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The Coseismic and Long-Term Roles of Earthquake Gates in Strike-Slip Faults

Description: 

Earthquake surface ruptures consist of fault segments bound by gaps, step-overs, and bends. Coseismically, these geometrical complexities, or earthquake gates, can act as barriers to rupture propagation, where the history of past earthquakes, material properties, and the availability and geometry of neighboring fault segments dictate the probability of throughgoing rupture. Over long timescales, these zones of geometrical complexity partly control the growth and evolution of the fault zone. In this contribution, we measure the passing probabilities of different earthquake gates as a function of their geometrical and stress attributes using the surface rupture maps of 31 strike-slip earthquakes from the Fault Displacement Hazard Initiative’s rupture database. Fitting logistic models through our data, we find that step-overs and gaps exceeding widths and lengths of 1.5 km are breached less than half of the time, as are bends with angles exceeding 45 degrees. We estimate the event likelihood of each of the earthquakes considered as the joint probabilities of all the breached gates in that event. These likelihoods serve as a retrospective indicator of the magnitude an earthquake grew to as a function of the geometrical complexity of the host fault network. We find that likelihood decreases with increasing magnitude, where, for a given magnitude, earthquakes that occurred on more mature faults (larger cumulative displacement) have higher likelihoods. Last, we consider earthquake gates in the context of the modern regional stress field and discuss the role of geometrical complexity in long-term fault stability.

Session: From Earthquakes to Plate Boundaries: Insights Into Fault Behavior Spanning Seconds to Millennia

Type: Oral

Date: 4/20/2023

Presentation Time: 10:15 AM (local time)

Presenting Author: Alba M. Rodriguez Padilla

Student Presenter: Yes

Invited Presentation: 

Authors