Aftershocks Preferentially Occur in Previously Active Areas

Morgan T. Page

Submitted August 14, 2020, SCEC Contribution #10546, 2020 SCEC Annual Meeting Poster #099

The clearest statistical signal in aftershock locations is that most aftershocks occur close to their mainshocks. More precisely, aftershocks are triggered at distances following a power-law decay in distance (Felzer and Brodsky, 2006). This distance decay kernel is used in Epidemic-type Aftershock Sequence (ETAS) modeling and is typically assumed to be isotropic, even though individual sequences show more clustered aftershock occurrence. The assumption of spatially isotropic triggering kernels can impact the estimation of ETAS parameters themselves, such as biasing the magnitude-productivity term alpha and assigning too much weight to secondary rather than primary (direct) triggering. Here we show that aftershock locations, at all mainshock-aftershock distances, preferentially occur in areas of previous seismicity.

Key Words
aftershocks, seismicity

Citation
Page, M. T. (2020, 08). Aftershocks Preferentially Occur in Previously Active Areas. Poster Presentation at 2020 SCEC Annual Meeting.


Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)