加拿大Sudbury地区地壳结构特征──AGT(1992)地震折射波资料初步解释

CRUSTAL STRUCTURE UNDER THE SUDBURY STRUCTURE(ONTARIO, CANADA):A PRELIMINARY INTERETATION OF THE AGT(1992)SEISMIC REFRACTION DATA

根据1992年加拿大岩石圈组织的Abitibi－GrenvilleTransect（AGT）实验计划中的高精度地震折射波资料的处理与解释，讨论了Sudbury地区的地壳结构特征对2条纵剖面及2条扇形剖面的地震折射波数据做了正反演计算．此外，应用层析成像技术对地震资料进行了处理根据数值计算结果，明确了该区Moho界面的变化形态并发现了Sudbury结构下部透镜状高速异常体的存在．

The Sudbtiry structure is located in south-central Ontdrio. In 1992, the Lithoprobe Abitibi-Grenville Transect (AGT) experiment included bath high resoluiton seismic reflection, regional seismic wide-angle reflection and refraction profiles (AB and XY) as the Sudbury subtransect. Some of the main objectives of this subtransect were for investigations of the geometry of the lower crust under the Sudbury structure and the geoledcal relationship betWeen the Grenville front boundary which separates the Southern and Grenville Provinces. Crustal structures in the Sudbury region are discussed in this Paper by processing and interpreting the AGT(1992) high resolution seismic reflection and refraction data. In-line and fan-shot seismic data were modeled by forward medelling and inverse approaches including a seismic tomographic inversion technique. A preliminary crustal model indicates that the Moho depth ranges from 37 to 44 km, from the northwest (Superior Province) to the southeaSt (Grenville Province). From the southwest to northeast across the structure, the Moho depth shows little variation (~37km). Inversion results from fan-shot data reveal that the crustal thickness in the vicinity of the two profiles increase from approximate 36 km in the northern part to about 40km in the southern part under the Grenville front tectonic zone (GFTZ) between the Southern and Grenville Provinces. A lenticular high velocity they under Sudbury structure is shown on in-line madals and also on the west-east seismic tomographic image profile. This high velocity ho may relate to the high density rocks of the Sudbury igneous complex (SIC).