Long-term persistence of subduction earthquake segment boundaries: Evidence from Mejillones Peninsula, northern Chile

Abstract

The Mejillones Peninsula in northern Chile has been recognized as the surface expression of a segment boundary for large subduction zone earthquakes. The sharp contact between the rupture planes of two instrumentally recorded earthquakes, the Mw = 8.0 Antofagasta (1995) and the Mw = 7.7 Tocopilla (2007) events, is located beneath the central part of Mejillones Peninsula. We present new chronostratigraphic and structural data that allow reconstructing the evolution of the Peninsula at the surface and correlation of the latter with seismic cycle deformation on the plate interface. Uplift commenced after 3.4 Myr, as recorded in the western highland. The central graben area on the Peninsula started uplifting above sea level as an anticlinal hinge zone prior to 400 kyr ago, most probably 790 kyr ago. The resulting E‐W trending hinge exactly overlies the limit between the rupture planes of the Antofagasta and Tocopilla earthquakes. By correlating the uplift data with the slip distribution of the above earthquakes, we demonstrate that deformation and uplift is focused during the postseismic and interseismic periods of the megathrust seismic cycle with coseismic deformation opposed to the long‐term motion. Additionally, the slip deficit beneath the Peninsula accumulating between events is probably largely recovered by creep. Hence we suggest that Mejillones Peninsula owes its existence to the lateral variation of the propensity for unstable slip at the interface. Since the latter is a material property, the long‐term spatial stability of the Peninsula as a barrier to rupture propagation since at least the middle Pleistocene is a necessary consequence.

Testing stress shadowing effects at the South American subduction zone

“…This requires persistent segment boundaries which prevent ruptures extending into neighbouring fault regions. While such boundaries might exist in some places (Victor et al 2011), this assumption is generally not based on observational evidence. In fact, rupture nucleation and termination seems to be mostly of stochastic nature associated to a GutenbergRichter type size distribution and variable nucleation sites.…”

Formation of Late Quaternary paleoshorelines in Crete, Eastern Mediterranean

“…In many cases these data have been used to derive estimates of eustatic sea-level changes and/or rock uplift arising from tectonic processes (e.g., Pirazzoli et al, 1982;Ota, 1986;Chappell et al, 1996;Victor et al, 2011). Studies of Late Quaternary paleoshorelines on the Eastern Mediterranean island of Crete have not universally produced results that can be unambiguously interpreted given our present understanding of eustatic sea-level changes, rock uplift and paleoshoreline histories (Pirazzoli et al, 1982(Pirazzoli et al, , 1996Shaw et al, 2008Shaw et al, , 2010Gallen et al, 2014;Strobl et al, 2014;Tiberti et al, 2014).…”

Analogue earthquakes and seismic cycles: experimental modelling across timescales

“…This mechanism could be responsible for the correlation of basins with source areas of megathrust earthquakes (Mogi, 1969;Nishenko and McCann, 1979;Wells et al, 2003) and peninsulas with barriers (e.g. Victor et al, 2011;Schurr et al, 2012;Saillard et al, 2017). moreover suggest a feedback between forearc deformation and seismogenesis along the megathrust: accordingly, because the stable wedge part overlying the seismogenic zone in segmented forearcs deforms quasi-elastically, characteristic great earthquakes tend to occur fairly periodically as in simple spring-slider experiments and numerical simulations of the experiments .…”