Evidence of the ambiguous critical state transition from aseismic to seismic slip
| Autor: | Salvage, Rebecca O., Furlong, Carolyn, Rojas Parra, Jesus, Eaton, David |
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| Jazyk: | angličtina |
| Rok vydání: | 2023 |
| Zdroj: | XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) |
| Popis: | The idea that earthquake processes occur on a continuum from aseismic (stable sliding) to seismic slip (event nucleation) is not new, however the mechanisms causing any evolution between the two end-members is not fully understood. Possible mechanisms may relate to dynamic fault weakening, static stress transfer, the concentration of shear stress at the boundary of an aseismic region, some combination of these, or a mechanism we have yet to detect. Moreover, the detection of aseismic processes is inherently difficult, adding to the challenges in detecting and understanding this evolution. Here, we investigate evidence for a critical state transition within the subsurface using data from several recent seismic sequences in western Canada. The first case investigates a potential change in seismic event rate following prolonged fluid injection at a water disposal well, suggesting that initial deformation in the subsurface related to the injection was aseismic. Twelve months into the injection program, a large change in the seismic event rate was observed, along with a change in the source characteristics of the events, suggesting a transition from dominantly aseismic to seismic slip. Another case investigates seismicity in a historically quiescent area where there is ongoing fluid injection. A M5.3 mainshock was followed by an unusual aftershock sequence, which showed limited evidence of Omori-like decay, and instead, remained persistent. We investigate these sequences using an array of techniques including ambient seismic noise, repeating seismicity and the identification of tremor-like signals to determine whether there is evidence of a critical state transition at depth. The 28th IUGG General Assembly (IUGG2023) (Berlin 2023) |
| Databáze: | OpenAIRE |
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