Reactivation of mantle lithosphere scars: deep sutures inducing shallow intraplate earthquakes?

Ancient plate tectonic processes (e.g., continental collisions) can generate deformation deep into the lithosphere, highlighted by seismological imaging showing mantle lithosphere heterogeneities (thought to be scarring from past events). As the mantle lithosphere is the largest (and often strongest) component part of a tectonic plate, it has the potential to control tectonic deformation at the surface. A number of numerical modelling studies indicate the closure of ancient plate boundaries could generate latent deep structures that could be ‘perennially’ reactivated in intraplate settings - dominating shallow geological features in activating tectonics in plate interiors. This work has often been linked to large-scale tectonic processes such as continental rifting and orogenesis. However, in order to fully understand such ‘bottom-up’ influences on plate tectonic processes, it is important to analyse such mechanisms in more ‘actualistic’ models (e.g., finding evidence in present-day tectonics) rather than applying to ancient activity (e.g., to events millions of years ago).

Here, we analyse the present-day intraplate earthquake database for any scenarios where deep latent lithosphere structures could drive shallower seismic events. Case studies for intraplate earthquakes of Central China, North America, Scotland, and Africa are presented using a new visualisation software we’ve developed to handle large amounts of seismic events. A potential present-day example of this theoretical deep trigger of shallow earthquakes is examined in detail, with careful attention given to the inherent uncertainty of this work. Finally, we highlight the difficulty in understanding the rheology and composition of latent structures deep in the lithosphere, and whether they can be passive or active in present-day tectonics.