5:15 PM - 7:15 PM
[SCG61-P14] Relationship between Slab Configuration, Slab Age, and Plate Motion
Keywords:Subduction dynamics, Slab geometry, Plate motion
Slab configuration (dip, curvature), slab age, and plate motion (convergence velocity and absolute plate velocity) are fundamental parameters in plate tectonics. However, the relationships between them can differ from studies. For example, Uyeda & Kanamori (1976) argued that younger slab ages are associated with lower dip angles from the observation of representative subduction zones. On the other hand, Jarrard (1986) and Lallemand et al. (2005) argued that such a relationship is not statistically significant based on comprehensive analyses of worldwide subduction zones. The reason for this disagreement is likely to be attributed to the difference in the selection of subduction zones and the data set they used. In this study, we reconsider the relationship between subduction zone parameters such as slab configuration, slab age, and plate motion.
For subduction zones with relatively uniform topography and gravity anomalies along their strikes, we investigate the relationship between the parameters. We use a model of Slab2.0 (Hayes et al., 2018) for slab configuration. Following Lallemand et al. (2005), the parameters of slab dip and curvature calculated from Salb2.0 are obtained for shallower and deeper parts than 125 km, respectively. For the parameters of plate motion, we use the slab age at the trench axis (Seton et al., 2020), convergence velocity (NUVEL1A; DeMets et al., 1994), and upper plate absolute velocity (MORVEL; DeMets et al., 2010). Through the investigation of the relationships between these parameters, we found some interesting relationships.
With respect to slab curvature, the shallow curvature exceeds the deep curvature in almost all subduction zones. This means that once a slab is bent at the shallow part, it tends to return to its original straight geometry. The weak correlation between shallow and deep curvatures was also shown. In other words, the returning of geometry is almost independent of the degree of curvature at the shallow part. These results suggest that oceanic plates keep a considerable degree of elasticity after subduction into the mantle.
A very strong negative correlation was found between the slab age and the upper plate absolute velocity. Here, the upper plate absolute velocity is positive in the direction from the arc to the seaward. It has been believed that when an older slab with a large negative buoyancy is subducted, it is accompanied by slab rollback and the upper plate follows the retreat of the trench axis (e.g., Schellert et al., 2023). However, the above relationship is at contrary to this slab rollback model.
Regarding slab age and shallow dip, the two were found to be weakly correlated for slabs younger than 80 Ma. This relationship is also valid even if we extract from the Lallemand et al. (2005) data set the segment closest to the subduction zone that we analyze. This suggests that the positive relationship found between slab age and shallow dip is valid for subduction zones with distinct two-dimensional features, but not necessarily for short-range subduction zones.
For subduction zones with relatively uniform topography and gravity anomalies along their strikes, we investigate the relationship between the parameters. We use a model of Slab2.0 (Hayes et al., 2018) for slab configuration. Following Lallemand et al. (2005), the parameters of slab dip and curvature calculated from Salb2.0 are obtained for shallower and deeper parts than 125 km, respectively. For the parameters of plate motion, we use the slab age at the trench axis (Seton et al., 2020), convergence velocity (NUVEL1A; DeMets et al., 1994), and upper plate absolute velocity (MORVEL; DeMets et al., 2010). Through the investigation of the relationships between these parameters, we found some interesting relationships.
With respect to slab curvature, the shallow curvature exceeds the deep curvature in almost all subduction zones. This means that once a slab is bent at the shallow part, it tends to return to its original straight geometry. The weak correlation between shallow and deep curvatures was also shown. In other words, the returning of geometry is almost independent of the degree of curvature at the shallow part. These results suggest that oceanic plates keep a considerable degree of elasticity after subduction into the mantle.
A very strong negative correlation was found between the slab age and the upper plate absolute velocity. Here, the upper plate absolute velocity is positive in the direction from the arc to the seaward. It has been believed that when an older slab with a large negative buoyancy is subducted, it is accompanied by slab rollback and the upper plate follows the retreat of the trench axis (e.g., Schellert et al., 2023). However, the above relationship is at contrary to this slab rollback model.
Regarding slab age and shallow dip, the two were found to be weakly correlated for slabs younger than 80 Ma. This relationship is also valid even if we extract from the Lallemand et al. (2005) data set the segment closest to the subduction zone that we analyze. This suggests that the positive relationship found between slab age and shallow dip is valid for subduction zones with distinct two-dimensional features, but not necessarily for short-range subduction zones.