Geo-acoustic modelling of late and postglacial sedimentary units in the Baltic Sea and their acoustic visibility
Geo-acoustic modelling of late and postglacial sedimentary units in the Baltic Sea and their acoustic visibility
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DOI：
10.1016/j.margeo.2016.03.015
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发表时间：
2016-06
期刊：
影响因子：
2.9
通讯作者：
M. Endler;R. Endler;J. Wunderlich;Bernd Bobertz;T. Leipe;M. Moros;J. Jensen;H. Arz
中科院分区：
文献类型：
--
作者：
M. Endler;R. Endler;J. Wunderlich;Bernd Bobertz;T. Leipe;M. Moros;J. Jensen;H. Arz
声学剖面法通常用于地球科学，以获得有关海洋沉积物沉积结构的知识。然而，它们的解释和声学反射体与沉积学边界的相互关系仍然很困难。声阻抗的梯度决定了声反射体的强度，声反射体不一定是沉积边界。尚未为波罗的海开发涵盖各种沉积物类型的适当地质声学模型。基于对梅克伦堡湾和Arkona盆地沉积物岩心的全面调查，我们开发了地质声学模型，该模型能够将实验室P波速度测量值转移到原位条件下，同时考虑压力、盐度、温度和P波速度（即声学色散）的频率依赖性的变化。该模型允许根据岩心测井和选定的沉积学数据（如含水量、烧失量和粒度）计算湿体积密度和现场P波速度（据此计算声阻抗）。现在可以将岩心数据精确地绘制成声学剖面图，这是解释这些剖面图的关键一步。模型P波速度用于将双向走时转换为深度。波罗的海不同发展阶段的平均沉积学参数是使用地质统计方法计算的，如果没有岩心测井数据，可以进行粗略的P波估计。
Acoustic profiling methods are commonly used in the geosciences to obtain knowledge about the sedimentary structures of marine deposits. However, their interpretation and the correlation of acoustic reflectors with sedimentological boundaries remain difficult. The gradient in acoustic impedance determines the intensity of acoustic reflectors, which are not necessarily sedimentary boundaries. Suitable geo-acoustic models that cover a wide range of sediment types have not yet been developed for the Baltic Sea. Based on comprehensive investigations of sediment cores from Mecklenburg Bay and the Arkona Basin, we developed geo-acoustic models that enable the transfer of laboratory p-wave velocity measurements to in situ conditions while considering changes in pressure, salinity, temperature and the frequency dependence of the p-wave velocity (i.e. acoustic dispersion). This modelling allows the calculation of the wet bulk density and in situ p-wave velocity (from which the acoustic impedance is calculated) from core logging and selected sedimentological data, such as the water content, loss on ignition, and grain size. Precise plotting of core data into the acoustic profiles is now possible and represents a crucial step towards the interpretation of these profiles. Modelled p-wave velocities are used to convert two-way-travel-time to depth. The average sedimentological parameters for the different development phases of the Baltic Sea are calculated using geo-statistical methods and may allow for rough p-wave estimations if core logging data are not available.