Éditeur(s) : HAL CCSD
Résumé : Spatial variability of ground motion may be explained by local soil conditions; it is the so-called "site effects". Site effects are responsible for increasing duration and important amplification of strong ground motion during earthquakes and must be considered as a key parameter in local seismic hazard assessment. French West Indies are prone to strong site effects because of a particular geology, characterized by soft soil deposits and strong alteration of volcanic deposits. In this framework, and considering that French West Indies are considered as a high seismicity level zone in the French building code, part of seismic hazard mitigation policy consists in technical studies to perform identification and mapping of zones characterized by homogeneous seismic response and quantification of associated ground motion. It is the aim of seismic microzonations. In this presentation, we will expose the methodology used on the scale of municipalities for mapping homogeneous seismic areas, based on a study of geological and geotechnical conditions and some geophysical testings. Then, a study of vulnerability of buildings allows to estimate the probability of damage on various sectors for a scenario of risk corresponding to the seismic microzonation.
19ème Conférence Géologique de la Caraïbe
Le Gosier, Guadeloupe, France

hal-00614300
https://hal-brgm.archives-ouvertes.fr/hal-00614300

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Northwest Iran is characterized by a high level of historical and instrumental seismicity related to the ongoing convergence between the Arabian and Eurasian plates. In this region, the main right-lateral strike-slip fault known as the North Tabriz fault (NTF) forms the central portion of a large crustal fault system called the Tabriz fault system (TFS). The NTF is a major seismic source along which at least three strong and destructive earthquakes have occurred since 858 AD. The two most recent destructive seismic events occurred in 1721 AD and 1780 AD, rupturing the SE and NW fault segments, respectively. This paper reports paleoseismological and quantitative geomorphologic investigations on the SE segment of the NTF, between the cities of Bostanabad and Tabriz. These observations help to improve our understanding of the seismic hazard for Tabriz city and its surrounding areas. Our field investigations revealed evidence of successive faulting events since the Late Quaternary. Paleoseismic investigations indicate that since 33.5 kyr, the SE segment of the NTF has experienced at least three major (M>7.5) seismic events, including the 1721 AD earthquake (M=7.6–7.7). Along the NW segment of the fault, however, our results suggest that the amount of strong (M~7.5) seismic events during the same period is significantly greater than along the SE segment. One possible explanation of such a difference in seismic activity is that the Late Quaternary-Holocene coseismic slip rate is decreasing along the NTF from the northwest to the southeast. This explanation contradicts the former hypothesis of a constant slip rate along the whole length of the NTF. In addition, more distributed deformation along several parallel fault branches, in a wider fault zone of the SE segment of the NTF may be considered as additional evidence for the estimation of lower rate of deformation along the fault segment. Such a slip distribution pattern can explain the existence of smaller (~300 m) Pliocene-Quaternary cumulative dextral offsets along the SE fault segment than the measured cumulative offsets along the NW segment (~800 m) of the NTF.
ISSN: 0040-1951

hal-01089420
http://hal.upmc.fr/hal-01089420
http://hal.upmc.fr/hal-01089420/document
http://hal.upmc.fr/hal-01089420/file/Solaymani%20Azad%20et%20al.%2C%202014%20%28accepted%29.pdf
DOI : 10.1016/j.tecto.2014.11.010