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TitleRheological separation of the megathrust seismogenic zone and Episodic Tremor and Slip
AuthorGao, X; Wang, K
SourceNature (London) vol. 543, (2017), 2017.,
Alt SeriesEarth Sciences Sector, Contribution Series 20160265
PublisherNature Publishing Group
Mediapaper; on-line; digital
File formatpdf
Lat/Long WENS 132.0000 136.0000 34.0000 32.0000
Subjectsgeophysics; structural geology; seismicity; faults, thrust; subduction zones; subduction; downgoing slab; faults, strike-slip; seismic zones; rheology; Mohorovicic discontinuity; mantle
Illustrationslocation maps; cross-sections, structural; graphs; formulae; tables
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractEpisodic Tremor and accompanying slow Slip, together called ETS, is most abundantly observed in subduction zones of young and warm subducting slabs. ETS holds keys to understanding the mechanics of subduction megathrusts, but its mechanism is still poorly understood. It is commonly assumed that ETS represents a transition from seismic to aseismic behaviour of the megathrust with increasing depth, but the assumption is in contradiction with an observed spatial separation between the seismogenic zone and ETS zone. Here we propose a unifying model for the necessary geological condition of ETS which explains the relationship between the two zones. By developing numerical thermal models, we examine the governing role of thermo-petrologically controlled fault zone rheology. High temperatures in the warm-slab environment cause the megathrust seismogenic zone to terminate at a depth much shallower than the mantle wedge corner. High pore-fluid pressures around the mantle wedge corner give rise to an isolated friction zone responsible for ETS. Separating the two zones is a segment of semi-frictional or viscous behaviour. The new model reconciles a wide range of seemingly disparate observations and defines a conceptual framework for the study of slip behaviour and seismogenesis of major faults.
Summary(Plain Language Summary, not published)
Episodic Tremor and Slip (ETS), discovered by NRCan Pacific Geoscience Centre scientists at the turn of the century, is one of the most celebrated discoveries in Earth science over the past six decades. Yet its physical mechanism is still poorly understood. Of practical importance is the relation between the zone of ETS and the megathrust seismogenic zone. In this work, we propose a conceptual model based on thermal and rheological modeling that explains the observed spatial separation between the two zones. The model also puts a wide range of seemingly disparate observations of ETS in a coherent and simple tectonic framework.