Two wide-angle seismic reflection/refraction profiles were acquired to determine the velocity characteristics of the Meguma terrane and adjacent Avalonia northeast of the Cobequid-Chedabucto Fault Zone (CCFZ) in eastern Canada. Line 99–1 is located along the Scotian margin whereas line 99–2 crosses the Scotian margin and onshore Nova Scotia and extends into the Gulf of St. Lawrence. Velocity models were derived by forward modelling of travel times. P-wave velocities of 5.5–6.0 km/s and 6.0–6.4 km/s are interpreted to be metasedimentary rocks of the Goldenville and Halifax groups and granitic rocks, respectively. This inference is based on comparison with laboratory velocities of a suite of rock samples, offshore sampling, links to onshore geology with multibeam bathymetry, and gravity modelling. On both lines a low velocity zone (LVZ) >350 km wide and up to 15 km thick is present at mid-crustal levels. The LVZ is not observed beneath onshore Nova Scotia or northeast of Orpheus Graben, the offshore extension of the CCFZ. The crustal thickness of the Meguma terrane varies between 31 and 38 km; in contrast, the Moho is at a depth of 41 km beneath Avalonia. The velocity of the lower crust on line 99–2 is 6.8–7.1 km/s beneath the LVZ and Avalonia, and 6.6 km/s beneath onshore Meguma terrane. Poisson's ratios calculated from P- and S-wave velocities are 0.19–0.23 in the Meguma terrane crust; in contrast, Poisson's ratios of 0.24–0.25 are indicated for Avalonian crust.

中文翻译：

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沿加拿大斯科舍省边缘和新斯科舍省的广角地震反射/折射剖面的地质解释

获取了两个广角地震反射/折射剖面，以确定加拿大东部科贝奎德-切达布托断层带 (CCFZ) 东北部 Meguma 地体和邻近 Avalonia 的速度特征。 99-1 号线位于斯科舍边缘，而 99-2 号线穿过斯科舍边缘和新斯科舍陆上并延伸至圣劳伦斯湾。速度模型是通过行程时间的正演模型得出的。 5.5-6.0 km/s 和 6.0-6.4 km/s 的 P 波速度分别被解释为 Goldenville 群和 Halifax 群的变沉积岩和花岗岩。这一推论基于与一组岩石样本的实验室速度的比较、海上采样、与多波束测深的陆上地质学的联系以及重力建模。两条线上的中地壳层均存在宽 >350 公里、厚达 15 公里的低速区 (LVZ)。在新斯科舍省陆上或奥菲斯地堑东北部（CCFZ 的海上延伸）下方未观察到 LVZ。 Meguma 地体的地壳厚度在 31 至 38 公里之间；相比之下，莫霍面位于阿瓦洛尼亚地下 41 公里深处。 99-2 线下地壳的速度在 LVZ 和 Avalonia 下方为 6.8-7.1 km/s，在陆上 Meguma 地体下方为 6.6 km/s。在 Meguma 地壳中，根据纵波和横波速度计算出的泊松比为 0.19–0.23；相比之下，阿瓦隆地壳的泊松比为 0.24-0.25。