Analysis of Regolith Properties Using Seismic Signals Generated by InSight’s HP3 Penetrator
Analysis of Regolith Properties Using Seismic Signals Generated by InSight’s HP3 Penetrator
复制标题
使用 InSight HP3 穿透器生成的地震信号分析风化层特性
DOI：
10.1007/s11214-017-0391-3
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发表时间：
2017
影响因子：
10.3
通讯作者：
J. Wookey
中科院分区：
文献类型：
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作者：
S. Kedar;J. Andrade;B. Banerdt;P. Delage;M. Golombek;M. Grott;T. Hudson;A. Kiely;M. Knapmeyer;B. Knapmeyer‐Endrun;C. Krause;T. Kawamura;P. Lognonné;T. Pike;Y. Ruan;T. Spohn;N. Teanby;J. Tromp;J. Wookey
洞察号的内部结构地震实验（SEIS）提供了一个独特的、前所未有的机会，通过利用由热流和物理性质包（HP3）产生的重复地震信号，对火星土壤进行首次地质技术调查。了解火星风化层的弹性特性对物质强度有影响，可以约束水含量模型，并为在极乐平原西部着陆点起作用的地质过程和历史提供背景。此外，它将有助于减少由于对浅层地下知之甚少而引入地震数据分析的走时误差。洞察号团队面临的挑战是克服尖锐锤信号的有限时间分辨率，这些信号的频率含量明显高于SEIS 100 Hz采样率。幸运的是，由于摩尔以每行程约1mm$\sim1~\mbox{mm}$的速率向下传播至5 m深度，我们预计会有数千个地震信号，随着摩尔的传播，这些信号将非常缓慢地变化。通过现场测量和建模的结合，我们模拟了模拟InSight HP3-SEIS场景的地震数据集，以及InSight地震仪数据的分辨率。我们证明了直接信号，更重要的是来自风化层底部和潜在熔岩流之间的界面的预期反射信号，可能被洞察号的甚宽波段（VBB）地震仪和短周期（SP）地震仪都观测到。我们概述了几种提高信号时间分辨率的策略，利用大量的锤击和内部定时信息来叠加和插值多个信号，并证明了尽管分辨率很低，但关键参数-地震速度和风化层深度-可以以很高的置信度检索。
InSight’s Seismic Experiment for Interior Structure (SEIS) provides a unique and unprecedented opportunity to conduct the first geotechnical survey of the Martian soil by taking advantage of the repeated seismic signals that will be generated by the mole of the Heat Flow and Physical Properties Package (HP3). Knowledge of the elastic properties of the Martian regolith have implications to material strength and can constrain models of water content, and provide context to geological processes and history that have acted on the landing site in western Elysium Planitia. Moreover, it will help to reduce travel-time errors introduced into the analysis of seismic data due to poor knowledge of the shallow subsurface. The challenge faced by the InSight team is to overcome the limited temporal resolution of the sharp hammer signals, which have significantly higher frequency content than the SEIS 100 Hz sampling rate. Fortunately, since the mole propagates at a rate of ∼1mm$\sim1~\mbox{mm}$ per stroke down to 5 m depth, we anticipate thousands of seismic signals, which will vary very gradually as the mole travels.Using a combination of field measurements and modeling we simulate a seismic data set that mimics the InSight HP3-SEIS scenario, and the resolution of the InSight seismometer data. We demonstrate that the direct signal, and more importantly an anticipated reflected signal from the interface between the bottom of the regolith layer and an underlying lava flow, are likely to be observed both by Insight’s Very Broad Band (VBB) seismometer and Short Period (SP) seismometer. We have outlined several strategies to increase the signal temporal resolution using the multitude of hammer stroke and internal timing information to stack and interpolate multiple signals, and demonstrated that in spite of the low resolution, the key parameters—seismic velocities and regolith depth—can be retrieved with a high degree of confidence.