10:30 AM - 11:00 AM
[J03-2-01] Postseismic Deformation Following the 2002 Mw7.9 Denali Fault Earthquake
invited
An Mw7.9 strike slip earthquake struck on November 3, 2002, in central Alaska, rupturing ~325 km of the Denali fault and two other faults. The earthquake caused a strong postseismic transient that continues to have a substantial effect today. Distinguishing between different mechanisms of postseismic deformation (e.g., afterslip, viscoelastic relaxation) remains a challenging problem for many earthquakes. Early studies done in the first few years after the Denali event demonstrated that the observed postseismic response could not be explained by a single mechanism, but estimates of the contributions of afterslip and viscoelastic relaxation were plagued by tradeoffs between unknown parameters. As a result, the postseismic models determined using the first few years of data did not predict the future observations well.
We use a homogeneously reprocessed time series of GPS data from before and after the earthquake to reassess the postseismic deformation using as much as 15 years of data after the event. We analyze the variations in the time series themselves to identify subsets of the data in space and time for which a single postseismic mechanism is dominant. We also assess tradeoffs between the imprecisely known “steady" deformation and the postseismic transient. We compute the postseismic deformation using finite element models including realistic 3D elastic and viscoelastic structures, and constrain models based on the observations. One complexity is that the afterslip distribution, in practice, generally needs to be estimated empirically, although we experiment with models that base the afterslip distribution on the coseismic stress changes (which are uncertain due to incomplete knowledge of the coseismic slip). Coseismic and postseismic models are self-consistent, using the same earth structure, which eliminates an inconsistency in the previous studies.
We use a homogeneously reprocessed time series of GPS data from before and after the earthquake to reassess the postseismic deformation using as much as 15 years of data after the event. We analyze the variations in the time series themselves to identify subsets of the data in space and time for which a single postseismic mechanism is dominant. We also assess tradeoffs between the imprecisely known “steady" deformation and the postseismic transient. We compute the postseismic deformation using finite element models including realistic 3D elastic and viscoelastic structures, and constrain models based on the observations. One complexity is that the afterslip distribution, in practice, generally needs to be estimated empirically, although we experiment with models that base the afterslip distribution on the coseismic stress changes (which are uncertain due to incomplete knowledge of the coseismic slip). Coseismic and postseismic models are self-consistent, using the same earth structure, which eliminates an inconsistency in the previous studies.