How Does Slow Slip Reshape Megathrust Locking?
Description:
Interseismic locking (or coupling) models are inferred from geodetic data—typically from GNSS velocity fields—are commonly treated as long-term, time-averaged representation of megathrust seismogenic potential between major earthquakes. However, a key and little-explored question remains whether such models are stable over time, or whether transient deformation processes—particularly slow slip events (SSEs)—modulate the megathrust locking state in ways that influence earthquake nucleation and timing but remain unresolved by long-term interseismic velocity alone. Here, we build on a probabilistic Metropolis-Hastings framework that estimates the probability of locking versus stable creep on subduction megathrusts directly from GNSS data, without prescribing asperity geometry a priori. We present an implementation that explicitly addresses temporal variations in locking rather relying on a single long-term snapshot. We apply this approach to the Cascadia subduction zone, an ideal natural laboratory with two decades of GNSS observations and a well-documented catalog of recurrent SSEs. Using a pseudo-dynamic framework, we pursue three complementary objectives: (1) inferring locking distributions from GNSS velocities computed over successive time intervals; (2) by defining these intervals based on the initiation and termination of documents SSEs; and (3) explicitly testing the effects of accounting for SSE-related transient signals when estimating long-term and inter-SSE coupling. This strategy enables direct comparison of locking and creeping states before, during, and between SSEs, and to evaluate whether transient slow slip episodes overprint the long-term coupling or imprint short-term transient coupling variation along the subduction megathrust.
Session: SSJ-SSOC-SSA Joint Session: From Slow to Fast Earthquakes: Bridging the Spectrum of Fault Slip [Poster]
Type: Poster
Date: 4/16/2026
Presentation Time: 08:00 AM (local time)
Presenting Author: Axel J. Periollat
Student Presenter: No
Invited Presentation:
Poster Number: 150
Authors
Axel Periollat Presenting Author Corresponding Author axel.periollat@ucr.edu University of California, Riverside |
Giuseppe Costantino giuseppe.costantino@ens.fr Ecole Normale Superieure |
Gareth Funning gareth.funning@ucr.edu University of California, Riverside |
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How Does Slow Slip Reshape Megathrust Locking?
Category
SSJ-SSOC-SSA Joint Session: From Slow to Fast Earthquakes: Bridging the Spectrum of Fault Slip