Improving Regional Earthquake Focal Depth Location in Oklahoma Using 3D Velocity Model
Session: Network Seismology: Keeping the Network Running While Integrating New Technologies [Poster]
Type: Poster
Date: 4/22/2021
Presentation Time: 11:30 AM Pacific
Description:
Earthquake activity in Oklahoma occurs in multiple geologic provinces characterized by dipping formations and stratigraphic layers of varying thickness. The earthquakes in the region have traditionally been located using a 1D velocity model applied to both the regional seismic network and local arrays. The regional 1D velocity model, that has the top of the relatively higher velocity Precambrian basement at 1.5 km depth, provides high precision earthquake epicentral locations with relatively higher focal depth uncertainties especially within the Anadarko basin, in western Oklahoma, where the top of basement deepens up to 10 km. Within the Anadarko basin, an upward focal depth shift of 3km can place numerous current earthquake depths into the sedimentary layers thereby significantly altering the interpretation of the earthquakes’ source analysis. We address the depth uncertainty by relocating the earthquakes using a 3D velocity model that reflects the varying stratigraphy of the region. The velocity model layering corresponds to the geologic deposition and the velocity of the structures atop the basement is constrained using sonic logs from wells near the 2010 Mw4.1 Lincoln County earthquake sequence. We[WJI1] apply the 3D velocity as the initial model in a local double‐difference tomography inversion. We use the tomoDD inversion method to simultaneously solve both absolute and differential travel times in order to improve both the earthquake locations and the 3D velocity heterogeneity. We will be presenting the results of the focal depth changes and the resulting final velocity model. We intend to further test and evaluate whether the final 3D velocity model would be suitable for routine regional earthquake locations for ANSS catalog products.
Presenting Author: Paul O. Ogwari
Student Presenter: No
Authors
Paul Ogwari Presenting Author Corresponding Author pogwari@ou.edu Oklahoma Geological Survey |
Jacob Walter jwalter@ou.edu Oklahoma Geological Survey |
Andrew Thiel athiel@ou.edu Oklahoma Geological Survey |
Fernando Ferrer fernando.ferrer@ou.edu Oklahoma Geological Survey |
Isaac Woelfel iewoelfel@ou.edu Oklahoma Geological Survey |
Xiaowei Chen xiaowei.chen@ou.edu University of Oklahoma |
Guoqing Lin glin@rsmas.miami.edu University of Miami |
|
|
Improving Regional Earthquake Focal Depth Location in Oklahoma Using 3D Velocity Model
Category
Network Seismology: Keeping the Network Running While Integrating New Technologies