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Piecemeal Rupture of the Central Andes Subduction Zone Megathrust

Description: 

How megathrusts rupture in space and time to keep up with the long-term plate convergence along subduction zones is a key question in both plate boundary dynamics and seismic and tsunami hazard assessments. However, our understanding is limited and mainly based on numerical/conceptual models because cases of one or more earthquake ruptures filling long sections of megathrusts are either too few to cover the full spectrum or too imprecise to be reliable. An example of an imprecise case is the rupture history of the central Andes section of the Nazca–South America plate boundary. This megathrust section, which spans Southern Peru and Northern Chile, was recently ruptured by great earthquakes in 1995 (M8.1), 2001 (M8.4), and 2014 (M8.2), and by two much greater earthquakes (M8.5-9) in 1868 and 1877. However, current estimates of the 1868 and 1877 rupture areas using historical accounts of their effects vary by up to a factor of 3 so there is debate whether they include or not the rupture areas of the recent earthquakes. Here, we attempt to solve this issue by pinpointing the main area of slip in each earthquake using unambiguous tsunami waveforms instrumentally recorded to the north (San Francisco, United States) and south (Sydney, Australia) of their rupture zones. We found that while the 1868 rupture area filled the gap between the 2001 and 2014 earthquakes, the 1877 earthquake ruptured the gap between the 2014 and 1995 earthquakes. Thus, collectively and with limited overlap of the main slip areas, the 1868, 1877, 1995, 2001 and 2014 earthquakes ruptured the entire length (1000 km) of the central Andes Subduction Zone megathrust. Such a piecemeal rupture contrasts the one in the 1000-km southernmost section of the same plate boundary megathrust, which was last ruptured entirely by the 1960 (M9.5) earthquake alone

Session: From Earthquakes to Plate Boundaries: Insights Into Fault Behavior Spanning Seconds to Millennia

Type: Oral

Date: 4/20/2023

Presentation Time: 02:30 PM (local time)

Presenting Author: Matias Carvajal

Student Presenter: No

Invited Presentation: 

Authors