Fault evolution and strain partitioning within deforming continents

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Diffuse deformation within continents and over broad plate boundary zones deviates from the prediction of plate tectonics theory. Some of the deforming continents are now well delineated by space geodetic measurements, but the cause of such diffuse deformation remains poorly understood. My Ph.D. research focuses on two regions: 1) Fault evolution and Strain partitioning in Southern California: High-precision GPS measurements have enabled kinematic modeling of the present-day strain partitioning between these faults, but the causes of such strain partitioning and fault evolution remain uncertain. Using a three-dimensional viscoelasto-plastic finite element model, I have explored how the plate boundary fault system evolves to accommodate the relative plate motion in Southern California. My results show that, when the plate boundary faults are not optimally orientated to accommodate the relative plate motion, new faults will be initiated. In particular, the Big Bend of the San Andreas Fault, which is the main plate boundary fault, impedes the relative plate motion, thus forces the development of a system of secondary faults. 2) Active strain rates of crustal deformation in mainland China: In the past decades Chinese scientists and international teams have measured GPS velocities at more than a thousand sites in mainland China, allowing calculation of detailed spatial distribution of the crustal strain rates. Using the latest GPS data, I have calculated strain rates in different tectonic provinces in China and compared them with neotectonic data. I have also calculated strain rates using earthquakes and geological fault slip rates. The differences of strain rates derived from different data sets show the time-scale dependence of strain rates. Comparing GPS strain rates with seismic moment release patterns illustrates the limitations of using earthquake catalog for earthquake hazard analysis.