Possible evidence of paleomarsquakes from fallen boulder populations, Cerberus Fossae, Mars

摘要

In order to differentiate between boulder avalanche deposits triggered by temperature/climate controlled melting of ice or triggered by ground shaking produced by paleomarsquakes, spatial variation in boulder size populations has been measured from High Resolution Imaging Science Experiment (HiRISE) images along Cerberus Fossae, one of the youngest fracture/graben systems on the Martian surface. The boulders have fallen from less than ～500 m high fault-controlled cliffs and rolled and bounced across relatively coarse-grained sediment, forming colluvial fans. The boulders have left trails in the dust in some cases, coming to rest on relatively fine-grained Aeolian sediment. The boulder size distribution varies along the graben contrary to what would be expected if boulder falls had been liberated by temperature/climate controlled melting of ice. Boulder size and boulder trail data peak close to the center of the fault system, decreasing along strike. Furthermore, evidence for relatively recent surface faulting of colluvial slopes along the fault-controlled cliffs is confined to the area with anomalously large boulder/trail size data. We interpret the above as consistent with observations of terrestrial earthquake-triggered boulder avalanches where boulder sizes decrease away from the epicenter and surface faulting. We discuss the implications of possible marsquakes along Cerberus Fossae in terms of active faulting associated with dike emplacement that is subradial to the Elysium Mons volcano.