Seminario
Leonardo Casini | DADU, Università degli Studi di Sassari

Tiny crystals tell a big story. Non double couple Carboniferous earthquakes Sardinia

   15 Dicembre 2022 dalle 15:00 alle 17:00 
   Complesso del Santa Chiara, Aula Juharia 1° piano 
   Codice e link Microsoft Teams: 02zv8lw,

https://teams.microsoft.com/l/channel/19%3ajyTJ4Xz7QQC0aR0s5dtP7QAR7kKUosXJ1RbXygSstVE1%40thread.tacv2/Generale?groupId=12f2ec8b-e964-4e51-b6c3-b30e7c60b233&tenantId=22a71226-3ad2-4e92-9bf8-d7d3540412b1

Caroniferous faults within migmatitic orthogneiss of N Sardinia (Pta Bianca, S Teresa di Gallura) preserve evidence of seismic deformation, such as associated ultra-mylonite and pseudotachylyte, that is, fine-grained fault rocks solidified from frictional melts. Small zircon and monazite grains collected from large pseudotachylyte veins constrain the seismic event between about 320 and 308 Ma in late Carboniferous time. The spatial arrangement of faults and the volume of pseudotachylyte veins correspond to an instantaneous nearly isotropic volume increment of about 4 to 7 vol. % during seismic slip. These observations argue for a dominant non-double couple (NDC) component during the earthquake, thus the Pta Bianca fault system can be used as a fossil source analog of seismically active regions characterized by aenigmatic NDC deformation.

Leonardo Casini è Professore Associato dell’Università di Sassari.