Sixty Years of Viscoelastic Stress Transfer Across the North Anatolian Fault
Phoebe Robinson, Harvard University
Since 1939, 11 strike-slip earthquakes greater than 6.7 Mw have ruptured across the North Anatolian Fault in Turkey from east to west. The series began with the 1939 Erzincan earthquake in eastern Turkey and the most recent 1999 Izmit earthquake extended the pattern of ruptures into the Sea of Marmara in western Turkey. The time between seismic events in this westward progression has ranged from years to decades, much greater than the timescale of seismic wave propagation (in seconds). This lag time between the ruptures is a challenge for rapid static or dynamic stress-triggering explanations of the earthquake sequence. However, the delayed triggering of these earthquakes may be explained by the propagation of earthquake-generated diffusive viscoelastic fronts within the upper mantle that slowly increase the Coulomb failure stress at each hypocenter. Using a three-dimensional semi-analytic code that can incorporate arbitrary earth layers with linear rheologies (Maxwell and Burgers), we examine the predicted time evolution of Coulomb failure stress changes along the North Anatolian Fault due to viscoelastic stress transfer, and find good agreement in both sequence and location with the historical earthquakes.
Abstract Author(s): Phoebe R. DeVries, Brendan J. Meade