Document Type


Publication Date



slow slip event, earthquake cycle, postseismic

Digital Object Identifier (DOI)


In February 2014 a Mw = 7.0 slow slip event (SSE) took place beneath the Nicoya Peninsula, Costa Rica. This event occurred 17 months after the 5 September 2012, Mw = 7.6, earthquake and along the same subduction zone segment, during a period when significant postseismic deformation was ongoing. A second SSE occurred in the middle of 2015, 21 months after the 2014 SSE and 38 months after the earthquake. The recurrence interval for Nicoya SSEs was unchanged by the earthquake. However, the spatial distribution of slip for the 2014 event differed significantly from previous events, having only deep (~40 km) slip, compared to previous events, which had both deep and shallow slip. The 2015 SSE marked a return to the combination of deep plus shallow slip of preearthquake SSEs. However, slip magnitude in 2015 was nearly twice as large (Mw = 7.2) as preearthquake SSEs. We employ Coulomb Failure Stress change modeling in order to explain these changes. Stress changes associated with the earthquake and afterslip were highest near the shallow portion of the megathrust, where preearthquake SSEs had significant slip. Lower stress change occurred on the deeper parts of the plate interface, perhaps explaining why the deep (~40 km) region for SSEs remained unchanged. The large amount of shallow slip in the 2015 SSE may reflect lack of shallow slip in the prior SSE. These observations highlight the variability of aseismic strain release rates throughout the earthquake cycle.

Rights Information

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Was this content written or created while at USF?


Citation / Publisher Attribution

Journal of Geophysical Research: Solid Earth, v. 122, issue 8, p. 6773-6786

Supporting Information S1.docx (1126 kB)
Supporting Information S1

Table S1.xlsx (49 kB)
Table S1

Table S2.xlsx (49 kB)
Table S2