Slow slip events in Mexico revised from the processing of 11 year GPS observations

Abstract

[1] The world's largest observed Slow Slip Events (SSE) occurred in 2001-2002 and 2006 in the Guerrero subduction zone, Mexico. Using an improved GPS processing that accounts for time-varying atmospheric phenomena as well as oceanic, atmospheric and hydrologic loading corrections, the 11 year GPS position time series in Guerrero show a noise reduction of ∼50% with respect to previous studies. Thanks to the improved position time series and, in particular, the simultaneous analysis of the three-dimensional GPS observations, we can provide new information about SSEs in the studied area. First, we detect seven nonperiodic anomalous displacements with subcentimeter amplitude, but no quasi-annual anomalies as proposed previously. The displacements seem to occur simultaneously with the observed peaks of non-volcanic tremor activity in the area. Second, we refine the characteristics of the two major SSEs in terms of timing, duration, and cumulative displacements, and highlight the complex surface spatiotemporal evolution of the displacements during these SSEs. In particular, we observe a clear initiation phase for the 2006 SSE as well as ending phases for both large SSEs. The ending phase shows a strong deceleration of the anomalous displacements with respect to the main displacement phase already observed, for the 2001-2002 and 2006 SSEs. The duration of the SSEs increases by 30-40% including the initiation and ending phases. For the 2006 SSE, the main displacement phase also shows spatiotemporal complexity. Our results demonstrate the need for improved three-dimensional GPS processing technique in order to undertake detailed studies of SSEs.

Episodic Aseismic Slip at Plate Boundaries

“…This is the largest SSE that has been recorded globally, and continued GPS monitoring has revealed that similar events repeated in 2006 (Larson et al, 2007), and 2009/10 (Walpersdorf et al, 2011), yielding a recurrence interval of approximately 4 years. This is consistent with Guerrero experiencing a shallower and larger magnitude transient slip than Oaxaca (Vergnolle et al, 2010). The pattern of interseismic strain accumulation indicated a locked plate interface at depths shallower than 25 km.…”

Possible control of subduction zone slow-earthquake periodicity by silica enrichment

“…Data sources for the recurrence times are listed in Extended Data Table 2. We note that Vergnolle et al 36 suggest that only the largest ETS at Guerrero recurring every four years are well documented. We also compile v P /v S estimates from various forms of seismic tomography models for each subduction zone (Extended Data Table 2).…”

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

“…The greatest concentration of slow-slip displacement has been located just downdip of the seismogenic zone, based on thermal models (Fig. 7b, thick yellow line;Kostoglodov et al, 2010). Non-volcanic tremors occur in two distinct regions above the flat slab ( Fig.…”

“…Subsequent studies showed a variety of slow slip behavior, in particular long-term (~1 year) slow-slip events (Kostoglodov et al, 2010;Larson et al, 2007;Vergnolle et al, 2010;Radiguet et al, 2011) and non-volcanic tremors and…”