Strain at radially fractured centers on Venus

Abstract

Radially fractured centers (RFCs) on Venus are distinctive, ∼100 km long radiating systems of graben, fissures, and fractures arranged around a central topographic high. We use cycle 1 and cycle 3 Magellan images to determine the depths and wall dip angles of several large radial graben, using two different methods, at four RFCs: Becuma Mons, Didilia Corona, H'uraru Corona, and Pavlova Corona. We record graben depths of 0.3-0.9 km and mean Wall dip angles of about 36°, which we interpret as a primary talus slope rather than a fault plane. Using the calculated depths and a more realistic fault dip of 60°, we find extension of between 0.5 and 1 km on graben between about 5 and 10 km wide. We use this extension, to estimate the hoop strain at each RFC. Maximum measured strains on the flanks are typically between ∼ and 4% and may be up to 7% toward the center. We conclude that this strain is too large to be explained by current plume-related uplift models and also by magma chamber inflation. We conclude that dikes are probably responsible for the majority of the strain at the large radial graben. Copyright 2005 by the American Geophysical Union.