"To discern spatial and explore the possible existence of temporal variations of upper crustal anisotropy along an ~15 km section of the San Jacinto Fault Zone (SJFZ) in California, and in the Fairview, Oklahoma, region, we conduct systematic shear wave splitting (SWS) investigations using local S-wave data recorded by seismic stations. Strong spatial variations in crustal anisotropy are revealed by 1694 and 405 pairs of splitting parameters (including the fast polarization orientation and the splitting time), respectively. For both areas, for raypaths traveling through the fault zones, the fast orientations are parallel to the faults and may be attributed to fluid-filled fractures in the fault zones. For non-fault-zone crossing raypaths, the fast orientations are consistent with the orientation of the regional maximum compressive stress (SHmax) and reflect the orientation of fluid-filled cracks. For the SJFZ, a three-dimensional model of upper crustal anisotropy is constructed based on observations. An apparent increase in the raypath length normalized splitting times is observed after the 03/11/2013 magnitude 4.7 earthquake, which is attributed to changes in the spatial distribution of earthquakes before and after the M4.7 earthquake rather than reflecting temporal changes of upper crustal anisotropy. For the Fairview region, the temporal variations in the raypath normalized delay time may suggest sequences of crack opening under increased pore pressure caused by wastewater injection and crack healing. In addition, possible precursory stress relaxation was revealed using the SWS measurements before a magnitude 5.1 earthquake occurred on 2/13/2016 in the Fairview region"--Abstract, page iv.
Liu, Kelly H.
Gao, Stephen S.
Geosciences and Geological and Petroleum Engineering
Ph. D. in Geology and Geophysics
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Spatial variations of upper crustal anisotropy along the San Jacinto fault zone in Southern California: Constraints from shear wave splitting analysis
- Fracture and regional stress-related upper crustal azimuthal anisotropy in the vicinity of the 2016 M5.1 Fairview, Oklahoma, earthquake
x, 60 pages
Southern California; Central Oklahoma
© 2021 Enyuan Jiang, All rights reserved.
Dissertation - Open Access
Jiang, Enyuan, "Spatiotemporal variations of upper crustal anisotropy along the San Jacinto Fault Zone in Southern California and the Fairview region in Central Oklahoma" (2021). Doctoral Dissertations. 2974.