Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults.
Many areas of the Earth's crust deform by distributed extensional faulting and complex fault interactions are often observed. Geodetic data generally indicate a simpler picture of continuum deformation over decades but relating this behaviour to earthquake occurrence over centuries, given numerous potentially active faults, remains a global problem in hazard assessment. We address this challenge for an array of seismogenic faults in the central Italian Apennines, where crustal extension and devastating earthquakes occur in response to regional surface uplift. We constrain fault slip-rates since ~18 ka using variations in cosmogenic36Cl measured on bedrock scarps, mapped using LiDAR and ground penetrating radar, and compare these rates to those inferred from geodesy. The36Cl data reveal that individual faults typically accumulate meters of displacement relatively rapidly over several thousand years, separated by similar length time intervals when slip-rates are much lower, and activity shifts between faults across strike. Our rates agree with continuum deformation rates when averaged over long spatial or temporal scales (104yr; 102km) but over shorter timescales most of the deformation may be accommodated by <30% of the across-strike fault array. We attribute the shifts in activity to temporal variations in the mechanical work of faulting.
University of Bergen, Bergen, Norway.
P A
PA
Cowie
University of Leeds, Leeds, United Kingdom.
R J
RJ
Phillips
Birkbeck College, University of London, London, United Kingdom.
G P
GP
Roberts
University of Durham, United Kingdom.
K
K
McCaffrey
University of Bergen, Bergen, Norway.
L J J
LJ
Zijerveld
University of Leeds, Leeds, United Kingdom.
L C
LC
Gregory
University College London, London, United Kingdom.
J
J
Faure Walker
University of Leeds, Leeds, United Kingdom.|University College London, London, United Kingdom.
L N J
LN
Wedmore
University of Cologne, Cologne, Germany.|University of Edinburgh, UK.
T J
TJ
Dunai
University of Cologne, Cologne, Germany.
S A
SA
Binnie
Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom.
S P H T
SP
Freeman
Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom.|Australian Nuclear Science &Technology Organisation, Sydney, New South Wales, Australia.
K
K
Wilcken
Scottish Universities Environmental Research Centre, East Kilbride, United Kingdom.
R P
RP
Shanks
University of Bergen, Bergen, Norway.
R S
RS
Huismans
Agricultural University of Athens, Athens, Greece.
I
I
Papanikolaou
Università degli Studi dell'Insubria, Como, Italy.
A M
AM
Michetti
University of Durham, United Kingdom.
M
M
Wilkinson