is ambiguous: the seismic intensity scales are different for different distances and grounds. The error in assessing the consequences of an earthquake in terms of ground acceleration can reach 2 points. Therefore, the calculation of the expected impacts should be based on other characteristics of the seismic waves. In addition, attempts to construct seismic hazard maps were built without taking into account the data of engineering seismology and with violations of the rules of probability theory and therefore have not only certain advantages, but also serious drawbacks. Some researchers believe that vibration velocities correlate better with structural damage, at least in multi-storey buildings and underground pipelines. However, the analysis of empirical data showed that the use of accelerations, velocities and displacements is characterized by approximately the same accuracy. Methods. Methods for constructing maps of general seismic zoning, which have a higher accuracy in comparison with existing maps, are considered. In the current scale of seismic intensity GOST R 57546.2017 estimates of the correlation of damage to buildings with various parameters of seismic vibrations are given: accelerations, velocities, displacements, power of ground vibrations. The influence of the duration of the oscillations is estimated. Results. It is shown that a further increase in the reliability of calculations of objects for seismic resistance is associated with the representation of seismic effects not with vibration amplitudes, but with the energy characteristics of seismic waves


2019 ◽  
Vol 6 (2) ◽  
Author(s):  
Ekaterina Pestriakova ◽  
Evgeny Kurbatskiy ◽  
Trong Tam Nguyen

Currently, the construction of railways for high-speed traffic is developing intensively. Overcoming water obstacles is carried out by the construction of artificial structures such as bridges and tunnels. It often becomes necessary to cross areas with increased seismic activity by rail lines. Which, in turn, increases the likelihood of crews on bridges and in tunnels during earthquakes. With adverse combinations of dynamic parameters during earthquakes, fluctuations may occur that threaten the safety of movement. In this regard, it is necessary to evaluate the response of rolling stock to the effects of this kind. Vertical and horizontal oscillations of rolling stock during earthquakes can reach large quantities, which is fraught with serious consequences. Dynamic characteristics of locomotives and cars have significant differences. Locomotives and wagons can be of different brands, in addition, wagons can be empty and loaded. The parameters of earthquakes that can occur in a given area can also be diverse. To solve such a complex task, the authors of the article use the widely used abroad concept of response spectra, which allows to evaluate the response of objects with different natural frequencies to all possible earthquakes. The amplitude Fourier spectra and the spectra of the maximum reactions at speeds have the same dimensions. There is a relationship between these functions, which is used to construct response spectra if the amplitude Fourier spectrum of the ground acceleration function is known. Therefore, to construct the response spectra of the crews for earthquakes, the Fourier amplitude spectra of the base oscillations were used as the initial data. The results presented in the article are part of the dissertation research «Assessment of the dynamic effects of railway and natural origin on underwater tunnels» Pestryakova E.A.


2002 ◽  
Vol 18 (1) ◽  
pp. 161-187 ◽  
Author(s):  
Vladimir Yu Sokolov

This paper presents a revised method for estimating the seismic intensity (MMI or MSK scale) using Fourier amplitude spectra (FAS) of ground acceleration. The improvement of the recently proposed technique (Sokolov and Chernov 1998) has been made on the basis of the data, which were obtained recently during strong earthquakes that occurred throughout the world. The total amount of the used data (horizontal components of ground-motion recordings) is about 1,150 records, while the database of 300 recordings was used in the previous study. The method implies that the seismic intensity is determined by the level of ground motion spectral amplitudes in the frequency range of 0.4–13 Hz. The corresponding empirical relationships between FAS and each intensity level were developed. The method is validated by comparison of the results of the technique application with the empirical data, which have not been included in the database. The Romanian earthquakes (intermediate-depth events of 1977, 1986, and 1990) and the recent 1999 Hector Mine earthquake in southern California were used for this purpose. In general, the FAS intensity shows a good agreement with the reported intensity, and the average residuals do not exceed ±0.3 intensity units and standard deviation is about 0.4-0.6. Evaluation of seismic intensity distribution using region- and site-dependent spectral models, as well as calculation of instrumental intensity map for the recent 1999 Chi-Chi earthquake, Taiwan, show that the FAS intensity clearly reflects the regional (source scaling and attenuation relation) and local (soil response) peculiarities of ground motion.


2008 ◽  
Vol 24 (2) ◽  
pp. 513-532 ◽  
Author(s):  
Vladimir Sokolov ◽  
Takashi Furumura

A database containing records from nine large earthquakes in Japan, obtained by K-NET and KIK-net strong motion stations, was used for the analysis of two techniques for the estimation of instrumental seismic intensity from accelerograms. The first technique is the standard method for JMA intensity evaluation from filtered three-component accelerograms. The second technique is the so-called FAS-intensity, which was developed for MM and MSK scales and which is based on the correlation between levels of the Fourier Amplitude spectrum (FAS) and observed intensity. The relation between these two types of instrumental intensities ( JMAI and spectral MMI) may be described by linear function for intensities larger than JMAI 3.5–4 and MMI 5.0–5.5, but large discrepancy arises at small intensities. The variation is most probably caused by differences in the spectral content of the ground motions, since the JMAI calculation is sensitive to the spectral amplitude within a narrow frequency band around 0.5 Hz.


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