The seismically active lobate scarps and co-seismic lunar boulder avalanches triggered by 3rd January 1975 (MW 4.1) shallow moonquake

The seismically active lobate scarps and co-seismic lunar boulder avalanches triggered by 3rd January 1975 (MW 4.1) shallow moonquake

Figure 1: LROC WAC image mosaic overlain by LOLA topography showing Lorentz basin wall and the superimposed and Laue crater. The lobate scarps are shown as white lines. Impact craters 1 and 2 exhibit boulder falls on their interior walls (yellow lines). The epicenter of 3rd January 1975 (MW 4.1) shallow moonquake has been relocated to the longest segment of the lobate scarps mapped in the study.

 

Like Earth, the Moon is also seismically active but with relatively lesser intensity. The seismometers installed by the Apollo missions detected 28 shallow moonquakes during 1969-1977. The moonquake that occurred at Laue crater on 3rd January 1975 is the largest recorded moonquake (MW 4.1). The fault responsible for the moonquake and origins of co-seismic boulder avalanches are unknown. Our analysis of high-resolution satellite images and topographic data obtained by NASA’s Lunar Reconnaissance Orbiter mission aided in the discovery of a set of young lobate scarps near the epicenter and its genetic link to the 1975 moonquake (Figure 1). The moonquake also generated strong ground motion around the epicenter and triggered formation of co-seismic boulder avalanches on the interior walls of near-by impact craters (Figure 1). We also found that boulder avalanches were formed during an earlier episode of seismic activity at 1.6 Ma. Furthermore, we deduce that the lobate scarps at Laue crater were formed in response to the reactivation of the basin wall normal fault of Lorentz peak-ring basin. Our study indicates that the lobate scarps in Laue crater are seismically active and their seismic activity could be further studied during future landing missions.

Reference:

P. Senthil Kumar, Rupali Mohanty, K.J.P. Lakshmi, S.T.G. Raghukanth, A. Dhabu, R.P. Rajesekar, and Rajeev Menon (2019), The seismically active lobate scarps and co-seismic lunar boulder avalanches triggered by 3rd January 1975 (MW 4.1) shallow moonquake, Geophysical Research Letters, 46, 7972-7981, DOI: 10.1029/2019GL083580.