Uncovering the relationship between subducting bathymetric ridges and volcanic chains with significant earthquakes using geophysical data mining

2015-10-08T14:01:17Z (GMT) by T. C. W. Landgrebe R. D. Müller
<div><p>The subduction of bathymetric asperities has been linked with the location and rupture characteristics of significant (moment magnitude > 5.0) thrust earthquakes in several regions, but a global analysis of these relationships is lacking. We carry out a global investigation of well-defined subducting bathymetric features including ridges, fracture zones and seamounts, and their spatial association with significant earthquakes. The NGDC global significant earthquake database has been filtered to include only those events occurring in the coupling zone between subducting and overriding plates, which includes the bulk of megathrust earthquakes. A statistical methodology is used to compare spatial associations between subducting linear asperities and significant earthquakes. Randomly sampled coupling zone locations are used to establish sensitivity/specificity relationships as a function of proximity, ruling out random effects and establishing meaningful spatial interpretations. In a previous study, we showed that there is a strong link between the largest earthquakes and proximity to fracture-zone subduction-zone intersections. Here, this analysis is extended using a game-formulation methodology, rigorously demonstrating that significant subduction-related earthquakes are more likely to be generated at, or very close to, the intersections between subduction zones and fracture zones, compared with arbitrary locations along subduction zones. A weaker, broader effect is exhibited by subducting volcanic ridges/seamount chains. Fracture zone associations are attributed to the large, localised, linear and mechanically strong bathymetric anomalies related to fracture zone ridges, leading to strong seismic coupling, whereas associations pertaining to volcanic ridges/seamount chains are explained by inherently broader, less elevated and poorly defined characteristics, combined with structural weaknesses that may reduce the long-term coupling effect.</p></div>