Diffraction around a Semi-Parabolic Canyon in an Elastic Half-Space by Out-of-Plane SH-Waves,II: Rocking and Resultant Rotations

This paper is the second of the two papers, discussing the rocking and resultant component of rotations, with the torsional components of motions presented earlier in the first paper for the case of out-of-plane SH waves excitation on a semi-parabolic canyon. The rotational motions are gaining importance in recent years in the field of strong-motion seismology and earthquake engineering. Many previous papers on out-of-plane SH waves excitation presented the associated torsion rotational motions, when in fact there is also a rocking rotational component of motions. Both the rocking and torsion rotational motions, in as much as the translational motions, had shown to play an important role in structural responses, even though rotations are not incorporated into building design codes at present. Studying the rotational motions can thus help to a better understanding of the behavior of surface topographies that are in the vicinity of structures in the event of seismic excitation. This paper included, besides the additional rocking motions, also the resultant rotational motions combining torsion and rocking.     

LES ORTSTEINS DU QUÉBEC: RÉPARTITION GEOGRAPHIQUE, RELATIONS GÉOMORPHOLOGIQUES ET ESSAI DE DATATION

Ce travail porte sur I'extension géographique des orts-teins au Québec et vise à déterminer les causes de leur répartition principalement pour la Côte-Nord du Saint-Laurent. Les données ont été puisées en partie dans des rapports pédologiques publiés sur le Québec, mais aussi observées dans des sites d'échantillonnage sur la Côte-Nord du Saint-Laurent, l'île d'Anticosti et en Gaspésie. Par ailleurs, pour les datations au ¹⁴C, six sites d'echantillonnage ont été choisis sur la Côte-Nord. Les résultats indiquent que les ortsteins se développent sous toutes les latitudes au sud de 55e parallèle et sous différentes conditions physiographiques et géologiques. On les retrouve aussi bien sur des silts sableux que sur des graviers grossiers et leur présence est favorisée lorsqu'il y a fluctuation de la nappe d'eau. Les datations au ¹⁴C ont donné des âges relativement jeunes pour les ortsteins, soit moins de 420 ans bp, indiquant qu'il y a une migration active de la matière organique dans les horizons concrétionnés. The present paper concerns the geographic delimitation of ortsteins in Québec and deals with the causes of their distribution mainly for the North Shore of the St. Lawrence River. Data was gathered in part in published geological reports in Quebec, and also acquired in the field along the North Shore of the St. Lawrence River, Anticosti Island, and in the Gaspé Peninsula. Furthermore, six study sites were selected for dating by ¹⁴C along the North Shore. Results indicate the ortsteins develop under all latitudes south of the 55th parallel and under different physiographic and geological conditions. They can be found on both sandy silts and coarse gravels, and their presence is enhanced whenever the water level fluctuates. ¹⁴C datings give relatively young ages for ortsteins, less than 420 years BP, indicating that an active migration of organic matter occurred in the indurated horizons.     

Pearl fishing in the ancient world: 7500 BP

The oldest pearl in the world was found in the United Arab Emirates and dates from 7500 BP. Gemmologists and jewellers have popularised the idea that the oldest pearl in the world is the 5000‐year‐old Jomon pearl from Japan. Discoveries made on the shores of south‐eastern Arabia show this to be untrue, as the archaeological pearls that have been found are 2500 years older. In this region, pearls still hold an important place. Indeed, today they remain a central, identifying element. The discovery of archaeological pearls demonstrates an ancient fishing tradition that no longer exists today.