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Mapping Outerrise Normal (and other) Dip-slip Fault Parameters using Semi-automated and Newly Developed Python Toolbox

Description: 

Previous studies report that there is a connection between the propagation of tsunamis and outer-rise normal fault characteristics in deep sea trench regions. However, the true seismic and tsunami potential of these faults are poorly understood, as their driving forces are controlled more from plate bending forces than tectonic rates. Such is the example along the Puerto Rico trench, where bathymetry reveals large normal faults outward of the trench, and its risk to nearby populations is not yet quantified. To help quantify the seismogenic and tsunami potential here, we created a set of tools to semi-automatically determine basic fault properties from topographic relief. We use bathymetric data compiled in the Global Multi-Resolution Topography (GMRT) synthesis. The data is presented as shaded relief within a Python figure that the operator visually inspects for suspected faults, selecting either a number of points or endpoints defining the raised footwall along one side of the fault. From here, transects are automatically determined orthogonal to these points, and the elevation, gradients, and extent of curvature are extracted. These are used to determine breaks in slope along the scarp associated with lower-bounds on fault offset, as well as extrapolated points to account for erosion and deposition along the scarp crown and toe, estimating the original, uneroded fault traces along the same transects. From these profiles, we then calculated the median and distribution of dip and offset values, for evaluation of the magnitude and robustness of individual fault profiles. With the compiled and cataloged dataset of significant outerrise faults, we can incorporate convergence rates to determine the total slip rate across these faults, putting an upper-bound on the earthquake and tsunami potential of these faults. Given the generalizable nature of this tool, we next plan to apply it to outerrise behaviors at other subduction zone environments.

Session: Learning Across Geological, Geophysical & Model-Derived Observations to Constrain Earthquake Behavior [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Quincey

Student Presenter: Yes

Invited Presentation: 

Authors