Linear Relationship Between Aftershock Productivity and Seismic Coupling in the Northern Chile Subduction Zone. Issue 8 (17th August 2019)

• Record Type: Journal Article
• Authors: Hainzl, S.; Sippl, C.; Schurr, B.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 8(2019)
• Page Start: 8726
• Page End: 8738
• Publication Date: 2019-08-17
• Subjects: seismic coupling -- aftershocks -- earthquake triggering; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2019JB017764
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: The aftershock productivity is known to strongly vary for different mainshocks of the same magnitude, which cannot be simply explained by random fluctuations. In addition to variable source mechanisms, different rheological properties might be responsible for the observed variations. Here we show, for the subduction zone of northern Chile, that the aftershock productivity is linearly related to the degree of mechanical coupling along the subduction interface. Using the earthquake catalog of Sippl et al. (2018, https://doi.org/10.1002/2017JB015384 ), which consists of more than 100, 000 events between 2007 and 2014, and three different coupling maps inferred from interseismic geodetic deformation data, we show that the observed aftershock numbers are significantly lower than expected from the Båth's law. Furthermore, the productivity decays systematically with depth in the uppermost 80 km, while the b value increases. We show that this lack of aftershocks and the observed depth dependence can be simply explained by a linear relationship between the productivity and the coupling coefficient, leading to Båth law only in the case of full coupling. Our results indicate that coupling maps might be useful to forecast aftershock productivity and vice versa. Key Points: Aftershock productivity decreases systematically with depth Aftershock productivity is proportional to the coupling coefficient Bath's law is expected to be only valid in the limit of full coupling