Crust mantle modelling
The so called Moho ( Mohorovičić discontinuity - the crust/ mantle structural interface) is imaged by few geophysical methods. Subterrane uses a gravity derived method in order to define the structure across the Earth. The boundary in theory informs us of structure above the Moho (crust) and something about the structure below it (top mantle). The Moho is also considered to have a thermal memory. In terms of gravity it defines the compositional transition from crustal material to more dense mantle material. The Moho can reach elevations as shallow as approximately 5 km in oceanic crustal realms, whereas in continental realms the interface can reach depths exceeding 65 km beneath sea level. Presented here is a video exploring the Moho and its relation to the major known subduction zones of the world, and associated volcanism, where the subduction zone has successfully evolved over geological time.
Subduction zones commonly are accompanied by an outer arc trench that defines the location of the subducting, underlying plate disappearing underneath the overlying crustal plate. Associated volcanism may occur forearc or backarc of a magmatic arc that usually forms. Magmatism is associated with elevated Moho, and it is possible to identify the various magmatic arcs formed at the subduction zone from the Moho structure. Dependent on the slab geometries and regional stress field, the subducting crust may evolve over a long period of geological time. Consequently there may be accompanying movement of the trench strike and associated arc volcanism, such as is hypothesized for the geological exposure of the Nicaraguan volcanic front comprising part of the Central American subduction zone.
In this low resolution video, it is possible to identify the trench zone as a local depression in the Moho elevation, and the associated (arc) magmatism which appears as prominent or mid-range narrow strike parallel structural highs.
Most of the Earth's seismicity lies along plate boundaries, and this also applies to convergent, destructive subduction margins. Subterrane is researching seismicity to explore why some assumed subduction zones appear aseismic, but regionally are related to significant phases of intraplate seismicity that produces pulses of pervasive seismicity, together with some high magnitude devastating events that shift over the course of time at a decades scale.
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