资源环境科技发展态势分析平台

Intermediate-depth earthquakes (focal depths 70-300km) are enigmatic with respect to their nucleation and rupture mechanism and the properties controlling their spatial distribution. Several recent studies have shown a link between intermediate-depth earthquakes and the thermal-petrological path of subducting slabs in relation to the stability field of hydrous minerals. Here we investigate whether the structural characteristics of incoming plates can be correlated with the intermediate-depth seismicity rate. We quantify the structural characteristics of 17 incoming plates by estimating the maximum fault throw of bending-related faults. Maximum fault throw exhibits a statistically significant correlation with the seismicity rate. We suggest that the correlation between fault throw and intermediate-depth seismicity rate indicates the role of hydration of the incoming plate, with larger faults reflecting increased damage, greater fluid circulation, and thus more extensive slab hydration.

Plain Language Summary In subduction zones, one tectonic plate plunges beneath another into the Earth's interior. Some of the earthquakes that occur at subduction zones are unusual due to their occurrence at depths of 70 to 300 km (intermediate depths), deeper than the expected limit of brittle failure. In this study, we evaluate whether the faults that form when a plate bends as it enters a subduction zone can explain the occurrence of these deep earthquakes. Sea water penetrates deep into these faults and forms new, hydrous minerals, but these new minerals are not stable deeper in the subduction zone. Laboratory experiments show that breakdown of these hydrous minerals can cause seismicity at depths of 70-300 km (intermediate depths). Here we examined a set of 17 subduction zone segments around the globe and found that the seismicity is correlated with the faults that formed due to plate bending. This observation can be explained if the amount of faulting prior to subduction controls the amount of hydrous mineral formation, which subsequently determines the intensity and rate of subduction zone-related intermediate-depth earthquakes.