Abstract
AbstractThe aftershock distribution of the 2014 Mw 8.1 Iquique earthquake offshore northern Chile, identified from a long‐term deployment of ocean bottom seismometers installed eight months after the mainshock, in conjunction with seismic reflection imaging, provides insights into the processes regulating the updip limit of coseismic rupture propagation. Aftershocks updip of the mainshock hypocenter frequently occur in the upper plate and are associated with normal faults identified from seismic reflection data. We propose that aftershock seismicity near the plate boundary documents subduction erosion that removes mass from the base of the wedge and results in normal faulting in the upper plate. The combination of very little or no sediment accretion and subduction erosion over millions of years has resulted in a very weak and aseismic frontal wedge. Our observations thus link the shallow subduction zone seismicity to subduction erosion processes that control the evolution of the overriding plate.
Highlights
The largest earthquakes on the globe occur along convergent plate margins, rupturing the boundary between upper overriding and lower subducting plates
We propose that aftershock seismicity near the plate boundary documents subduction erosion that removes mass from the base of the wedge and results in normal faulting in the upper plate
We suggest that the updip limit of the 2014 Iquique earthquake activates subduction erosion at the updip limit of the seismogenic zone during the postseismic and possibly the coseismic phase, which leads to extensive faulting of the upper plate, thereby manifesting the location of the updip limit over many earthquake cycles
Summary
The largest earthquakes on the globe occur along convergent plate margins, rupturing the boundary between upper overriding and lower subducting plates. The precise location of the far offshore located updip limit of coseismic slip and its controlling parameters remain poorly resolved, despite being of fundamental importance for earthquake hazard assessment. Controls on the updip limit were suggested to be related to forearc structure and morphology (Tilmann et al, 2010; Wang & Hu, 2006), metamorphic processes (Moore & Saffer, 2001), or thermal properties (Moore & Saffer, 2001; Oleskevich et al, 1999). Knowledge of the seismogenic updip limit and its controlling factors are essential for assessing subduction zone hazards. It has been suggested that subduction erosion and the occurrence of seismicity along subduction zone megathrusts and in the upper overriding plates are inherently related (Wang et al, 2010). Long-term permanent subsidence of the forearc (von Huene & Lallemand, 1990) and the PETERSEN ET AL
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