Subduction Zone

 

<<Back

In plate tectonics, a subduction zone is the region where one plate (the slab) moves under another (the upper plate) and sinks into the mantle beneath it. This process results in a convergent movement of the two involved plates which is known to generate earthquake ruptures of different types. These ruptures are classified according to the part of the subduction zone where they occur. Therefore, subduction zones can generate interface earthquake ruptures at the contact of the two plates; intra-slab and outer-rise earthquake ruptures within the slab; and megasplay ruptures which are those that propagate from the slab interface into the upper plate (Satake and Tanioka, 1999). All these ruptures differ from crustal seismogenic faulting as they tend to follow different earthquake scaling laws (Strasser et al., 2010) and rheology (Bilek and Lay, 1999).

In the DISS, the subduction zone layer has been designed to include a simplified model of this complex tectonic environment. It represents the dipping slab at mantle depth, the interface between the two plates at crustal depth, and also the detachment at the base of the accretionary wedge. In map view, a set of depth contour lines depicts the geometry of the subducted slab. At the upper end of the slab, a fault trace marks the boundary of the two plates, generally coinciding with the so-called trench located at the outer edge of the accretionary wedge. Also traces of active faults and axes of active folds (usually structural features with documented Late Pleistocene - Holocene activity) can be shown to illustrate deformation features within the accretionary wedge.

SubductionScheme
The subduction zone structure is essentially inferred from studies of regional surface and subsurface data, including interpreted seismic profiles, gravity and tomography data, receiver function analysis and earthquake focal mechanisms. The information included in this layer is thus based on geological and geophysical data that characterizes the subduction zone in terms of geometry (depth, dip direction) and behavior (convergence azimuth and rate) parameters. Minimum and maximum values of each parameter are provided to capture their range of variability. Among the behavior parameters we also provide an estimate of the maximum magnitude as resulting from the largest historical earthquake or the largest identified fault segment comprised within the subduction zone; as such, this estimate does not represent the largest potential earthquake of the subduction zone.

As recalled above, several types of earthquakes can be generated in the subduction zone; however, the largest earthquakes are commonly expected to occur at the slab interface. We thus identify the main seismogenic source with the slab interface and provide its extent in terms of its minimum and maximum depth limits. Subduction zones are not assumed to be capable of a specific-size earthquake or specific recurrence behavior, but their seismic potential can be assessed in various ways, including estimates from their tectonic or geodetic moment rate or from the analysis of earthquake catalogs.

Similarly to the other categories of DISS sources, each Subduction Zone is identified by the code CCSD###, where:
CC is the two-letter ISO 3166-1 code for names of officially recognized countries;
SD identifies specifically the Subduction Zone;
### is an ordinal between 1 and 999 (including leading zeroes).

 

References

  • Bilek, S. L., and T. Lay (1999). Rigidity variations with depth along interplate megathrust faults in subduction zones. Nature, 400, 6743, 443-446, 10.1038/22739.
  • Satake, K., and Y. Tanioka (1999). Sources of Tsunami and Tsunamigenic Earthquakes in Subduction Zones. Pure Appl. Geophys., 154, 3, 467-483, 10.1007/s000240050240.
  • Strasser, F. O., M. C. Arango, and J. J. Bommer (2010). Scaling of the Source Dimensions of Interface and Intraslab Subduction-zone Earthquakes with Moment Magnitude. Seismol. Res. Lett., 81, 6, 941-950, 10.1785/gssrl.81.6.941.

 



Cookies help us deliver our services. By using our services, you agree to our use of cookies.
I cokies ci aiutano a offrire un servizio migliore. Utilizzando questo sito web voi acconsentite all’uso dei nostri cookies.