HR: 0800h
AN: S41B-0997    [Abstracts]
TI: Seismic Energy Partitioning Inferred from Pseudotachylyte-bearing Faults (Gole Larghe Fault, Adamello batholith, Italy)
AU: Pittarello, L
EM: lidia.pittarello@unipd.it
AF: Uiversita' di Padova Dipartimento di Geologia, Paleontologia e Geofisica, Via Giotto 1 , Padova, 35137 Italy
AU: * Di Toro, G
EM: giulio.ditoro@unipd.it
AF: Uiversita' di Padova Dipartimento di Geologia, Paleontologia e Geofisica, Via Giotto 1 , Padova, 35137 Italy
AU: Bizzarri, A
EM: bizzarri@bo.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via Donato Creti, 12, Bologna, 40128 Italy
AU: Hadizadeh, J
EM: hadizadeh@louisville.edu
AF: University of Lousville Department of Geography & Geosciences, 212 Lutz Hall, Louisville, KY 40292 United States
AU: Pennacchioni, G
EM: giorgio.pennacchioni@unipd.it
AF: Uiversita' di Padova Dipartimento di Geologia, Paleontologia e Geofisica, Via Giotto 1 , Padova, 35137 Italy
AB: Fracture energy E_g (the energy used for expanding a rupture surface area) is the fraction of work during seismic faulting that is required for creation of (1) New surfaces in the slip zone, and (2) Damage zone in the wall rocks. Partitioning of the earthquake energy between E_g and frictional heat E_h, determines the features of the rupture propagation and the mechanical behavior of the fault. The cataclastic microstructures associated with pseudotachylyte (solidified clast-laden friction-induced melt produced during coseismic slip) veins might contain information about the partitioning. In this preliminary study we used microstructural observations on pseudotachylytes from the Gole Larghe Fault zone (Southern Alps, Italy) to determine both E_h and E_g. The E_h for unit fault surface area A is estimated from pseudotachylyte vein thickness t. The energy required to produce friction melt is E_h/ A= [(1-Φ) H+ c_p ( T_i- T_hr)]ρt where Φ is the volume ratio of lithic clasts within the pseudotachylyte, H is the latent heat of fusion, c_p is the specific heat at constant pressure, ( T_i- T_hr) is the difference between initial melt temperature and host rock temperature and ρ is the density. The E_g is estimated by multiplying the newly created grain surface per unit of fault area A by the specific surface energy (J m^-2). In fact the studied pseudotachylyte vein contains plagioclase clasts displaying a characteristic internal fragmentation not observed in the host rock. This indicates a direct association between newly created grain surfaces and the seismic rupture process via pseudotachylyte production. It follows that pseudotachylytes might yield information on the energy partitioning between E_g and E_h.
DE: 5112 Microstructure
DE: 7209 Earthquake dynamics (1242)
DE: 8000 STRUCTURAL GEOLOGY
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8010 Fractures and faults
SC: Seismology [S]
MN: Fall Meeting 2005