P062-06
Cross-Correlation of LO and LRO Images suggests an Upper Limit of Lunar Wrinkle Ridge Co-Seismic Displacement Velocities
Cross-Correlation of LO and LRO Images suggests an Upper Limit of Lunar Wrinkle Ridge Co-Seismic Displacement Velocities
Monday, 14 December 2020: 20:50
Virtual
Abstract:
Recent work found evidence that the nearside maria of the Moon have been tectonically active in the recent past or are still active today. The potential activity of so called wrinkle ridge systems is expressed by extensive boulder fields, the absence of superposed craters, and other features.
Currently, we do not know if these features form sporadically - in direct response to excessive tectonic stress and fault movements underneath the surface - or continuously over time. We also do not know how often or quickly displacements of the lunar surface occur – and if displacements still occur today.
Addressing this issue, we cross-correlate Lunar Orbiter V (1960s) and Lunar Reconnaissance Orbiter (2000s and 2010s) images – practically the longest possible temporal baseline - over sites with presumably active wrinkle ridges in the Marius Hills (14.45°N 56.48°W, LO-LRO), Sulpicius Gallus (21.6°N 11.36°E, LRO-LRO), and Flamsteed (3.63°S 48.71°W, LRO-LRO) regions to study and measure displacement types and velocities. Analysis has been limited to these three regions due to the limited availability of LO and LRO image pair data with sufficient quality, appropriate lighting conditions, viewing geometry, and spatial resolution.
Using temporal baselines of between 3 and 45 years as well as images with spatial resolutions of 1 to 2.1 m/pixel, we are currently not able to observe any physical displacement of the lunar surface along or across the wrinkle ridges in these regions.
Our current observations suggest that displacement along wrinkle ridges in the Marius Hills, Sulpicius Gallus, and Flamsteed regions is either 1) instantaneous, but inactive since 45, 5.5, or 3 (or more) years respectively, or 2) continuous, but with average displacement velocities < 2.8 cm/a, < 21.81 cm/a, or < 141.86 cm/a on average, i.e., below the detection sensitivity of the applied digital image correlation method for the available data. Manual inspection of ‘before’ and ‘after’ imagery in these regions does not reveal any signs of change or activity, such as new boulder fields, fractures, graben, or rockfalls, which does not unambiguously support any of the two hypotheses, however.
The applied cross-correlation code is called DIC_FFT and is freely accessible here: https://github.com/bickelmps/DIC_FFT_ETHZ
Currently, we do not know if these features form sporadically - in direct response to excessive tectonic stress and fault movements underneath the surface - or continuously over time. We also do not know how often or quickly displacements of the lunar surface occur – and if displacements still occur today.
Addressing this issue, we cross-correlate Lunar Orbiter V (1960s) and Lunar Reconnaissance Orbiter (2000s and 2010s) images – practically the longest possible temporal baseline - over sites with presumably active wrinkle ridges in the Marius Hills (14.45°N 56.48°W, LO-LRO), Sulpicius Gallus (21.6°N 11.36°E, LRO-LRO), and Flamsteed (3.63°S 48.71°W, LRO-LRO) regions to study and measure displacement types and velocities. Analysis has been limited to these three regions due to the limited availability of LO and LRO image pair data with sufficient quality, appropriate lighting conditions, viewing geometry, and spatial resolution.
Using temporal baselines of between 3 and 45 years as well as images with spatial resolutions of 1 to 2.1 m/pixel, we are currently not able to observe any physical displacement of the lunar surface along or across the wrinkle ridges in these regions.
Our current observations suggest that displacement along wrinkle ridges in the Marius Hills, Sulpicius Gallus, and Flamsteed regions is either 1) instantaneous, but inactive since 45, 5.5, or 3 (or more) years respectively, or 2) continuous, but with average displacement velocities < 2.8 cm/a, < 21.81 cm/a, or < 141.86 cm/a on average, i.e., below the detection sensitivity of the applied digital image correlation method for the available data. Manual inspection of ‘before’ and ‘after’ imagery in these regions does not reveal any signs of change or activity, such as new boulder fields, fractures, graben, or rockfalls, which does not unambiguously support any of the two hypotheses, however.
The applied cross-correlation code is called DIC_FFT and is freely accessible here: https://github.com/bickelmps/DIC_FFT_ETHZ