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- Title
Using InSight Data to Calibrate Seismicity From Remote Observations of Surface Faulting.
- Authors
Sabbeth, L.; Smrekar, S. E.; Stock, J. M.
- Abstract
We use a scaling relationship between fault length and scalar moment to predict seismicity from the Cerberus Fossae graben using shear modulus and fault lengths. Cerberus Fossae is 20–40° (1,200–2,300 km) from the InSight lander and matches the location of 21 recorded seismic events with Mw ≥ 3. These unique seismic observations make an ideal laboratory to test our method of predicting seismicity on another planet using surface fault observations. Terrestrial faults have observed patterns of rupture depth distributions and segmentation. We use these patterns and magnitudes of detected marsquakes to predict moment release of events in Cerberus Fossae over a range of plausible Martian rupture vertical slip extents (VSEs) of 2, 20, and 40 km, which are rooted in estimates of crustal thickness, elastic thickness, and seismicity depth. We sum individual events for each case to determine cumulative moment release and use deformation duration to determine annual moment release. Predicted seismicity rates are dependent on the duration of deformation, which in this case is well constrained to 2–10 Ma. We compare our results to events recorded at Cerberus Fossae by InSight and find that seismicity rates for the cases with a 40 km maximum VSE or no limit on VSE are within an order of magnitude of observed seismicity. Faults with maximum VSEs of 2 km best match observed magnitudes. Our approach, using only observed fault lengths, segmentation, seismogenic thickness estimates, and deformation duration, produces seismicity estimates that are as accurate as methods that take rupture offset into account. Plain Language Summary: We develop a method to estimate the magnitudes and frequencies of quakes on Mars in the Cerberus Fossae region using a scaling relationship between fault length and quake magnitude. Our method estimates quake magnitude for each fault length, and ultimately estimates cumulative seismic moment release, or total energy released by the formation of the geologic structure. We calculate seismicity rate by dividing the cumulative moment release by the time of deformation for the geological structure. Our method to estimate seismicity requires fewer assumptions and assumed geophysical constants than previously proposed methods. We use Leonard's (2010, https://doi.org/10.1785/0120090189) aspect ratio of fault length and width. Thus, a maximum faulting depth informs the maximum vertical slip extent (VSE), which in turn limits the maximum fault length and the maximum allowable quake magnitude. Segmentation patterns of the faults inform the magnitude‐frequency distribution of marsquakes but do not account for a high enough occurrence of small quakes. Resulting seismicity rates are within an order of magnitude of what has been measured by the InSight seismometer with a VSE of 40 km or no VSE, and marsquake magnitudes are best represented by a VSE of 2 km. Key Points: We estimate seismicity using a fault length‐moment release scaling relationship. Our results align with InSight seismometer observationsMarsquake magnitudes are limited by vertical slip extents, which are constrained by likely faulting depthsMarsquake magnitude distribution is constrained by segmentation patterns of the graben. Seismicity rate is constrained by deformation time
- Subjects
MODULUS of rigidity; GEOLOGICAL formations; GEOLOGICAL time scales; PLANETARY surfaces; SEISMOMETERS; FAULT zones; SURFACE fault ruptures
- Publication
Journal of Geophysical Research. Planets, 2023, Vol 128, Issue 6, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2022JE007686