Interpretation of borehole magnetometer data
Interpretation of borehole magnetometer data
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钻孔磁力计数据的解释
DOI：
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发表时间：
1979
期刊：
影响因子：
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通讯作者：
G. Daniell
中科院分区：
文献类型：
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作者：
R. Parker;G. Daniell
从深海钻探项目（DSDP）的玄武岩层孔中回收的样品强烈表明，一个好的磁化模型将是一个空间随机的。为了解释未来的磁力计观测孔，我们开发了一个理论，所观察到的磁场的磁化自相关张量，一个功能完全描述的介质的二阶统计。我们研究特殊的模型与长期和短期的顺序，并得出结论，某些属性的介质是非常可取的，使解释成为可能。其中包括自相关张量与水平面中的方向无关以及磁化方向是均匀的。此外，只有当测量磁场的三个分量时，才能进行有用的解释，并且最好（但不是必须）磁力计绝对围绕垂直轴定向。我们证明，只有在特殊情况下（例如，介质的水平分层）磁场是否与磁力计周围区域的平均磁化强度直接相关。我们分析了DSDP第37段的自然反射磁化数据，以获得空间统计的部分信息。在10米以上的尺度上，垂直方向上没有明显的顺序，但在5个孔中的两个孔中，在0.3-2米的范围内存在相关性。在三个孔中，有证据表明方向具有相当好的均匀性，这是解释目的非常理想的属性。不幸的是，钻孔样本没有给我们关于自相关张量作为水平距离的函数的行为的信息。
Samples recovered from Deep-Sea Drilling Project (DSDP) holes into the basaltic layer strongly suggest that a good model of the magnetization would be a spatially random one. To interpret future magnetometer observations made in the holes, we develop a theory relating the observed fields to the magnetization autocorrelation tensor, a function completely describing the second-order statistics of the medium. We examine special models with long- and short-range order and conclude that certain properties of the medium are highly desirable in making interpretation possible. Among these are that the autocorrelation tensor be independent of direction in a horizontal plane and that the direction of magnetization be uniform. Furthermore, useful interpretation is feasible only if three components of the magnetic field are measured, and it is preferable (but not essential) that the magnetometer is absolutely orientated about a vertical axis. We show that only in special circumstances (e.g., horizontal layering of the medium) does the magnetic field correlate directly with the average magnetization in a region surrounding the magnetometer. We analyze the natural remanent magnetization data from leg 37 of the DSDP to obtain partial information on the spatial statistics. There is no significant order vertically on scales longer than 10 m, but in two of the five holes there is correlation in the range 0.3–2 m. In three holes there is evidence of fairly good uniformity of direction, a highly desirable property for interpretational purposes. Unfortunately, drill hole samples give us no information about the behavior of the autocorrelation tensor as a function of horizontal distance.