Fault-population statistics at the Valles Marineris Extensional Province, Mars: implications for segment linkage, crustal strains, and its geodynamical development

The length distribution of normal faults and grabens in the Valles Marineri s region of Mars reveals the importance of fault linkage on fault-length da ta sets. Fault-length data for the normal-fault segments produce a continuo usly curving distribution on a cumulative-length vs. frequency plot, assumi ng that the faults all slip independently, with an approximate slope of -2 for lengths 30 < L < 200 km. When the Martian fault lengths are modified to account for their interaction and linkage, a more shallowly sloping (appro ximately -1) distribution is produced for fault lengths 30 < L < 300 km, re flecting the greater importance of large linked faults in accommodating the regional strains. Incremental-frequency and R-plots of fault lengths demon strate variations in fault density with linkage and the importance of consi dering grabens as single structures. Unlike some terrestrial earthquake dat a, the Martian fault population does not reveal persuasive evidence for a s mall-to-large fault transition associated with lithospheric thickness or rh eology, or with long-term strain. However, the decoupling of maximum fault displacement and length over the full range of the data is consistent with the dependence of displacement-size scaling on fault segment aspect ratio, rather than on the total fault length. The important inverse dependence of population power-law exponent and natural inhomogeneous fault strain, obtai ned previously from terrestrial fault sets and fault-growth simulations, is supported by using this Martian fault array. (C) 2000 Elsevier Science B.V . All rights reserved.