Is the Tibetan Plateau Rising?

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The Tibetan Plateau is the largest area of high topography on the planet. Is the Tibetan Plateau rising higher today? Is it growing taller due to ongoing contraction as India continues to collide with Eurasia? Is it collapsing due to extension driven by its excess gravitational potential energy? Is it roughly in balance, no longer growing higher, but simply changing shape? Are parts of the plateau presently evolving in different ways? This project, a joint effort between researchers at the University of Alaska and several Chinese research institutions, aims to address these questions. Global Positioning System (GPS) measurements from the Tibetan Plateau and its surroundings are dense enough and precise enough to make meaningful measurements of vertical motions in Tibet and the rest of the India-Eurasia collision zone. Using several years of GPS data and careful attention to detail in the data analysis, a realistic vertical measurement precision of approximately 1 millimeter per year can be attained even with campaign surveys. Hundreds of campaign GPS sites in China and the rest of the India-Eurasia collision zone now have enough data to provide robust estimates of vertical velocities. These data will be completely reanalyzed the using the next generation of models and orbits, and models to explain the observed rates and spatial variation will be developed. Accuracy will be assessed using vertical rates over a wide area, including regions of no expected deformation, and by comparing estimated GPS vertical motions with complementary data from repeated leveling and InSAR. The relationship of instantaneous vertical rates to long-term geologic uplift or subsidence rates requires more investigation, and this study will be first to focus on systematic regional measurement and modeling of vertical motions in a region of spectacular active tectonics. Improved understanding of crustal deformation will lead to a better understanding of earthquake hazards in China, a heavily populated region prone to earthquakes. Although this project focuses on vertical motions, we a more precise estimate of horizontal motions will also obtained, and the modeling of elastic deformation using both vertical and horizontal motions may produce significant new understanding of some of the tectonically active regions in China. The occurrence in May 2008 of the devastating Wenchuan earthquake, in a region of slow convergence yet extremely steep topography, drives home the need to better understand deformation processes in China. This study will make GPS time series and velocities from China, which are not easily accessible to US investigators, available in a usable form.