講演情報
[PPS02-P07]Relocating Shallow Moonquakes Through Joint Data Analysis of Apollo Short-Period Seismometers and Lunar Surface Gravimeter
*小野寺 圭祐1、川村 太一2 (1.岡山大学惑星物質研究所、2.パリシテ大学パリ地球物理研究所)
キーワード：
月、惑星地震学、月震
Even after half a century since the termination of the Apollo seismic observations, new discoveries about lunar seismicity and the internal structure have still been reported through the analysis of the Apollo seismic data. Here, we report another progress, especially on understanding the most energetic moonquakes (shallow moonquakes).
Among the reported seismic events on the Moon, shallow moonquakes are known for their unique features, such as high-frequency energy excitation, similarity to intraplate earthquakes, and the largest energy release of any other moonquakes reported. Despite these interesting features, a small number of samples (< 80 events) and a sparse seismic network observation (4 seismic stations: Apollo 12, 14, 15, 16) prevented us from gaining an in-depth understanding of shallow moonquakes, such as their spatial distribution and source mechanism.
The underlying idea of this study is to utilize a gravimeter installed at the Apollo 17 landing site as a pseudo-seismometer to expand the original Apollo seismic network and better locate shallow moonquake sources. While the Apollo 12, 14, 15, and 16 seismometers were located in a range of 23.4°W ~ 15.5°E, the Apollo 17 was situated at 30.8°E. Thus, including the Apollo 17 gravimeter data in the analysis allow us to expand the network eastward.
In this study, analyzing three shallow moonquakes simultaneously recorded by both seismometers and a gravimeter, we were able to more accurately locate the shallow moonquake sources. Interestingly, one of which possibly originates from the highest latitude in the northern hemisphere. Since lunar seismicity in polar regions is little known, this finding will be a significant milestone towards further understanding the seismic/tectonic activities in lunar polar regions.
In the presentation, we will report the updated source locations of the analyzed shallow moonquakes and show initial results about the comparison between the source locations and the surface/subsurface geological features, particularly in the north polar region.
Among the reported seismic events on the Moon, shallow moonquakes are known for their unique features, such as high-frequency energy excitation, similarity to intraplate earthquakes, and the largest energy release of any other moonquakes reported. Despite these interesting features, a small number of samples (< 80 events) and a sparse seismic network observation (4 seismic stations: Apollo 12, 14, 15, 16) prevented us from gaining an in-depth understanding of shallow moonquakes, such as their spatial distribution and source mechanism.
The underlying idea of this study is to utilize a gravimeter installed at the Apollo 17 landing site as a pseudo-seismometer to expand the original Apollo seismic network and better locate shallow moonquake sources. While the Apollo 12, 14, 15, and 16 seismometers were located in a range of 23.4°W ~ 15.5°E, the Apollo 17 was situated at 30.8°E. Thus, including the Apollo 17 gravimeter data in the analysis allow us to expand the network eastward.
In this study, analyzing three shallow moonquakes simultaneously recorded by both seismometers and a gravimeter, we were able to more accurately locate the shallow moonquake sources. Interestingly, one of which possibly originates from the highest latitude in the northern hemisphere. Since lunar seismicity in polar regions is little known, this finding will be a significant milestone towards further understanding the seismic/tectonic activities in lunar polar regions.
In the presentation, we will report the updated source locations of the analyzed shallow moonquakes and show initial results about the comparison between the source locations and the surface/subsurface geological features, particularly in the north polar region.