Deep moonquake properties: deciphering stresses and deformation patterns

深层月震特性：破译应力和变形模式

• 批准号: 2272655
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2272655
• 关键词: Deep; moonquake; properties; deciphering; stresses

Between 1969 and 1972, five seismometers were placed on the near side of the moon as part of the Apollo space missions. Four of these stations operated until 1977, forming the lunar seismic network. This lunar seismic data provides unique insights into the structure and dynamics of the lunar interior. A range of seismic signals were recorded during the 7-year operation of the seismic network, including meteoroid impacts, artificial impacts, shallow moonquakes and deep moonquakes. This project will focus on deep moonquakes. There are notable similarities between deep moonquakes and intermediate earthquakes. Both are thought to occur at conditions that inhibit brittle failure. Likewise, both quakes repeatedly arise in the same small area, referred to as nests. Finally, the physical mechanism of both events remains unclear. Understanding the source properties of deep moonquakes may provide insight into the processes occurring on Earth. Deep moonquakes also exhibit more enigmatic behaviours that are not observed in intermediate earthquakes, including a strong periodicity linked to the solid Moon tides. However, the relationship between tidal stress and moonquake occurrence is not simple, and moonquakes respond to a range of different orbital characteristics. It is still unclear if this periodicity indicates whether tidal or tectonic stresses drive moonquakes. Despite deep moonquakes making up nearly half of the moonquake catalogue, their source mechanisms are still poorly explained, and few studies have focused on the properties of rupture. The focus of this project will be to investigate the relationship between coseismic stress drop and tidal phase. There has been a range of studies evaluating the tidal stress acting on deep earthquakes, but they do not adequately describe the stress drop of the seismic source. Further analysis of the source properties of deep moonquake nests could provide insight into the rupture processes in the moon's interior and the relationship between rupture and tidal stresses. A range of seismic techniques commonly applied to terrestrial data will be modified appropriately and applied to the Apollo data. This will include spectral fitting, empirical Green's Functions and inter-station phase coherence analysis to determine the rupture extent, stress drop and radiated energy of previously unstudied deep moonquakes. This project falls within the Lunar Science topic of the Astronomy and Space Science research area.

在1969年至1972年之间，作为阿波罗太空任务的一部分，五个地震仪被放置在月球的近侧。其中四个观测站一直运行到1977年，形成了月球地震网络。这些月球地震数据为月球内部的结构和动力学提供了独特的见解。在地震网络7年的运行期间，记录了一系列地震信号，包括流星体撞击、人工撞击、浅月震和深月震。该项目将重点关注深月震。深月震和中等地震之间有着显著的相似性。两者都被认为发生在抑制脆性破坏的条件下。同样地，两次地震都在同一个小区域反复发生，被称为巢穴。最后，这两个事件的物理机制仍然不清楚。了解深月震的来源特性可能会提供对地球上发生的过程的洞察力。 深月震还表现出在中等地震中没有观察到的更神秘的行为，包括与固体月球潮汐有关的强烈周期性。然而，潮汐应力和月震发生之间的关系并不简单，月震响应于一系列不同的轨道特征。目前还不清楚这种周期性是否表明潮汐或构造应力驱动月震。尽管深月震占月震目录的近一半，但它们的震源机制仍然很难解释，而且很少有研究关注破裂的性质。本计画的重点将是探讨同震应力降与潮汐相位的关系。已经有一系列的研究评估潮汐应力作用于深源地震，但他们没有充分描述的应力降的震源。进一步分析深月震巢的震源特性可以深入了解月球内部的破裂过程以及破裂与潮汐应力之间的关系。通常用于地面数据的一系列地震技术将作适当修改，并应用于阿波罗数据。这将包括谱拟合、经验绿色函数和站间相位相干分析，以确定以前未研究的深月震的破裂程度、应力降和辐射能量。该项目属于天文学和空间科学研究领域的月球科学专题福尔斯。