In a nutshell
- The model is based on the largest self-consistent set of secular velocities
- It is the best estimate of present-day plate motions and strain accumulation, being potentially released through earthquake events
- The model is a significant improvement over the v.1.2 that was produced in 2004
- The model includes estimates of uncertainty; while GPS velocity uncertainties are typically 0.1-0.3 mm/yr, the strain rate uncertainty at any point is largely dependent on the GPS station density.
Figure – Second invariant of the strain rate model v.2.1. Strain rates were not modeled in white areas, which were assumed to behave as rigid plates
- incorporates velocities for 6705 GPS stations worldwide, determined through this project
- incorporates 15710 additional velocities from 233 literature studies, including 1143 new velocities for China determined through this project
- consists of a grid with 50 rigid plates/blocks and ~145,086 deforming cells of 0.2º by 0.25º
- indicates robust areas of elevated strain rates where data coverage is strong
- seems to suggest a strong correlation between earthquake productivity rates and geodetic strain/moment rates - earthquake rate is however much lower than expected in fastest deforming areas
Who developed the model?
Corné Kreemer from the University of Nevada coordinated model development, data analysis and data gathering together with his team. Zheng-Kang Shen from UCLA contributed a new GPS velocity field for China. Francis Boler from UNAVCO leads the efforts on archiving and visualising model results and data input.
Figure 3.1 Locations for all 22,415 velocities used in the project. Blue are analyzed through this project by UCLA (for China) and UNR (rest of the world), red are from the literature
How is it of relevance?
Strain rate measures how fast the outer solid part of the earth (the lithosphere) is being deformed due to tectonic plate movement. At some places, the lithosphere is brittle enough to produce earthquakes by faulting, such as within a subducted oceanic plate. When earthquakes happen they release the accumulated crustal strain and therefore strain rate is a proxy for earthquake potential. Strain rate measurements can also be compared to the rate with which faults slip and with earthquake activity rates, to better understand seismicity in an area.
- Any offset and seasonal variation in GPS time-series is estimated in the velocity determination
- Parts of the time-series with transient behavior were excluded in the general analysis, but modeled for China
- Stations affected by hydrology or magmatism were excluded
- Results from the literature were filtered to exclude earthquake effects. Outliers are removed
- All results have been transformed into a single reference frame
The 2014 model
The new model contains 144,827 deforming cells, compared to 22,310 cells in the previous model.
Figure 4.1 Red areas comprise the deforming grid cells, each 0.2° (latitudinal) by 0.25° (longitudinal) in dimension
Geodetic coverage and Strain rate
GPS velocities in regional reference frame.
See more figures in the Global geodetic Strain Rate report (pp.38 - APPENDIX A).
GPS velocities in regional reference frame - Northern Italy
GPS velocities in regional reference frame -Greece
GPS velocities in regional reference frame - Taiwan
How can I get it?
The data will be featured in the OpenQuake platform, together with tools to explore strain rate and to combine it with other datasets.
In addition to that, the following files can be downloaded via your browser:
How can I contribute?
- If you possess data or know of studies that could enhance the dataset/model we are keen to hear from you
- We look forward to receiving your comments and feedback on the model
- If you have other ideas or questions, feel free to get in touch as well
Contact us through Corné Kreemer through firstname.lastname@example.org