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Data from: What can surface slip distributions tell us about fault connectivity at depth?

Citation

Oglesby, David (2020), Data from: What can surface slip distributions tell us about fault connectivity at depth?, Dryad, Dataset, https://doi.org/10.6086/D1CD5H

Abstract

Fault systems with stepovers and gaps along strike are ubiquitous in nature, and many modern earthquakes (e.g. 1992 Landers, 1999 Hector Mine, 2016 Kaikoura, and 2019 Ridgecrest) have shown that ruptures can readily propagate across some disconnections, while being halted by others. It is quite possible, however, that many faults that appear discontinuous at the surface are in fact connected at depth, facilitating through-going rupture, and potentially increasing earthquake size. The present work explores whether the mapped surface slip in an earthquake is indicative of the connectivity of the fault system at depth. If there is a signal of subsurface connectivity in the surface slip pattern, then the connectivity of the system could potentially be inferred. Through 3D Dynamic rupture modeling of faults with along-strike gaps of various depths, I explore whether the amplitude or the spatial distribution of slip after an earthquake could be used to diagnose fault connectivity at depth. I find that in general, fault segments that are connected up to shallow depths of 1-2 km and are relatively long along strike compared to the seismogenic depth tend to have higher slip gradients at their edges than faults that are connected at greater depth, or that are disconnected to the bottom of the seismogenic zone. Systematic slip gradient differences at fault segment edges have been recorded in past earthquakes, giving hope that the modeled effect can be detected in many cases, even though mapped surface slip is affected by a number of different sources of heterogeneity. The results provide an alternative explanation for observations that stepovers that allow through-going rupture tend to have higher slip gradients than those at which rupture terminates: perhaps many such stepovers are connected at depth, which could persistently favor through-going rupture. There may be implications for interpretation of apparent fault discontinuities worldwide.

Methods

These are the restults of Finite Element models of earthquakes on a fault system that is segmented at the surface but connected at depth.

Usage Notes

The numerical results are in Matlab binary (.mat) format. Each result figure in the paper has a corresponding Matlab variable file. In each file are multiple variables, with each variable corresponding to one of the surface slip patterns in the figure. Variable names are of the format "sx2_4segs," which corresponds to a fault with 4 interior segments,  connected below a depth of 2 km.