Publications des scientifiques de l'IRD

Brax M., Bard P. Y., Duval A. M., Bertrand E., Rahhal M. E., Jomaa R., Cornou Cécile, Voisin C., Sursock A. (2018). Towards a microzonation of the Greater Beirut area: an instrumental approach combining earthquake and ambient vibration recordings. Bulletin of Earthquake Engineering, 16 (12), p. 5735-5767. ISSN 1570-761X.

Titre du document
Towards a microzonation of the Greater Beirut area: an instrumental approach combining earthquake and ambient vibration recordings
Année de publication
2018
Type de document
Article référencé dans le Web of Science WOS:000450798200002
Auteurs
Brax M., Bard P. Y., Duval A. M., Bertrand E., Rahhal M. E., Jomaa R., Cornou Cécile, Voisin C., Sursock A.
Source
Bulletin of Earthquake Engineering, 2018, 16 (12), p. 5735-5767 ISSN 1570-761X
Lebanon is situated on the 1000km long Levant transform fault that separates the Arabic from the African tectonic plates. In Lebanon, the Levant fault splits up into a set of ramifications that had, in the past, generated major destructive earthquakes causing a lot of destruction and thousands of casualties. The most devastating one was the 551 A.D. offshore earthquake that destroyed Beirut, the capital of Lebanon. This paper presents a site effect study in Beirut, aimed at proposing a framework for future microzonation works in the city. It includes two complementary parts. A 6-month, temporary seismological experiment was first conducted to estimate the site response at 10 sites sampling the main geological units of Beirut on the basis of local and regional earthquake recordings. This spatially sparse information was then complemented by a large number (615) of microtremor measurements covering the Beirut municipality and part of its suburbs with a 400m dense grid. The recordings were analysed with the standard site-to-reference and horizontal-to-vertical spectral ratio methods for earthquake recordings, and the horizontal-to-vertical ratio for ambient noise recordings. Significant ground motion amplification effects (up to a factor of 8) are found in a few areas corresponding to recent deposits. The consistency between results from earthquake and microtremor recordings allows proposing a map of the resonance frequencies within the city and its suburbs, with frequencies ranging from 0.5 to 5Hz for the deepest deposits, and 5-10Hz for shallow areas. Finally, the results are discussed and a way to combine the results obtained from the temporary stations to the great number of recordings coming from the permanent Lebanese network is proposed.
Plan de classement
Géologie et formations superficielles [064] ; Géophysique interne [066]
Description Géographique
LIBAN ; BEYROUTH
Localisation
Fonds IRD [F B010074485]
Identifiant IRD
fdi:010074485
Contact