Tremor-informed kinematic slip modeling of the 2009-2010 slow-slip event doublet in the Mexican subduction zone

Slow-slip events (SSEs) release an important part of the accumulated strain at plate boundaries and can interact with large earthquakes. It is thus crucial to analyse in detail their temporal dynamics. While GNSS observations robustly capture the cumulative, static displacements associated with SSEs, their noise level limits the temporal resolution of transient, short-timescale potential variations in slip rate. In contrast, co-occurring tectonic tremor, sampled at much finer temporal resolution, reveals pronounced short-term intermittency within SSEs. Despite this, tremor-derived temporal variability has not yet been incorporated into kinematic SSE models, leaving the short-timescale dynamics largely unresolved.

 

In the Mexican subduction zone, large SSEs persist for several months,recur every few years, and GNSS-based kinematic models resolve only first-order spatiotemporal evolution at these long timescales. Here we investigate the spatio-temporal evolution of the 2009–2010 SSE sequence in Guerrero, Mexico. This sequence is of particular interest because it consists of two distinct sub-events, with the onset of the second coinciding with the occurrence of the distant Maule earthquake. A detailed kinematic analysis of this SSE, combining geodetic observations and tremor activity, therefore provides a unique opportunity to assess the potential role of dynamic stress perturbations during large SSEs.

We construct a tremor catalog covering the SSE sequence, using the temporary mini-array seismic network GGAP and a beamforming method at the tremor frequency band.

In parallel, we use GNSS time series from the local network, to jointly analyze the SSE crustal displacement signal with the resulting tremor catalog to observe the finer dynamics of the SSE sequence.

 

We develop two kinematic slip modeling schemes based on a least-squares formulation with regularization. In the first scheme, GNSS positions on fixed time windows are inverted sequentially as independent time steps. In the second scheme, the full GNSS time series are inverted simultaneously, which improves the recovery of displacement amplitudes and allows the incorporation of tremor-derived temporal constraints. Tremor burst timings are defined based on events clustering properties, and introduced as prior information in the kinematic inversion, allowing larger slip rates during tremor dense periods.

 

Our results show that the studied 2009-2010 SSE sequence includes 7 major tremor bursts that are accompanied by a slip acceleration. In 2009, two major episodes of tremor and slow-slip occurred in the westernmost part of Guerrero. Immediately following the 2010 Maule earthquake, a persistent and energetic tremor and slip episode was triggered, extending the slipping region eastward along strike, where multiple additional tremor and slip episodes were subsequently observed.

 

Although aseismic slip releases the largest moment, the accompanying tremor provides a high-resolution temporal proxy for fault slip. This enables improved temporal resolution in kinematic SSE models, and allows the identification of short-term slip accelerations that coincide with tremor timings. The complex 2009–2010 Guerrero slow-slip and tremor sequence analyzed here highlights the sensitivity of SSE slip rates and migration to far-field dynamic stress perturbations.