Abstract

Mutability is an information theory tool intended to characterize sequences of non-linear phenomena (e.g., earthquakes). In this study, we used mutability to identify and analyze the depth propagation of seismicity in northern Chile. During March/April 2014, several important earthquakes struck northern Chile, including one of magnitude 8.1, producing intense but short-lived aftershock regimes. To better understand this behavior, we used data from the Integrated Plate Boundary Observatory Chile (IPOC) catalog. In a first approach, we considered 101,601 earthquakes registered from January 1, 2007 to December 31, 2014 within a rectangle defined by the coordinates 68 W-72 W and 18S-22S. Based on Gutenberg-Richter analysis, earthquakes with magnitudes of >2.3 (a subset of 79,321 seisms) were selected for further analysis and were grouped by depth into overlapping bins in order to identify the depth propagation of the aftershock regimes. The largest two March 2014 earthquakes produced responses from near the surface to similar to 18 km depth. The largest two early April earthquakes had deeper aftershock regimes. In addition, using static information theory, we performed a detailed layer-by-layer analysis that shows that the March 2014 activity had larger response towards the surface, while the April 2014 activity showed larger activity towards the inner layers. To reach more recent years data from Centro Sismologico Nacional (CSN) covering from 2012 to the end of 2021 as used. The results show a similarity between the mutability and dynamic average depths of seismicity from 2012 to 2021. The mutability of recent years is slightly less than the historic average, which can be interpreted to reflect relaxing mechanisms that are postponing the expected megathrust event in this zone.