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Near-Field Seismic Propagation and Coupling Through Mars’ Regolith: Implications for the InSight Mission
Space Science Reviews ( IF 9.1 ) Pub Date : 2018-07-09 , DOI: 10.1007/s11214-018-0514-5 R. Myhill , N. A. Teanby , J. Wookey , N. Murdoch
Space Science Reviews ( IF 9.1 ) Pub Date : 2018-07-09 , DOI: 10.1007/s11214-018-0514-5 R. Myhill , N. A. Teanby , J. Wookey , N. Murdoch
NASA’s InSight Mission will deploy two three-component seismometers on Mars in 2018. These short period and very broadband seismometers will be mounted on a three-legged levelling system, which will sit directly on the sandy regolith some 2–3 meters from the lander. Although the deployment will be covered by a wind and thermal shield, atmospheric noise is still expected to couple to the seismometers through the regolith. Seismic activity on Mars is expected to be significantly lower than on Earth, so a characterisation of the extent of coupling to noise and seismic signals is an important step towards maximising scientific return.In this study, we conduct field testing on a simplified model of the seismometer assembly. We constrain the transfer function between the wind and thermal shield and tripod-mounted seismometers over a range of frequencies (1–40 Hz) relevant to the deployment on Mars. At 1–20 Hz the displacement amplitude ratio is approximately constant, with a value that depends on the site (0.03–0.06). The value of the ratio in this range is 25–50% of the value expected from the deformation of a homogeneous isotropic elastic halfspace. At 20–40 Hz, the ratio increases as a result of resonance between the tripod mass and regolith. We predict that mounting the InSight instruments on a tripod will not adversely affect the recorded amplitudes of vertical seismic energy, although particle motions will be more complex than observed in recordings generated by more conventional buried deployments. Higher frequency signals will be amplified by tripod-regolith resonance, probably reaching peak-amplification at ∼50$\sim 50$ Hz. The tripod deployment will lose sensitivity at frequencies >50$>50$ Hz as a result of the tripod mass and compliant regolith.We also investigate the attenuation of seismic energy within the shallow regolith covering the range of seismometer deployment distances. The amplitude of surface displacement decays as r−n$r^{-n}$, where 1.5
中文翻译：
通过火星风化层的近场地震传播和耦合：对洞察号任务的影响
NASA 的 InSight 任务将在 2018 年在火星上部署两个三分量地震仪。这些短周期和超宽带地震仪将安装在一个三腿水平系统上，该系统将直接位于距离着陆器约 2-3 米的沙质风化层上。尽管部署将被防风和隔热罩覆盖，但预计大气噪声仍会通过风化层耦合到地震仪。预计火星上的地震活动将明显低于地球，因此表征与噪声和地震信号的耦合程度是实现科学回报最大化的重要一步。在这项研究中，我们对简化的火星模型进行了现场测试。地震仪组件。我们在与火星部署相关的一系列频率（1-40 Hz）上限制了风和隔热罩与安装在三脚架上的地震仪之间的传递函数。在 1–20 Hz 时，位移幅度比近似恒定，其值取决于站点 (0.03–0.06)。此范围内的比率值是均匀各向同性弹性半空间变形预期值的 25-50%。在 20–40 Hz 时，由于三脚架质量和风化层之间的共振，该比率增加。我们预测，将 InSight 仪器安装在三脚架上不会对记录的垂直地震能量振幅产生不利影响，尽管粒子运动将比更传统的埋地部署产生的记录中观察到的更复杂。高频信号将通过三脚架-风化层共振放大，可能在 ~50$\sim 50$Hz 处达到峰值放大。由于三脚架质量和顺应风化层，三脚架部署将在频率 >50$>50$Hz 时失去灵敏度。我们还研究了覆盖地震仪部署距离范围的浅表层风化层内地震能量的衰减。表面位移的幅度衰减为 r−n$r^{-n}$，其中 1.5
更新日期：2018-07-09
中文翻译：
通过火星风化层的近场地震传播和耦合：对洞察号任务的影响
NASA 的 InSight 任务将在 2018 年在火星上部署两个三分量地震仪。这些短周期和超宽带地震仪将安装在一个三腿水平系统上，该系统将直接位于距离着陆器约 2-3 米的沙质风化层上。尽管部署将被防风和隔热罩覆盖，但预计大气噪声仍会通过风化层耦合到地震仪。预计火星上的地震活动将明显低于地球，因此表征与噪声和地震信号的耦合程度是实现科学回报最大化的重要一步。在这项研究中，我们对简化的火星模型进行了现场测试。地震仪组件。我们在与火星部署相关的一系列频率（1-40 Hz）上限制了风和隔热罩与安装在三脚架上的地震仪之间的传递函数。在 1–20 Hz 时，位移幅度比近似恒定，其值取决于站点 (0.03–0.06)。此范围内的比率值是均匀各向同性弹性半空间变形预期值的 25-50%。在 20–40 Hz 时，由于三脚架质量和风化层之间的共振，该比率增加。我们预测，将 InSight 仪器安装在三脚架上不会对记录的垂直地震能量振幅产生不利影响，尽管粒子运动将比更传统的埋地部署产生的记录中观察到的更复杂。高频信号将通过三脚架-风化层共振放大，可能在 ~50$\sim 50$Hz 处达到峰值放大。由于三脚架质量和顺应风化层，三脚架部署将在频率 >50$>50$Hz 时失去灵敏度。我们还研究了覆盖地震仪部署距离范围的浅表层风化层内地震能量的衰减。表面位移的幅度衰减为 r−n$r^{-n}$，其中 1.5
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