8 OCT 2019 - 10:42 CET

Seismic radiation and spectral  properties of intermediate  depth earthquakes in Chile
Raul Madariaga, Benoit Dérode, Jaime Campos, Leoncio Cabrera
and Sergio Ruizs
Programa de Riesgo Sísmico, Departamento de Geofísica,
Universidad de Chile, Santiago de Chile
We have studied a set of large intermediate depth earthquake in
North and Central Chile in order to determine whether they match
the properties observed in other subduction zones around the
world. Our study particularly addresses events that occurred at
different depths inside the double layered subduction zone of
Northern Chile. We compare events that occurred in the upper and
lower layers of the Nazca Plate.
We observe that as shallower megathrust earthquakes, these
events have spectra that differ quite significantly with respect to
the standard Brune (1970) model. They also have quite remarkable
spectral differences with each other. We compare the spectra
observed for a shallow subduction event that occurred in 2013 with
the recent intermediate depth event of January 2019. Both events
have the same Moment but different depth. The deeper event has
almost 10 times more seismic radiation at high frequencies than
the subduction event. We discuss possible explanations in terms of
stress drop or source complexity.
This research is possible thanks to the data from the
accelerometric network deployed by Servicio Sísmico Nacional de
la Universidad de Chile