Chapter 3 Aseismic-Seismic Transition and Fluid Regime along Subduction Plate Boundaries and a Fossil Example from the Northern Apennines of Italy

摘要: This chapter reviews observations and theories for the aseismic-seismic transition in megathrust between incoming overriding plates at a subduction zone. The temperature of appears to be quite similar erosive accretionary margins, despite large differences them lithology seismogenic channel that composes “megathrust” plate interface. fact, recent laboratory demonstration both smectite illite are velocity-strengthening creep, suggests oft-postulated change mechanical behavior due smectite-illite clay mineral transformation ∼150°C is not cause onset seismogenesis these conditions within channel. Field from fossil zones suggest temperature-dependent availability situ fluid likely play key role seismogenesis. Perhaps causal link other metamorphic dewatering reactions liberate water ∼150°C, under where an important local source hydrous fluids. studies megathrusts support hypothesis fluids “control” seismogenesis, indicate there pressure variations during seismic cycle. In system preserved Apennines, two decollements simultaneously active roof base uppermost (nonseismogenic) portion even alternate tensional compressional modes failure cycle along deeper portions megathrust.