| Title | Slow slip and inter-transient locking on the Nicoya megathrust in the late and early stages of an earthquake cycle |
| |
| Author | Xie, S ; Dixon, T
H; Malservisi, R; Jiang, Y; Protti, M |
| Source | Journal of Geophysical Research, Solid Earth 2020 p. 1-22, https://doi.org/10.1029/2020JB020503 |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200459 |
| Publisher | American Geophysical Union |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Area | Costa Rica |
| Lat/Long WENS | -86.0000 -84.0000 11.0000 9.0000 |
| Subjects | Nature and Environment; Science and Technology; tectonics; plate tectonics; faults, slip; earthquakes; earthquake studies; seismic energy; seismic surveys; seismic data; Caribbean Plate |
| Illustrations | location maps; plots; graphs; tables; models |
| Program | Public
Safety Geoscience Plate Boundary Earthquakes |
| Released | 2020 10 20 |
| Abstract | We analyzed continuous GPS data collected from 2002-2020 to characterize slow slip events (SSEs) in and near the Nicoya Peninsula, Costa Rica. These data are bisected by the 5 September 2012 Mw 7.6
earthquake. The displacement time series contain multiple signals, including plate convergence, plate interface locking, coseismic and postseismic deformation, seasonal oscillations, SSEs, and noise. GPS-measured coseismic and postseismic
displacements associated with the Mw 7.6 earthquake are modeled and removed by a step function plus multiple timescale relaxation processes with four characteristic times: 11, 94, 470, and 1,865 days. Seasonal oscillations are eliminated using a
multichannel singular spectrum analysis (M-SSA). Ten major SSEs (Mw > 6.6) are observed in the remaining time series, with a constant recurrence interval of 21.7 ± 2.6 months. SSEs occur in both shallow (~10 km) and deep (~35 km) portions of the
plate interface, but the latter last longer and have larger magnitudes. There is minimum to no slow slip in theMw 7.6 seismic rupture area and a persistent slow slip patch beneath the Nicoya Gulf entrance. Despite strong earthquake-related stress
perturbations, the inter-SSE locking status on the megathrust is very similar between the late and early stages of the earthquake cycle and includes locked patches that ruptured in the 2012 earthquake or continue to rupture via SSEs. Some locked
patches offshore south of the Nicoya Peninsula did not rupture in 2012, do not participate in SSEs, and may be indicative of supercycle behavior, that is, strain accumulation over several seismic cycles. These areas warrant heightened monitoring.
|
| Summary | (Plain Language Summary, not published)
Slow slip events are different ways than earthquakes to release stored energy in Earth's crust, but they do not cause damage. We build a database of slow
slip events in Northwestern Costa Rica from GPS measurements with millimeter precision. We found that these events happened about every 22 months, and the repeating time remain unchanged by the 5 September 2012 Mw 7.6 Costa Rica earthquake. Modeling
work that connects ground GPS measurements with crustal motion suggests the largest slow slip motion is under the entrance of the Nicoya Gulf. Strain accumulation patterns before and after the 5 September 2012 Mw 7.6 are similar. |
| GEOSCAN ID | 327286 |
|
|