Abstract:
We present a non-stationary epidemic-type aftershock sequence (ETAS) model in which the usual assumption of stationary
background rate is relaxed. Such a model could be used for modeling seismic sequences afected by aseismic
transients such as fuid/magma intrusion, slow slip earthquakes (SSEs), etc. The non-stationary background rate is
expressed as a linear combination of B-splines, and a method is proposed that allows for simultaneous estimation of
background rate as well as other ETAS model parameters. We also present an extension to this non-stationary ETAS
model where an adaptive roughness penalty function is used and consequently provides better estimates of rapidly
varying background rate functions. The performance of the proposed methods is demonstrated on synthetic catalogs
and an application to detect earthquake swarms (possibly associated with SSEs) in Hikurangi margin (North Island,
New Zealand) is presented.
