Site effects in Mexico City eight years after the September 1985 Michoacan earthquakes

Chávez-García, Francisco J.; Bard, Pierre‐Yves

doi:10.1016/0267-7261(94)90028-0

Cited by 126 publications

(88 citation statements)

References 27 publications

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“…Here, the variable spacing, irregular sizes and aspect ratios of the blocks spoil the regular standing wave pattern of a pure Love mode or of a quasi-Love mode relative to a periodic structure. Moreover, two successive blocks act in a manner similar to that of the edges of a basin 5,6 (absent in our model since the lateral extent of the layer is infinite). Indeed, they constitute diffractors whereby Love waves are locally generated, which then presumably travel back and forth in between pairs of blocks, thus resulting in some degree of coupling of the motions of the blocks via the soil so as to result in a duration of the shaking inside the blocks which is apparently longer than the one observed in the one-block configuration (this is substantiated more quantitatively in figs.…”

Section: Resultsmentioning

confidence: 99%

“…However, the 1D model does not account either for the beating phenomena and very long codas in the building vibrations, nor for the large spatial variability of response, repeatedly observed in sites such as Mexico City 5,6 .…”

Section: Abstract: Earthquakes Cities Beating Amplification and Lomentioning

confidence: 99%

“…The translation of this in the time domain is that some buildings will have motion: which is more ample than that of the ground (in the absence of the buildings), which varies from building to building (if these are different from one another), and which may last longer than that of the ground (in the absence of the buildings). Grossly speaking, this is what has been observed in the above-mentioned cities, so that the paradigm we have just described is the one that is usually implicit in attempts 3,[5][6][7][8][9][10]19 to describe and understand what is likely to happen when a seismic wave hits a city built on soft soil. Now suppose that the substratum (especially its irregularities) of the city is not known other than by the fact that it is thought to consist of a soft component of approximate (or average) thickness τ , wherein the density and shear wavespeed are approximately (or on the average) ρ and c respectively, overlying hard rock.…”

mentioning

confidence: 95%

“…A noticeable feature of many earthquake-prone cities such as Kobe 1 (Japan), Izmit 2 (Turkey), Nice 3 (France), Mexico City [4][5][6] , Los Angeles 7-10 etc., is that they are partially or wholly built on soft soil. A straightforward 1D analysis 11 (which takes no account of the presence of the buildings) shows that the soft layer increases the seismic vulnerability of the city in that it is responsible for amplification of ground motion during an earthquake.…”

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confidence: 99%

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Simulation of seismic response in an idealized city

Tsogka

Wirgin

2003

Soil Dynamics and Earthquake Engineering

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We study the seismic response of an idealized 2D 'city', constituted by ten non equallyspaced, non equally-sized, homogenized blocks (i.e., buildings or groups of buildings) anchored in a soft soil layer overlying a hard halfspace. Our results display strong response inside the blocks and on the ground which qualitatively match the responses observed in some earthquake-prone cities. Keywords: earthquakes, cities, beating, amplification and long coda of vibrationsA noticeable feature of many earthquake-prone cities such as Kobe 1 (Japan), Izmit 2 (Turkey), Nice 3 (France), Mexico City 4-6 , Los Angeles 7-10 etc., is that they are partially or wholly built on soft soil. A straightforward 1D analysis 11 (which takes no account of the presence of the buildings) shows that the soft layer increases the seismic vulnerability of the city in that it is responsible for amplification of ground motion during an earthquake.However, the 1D model does not account either for the beating phenomena and very long codas in the building vibrations, nor for the large spatial variability of response, repeatedly observed in sites such as Mexico City 5,6 .To analyze the possible causes of these puzzling effects, we study the action of a seismic wave on a relatively-simple structural model with both geological and man-made features. Our 2D model has three components (from bottom to top in Fig.1): a hard half space (HHS), overlaid by a soft soil layer (SL), in which are partially imbedded a set of even softer blocks (SB). HHS and SL are geological features, the set of SB, which are homogenized for the purpose of the analysis (see fig.2), is man-made and constitutes the 'visible' component of an idealized city.First consider the case in which the blocks are absent. Then the stress-free surface (upper boundary of the soft layer constituting the ground) is a straight horizontal line (in Fig. 1

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Section: Resultsmentioning

confidence: 99%

Section: Abstract: Earthquakes Cities Beating Amplification and Lomentioning

confidence: 99%

mentioning

confidence: 95%

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confidence: 99%

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Simulation of seismic response in an idealized city

Tsogka

Wirgin

2003

Soil Dynamics and Earthquake Engineering

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“…One of the most dramatic examples of such a phenomenon is the Michoacán earthquake of 19th September 1985, which caused more than 10,000 causalities and large economic losses in Mexico City situated more than 350 km from the rupture zone. The damage was essentially due to the presence of a very soft superficial clay layer [Chávez-García and Bard, 1994]. Topographic effects can also cause large ground motions [e.g.…”

Section: Site Effects At Strong-motion Stationsmentioning

confidence: 99%

A preliminary investigation of strong-motion data from the French Antilles

et al. 2006

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Strong-motion networks have been operating in the Caribbean region since the 1970s, however, until the mid-1990s only a few analogue stations were operational and the quantity of data recorded was very low. Since the mid-1990s, digital accelerometric networks have been established on islands within the region. At present there are thought to be about 160 stations operating in this region with a handful on Cuba, 65 on the French Antilles (mainly Guadeloupe and Martinique), eight on Jamaica, 78 on Puerto Rico (plus others on adjacent islands) and four on Trinidad.After briefly summarising the available data from the Caribbean islands, this article is mainly concerned with analysing the data that has been recorded by the networks operating on the French Antilles in terms of their distribution with respect to magnitude, source-to-site distance, focal depth and event type; site effects at certain stations; and also with respect to their predictability by ground motion estimation equations developed using data from different regions of the world. More than 300 good quality triaxial acceleration time-histories have been recorded on Guadeloupe and Martinique at a large number of stations from earthquakes with moment magnitudes larger than 4.8, however, most of the records are from considerable source-to-site distances. From the data available it is found that many of the commonly-used ground motion estimation equations for shallow crustal earthquakes poorly estimate the observed ground motions on the two islands; ground motions on Guadeloupe and Martinique have smaller amplitudes and are more variable than expected. This difference could be due to regional dependence of ground motions because of, for example, differing tectonics or crustal structures or because the ground motions so far recorded are, in general, from smaller earthquakes and greater distances than the range of applicability of the investigated equations.

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Two‐dimensional Scattering of P, Sv and Rayleigh Waves: Preliminary Results for the Valley of Mexico

Reinoso

Wrobel

Power

1997

Earthquake Engng. Struct. Dyn.

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SUMMARYA direct boundary element method for calculating the two-dimensional scattering of seismic waves from irregular topographies and buried valleys due to incident P-, SV-and Rayleigh waves is employed to model a section of the Mexico City Valley. The method has been formulated with isoparametric quadratic boundary elements and contains, with respect to previous works in the ÿeld, some improvements that are brie y presented.Because the Mexico City Valley is relatively at and shallow and the contrast of S-waves between the clays and the basement rock is very high, it is believed that the one-dimensional theory is enough to explain the ampliÿcation patterns. Although this is true for most sites, results from recent accelerometric data suggest that two-and three-dimensional models are needed to explain the ampliÿcation behaviour at some places.In this work, two accelerometric sites have been chosen: Site 84 to probe that the one-dimensional model works well for most sites, and Site TB, as an example of irregular response. The two-dimensional method presented here was used to model a section of the valley where site TB is located, showing that this method yields results closer to the observations than the one-dimensional approach. c

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Site effects in Mexico City eight years after the September 1985 Michoacan earthquakes

Cited by 126 publications

References 27 publications

Simulation of seismic response in an idealized city

Simulation of seismic response in an idealized city

A preliminary investigation of strong-motion data from the French Antilles

Two‐dimensional Scattering of P, Sv and Rayleigh Waves: Preliminary Results for the Valley of Mexico

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