Hardrock seismic imaging

在像加拿大地盾这样的非均匀（硬岩）环境中，需要考虑一些与规模和成分相关的参数，这使得地震研究更加困难。为了模拟地震波在这些地区的传播，需要了解岩石物理参数（纵波和横波速度和密度）及其在地壳中的分布，这些参数可以直接从井眼测井（一维）中获得，也可以间接从地质图和岩性分析中获得。我们将从各种来源收集速度和密度日志，并分析它们的一阶和二阶统计量。这不仅为我们提供了垂直维度的一维参数，而且通过将几个钻孔相关联，将为构建地壳非均质性的三维模型提供手段。背景模型将添加大量硫化物矿床，已知这些矿床会根据其形状、大小和组成分散地震能量。三维弹性/粘弹性正演模型研究将用于优化三维地面和井眼地震数据采集策略。此外，非均质性可能导致衰减。当波在非均匀介质中传播时，由于球形发散和吸收，它们随着距离和时间的推移而损失能量。人们普遍认为固体地球存在平坦的吸收带。在不同频率（即地面（Hz）、钻孔（KHz）和实验室地震（MHz））的勘探地震学中，已经观察到吸收和色散的影响有一段时间了。我们将使用不相关的（原始）可控震源数据来测量勘探地震频带中的速度频散和衰减。正在进行的研究项目将集中在与陨石撞击有关的独特压力-温度条件（和矿床）（在加纳的Bosumtwi、墨西哥的Chicxulub、安大略省的Sudbury、安大略省的Wanapitei）、永久冻土和天然气水合物的物理性质（在NWT的Mallik）以及深部矿产勘探的3D地震研究项目（在安大略省、魁北克省和新不伦瑞克省）。

In heterogeneous (hardrock) environments such as the Canadian Shield, a number of parameters related to scale and composition need to be considered that render seismic studies more problematic. To model the propagation of seismic waves in these areas requires knowledge of petrophysical parameters (compressional and shear wave velocities and densities) and their distribution within the crust, which can be derived directly from borehole logs (in 1-D) or indirectly from geological maps and lithological analysis. We will collect velocity and density logs from various sources and analyze them for their first and second order statistics. These not only give us the 1-D parameters in the vertical dimension but by correlating several boreholes will provide the means of constructing a 3-D model of crustal heterogeneity. Added to the background model will be massive sulfide deposits, which are known to scatter seismic energy according to their shape, size and composition. 3D elastic/visco-elastic forward modeling studies will be used to optimize 3D surface and borehole seismic data acquisition strategies. In addition, heterogeneities may cause attenuation. As waves travel in heterogeneous media, they lose energy with distance and time due to spherical divergence and absorption. It is commonly accepted that a flat absorption band exists for the solid earth. The effects of absorption and dispersion have been observed in exploration seismology at various frequencies (i.e. surface (Hz), borehole (KHz), and laboratory seismics (MHz)) for some time. We will use uncorrelated (raw) Vibroseis data to measure velocity dispersion and attenuation in the exploration seismic frequency band. Ongoing research projects will focus on unique pressure-temperature conditions (and mineral deposits) related to meteorite impacts (Bosumtwi, Ghana; Chicxulub, Mexico; Sudbury, Ontario; Wanapitei, Ontario; the physical properties of permafrost and gas hydrates (Mallik, NWT) and 3D seismic research projects for deep mineral exploration (Ontario, Quebec and New Brunswick).