An integrated global model of present-day plate motions and plate boundary deformation

Abstract

SUMMARY In this paper we present a global model (GSRM‐1) of both horizontal velocities on the Earth's surface and horizontal strain rates for almost all deforming plate boundary zones. A model strain rate field is obtained jointly with a global velocity field in the process of solving for a global velocity gradient tensor field. In our model we perform a least‐squares fit between model velocities and observed geodetic velocities, as well as between model strain rates and observed geological strain rates. Model velocities and strain rates are interpolated over a spherical Earth using bi‐cubic Bessel splines. We include 3000 geodetic velocities from 50 different, mostly published, studies. Geological strain rates are obtained for central Asia only and they are inferred from Quaternary fault slip rates. For all areas where no geological information is included a priori constraints are placed on the style and direction (but not magnitude) of the model strain rate field. These constraints are taken from a seismic strain rate field inferred from (normalized) focal mechanisms of shallow earthquakes. We present a global solution of the second invariant of the model strain rate field as well as strain rate solutions for a few selected plate boundary zones. Generally, the strain rate tensor field is consistent with geological and seismological data. With the assumption of plate rigidity for all areas other than the plate boundary zones we also present relative angular velocities for most plate pairs. We find that in general there is a good agreement between the present‐day plate motions we obtain and long‐term plate motions, but a few significant differences exist. The rotation rates for the Indian, Arabian and Nubian plates relative to Eurasia are 30, 13 and 50 per cent slower than the NUVEL‐1A estimate, respectively, and the rotation rate for the Nazca Plate relative to South America is 17 per cent slower. On the other hand, Caribbean–North America motion is 76 per cent faster than the NUVEL‐1A estimate. While crustal blocks in the India–Eurasia collision zone move significantly and self‐consistently with respect to bounding plates, only a very small motion is predicted between the Nubian and Somalian plates. By integrating plate boundary zone deformation with the traditional modelling of angular velocities of rigid plates we have obtained a model that has already been proven valuable in, for instance, redefining a no‐net‐rotation model of surface motions and by confirming a global correlation between seismicity rates and tectonic moment rates along subduction zones and within zones of continental deformation.

The earthquake deformation cycle

“…Their latest model has is posted on a~25 km grid and uses~20,000 individual point velocities. This has improved greatly since their first model (Kreemer et al, 2003), which was constrained by only~4000 velocities; data coverage will continue to improve in coming years as the community makes new and improved measurements. However, there are large gaps in the coverage in many tectonic areas, particularly in developing countries, which are not able to afford the installation and maintenance costs of dense permanent GNSS networks.…”

“…Figure 4: Cumulative histogram comparing the 1.2 million fatalities in onshore earthquakes (USGS, 1900(USGS, -2010 to geodetic strain rates from the Global Strain Rate Model (Kreemer et al, 2003). 96% of fatalities in earthquakes occur in areas straining at rates higher than 10 -8 per year; 77% of fatalities occur in areas straining at rates of less than 5 x 10 -8 per year.…”

Joint modeling of lithosphere and mantle dynamics elucidating lithosphere‐mantle coupling

“…[10] We test our modeled deviatoric stresses quantitatively with strain indicators from the GSRM [Kreemer et al, 2003]. GSRM is a high resolution model based on 5170 GPS stations and Quarternary fault slip data, confined along the deforming plate boundary zones.…”

“…If the initial plate-mantle coupling model is correct, then the predicted velocities will match the observed plate motions and the modeled stress field will match the stress observations. Here, we investigate the problem of lithosphere-mantle coupling by modeling the lithospheric stress field and comparing our results with strain rate tensor observations from the Global Strain Rate Map (GSRM) [Kreemer et al, 2003].…”

Crustal deformation induced by mantle dynamics: insights from models of gravitational lithosphere removal

“…Such events contrast with the traditional view of rigid tectonic plate, where deformation is limited to plate boundaries (e.g. Kreemer et al 2003). Two main causes have been proposed to explain intraplate deformation: (1) stresses transmitted laterally from plate boundaries that localize in weak intraplate regions (e.g.…”