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Carboneras & SAF (Faulkner) (Carboneras Fault Zone Structures…
Carboneras
& SAF (Faulkner)
Carboneras Fault Zone Structures
Layering:
Fault gouge & fractured protolith
Linkage:
Anastamosing & branching strands
En echelon pattern of localised fault planes
in dolomite blocks
No linkage of larger features
Isolated fault planes
within dolomite blocks in fault zone
Width
: 1 - 1.5 km
Parkfield Geophysical
Layered
fault zone structure
Linkage
: Fault strands linked @ depth
En echelon pattern micro earthquakes in fault zone
Width: ~2 km
No linkage
between 4 larger equakes
Carboneras
Fault
Internal structure does not fit previous models s.s. faults
wider deformation zone
heterogeneous distribution of rock types & strain
Phyllosilicate rich fault gouge
produces distributed deformation
in well-defined layers
widening of
def zone
becomes
easier to deform previously undeformed host rock
vs fault rock
strain hardening behaviour
becomes harder to deform
why def zone wide?
Dolomite blocks
float’ in matrix of fault gouge
exhibit localized fault surfaces
(highly striated & polished )
differing mechanical response to fault gouge
strain weakening of more competent rock
becomes easier to deform than surrounding fault rock
Carboneras
Fault Zone
~1 km fault zone bounded on either side by fracture & damage zone
multiple strands of phyllosilicate-rich fault gouge
bounds lenses of variably fractured protolith
fractured 'damage zone' at margins of fault zone
Inferred Carboneras
def mechanism ?
Fault creep phyllosilicate-rich fault gouge
producing a mixed mode seismic signature,
--> as seen around Parkfield area.
Punctuated by larger events nucleating within dolomite blocks
analogue for fault structure at depth around Parkfield?
Parkfield geophysical obvs suggest
large deformation zone (1–2 km) w/fault creep & ~M6 recurrent earthquakes.
Creeping fault sections
produce lots of small earthquakes
localized fault surface patches -->
undergoing stick slip sliding
surrounded by
stable sliding
areas -->
that slowly feed displacements
En echelon arrangement
Parkfield: background seismicity for M6 nucleation zone
Carboneras: fault planes in dolomite blocks